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08db0e4d74
freebsd-skq/contrib/gcc/unroll.c
kan 08db0e4d74 Gcc 3.3.1-release.
2003-08-22 02:56:07 +00:00

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/* Try to unroll loops, and split induction variables.
Copyright (C) 1992, 1993, 1994, 1995, 1997, 1998, 1999, 2000, 2001, 2002
Free Software Foundation, Inc.
Contributed by James E. Wilson, Cygnus Support/UC Berkeley.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2, or (at your option) any later
version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING. If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA. */
/* Try to unroll a loop, and split induction variables.
Loops for which the number of iterations can be calculated exactly are
handled specially. If the number of iterations times the insn_count is
less than MAX_UNROLLED_INSNS, then the loop is unrolled completely.
Otherwise, we try to unroll the loop a number of times modulo the number
of iterations, so that only one exit test will be needed. It is unrolled
a number of times approximately equal to MAX_UNROLLED_INSNS divided by
the insn count.
Otherwise, if the number of iterations can be calculated exactly at
run time, and the loop is always entered at the top, then we try to
precondition the loop. That is, at run time, calculate how many times
the loop will execute, and then execute the loop body a few times so
that the remaining iterations will be some multiple of 4 (or 2 if the
loop is large). Then fall through to a loop unrolled 4 (or 2) times,
with only one exit test needed at the end of the loop.
Otherwise, if the number of iterations can not be calculated exactly,
not even at run time, then we still unroll the loop a number of times
approximately equal to MAX_UNROLLED_INSNS divided by the insn count,
but there must be an exit test after each copy of the loop body.
For each induction variable, which is dead outside the loop (replaceable)
or for which we can easily calculate the final value, if we can easily
calculate its value at each place where it is set as a function of the
current loop unroll count and the variable's value at loop entry, then
the induction variable is split into `N' different variables, one for
each copy of the loop body. One variable is live across the backward
branch, and the others are all calculated as a function of this variable.
This helps eliminate data dependencies, and leads to further opportunities
for cse. */
/* Possible improvements follow: */
/* ??? Add an extra pass somewhere to determine whether unrolling will
give any benefit. E.g. after generating all unrolled insns, compute the
cost of all insns and compare against cost of insns in rolled loop.
- On traditional architectures, unrolling a non-constant bound loop
is a win if there is a giv whose only use is in memory addresses, the
memory addresses can be split, and hence giv increments can be
eliminated.
- It is also a win if the loop is executed many times, and preconditioning
can be performed for the loop.
Add code to check for these and similar cases. */
/* ??? Improve control of which loops get unrolled. Could use profiling
info to only unroll the most commonly executed loops. Perhaps have
a user specifyable option to control the amount of code expansion,
or the percent of loops to consider for unrolling. Etc. */
/* ??? Look at the register copies inside the loop to see if they form a
simple permutation. If so, iterate the permutation until it gets back to
the start state. This is how many times we should unroll the loop, for
best results, because then all register copies can be eliminated.
For example, the lisp nreverse function should be unrolled 3 times
while (this)
{
next = this->cdr;
this->cdr = prev;
prev = this;
this = next;
}
??? The number of times to unroll the loop may also be based on data
references in the loop. For example, if we have a loop that references
x[i-1], x[i], and x[i+1], we should unroll it a multiple of 3 times. */
/* ??? Add some simple linear equation solving capability so that we can
determine the number of loop iterations for more complex loops.
For example, consider this loop from gdb
#define SWAP_TARGET_AND_HOST(buffer,len)
{
char tmp;
char *p = (char *) buffer;
char *q = ((char *) buffer) + len - 1;
int iterations = (len + 1) >> 1;
int i;
for (p; p < q; p++, q--;)
{
tmp = *q;
*q = *p;
*p = tmp;
}
}
Note that:
start value = p = &buffer + current_iteration
end value = q = &buffer + len - 1 - current_iteration
Given the loop exit test of "p < q", then there must be "q - p" iterations,
set equal to zero and solve for number of iterations:
q - p = len - 1 - 2*current_iteration = 0
current_iteration = (len - 1) / 2
Hence, there are (len - 1) / 2 (rounded up to the nearest integer)
iterations of this loop. */
/* ??? Currently, no labels are marked as loop invariant when doing loop
unrolling. This is because an insn inside the loop, that loads the address
of a label inside the loop into a register, could be moved outside the loop
by the invariant code motion pass if labels were invariant. If the loop
is subsequently unrolled, the code will be wrong because each unrolled
body of the loop will use the same address, whereas each actually needs a
different address. A case where this happens is when a loop containing
a switch statement is unrolled.
It would be better to let labels be considered invariant. When we
unroll loops here, check to see if any insns using a label local to the
loop were moved before the loop. If so, then correct the problem, by
moving the insn back into the loop, or perhaps replicate the insn before
the loop, one copy for each time the loop is unrolled. */
#include "config.h"
#include "system.h"
#include "rtl.h"
#include "tm_p.h"
#include "insn-config.h"
#include "integrate.h"
#include "regs.h"
#include "recog.h"
#include "flags.h"
#include "function.h"
#include "expr.h"
#include "loop.h"
#include "toplev.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "predict.h"
#include "params.h"
/* The prime factors looked for when trying to unroll a loop by some
number which is modulo the total number of iterations. Just checking
for these 4 prime factors will find at least one factor for 75% of
all numbers theoretically. Practically speaking, this will succeed
almost all of the time since loops are generally a multiple of 2
and/or 5. */
#define NUM_FACTORS 4
static struct _factor { const int factor; int count; }
factors[NUM_FACTORS] = { {2, 0}, {3, 0}, {5, 0}, {7, 0}};
/* Describes the different types of loop unrolling performed. */
enum unroll_types
{
UNROLL_COMPLETELY,
UNROLL_MODULO,
UNROLL_NAIVE
};
/* Indexed by register number, if nonzero, then it contains a pointer
to a struct induction for a DEST_REG giv which has been combined with
one of more address givs. This is needed because whenever such a DEST_REG
giv is modified, we must modify the value of all split address givs
that were combined with this DEST_REG giv. */
static struct induction **addr_combined_regs;
/* Indexed by register number, if this is a splittable induction variable,
then this will hold the current value of the register, which depends on the
iteration number. */
static rtx *splittable_regs;
/* Indexed by register number, if this is a splittable induction variable,
then this will hold the number of instructions in the loop that modify
the induction variable. Used to ensure that only the last insn modifying
a split iv will update the original iv of the dest. */
static int *splittable_regs_updates;
/* Forward declarations. */
static rtx simplify_cmp_and_jump_insns PARAMS ((enum rtx_code,
enum machine_mode,
rtx, rtx, rtx));
static void init_reg_map PARAMS ((struct inline_remap *, int));
static rtx calculate_giv_inc PARAMS ((rtx, rtx, unsigned int));
static rtx initial_reg_note_copy PARAMS ((rtx, struct inline_remap *));
static void final_reg_note_copy PARAMS ((rtx *, struct inline_remap *));
static void copy_loop_body PARAMS ((struct loop *, rtx, rtx,
struct inline_remap *, rtx, int,
enum unroll_types, rtx, rtx, rtx, rtx));
static int find_splittable_regs PARAMS ((const struct loop *,
enum unroll_types, int));
static int find_splittable_givs PARAMS ((const struct loop *,
struct iv_class *, enum unroll_types,
rtx, int));
static int reg_dead_after_loop PARAMS ((const struct loop *, rtx));
static rtx fold_rtx_mult_add PARAMS ((rtx, rtx, rtx, enum machine_mode));
static rtx remap_split_bivs PARAMS ((struct loop *, rtx));
static rtx find_common_reg_term PARAMS ((rtx, rtx));
static rtx subtract_reg_term PARAMS ((rtx, rtx));
static rtx loop_find_equiv_value PARAMS ((const struct loop *, rtx));
static rtx ujump_to_loop_cont PARAMS ((rtx, rtx));
/* Try to unroll one loop and split induction variables in the loop.
The loop is described by the arguments LOOP and INSN_COUNT.
STRENGTH_REDUCTION_P indicates whether information generated in the
strength reduction pass is available.
This function is intended to be called from within `strength_reduce'
in loop.c. */
void
unroll_loop (loop, insn_count, strength_reduce_p)
struct loop *loop;
int insn_count;
int strength_reduce_p;
{
struct loop_info *loop_info = LOOP_INFO (loop);
struct loop_ivs *ivs = LOOP_IVS (loop);
int i, j;
unsigned int r;
unsigned HOST_WIDE_INT temp;
int unroll_number = 1;
rtx copy_start, copy_end;
rtx insn, sequence, pattern, tem;
int max_labelno, max_insnno;
rtx insert_before;
struct inline_remap *map;
char *local_label = NULL;
char *local_regno;
unsigned int max_local_regnum;
unsigned int maxregnum;
rtx exit_label = 0;
rtx start_label;
struct iv_class *bl;
int splitting_not_safe = 0;
enum unroll_types unroll_type = UNROLL_NAIVE;
int loop_preconditioned = 0;
rtx safety_label;
/* This points to the last real insn in the loop, which should be either
a JUMP_INSN (for conditional jumps) or a BARRIER (for unconditional
jumps). */
rtx last_loop_insn;
rtx loop_start = loop->start;
rtx loop_end = loop->end;
/* Don't bother unrolling huge loops. Since the minimum factor is
two, loops greater than one half of MAX_UNROLLED_INSNS will never
be unrolled. */
if (insn_count > MAX_UNROLLED_INSNS / 2)
{
if (loop_dump_stream)
fprintf (loop_dump_stream, "Unrolling failure: Loop too big.\n");
return;
}
/* Determine type of unroll to perform. Depends on the number of iterations
and the size of the loop. */
/* If there is no strength reduce info, then set
loop_info->n_iterations to zero. This can happen if
strength_reduce can't find any bivs in the loop. A value of zero
indicates that the number of iterations could not be calculated. */
if (! strength_reduce_p)
loop_info->n_iterations = 0;
if (loop_dump_stream && loop_info->n_iterations > 0)
{
fputs ("Loop unrolling: ", loop_dump_stream);
fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC,
loop_info->n_iterations);
fputs (" iterations.\n", loop_dump_stream);
}
/* Find and save a pointer to the last nonnote insn in the loop. */
last_loop_insn = prev_nonnote_insn (loop_end);
/* Calculate how many times to unroll the loop. Indicate whether or
not the loop is being completely unrolled. */
if (loop_info->n_iterations == 1)
{
/* Handle the case where the loop begins with an unconditional
jump to the loop condition. Make sure to delete the jump
insn, otherwise the loop body will never execute. */
/* FIXME this actually checks for a jump to the continue point, which
is not the same as the condition in a for loop. As a result, this
optimization fails for most for loops. We should really use flow
information rather than instruction pattern matching. */
rtx ujump = ujump_to_loop_cont (loop->start, loop->cont);
/* If number of iterations is exactly 1, then eliminate the compare and
branch at the end of the loop since they will never be taken.
Then return, since no other action is needed here. */
/* If the last instruction is not a BARRIER or a JUMP_INSN, then
don't do anything. */
if (GET_CODE (last_loop_insn) == BARRIER)
{
/* Delete the jump insn. This will delete the barrier also. */
last_loop_insn = PREV_INSN (last_loop_insn);
}
if (ujump && GET_CODE (last_loop_insn) == JUMP_INSN)
{
#ifdef HAVE_cc0
rtx prev = PREV_INSN (last_loop_insn);
#endif
delete_related_insns (last_loop_insn);
#ifdef HAVE_cc0
/* The immediately preceding insn may be a compare which must be
deleted. */
if (only_sets_cc0_p (prev))
delete_related_insns (prev);
#endif
delete_related_insns (ujump);
/* Remove the loop notes since this is no longer a loop. */
if (loop->vtop)
delete_related_insns (loop->vtop);
if (loop->cont)
delete_related_insns (loop->cont);
if (loop_start)
delete_related_insns (loop_start);
if (loop_end)
delete_related_insns (loop_end);
return;
}
}
if (loop_info->n_iterations > 0
/* Avoid overflow in the next expression. */
&& loop_info->n_iterations < (unsigned) MAX_UNROLLED_INSNS
&& loop_info->n_iterations * insn_count < (unsigned) MAX_UNROLLED_INSNS)
{
unroll_number = loop_info->n_iterations;
unroll_type = UNROLL_COMPLETELY;
}
else if (loop_info->n_iterations > 0)
{
/* Try to factor the number of iterations. Don't bother with the
general case, only using 2, 3, 5, and 7 will get 75% of all
numbers theoretically, and almost all in practice. */
for (i = 0; i < NUM_FACTORS; i++)
factors[i].count = 0;
temp = loop_info->n_iterations;
for (i = NUM_FACTORS - 1; i >= 0; i--)
while (temp % factors[i].factor == 0)
{
factors[i].count++;
temp = temp / factors[i].factor;
}
/* Start with the larger factors first so that we generally
get lots of unrolling. */
unroll_number = 1;
temp = insn_count;
for (i = 3; i >= 0; i--)
while (factors[i].count--)
{
if (temp * factors[i].factor < (unsigned) MAX_UNROLLED_INSNS)
{
unroll_number *= factors[i].factor;
temp *= factors[i].factor;
}
else
break;
}
/* If we couldn't find any factors, then unroll as in the normal
case. */
if (unroll_number == 1)
{
if (loop_dump_stream)
fprintf (loop_dump_stream, "Loop unrolling: No factors found.\n");
}
else
unroll_type = UNROLL_MODULO;
}
/* Default case, calculate number of times to unroll loop based on its
size. */
if (unroll_type == UNROLL_NAIVE)
{
if (8 * insn_count < MAX_UNROLLED_INSNS)
unroll_number = 8;
else if (4 * insn_count < MAX_UNROLLED_INSNS)
unroll_number = 4;
else
unroll_number = 2;
}
/* Now we know how many times to unroll the loop. */
if (loop_dump_stream)
fprintf (loop_dump_stream, "Unrolling loop %d times.\n", unroll_number);
if (unroll_type == UNROLL_COMPLETELY || unroll_type == UNROLL_MODULO)
{
/* Loops of these types can start with jump down to the exit condition
in rare circumstances.
Consider a pair of nested loops where the inner loop is part
of the exit code for the outer loop.
In this case jump.c will not duplicate the exit test for the outer
loop, so it will start with a jump to the exit code.
Then consider if the inner loop turns out to iterate once and
only once. We will end up deleting the jumps associated with
the inner loop. However, the loop notes are not removed from
the instruction stream.
And finally assume that we can compute the number of iterations
for the outer loop.
In this case unroll may want to unroll the outer loop even though
it starts with a jump to the outer loop's exit code.
We could try to optimize this case, but it hardly seems worth it.
Just return without unrolling the loop in such cases. */
insn = loop_start;
while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
insn = NEXT_INSN (insn);
if (GET_CODE (insn) == JUMP_INSN)
return;
}
if (unroll_type == UNROLL_COMPLETELY)
{
/* Completely unrolling the loop: Delete the compare and branch at
the end (the last two instructions). This delete must done at the
very end of loop unrolling, to avoid problems with calls to
back_branch_in_range_p, which is called by find_splittable_regs.
All increments of splittable bivs/givs are changed to load constant
instructions. */
copy_start = loop_start;
/* Set insert_before to the instruction immediately after the JUMP_INSN
(or BARRIER), so that any NOTEs between the JUMP_INSN and the end of
the loop will be correctly handled by copy_loop_body. */
insert_before = NEXT_INSN (last_loop_insn);
/* Set copy_end to the insn before the jump at the end of the loop. */
if (GET_CODE (last_loop_insn) == BARRIER)
copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
else if (GET_CODE (last_loop_insn) == JUMP_INSN)
{
copy_end = PREV_INSN (last_loop_insn);
#ifdef HAVE_cc0
/* The instruction immediately before the JUMP_INSN may be a compare
instruction which we do not want to copy. */
if (sets_cc0_p (PREV_INSN (copy_end)))
copy_end = PREV_INSN (copy_end);
#endif
}
else
{
/* We currently can't unroll a loop if it doesn't end with a
JUMP_INSN. There would need to be a mechanism that recognizes
this case, and then inserts a jump after each loop body, which
jumps to after the last loop body. */
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Unrolling failure: loop does not end with a JUMP_INSN.\n");
return;
}
}
else if (unroll_type == UNROLL_MODULO)
{
/* Partially unrolling the loop: The compare and branch at the end
(the last two instructions) must remain. Don't copy the compare
and branch instructions at the end of the loop. Insert the unrolled
code immediately before the compare/branch at the end so that the
code will fall through to them as before. */
copy_start = loop_start;
/* Set insert_before to the jump insn at the end of the loop.
Set copy_end to before the jump insn at the end of the loop. */
if (GET_CODE (last_loop_insn) == BARRIER)
{
insert_before = PREV_INSN (last_loop_insn);
copy_end = PREV_INSN (insert_before);
}
else if (GET_CODE (last_loop_insn) == JUMP_INSN)
{
insert_before = last_loop_insn;
#ifdef HAVE_cc0
/* The instruction immediately before the JUMP_INSN may be a compare
instruction which we do not want to copy or delete. */
if (sets_cc0_p (PREV_INSN (insert_before)))
insert_before = PREV_INSN (insert_before);
#endif
copy_end = PREV_INSN (insert_before);
}
else
{
/* We currently can't unroll a loop if it doesn't end with a
JUMP_INSN. There would need to be a mechanism that recognizes
this case, and then inserts a jump after each loop body, which
jumps to after the last loop body. */
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Unrolling failure: loop does not end with a JUMP_INSN.\n");
return;
}
}
else
{
/* Normal case: Must copy the compare and branch instructions at the
end of the loop. */
if (GET_CODE (last_loop_insn) == BARRIER)
{
/* Loop ends with an unconditional jump and a barrier.
Handle this like above, don't copy jump and barrier.
This is not strictly necessary, but doing so prevents generating
unconditional jumps to an immediately following label.
This will be corrected below if the target of this jump is
not the start_label. */
insert_before = PREV_INSN (last_loop_insn);
copy_end = PREV_INSN (insert_before);
}
else if (GET_CODE (last_loop_insn) == JUMP_INSN)
{
/* Set insert_before to immediately after the JUMP_INSN, so that
NOTEs at the end of the loop will be correctly handled by
copy_loop_body. */
insert_before = NEXT_INSN (last_loop_insn);
copy_end = last_loop_insn;
}
else
{
/* We currently can't unroll a loop if it doesn't end with a
JUMP_INSN. There would need to be a mechanism that recognizes
this case, and then inserts a jump after each loop body, which
jumps to after the last loop body. */
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Unrolling failure: loop does not end with a JUMP_INSN.\n");
return;
}
/* If copying exit test branches because they can not be eliminated,
then must convert the fall through case of the branch to a jump past
the end of the loop. Create a label to emit after the loop and save
it for later use. Do not use the label after the loop, if any, since
it might be used by insns outside the loop, or there might be insns
added before it later by final_[bg]iv_value which must be after
the real exit label. */
exit_label = gen_label_rtx ();
insn = loop_start;
while (GET_CODE (insn) != CODE_LABEL && GET_CODE (insn) != JUMP_INSN)
insn = NEXT_INSN (insn);
if (GET_CODE (insn) == JUMP_INSN)
{
/* The loop starts with a jump down to the exit condition test.
Start copying the loop after the barrier following this
jump insn. */
copy_start = NEXT_INSN (insn);
/* Splitting induction variables doesn't work when the loop is
entered via a jump to the bottom, because then we end up doing
a comparison against a new register for a split variable, but
we did not execute the set insn for the new register because
it was skipped over. */
splitting_not_safe = 1;
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Splitting not safe, because loop not entered at top.\n");
}
else
copy_start = loop_start;
}
/* This should always be the first label in the loop. */
start_label = NEXT_INSN (copy_start);
/* There may be a line number note and/or a loop continue note here. */
while (GET_CODE (start_label) == NOTE)
start_label = NEXT_INSN (start_label);
if (GET_CODE (start_label) != CODE_LABEL)
{
/* This can happen as a result of jump threading. If the first insns in
the loop test the same condition as the loop's backward jump, or the
opposite condition, then the backward jump will be modified to point
to elsewhere, and the loop's start label is deleted.
This case currently can not be handled by the loop unrolling code. */
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Unrolling failure: unknown insns between BEG note and loop label.\n");
return;
}
if (LABEL_NAME (start_label))
{
/* The jump optimization pass must have combined the original start label
with a named label for a goto. We can't unroll this case because
jumps which go to the named label must be handled differently than
jumps to the loop start, and it is impossible to differentiate them
in this case. */
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Unrolling failure: loop start label is gone\n");
return;
}
if (unroll_type == UNROLL_NAIVE
&& GET_CODE (last_loop_insn) == BARRIER
&& GET_CODE (PREV_INSN (last_loop_insn)) == JUMP_INSN
&& start_label != JUMP_LABEL (PREV_INSN (last_loop_insn)))
{
/* In this case, we must copy the jump and barrier, because they will
not be converted to jumps to an immediately following label. */
insert_before = NEXT_INSN (last_loop_insn);
copy_end = last_loop_insn;
}
if (unroll_type == UNROLL_NAIVE
&& GET_CODE (last_loop_insn) == JUMP_INSN
&& start_label != JUMP_LABEL (last_loop_insn))
{
/* ??? The loop ends with a conditional branch that does not branch back
to the loop start label. In this case, we must emit an unconditional
branch to the loop exit after emitting the final branch.
copy_loop_body does not have support for this currently, so we
give up. It doesn't seem worthwhile to unroll anyways since
unrolling would increase the number of branch instructions
executed. */
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Unrolling failure: final conditional branch not to loop start\n");
return;
}
/* Allocate a translation table for the labels and insn numbers.
They will be filled in as we copy the insns in the loop. */
max_labelno = max_label_num ();
max_insnno = get_max_uid ();
/* Various paths through the unroll code may reach the "egress" label
without initializing fields within the map structure.
To be safe, we use xcalloc to zero the memory. */
map = (struct inline_remap *) xcalloc (1, sizeof (struct inline_remap));
/* Allocate the label map. */
if (max_labelno > 0)
{
map->label_map = (rtx *) xcalloc (max_labelno, sizeof (rtx));
local_label = (char *) xcalloc (max_labelno, sizeof (char));
}
/* Search the loop and mark all local labels, i.e. the ones which have to
be distinct labels when copied. For all labels which might be
non-local, set their label_map entries to point to themselves.
If they happen to be local their label_map entries will be overwritten
before the loop body is copied. The label_map entries for local labels
will be set to a different value each time the loop body is copied. */
for (insn = copy_start; insn != loop_end; insn = NEXT_INSN (insn))
{
rtx note;
if (GET_CODE (insn) == CODE_LABEL)
local_label[CODE_LABEL_NUMBER (insn)] = 1;
else if (GET_CODE (insn) == JUMP_INSN)
{
if (JUMP_LABEL (insn))
set_label_in_map (map,
CODE_LABEL_NUMBER (JUMP_LABEL (insn)),
JUMP_LABEL (insn));
else if (GET_CODE (PATTERN (insn)) == ADDR_VEC
|| GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
{
rtx pat = PATTERN (insn);
int diff_vec_p = GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC;
int len = XVECLEN (pat, diff_vec_p);
rtx label;
for (i = 0; i < len; i++)
{
label = XEXP (XVECEXP (pat, diff_vec_p, i), 0);
set_label_in_map (map, CODE_LABEL_NUMBER (label), label);
}
}
}
if ((note = find_reg_note (insn, REG_LABEL, NULL_RTX)))
set_label_in_map (map, CODE_LABEL_NUMBER (XEXP (note, 0)),
XEXP (note, 0));
}
/* Allocate space for the insn map. */
map->insn_map = (rtx *) xmalloc (max_insnno * sizeof (rtx));
/* Set this to zero, to indicate that we are doing loop unrolling,
not function inlining. */
map->inline_target = 0;
/* The register and constant maps depend on the number of registers
present, so the final maps can't be created until after
find_splittable_regs is called. However, they are needed for
preconditioning, so we create temporary maps when preconditioning
is performed. */
/* The preconditioning code may allocate two new pseudo registers. */
maxregnum = max_reg_num ();
/* local_regno is only valid for regnos < max_local_regnum. */
max_local_regnum = maxregnum;
/* Allocate and zero out the splittable_regs and addr_combined_regs
arrays. These must be zeroed here because they will be used if
loop preconditioning is performed, and must be zero for that case.
It is safe to do this here, since the extra registers created by the
preconditioning code and find_splittable_regs will never be used
to access the splittable_regs[] and addr_combined_regs[] arrays. */
splittable_regs = (rtx *) xcalloc (maxregnum, sizeof (rtx));
splittable_regs_updates = (int *) xcalloc (maxregnum, sizeof (int));
addr_combined_regs
= (struct induction **) xcalloc (maxregnum, sizeof (struct induction *));
local_regno = (char *) xcalloc (maxregnum, sizeof (char));
/* Mark all local registers, i.e. the ones which are referenced only
inside the loop. */
if (INSN_UID (copy_end) < max_uid_for_loop)
{
int copy_start_luid = INSN_LUID (copy_start);
int copy_end_luid = INSN_LUID (copy_end);
/* If a register is used in the jump insn, we must not duplicate it
since it will also be used outside the loop. */
if (GET_CODE (copy_end) == JUMP_INSN)
copy_end_luid--;
/* If we have a target that uses cc0, then we also must not duplicate
the insn that sets cc0 before the jump insn, if one is present. */
#ifdef HAVE_cc0
if (GET_CODE (copy_end) == JUMP_INSN
&& sets_cc0_p (PREV_INSN (copy_end)))
copy_end_luid--;
#endif
/* If copy_start points to the NOTE that starts the loop, then we must
use the next luid, because invariant pseudo-regs moved out of the loop
have their lifetimes modified to start here, but they are not safe
to duplicate. */
if (copy_start == loop_start)
copy_start_luid++;
/* If a pseudo's lifetime is entirely contained within this loop, then we
can use a different pseudo in each unrolled copy of the loop. This
results in better code. */
/* We must limit the generic test to max_reg_before_loop, because only
these pseudo registers have valid regno_first_uid info. */
for (r = FIRST_PSEUDO_REGISTER; r < max_reg_before_loop; ++r)
if (REGNO_FIRST_UID (r) > 0 && REGNO_FIRST_UID (r) < max_uid_for_loop
&& REGNO_FIRST_LUID (r) >= copy_start_luid
&& REGNO_LAST_UID (r) > 0 && REGNO_LAST_UID (r) < max_uid_for_loop
&& REGNO_LAST_LUID (r) <= copy_end_luid)
{
/* However, we must also check for loop-carried dependencies.
If the value the pseudo has at the end of iteration X is
used by iteration X+1, then we can not use a different pseudo
for each unrolled copy of the loop. */
/* A pseudo is safe if regno_first_uid is a set, and this
set dominates all instructions from regno_first_uid to
regno_last_uid. */
/* ??? This check is simplistic. We would get better code if
this check was more sophisticated. */
if (set_dominates_use (r, REGNO_FIRST_UID (r), REGNO_LAST_UID (r),
copy_start, copy_end))
local_regno[r] = 1;
if (loop_dump_stream)
{
if (local_regno[r])
fprintf (loop_dump_stream, "Marked reg %d as local\n", r);
else
fprintf (loop_dump_stream, "Did not mark reg %d as local\n",
r);
}
}
}
/* If this loop requires exit tests when unrolled, check to see if we
can precondition the loop so as to make the exit tests unnecessary.
Just like variable splitting, this is not safe if the loop is entered
via a jump to the bottom. Also, can not do this if no strength
reduce info, because precondition_loop_p uses this info. */
/* Must copy the loop body for preconditioning before the following
find_splittable_regs call since that will emit insns which need to
be after the preconditioned loop copies, but immediately before the
unrolled loop copies. */
/* Also, it is not safe to split induction variables for the preconditioned
copies of the loop body. If we split induction variables, then the code
assumes that each induction variable can be represented as a function
of its initial value and the loop iteration number. This is not true
in this case, because the last preconditioned copy of the loop body
could be any iteration from the first up to the `unroll_number-1'th,
depending on the initial value of the iteration variable. Therefore
we can not split induction variables here, because we can not calculate
their value. Hence, this code must occur before find_splittable_regs
is called. */
if (unroll_type == UNROLL_NAIVE && ! splitting_not_safe && strength_reduce_p)
{
rtx initial_value, final_value, increment;
enum machine_mode mode;
if (precondition_loop_p (loop,
&initial_value, &final_value, &increment,
&mode))
{
rtx diff, insn;
rtx *labels;
int abs_inc, neg_inc;
enum rtx_code cc = loop_info->comparison_code;
int less_p = (cc == LE || cc == LEU || cc == LT || cc == LTU);
int unsigned_p = (cc == LEU || cc == GEU || cc == LTU || cc == GTU);
map->reg_map = (rtx *) xmalloc (maxregnum * sizeof (rtx));
VARRAY_CONST_EQUIV_INIT (map->const_equiv_varray, maxregnum,
"unroll_loop_precondition");
global_const_equiv_varray = map->const_equiv_varray;
init_reg_map (map, maxregnum);
/* Limit loop unrolling to 4, since this will make 7 copies of
the loop body. */
if (unroll_number > 4)
unroll_number = 4;
/* Save the absolute value of the increment, and also whether or
not it is negative. */
neg_inc = 0;
abs_inc = INTVAL (increment);
if (abs_inc < 0)
{
abs_inc = -abs_inc;
neg_inc = 1;
}
start_sequence ();
/* We must copy the final and initial values here to avoid
improperly shared rtl. */
final_value = copy_rtx (final_value);
initial_value = copy_rtx (initial_value);
/* Final value may have form of (PLUS val1 const1_rtx). We need
to convert it into general operand, so compute the real value. */
final_value = force_operand (final_value, NULL_RTX);
if (!nonmemory_operand (final_value, VOIDmode))
final_value = force_reg (mode, final_value);
/* Calculate the difference between the final and initial values.
Final value may be a (plus (reg x) (const_int 1)) rtx.
We have to deal with for (i = 0; --i < 6;) type loops.
For such loops the real final value is the first time the
loop variable overflows, so the diff we calculate is the
distance from the overflow value. This is 0 or ~0 for
unsigned loops depending on the direction, or INT_MAX,
INT_MAX+1 for signed loops. We really do not need the
exact value, since we are only interested in the diff
modulo the increment, and the increment is a power of 2,
so we can pretend that the overflow value is 0/~0. */
if (cc == NE || less_p != neg_inc)
diff = simplify_gen_binary (MINUS, mode, final_value,
initial_value);
else
diff = simplify_gen_unary (neg_inc ? NOT : NEG, mode,
initial_value, mode);
diff = force_operand (diff, NULL_RTX);
/* Now calculate (diff % (unroll * abs (increment))) by using an
and instruction. */
diff = simplify_gen_binary (AND, mode, diff,
GEN_INT (unroll_number*abs_inc - 1));
diff = force_operand (diff, NULL_RTX);
/* Now emit a sequence of branches to jump to the proper precond
loop entry point. */
labels = (rtx *) xmalloc (sizeof (rtx) * unroll_number);
for (i = 0; i < unroll_number; i++)
labels[i] = gen_label_rtx ();
/* Check for the case where the initial value is greater than or
equal to the final value. In that case, we want to execute
exactly one loop iteration. The code below will fail for this
case. This check does not apply if the loop has a NE
comparison at the end. */
if (cc != NE)
{
rtx incremented_initval;
enum rtx_code cmp_code;
incremented_initval
= simplify_gen_binary (PLUS, mode, initial_value, increment);
incremented_initval
= force_operand (incremented_initval, NULL_RTX);
cmp_code = (less_p
? (unsigned_p ? GEU : GE)
: (unsigned_p ? LEU : LE));
insn = simplify_cmp_and_jump_insns (cmp_code, mode,
incremented_initval,
final_value, labels[1]);
if (insn)
predict_insn_def (insn, PRED_LOOP_CONDITION, TAKEN);
}
/* Assuming the unroll_number is 4, and the increment is 2, then
for a negative increment: for a positive increment:
diff = 0,1 precond 0 diff = 0,7 precond 0
diff = 2,3 precond 3 diff = 1,2 precond 1
diff = 4,5 precond 2 diff = 3,4 precond 2
diff = 6,7 precond 1 diff = 5,6 precond 3 */
/* We only need to emit (unroll_number - 1) branches here, the
last case just falls through to the following code. */
/* ??? This would give better code if we emitted a tree of branches
instead of the current linear list of branches. */
for (i = 0; i < unroll_number - 1; i++)
{
int cmp_const;
enum rtx_code cmp_code;
/* For negative increments, must invert the constant compared
against, except when comparing against zero. */
if (i == 0)
{
cmp_const = 0;
cmp_code = EQ;
}
else if (neg_inc)
{
cmp_const = unroll_number - i;
cmp_code = GE;
}
else
{
cmp_const = i;
cmp_code = LE;
}
insn = simplify_cmp_and_jump_insns (cmp_code, mode, diff,
GEN_INT (abs_inc*cmp_const),
labels[i]);
if (insn)
predict_insn (insn, PRED_LOOP_PRECONDITIONING,
REG_BR_PROB_BASE / (unroll_number - i));
}
/* If the increment is greater than one, then we need another branch,
to handle other cases equivalent to 0. */
/* ??? This should be merged into the code above somehow to help
simplify the code here, and reduce the number of branches emitted.
For the negative increment case, the branch here could easily
be merged with the `0' case branch above. For the positive
increment case, it is not clear how this can be simplified. */
if (abs_inc != 1)
{
int cmp_const;
enum rtx_code cmp_code;
if (neg_inc)
{
cmp_const = abs_inc - 1;
cmp_code = LE;
}
else
{
cmp_const = abs_inc * (unroll_number - 1) + 1;
cmp_code = GE;
}
simplify_cmp_and_jump_insns (cmp_code, mode, diff,
GEN_INT (cmp_const), labels[0]);
}
sequence = get_insns ();
end_sequence ();
loop_insn_hoist (loop, sequence);
/* Only the last copy of the loop body here needs the exit
test, so set copy_end to exclude the compare/branch here,
and then reset it inside the loop when get to the last
copy. */
if (GET_CODE (last_loop_insn) == BARRIER)
copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
else if (GET_CODE (last_loop_insn) == JUMP_INSN)
{
copy_end = PREV_INSN (last_loop_insn);
#ifdef HAVE_cc0
/* The immediately preceding insn may be a compare which
we do not want to copy. */
if (sets_cc0_p (PREV_INSN (copy_end)))
copy_end = PREV_INSN (copy_end);
#endif
}
else
abort ();
for (i = 1; i < unroll_number; i++)
{
emit_label_after (labels[unroll_number - i],
PREV_INSN (loop_start));
memset ((char *) map->insn_map, 0, max_insnno * sizeof (rtx));
memset ((char *) &VARRAY_CONST_EQUIV (map->const_equiv_varray, 0),
0, (VARRAY_SIZE (map->const_equiv_varray)
* sizeof (struct const_equiv_data)));
map->const_age = 0;
for (j = 0; j < max_labelno; j++)
if (local_label[j])
set_label_in_map (map, j, gen_label_rtx ());
for (r = FIRST_PSEUDO_REGISTER; r < max_local_regnum; r++)
if (local_regno[r])
{
map->reg_map[r]
= gen_reg_rtx (GET_MODE (regno_reg_rtx[r]));
record_base_value (REGNO (map->reg_map[r]),
regno_reg_rtx[r], 0);
}
/* The last copy needs the compare/branch insns at the end,
so reset copy_end here if the loop ends with a conditional
branch. */
if (i == unroll_number - 1)
{
if (GET_CODE (last_loop_insn) == BARRIER)
copy_end = PREV_INSN (PREV_INSN (last_loop_insn));
else
copy_end = last_loop_insn;
}
/* None of the copies are the `last_iteration', so just
pass zero for that parameter. */
copy_loop_body (loop, copy_start, copy_end, map, exit_label, 0,
unroll_type, start_label, loop_end,
loop_start, copy_end);
}
emit_label_after (labels[0], PREV_INSN (loop_start));
if (GET_CODE (last_loop_insn) == BARRIER)
{
insert_before = PREV_INSN (last_loop_insn);
copy_end = PREV_INSN (insert_before);
}
else
{
insert_before = last_loop_insn;
#ifdef HAVE_cc0
/* The instruction immediately before the JUMP_INSN may
be a compare instruction which we do not want to copy
or delete. */
if (sets_cc0_p (PREV_INSN (insert_before)))
insert_before = PREV_INSN (insert_before);
#endif
copy_end = PREV_INSN (insert_before);
}
/* Set unroll type to MODULO now. */
unroll_type = UNROLL_MODULO;
loop_preconditioned = 1;
/* Clean up. */
free (labels);
}
}
/* If reach here, and the loop type is UNROLL_NAIVE, then don't unroll
the loop unless all loops are being unrolled. */
if (unroll_type == UNROLL_NAIVE && ! flag_unroll_all_loops)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Unrolling failure: Naive unrolling not being done.\n");
goto egress;
}
/* At this point, we are guaranteed to unroll the loop. */
/* Keep track of the unroll factor for the loop. */
loop_info->unroll_number = unroll_number;
/* And whether the loop has been preconditioned. */
loop_info->preconditioned = loop_preconditioned;
/* Remember whether it was preconditioned for the second loop pass. */
NOTE_PRECONDITIONED (loop->end) = loop_preconditioned;
/* For each biv and giv, determine whether it can be safely split into
a different variable for each unrolled copy of the loop body.
We precalculate and save this info here, since computing it is
expensive.
Do this before deleting any instructions from the loop, so that
back_branch_in_range_p will work correctly. */
if (splitting_not_safe)
temp = 0;
else
temp = find_splittable_regs (loop, unroll_type, unroll_number);
/* find_splittable_regs may have created some new registers, so must
reallocate the reg_map with the new larger size, and must realloc
the constant maps also. */
maxregnum = max_reg_num ();
map->reg_map = (rtx *) xmalloc (maxregnum * sizeof (rtx));
init_reg_map (map, maxregnum);
if (map->const_equiv_varray == 0)
VARRAY_CONST_EQUIV_INIT (map->const_equiv_varray,
maxregnum + temp * unroll_number * 2,
"unroll_loop");
global_const_equiv_varray = map->const_equiv_varray;
/* Search the list of bivs and givs to find ones which need to be remapped
when split, and set their reg_map entry appropriately. */
for (bl = ivs->list; bl; bl = bl->next)
{
if (REGNO (bl->biv->src_reg) != bl->regno)
map->reg_map[bl->regno] = bl->biv->src_reg;
#if 0
/* Currently, non-reduced/final-value givs are never split. */
for (v = bl->giv; v; v = v->next_iv)
if (REGNO (v->src_reg) != bl->regno)
map->reg_map[REGNO (v->dest_reg)] = v->src_reg;
#endif
}
/* Use our current register alignment and pointer flags. */
map->regno_pointer_align = cfun->emit->regno_pointer_align;
map->x_regno_reg_rtx = cfun->emit->x_regno_reg_rtx;
/* If the loop is being partially unrolled, and the iteration variables
are being split, and are being renamed for the split, then must fix up
the compare/jump instruction at the end of the loop to refer to the new
registers. This compare isn't copied, so the registers used in it
will never be replaced if it isn't done here. */
if (unroll_type == UNROLL_MODULO)
{
insn = NEXT_INSN (copy_end);
if (GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN)
PATTERN (insn) = remap_split_bivs (loop, PATTERN (insn));
}
/* For unroll_number times, make a copy of each instruction
between copy_start and copy_end, and insert these new instructions
before the end of the loop. */
for (i = 0; i < unroll_number; i++)
{
memset ((char *) map->insn_map, 0, max_insnno * sizeof (rtx));
memset ((char *) &VARRAY_CONST_EQUIV (map->const_equiv_varray, 0), 0,
VARRAY_SIZE (map->const_equiv_varray) * sizeof (struct const_equiv_data));
map->const_age = 0;
for (j = 0; j < max_labelno; j++)
if (local_label[j])
set_label_in_map (map, j, gen_label_rtx ());
for (r = FIRST_PSEUDO_REGISTER; r < max_local_regnum; r++)
if (local_regno[r])
{
map->reg_map[r] = gen_reg_rtx (GET_MODE (regno_reg_rtx[r]));
record_base_value (REGNO (map->reg_map[r]),
regno_reg_rtx[r], 0);
}
/* If loop starts with a branch to the test, then fix it so that
it points to the test of the first unrolled copy of the loop. */
if (i == 0 && loop_start != copy_start)
{
insn = PREV_INSN (copy_start);
pattern = PATTERN (insn);
tem = get_label_from_map (map,
CODE_LABEL_NUMBER
(XEXP (SET_SRC (pattern), 0)));
SET_SRC (pattern) = gen_rtx_LABEL_REF (VOIDmode, tem);
/* Set the jump label so that it can be used by later loop unrolling
passes. */
JUMP_LABEL (insn) = tem;
LABEL_NUSES (tem)++;
}
copy_loop_body (loop, copy_start, copy_end, map, exit_label,
i == unroll_number - 1, unroll_type, start_label,
loop_end, insert_before, insert_before);
}
/* Before deleting any insns, emit a CODE_LABEL immediately after the last
insn to be deleted. This prevents any runaway delete_insn call from
more insns that it should, as it always stops at a CODE_LABEL. */
/* Delete the compare and branch at the end of the loop if completely
unrolling the loop. Deleting the backward branch at the end also
deletes the code label at the start of the loop. This is done at
the very end to avoid problems with back_branch_in_range_p. */
if (unroll_type == UNROLL_COMPLETELY)
safety_label = emit_label_after (gen_label_rtx (), last_loop_insn);
else
safety_label = emit_label_after (gen_label_rtx (), copy_end);
/* Delete all of the original loop instructions. Don't delete the
LOOP_BEG note, or the first code label in the loop. */
insn = NEXT_INSN (copy_start);
while (insn != safety_label)
{
/* ??? Don't delete named code labels. They will be deleted when the
jump that references them is deleted. Otherwise, we end up deleting
them twice, which causes them to completely disappear instead of turn
into NOTE_INSN_DELETED_LABEL notes. This in turn causes aborts in
dwarfout.c/dwarf2out.c. We could perhaps fix the dwarf*out.c files
to handle deleted labels instead. Or perhaps fix DECL_RTL of the
associated LABEL_DECL to point to one of the new label instances. */
/* ??? Likewise, we can't delete a NOTE_INSN_DELETED_LABEL note. */
if (insn != start_label
&& ! (GET_CODE (insn) == CODE_LABEL && LABEL_NAME (insn))
&& ! (GET_CODE (insn) == NOTE
&& NOTE_LINE_NUMBER (insn) == NOTE_INSN_DELETED_LABEL))
insn = delete_related_insns (insn);
else
insn = NEXT_INSN (insn);
}
/* Can now delete the 'safety' label emitted to protect us from runaway
delete_related_insns calls. */
if (INSN_DELETED_P (safety_label))
abort ();
delete_related_insns (safety_label);
/* If exit_label exists, emit it after the loop. Doing the emit here
forces it to have a higher INSN_UID than any insn in the unrolled loop.
This is needed so that mostly_true_jump in reorg.c will treat jumps
to this loop end label correctly, i.e. predict that they are usually
not taken. */
if (exit_label)
emit_label_after (exit_label, loop_end);
egress:
if (unroll_type == UNROLL_COMPLETELY)
{
/* Remove the loop notes since this is no longer a loop. */
if (loop->vtop)
delete_related_insns (loop->vtop);
if (loop->cont)
delete_related_insns (loop->cont);
if (loop_start)
delete_related_insns (loop_start);
if (loop_end)
delete_related_insns (loop_end);
}
if (map->const_equiv_varray)
VARRAY_FREE (map->const_equiv_varray);
if (map->label_map)
{
free (map->label_map);
free (local_label);
}
free (map->insn_map);
free (splittable_regs);
free (splittable_regs_updates);
free (addr_combined_regs);
free (local_regno);
if (map->reg_map)
free (map->reg_map);
free (map);
}
/* A helper function for unroll_loop. Emit a compare and branch to
satisfy (CMP OP1 OP2), but pass this through the simplifier first.
If the branch turned out to be conditional, return it, otherwise
return NULL. */
static rtx
simplify_cmp_and_jump_insns (code, mode, op0, op1, label)
enum rtx_code code;
enum machine_mode mode;
rtx op0, op1, label;
{
rtx t, insn;
t = simplify_relational_operation (code, mode, op0, op1);
if (!t)
{
enum rtx_code scode = signed_condition (code);
emit_cmp_and_jump_insns (op0, op1, scode, NULL_RTX, mode,
code != scode, label);
insn = get_last_insn ();
JUMP_LABEL (insn) = label;
LABEL_NUSES (label) += 1;
return insn;
}
else if (t == const_true_rtx)
{
insn = emit_jump_insn (gen_jump (label));
emit_barrier ();
JUMP_LABEL (insn) = label;
LABEL_NUSES (label) += 1;
}
return NULL_RTX;
}
/* Return true if the loop can be safely, and profitably, preconditioned
so that the unrolled copies of the loop body don't need exit tests.
This only works if final_value, initial_value and increment can be
determined, and if increment is a constant power of 2.
If increment is not a power of 2, then the preconditioning modulo
operation would require a real modulo instead of a boolean AND, and this
is not considered `profitable'. */
/* ??? If the loop is known to be executed very many times, or the machine
has a very cheap divide instruction, then preconditioning is a win even
when the increment is not a power of 2. Use RTX_COST to compute
whether divide is cheap.
??? A divide by constant doesn't actually need a divide, look at
expand_divmod. The reduced cost of this optimized modulo is not
reflected in RTX_COST. */
int
precondition_loop_p (loop, initial_value, final_value, increment, mode)
const struct loop *loop;
rtx *initial_value, *final_value, *increment;
enum machine_mode *mode;
{
rtx loop_start = loop->start;
struct loop_info *loop_info = LOOP_INFO (loop);
if (loop_info->n_iterations > 0)
{
if (INTVAL (loop_info->increment) > 0)
{
*initial_value = const0_rtx;
*increment = const1_rtx;
*final_value = GEN_INT (loop_info->n_iterations);
}
else
{
*initial_value = GEN_INT (loop_info->n_iterations);
*increment = constm1_rtx;
*final_value = const0_rtx;
}
*mode = word_mode;
if (loop_dump_stream)
{
fputs ("Preconditioning: Success, number of iterations known, ",
loop_dump_stream);
fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC,
loop_info->n_iterations);
fputs (".\n", loop_dump_stream);
}
return 1;
}
if (loop_info->iteration_var == 0)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Preconditioning: Could not find iteration variable.\n");
return 0;
}
else if (loop_info->initial_value == 0)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Preconditioning: Could not find initial value.\n");
return 0;
}
else if (loop_info->increment == 0)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Preconditioning: Could not find increment value.\n");
return 0;
}
else if (GET_CODE (loop_info->increment) != CONST_INT)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Preconditioning: Increment not a constant.\n");
return 0;
}
else if ((exact_log2 (INTVAL (loop_info->increment)) < 0)
&& (exact_log2 (-INTVAL (loop_info->increment)) < 0))
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Preconditioning: Increment not a constant power of 2.\n");
return 0;
}
/* Unsigned_compare and compare_dir can be ignored here, since they do
not matter for preconditioning. */
if (loop_info->final_value == 0)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Preconditioning: EQ comparison loop.\n");
return 0;
}
/* Must ensure that final_value is invariant, so call
loop_invariant_p to check. Before doing so, must check regno
against max_reg_before_loop to make sure that the register is in
the range covered by loop_invariant_p. If it isn't, then it is
most likely a biv/giv which by definition are not invariant. */
if ((GET_CODE (loop_info->final_value) == REG
&& REGNO (loop_info->final_value) >= max_reg_before_loop)
|| (GET_CODE (loop_info->final_value) == PLUS
&& REGNO (XEXP (loop_info->final_value, 0)) >= max_reg_before_loop)
|| ! loop_invariant_p (loop, loop_info->final_value))
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Preconditioning: Final value not invariant.\n");
return 0;
}
/* Fail for floating point values, since the caller of this function
does not have code to deal with them. */
if (GET_MODE_CLASS (GET_MODE (loop_info->final_value)) == MODE_FLOAT
|| GET_MODE_CLASS (GET_MODE (loop_info->initial_value)) == MODE_FLOAT)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Preconditioning: Floating point final or initial value.\n");
return 0;
}
/* Fail if loop_info->iteration_var is not live before loop_start,
since we need to test its value in the preconditioning code. */
if (REGNO_FIRST_LUID (REGNO (loop_info->iteration_var))
> INSN_LUID (loop_start))
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Preconditioning: Iteration var not live before loop start.\n");
return 0;
}
/* Note that loop_iterations biases the initial value for GIV iterators
such as "while (i-- > 0)" so that we can calculate the number of
iterations just like for BIV iterators.
Also note that the absolute values of initial_value and
final_value are unimportant as only their difference is used for
calculating the number of loop iterations. */
*initial_value = loop_info->initial_value;
*increment = loop_info->increment;
*final_value = loop_info->final_value;
/* Decide what mode to do these calculations in. Choose the larger
of final_value's mode and initial_value's mode, or a full-word if
both are constants. */
*mode = GET_MODE (*final_value);
if (*mode == VOIDmode)
{
*mode = GET_MODE (*initial_value);
if (*mode == VOIDmode)
*mode = word_mode;
}
else if (*mode != GET_MODE (*initial_value)
&& (GET_MODE_SIZE (*mode)
< GET_MODE_SIZE (GET_MODE (*initial_value))))
*mode = GET_MODE (*initial_value);
/* Success! */
if (loop_dump_stream)
fprintf (loop_dump_stream, "Preconditioning: Successful.\n");
return 1;
}
/* All pseudo-registers must be mapped to themselves. Two hard registers
must be mapped, VIRTUAL_STACK_VARS_REGNUM and VIRTUAL_INCOMING_ARGS_
REGNUM, to avoid function-inlining specific conversions of these
registers. All other hard regs can not be mapped because they may be
used with different
modes. */
static void
init_reg_map (map, maxregnum)
struct inline_remap *map;
int maxregnum;
{
int i;
for (i = maxregnum - 1; i > LAST_VIRTUAL_REGISTER; i--)
map->reg_map[i] = regno_reg_rtx[i];
/* Just clear the rest of the entries. */
for (i = LAST_VIRTUAL_REGISTER; i >= 0; i--)
map->reg_map[i] = 0;
map->reg_map[VIRTUAL_STACK_VARS_REGNUM]
= regno_reg_rtx[VIRTUAL_STACK_VARS_REGNUM];
map->reg_map[VIRTUAL_INCOMING_ARGS_REGNUM]
= regno_reg_rtx[VIRTUAL_INCOMING_ARGS_REGNUM];
}
/* Strength-reduction will often emit code for optimized biv/givs which
calculates their value in a temporary register, and then copies the result
to the iv. This procedure reconstructs the pattern computing the iv;
verifying that all operands are of the proper form.
PATTERN must be the result of single_set.
The return value is the amount that the giv is incremented by. */
static rtx
calculate_giv_inc (pattern, src_insn, regno)
rtx pattern, src_insn;
unsigned int regno;
{
rtx increment;
rtx increment_total = 0;
int tries = 0;
retry:
/* Verify that we have an increment insn here. First check for a plus
as the set source. */
if (GET_CODE (SET_SRC (pattern)) != PLUS)
{
/* SR sometimes computes the new giv value in a temp, then copies it
to the new_reg. */
src_insn = PREV_INSN (src_insn);
pattern = single_set (src_insn);
if (GET_CODE (SET_SRC (pattern)) != PLUS)
abort ();
/* The last insn emitted is not needed, so delete it to avoid confusing
the second cse pass. This insn sets the giv unnecessarily. */
delete_related_insns (get_last_insn ());
}
/* Verify that we have a constant as the second operand of the plus. */
increment = XEXP (SET_SRC (pattern), 1);
if (GET_CODE (increment) != CONST_INT)
{
/* SR sometimes puts the constant in a register, especially if it is
too big to be an add immed operand. */
increment = find_last_value (increment, &src_insn, NULL_RTX, 0);
/* SR may have used LO_SUM to compute the constant if it is too large
for a load immed operand. In this case, the constant is in operand
one of the LO_SUM rtx. */
if (GET_CODE (increment) == LO_SUM)
increment = XEXP (increment, 1);
/* Some ports store large constants in memory and add a REG_EQUAL
note to the store insn. */
else if (GET_CODE (increment) == MEM)
{
rtx note = find_reg_note (src_insn, REG_EQUAL, 0);
if (note)
increment = XEXP (note, 0);
}
else if (GET_CODE (increment) == IOR
|| GET_CODE (increment) == PLUS
|| GET_CODE (increment) == ASHIFT
|| GET_CODE (increment) == LSHIFTRT)
{
/* The rs6000 port loads some constants with IOR.
The alpha port loads some constants with ASHIFT and PLUS.
The sparc64 port loads some constants with LSHIFTRT. */
rtx second_part = XEXP (increment, 1);
enum rtx_code code = GET_CODE (increment);
increment = find_last_value (XEXP (increment, 0),
&src_insn, NULL_RTX, 0);
/* Don't need the last insn anymore. */
delete_related_insns (get_last_insn ());
if (GET_CODE (second_part) != CONST_INT
|| GET_CODE (increment) != CONST_INT)
abort ();
if (code == IOR)
increment = GEN_INT (INTVAL (increment) | INTVAL (second_part));
else if (code == PLUS)
increment = GEN_INT (INTVAL (increment) + INTVAL (second_part));
else if (code == ASHIFT)
increment = GEN_INT (INTVAL (increment) << INTVAL (second_part));
else
increment = GEN_INT ((unsigned HOST_WIDE_INT) INTVAL (increment) >> INTVAL (second_part));
}
if (GET_CODE (increment) != CONST_INT)
abort ();
/* The insn loading the constant into a register is no longer needed,
so delete it. */
delete_related_insns (get_last_insn ());
}
if (increment_total)
increment_total = GEN_INT (INTVAL (increment_total) + INTVAL (increment));
else
increment_total = increment;
/* Check that the source register is the same as the register we expected
to see as the source. If not, something is seriously wrong. */
if (GET_CODE (XEXP (SET_SRC (pattern), 0)) != REG
|| REGNO (XEXP (SET_SRC (pattern), 0)) != regno)
{
/* Some machines (e.g. the romp), may emit two add instructions for
certain constants, so lets try looking for another add immediately
before this one if we have only seen one add insn so far. */
if (tries == 0)
{
tries++;
src_insn = PREV_INSN (src_insn);
pattern = single_set (src_insn);
delete_related_insns (get_last_insn ());
goto retry;
}
abort ();
}
return increment_total;
}
/* Copy REG_NOTES, except for insn references, because not all insn_map
entries are valid yet. We do need to copy registers now though, because
the reg_map entries can change during copying. */
static rtx
initial_reg_note_copy (notes, map)
rtx notes;
struct inline_remap *map;
{
rtx copy;
if (notes == 0)
return 0;
copy = rtx_alloc (GET_CODE (notes));
PUT_REG_NOTE_KIND (copy, REG_NOTE_KIND (notes));
if (GET_CODE (notes) == EXPR_LIST)
XEXP (copy, 0) = copy_rtx_and_substitute (XEXP (notes, 0), map, 0);
else if (GET_CODE (notes) == INSN_LIST)
/* Don't substitute for these yet. */
XEXP (copy, 0) = copy_rtx (XEXP (notes, 0));
else
abort ();
XEXP (copy, 1) = initial_reg_note_copy (XEXP (notes, 1), map);
return copy;
}
/* Fixup insn references in copied REG_NOTES. */
static void
final_reg_note_copy (notesp, map)
rtx *notesp;
struct inline_remap *map;
{
while (*notesp)
{
rtx note = *notesp;
if (GET_CODE (note) == INSN_LIST)
{
/* Sometimes, we have a REG_WAS_0 note that points to a
deleted instruction. In that case, we can just delete the
note. */
if (REG_NOTE_KIND (note) == REG_WAS_0)
{
*notesp = XEXP (note, 1);
continue;
}
else
{
rtx insn = map->insn_map[INSN_UID (XEXP (note, 0))];
/* If we failed to remap the note, something is awry.
Allow REG_LABEL as it may reference label outside
the unrolled loop. */
if (!insn)
{
if (REG_NOTE_KIND (note) != REG_LABEL)
abort ();
}
else
XEXP (note, 0) = insn;
}
}
notesp = &XEXP (note, 1);
}
}
/* Copy each instruction in the loop, substituting from map as appropriate.
This is very similar to a loop in expand_inline_function. */
static void
copy_loop_body (loop, copy_start, copy_end, map, exit_label, last_iteration,
unroll_type, start_label, loop_end, insert_before,
copy_notes_from)
struct loop *loop;
rtx copy_start, copy_end;
struct inline_remap *map;
rtx exit_label;
int last_iteration;
enum unroll_types unroll_type;
rtx start_label, loop_end, insert_before, copy_notes_from;
{
struct loop_ivs *ivs = LOOP_IVS (loop);
rtx insn, pattern;
rtx set, tem, copy = NULL_RTX;
int dest_reg_was_split, i;
#ifdef HAVE_cc0
rtx cc0_insn = 0;
#endif
rtx final_label = 0;
rtx giv_inc, giv_dest_reg, giv_src_reg;
/* If this isn't the last iteration, then map any references to the
start_label to final_label. Final label will then be emitted immediately
after the end of this loop body if it was ever used.
If this is the last iteration, then map references to the start_label
to itself. */
if (! last_iteration)
{
final_label = gen_label_rtx ();
set_label_in_map (map, CODE_LABEL_NUMBER (start_label), final_label);
}
else
set_label_in_map (map, CODE_LABEL_NUMBER (start_label), start_label);
start_sequence ();
insn = copy_start;
do
{
insn = NEXT_INSN (insn);
map->orig_asm_operands_vector = 0;
switch (GET_CODE (insn))
{
case INSN:
pattern = PATTERN (insn);
copy = 0;
giv_inc = 0;
/* Check to see if this is a giv that has been combined with
some split address givs. (Combined in the sense that
`combine_givs' in loop.c has put two givs in the same register.)
In this case, we must search all givs based on the same biv to
find the address givs. Then split the address givs.
Do this before splitting the giv, since that may map the
SET_DEST to a new register. */
if ((set = single_set (insn))
&& GET_CODE (SET_DEST (set)) == REG
&& addr_combined_regs[REGNO (SET_DEST (set))])
{
struct iv_class *bl;
struct induction *v, *tv;
unsigned int regno = REGNO (SET_DEST (set));
v = addr_combined_regs[REGNO (SET_DEST (set))];
bl = REG_IV_CLASS (ivs, REGNO (v->src_reg));
/* Although the giv_inc amount is not needed here, we must call
calculate_giv_inc here since it might try to delete the
last insn emitted. If we wait until later to call it,
we might accidentally delete insns generated immediately
below by emit_unrolled_add. */
giv_inc = calculate_giv_inc (set, insn, regno);
/* Now find all address giv's that were combined with this
giv 'v'. */
for (tv = bl->giv; tv; tv = tv->next_iv)
if (tv->giv_type == DEST_ADDR && tv->same == v)
{
int this_giv_inc;
/* If this DEST_ADDR giv was not split, then ignore it. */
if (*tv->location != tv->dest_reg)
continue;
/* Scale this_giv_inc if the multiplicative factors of
the two givs are different. */
this_giv_inc = INTVAL (giv_inc);
if (tv->mult_val != v->mult_val)
this_giv_inc = (this_giv_inc / INTVAL (v->mult_val)
* INTVAL (tv->mult_val));
tv->dest_reg = plus_constant (tv->dest_reg, this_giv_inc);
*tv->location = tv->dest_reg;
if (last_iteration && unroll_type != UNROLL_COMPLETELY)
{
/* Must emit an insn to increment the split address
giv. Add in the const_adjust field in case there
was a constant eliminated from the address. */
rtx value, dest_reg;
/* tv->dest_reg will be either a bare register,
or else a register plus a constant. */
if (GET_CODE (tv->dest_reg) == REG)
dest_reg = tv->dest_reg;
else
dest_reg = XEXP (tv->dest_reg, 0);
/* Check for shared address givs, and avoid
incrementing the shared pseudo reg more than
once. */
if (! tv->same_insn && ! tv->shared)
{
/* tv->dest_reg may actually be a (PLUS (REG)
(CONST)) here, so we must call plus_constant
to add the const_adjust amount before calling
emit_unrolled_add below. */
value = plus_constant (tv->dest_reg,
tv->const_adjust);
if (GET_CODE (value) == PLUS)
{
/* The constant could be too large for an add
immediate, so can't directly emit an insn
here. */
emit_unrolled_add (dest_reg, XEXP (value, 0),
XEXP (value, 1));
}
}
/* Reset the giv to be just the register again, in case
it is used after the set we have just emitted.
We must subtract the const_adjust factor added in
above. */
tv->dest_reg = plus_constant (dest_reg,
-tv->const_adjust);
*tv->location = tv->dest_reg;
}
}
}
/* If this is a setting of a splittable variable, then determine
how to split the variable, create a new set based on this split,
and set up the reg_map so that later uses of the variable will
use the new split variable. */
dest_reg_was_split = 0;
if ((set = single_set (insn))
&& GET_CODE (SET_DEST (set)) == REG
&& splittable_regs[REGNO (SET_DEST (set))])
{
unsigned int regno = REGNO (SET_DEST (set));
unsigned int src_regno;
dest_reg_was_split = 1;
giv_dest_reg = SET_DEST (set);
giv_src_reg = giv_dest_reg;
/* Compute the increment value for the giv, if it wasn't
already computed above. */
if (giv_inc == 0)
giv_inc = calculate_giv_inc (set, insn, regno);
src_regno = REGNO (giv_src_reg);
if (unroll_type == UNROLL_COMPLETELY)
{
/* Completely unrolling the loop. Set the induction
variable to a known constant value. */
/* The value in splittable_regs may be an invariant
value, so we must use plus_constant here. */
splittable_regs[regno]
= plus_constant (splittable_regs[src_regno],
INTVAL (giv_inc));
if (GET_CODE (splittable_regs[regno]) == PLUS)
{
giv_src_reg = XEXP (splittable_regs[regno], 0);
giv_inc = XEXP (splittable_regs[regno], 1);
}
else
{
/* The splittable_regs value must be a REG or a
CONST_INT, so put the entire value in the giv_src_reg
variable. */
giv_src_reg = splittable_regs[regno];
giv_inc = const0_rtx;
}
}
else
{
/* Partially unrolling loop. Create a new pseudo
register for the iteration variable, and set it to
be a constant plus the original register. Except
on the last iteration, when the result has to
go back into the original iteration var register. */
/* Handle bivs which must be mapped to a new register
when split. This happens for bivs which need their
final value set before loop entry. The new register
for the biv was stored in the biv's first struct
induction entry by find_splittable_regs. */
if (regno < ivs->n_regs
&& REG_IV_TYPE (ivs, regno) == BASIC_INDUCT)
{
giv_src_reg = REG_IV_CLASS (ivs, regno)->biv->src_reg;
giv_dest_reg = giv_src_reg;
}
#if 0
/* If non-reduced/final-value givs were split, then
this would have to remap those givs also. See
find_splittable_regs. */
#endif
splittable_regs[regno]
= simplify_gen_binary (PLUS, GET_MODE (giv_src_reg),
giv_inc,
splittable_regs[src_regno]);
giv_inc = splittable_regs[regno];
/* Now split the induction variable by changing the dest
of this insn to a new register, and setting its
reg_map entry to point to this new register.
If this is the last iteration, and this is the last insn
that will update the iv, then reuse the original dest,
to ensure that the iv will have the proper value when
the loop exits or repeats.
Using splittable_regs_updates here like this is safe,
because it can only be greater than one if all
instructions modifying the iv are always executed in
order. */
if (! last_iteration
|| (splittable_regs_updates[regno]-- != 1))
{
tem = gen_reg_rtx (GET_MODE (giv_src_reg));
giv_dest_reg = tem;
map->reg_map[regno] = tem;
record_base_value (REGNO (tem),
giv_inc == const0_rtx
? giv_src_reg
: gen_rtx_PLUS (GET_MODE (giv_src_reg),
giv_src_reg, giv_inc),
1);
}
else
map->reg_map[regno] = giv_src_reg;
}
/* The constant being added could be too large for an add
immediate, so can't directly emit an insn here. */
emit_unrolled_add (giv_dest_reg, giv_src_reg, giv_inc);
copy = get_last_insn ();
pattern = PATTERN (copy);
}
else
{
pattern = copy_rtx_and_substitute (pattern, map, 0);
copy = emit_insn (pattern);
}
REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
INSN_SCOPE (copy) = INSN_SCOPE (insn);
/* If there is a REG_EQUAL note present whose value
is not loop invariant, then delete it, since it
may cause problems with later optimization passes. */
if ((tem = find_reg_note (copy, REG_EQUAL, NULL_RTX))
&& !loop_invariant_p (loop, XEXP (tem, 0)))
remove_note (copy, tem);
#ifdef HAVE_cc0
/* If this insn is setting CC0, it may need to look at
the insn that uses CC0 to see what type of insn it is.
In that case, the call to recog via validate_change will
fail. So don't substitute constants here. Instead,
do it when we emit the following insn.
For example, see the pyr.md file. That machine has signed and
unsigned compares. The compare patterns must check the
following branch insn to see which what kind of compare to
emit.
If the previous insn set CC0, substitute constants on it as
well. */
if (sets_cc0_p (PATTERN (copy)) != 0)
cc0_insn = copy;
else
{
if (cc0_insn)
try_constants (cc0_insn, map);
cc0_insn = 0;
try_constants (copy, map);
}
#else
try_constants (copy, map);
#endif
/* Make split induction variable constants `permanent' since we
know there are no backward branches across iteration variable
settings which would invalidate this. */
if (dest_reg_was_split)
{
int regno = REGNO (SET_DEST (set));
if ((size_t) regno < VARRAY_SIZE (map->const_equiv_varray)
&& (VARRAY_CONST_EQUIV (map->const_equiv_varray, regno).age
== map->const_age))
VARRAY_CONST_EQUIV (map->const_equiv_varray, regno).age = -1;
}
break;
case JUMP_INSN:
pattern = copy_rtx_and_substitute (PATTERN (insn), map, 0);
copy = emit_jump_insn (pattern);
REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
INSN_SCOPE (copy) = INSN_SCOPE (insn);
if (JUMP_LABEL (insn))
{
JUMP_LABEL (copy) = get_label_from_map (map,
CODE_LABEL_NUMBER
(JUMP_LABEL (insn)));
LABEL_NUSES (JUMP_LABEL (copy))++;
}
if (JUMP_LABEL (insn) == start_label && insn == copy_end
&& ! last_iteration)
{
/* This is a branch to the beginning of the loop; this is the
last insn being copied; and this is not the last iteration.
In this case, we want to change the original fall through
case to be a branch past the end of the loop, and the
original jump label case to fall_through. */
if (!invert_jump (copy, exit_label, 0))
{
rtx jmp;
rtx lab = gen_label_rtx ();
/* Can't do it by reversing the jump (probably because we
couldn't reverse the conditions), so emit a new
jump_insn after COPY, and redirect the jump around
that. */
jmp = emit_jump_insn_after (gen_jump (exit_label), copy);
JUMP_LABEL (jmp) = exit_label;
LABEL_NUSES (exit_label)++;
jmp = emit_barrier_after (jmp);
emit_label_after (lab, jmp);
LABEL_NUSES (lab) = 0;
if (!redirect_jump (copy, lab, 0))
abort ();
}
}
#ifdef HAVE_cc0
if (cc0_insn)
try_constants (cc0_insn, map);
cc0_insn = 0;
#endif
try_constants (copy, map);
/* Set the jump label of COPY correctly to avoid problems with
later passes of unroll_loop, if INSN had jump label set. */
if (JUMP_LABEL (insn))
{
rtx label = 0;
/* Can't use the label_map for every insn, since this may be
the backward branch, and hence the label was not mapped. */
if ((set = single_set (copy)))
{
tem = SET_SRC (set);
if (GET_CODE (tem) == LABEL_REF)
label = XEXP (tem, 0);
else if (GET_CODE (tem) == IF_THEN_ELSE)
{
if (XEXP (tem, 1) != pc_rtx)
label = XEXP (XEXP (tem, 1), 0);
else
label = XEXP (XEXP (tem, 2), 0);
}
}
if (label && GET_CODE (label) == CODE_LABEL)
JUMP_LABEL (copy) = label;
else
{
/* An unrecognizable jump insn, probably the entry jump
for a switch statement. This label must have been mapped,
so just use the label_map to get the new jump label. */
JUMP_LABEL (copy)
= get_label_from_map (map,
CODE_LABEL_NUMBER (JUMP_LABEL (insn)));
}
/* If this is a non-local jump, then must increase the label
use count so that the label will not be deleted when the
original jump is deleted. */
LABEL_NUSES (JUMP_LABEL (copy))++;
}
else if (GET_CODE (PATTERN (copy)) == ADDR_VEC
|| GET_CODE (PATTERN (copy)) == ADDR_DIFF_VEC)
{
rtx pat = PATTERN (copy);
int diff_vec_p = GET_CODE (pat) == ADDR_DIFF_VEC;
int len = XVECLEN (pat, diff_vec_p);
int i;
for (i = 0; i < len; i++)
LABEL_NUSES (XEXP (XVECEXP (pat, diff_vec_p, i), 0))++;
}
/* If this used to be a conditional jump insn but whose branch
direction is now known, we must do something special. */
if (any_condjump_p (insn) && onlyjump_p (insn) && map->last_pc_value)
{
#ifdef HAVE_cc0
/* If the previous insn set cc0 for us, delete it. */
if (only_sets_cc0_p (PREV_INSN (copy)))
delete_related_insns (PREV_INSN (copy));
#endif
/* If this is now a no-op, delete it. */
if (map->last_pc_value == pc_rtx)
{
delete_insn (copy);
copy = 0;
}
else
/* Otherwise, this is unconditional jump so we must put a
BARRIER after it. We could do some dead code elimination
here, but jump.c will do it just as well. */
emit_barrier ();
}
break;
case CALL_INSN:
pattern = copy_rtx_and_substitute (PATTERN (insn), map, 0);
copy = emit_call_insn (pattern);
REG_NOTES (copy) = initial_reg_note_copy (REG_NOTES (insn), map);
INSN_SCOPE (copy) = INSN_SCOPE (insn);
SIBLING_CALL_P (copy) = SIBLING_CALL_P (insn);
CONST_OR_PURE_CALL_P (copy) = CONST_OR_PURE_CALL_P (insn);
/* Because the USAGE information potentially contains objects other
than hard registers, we need to copy it. */
CALL_INSN_FUNCTION_USAGE (copy)
= copy_rtx_and_substitute (CALL_INSN_FUNCTION_USAGE (insn),
map, 0);
#ifdef HAVE_cc0
if (cc0_insn)
try_constants (cc0_insn, map);
cc0_insn = 0;
#endif
try_constants (copy, map);
/* Be lazy and assume CALL_INSNs clobber all hard registers. */
for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
VARRAY_CONST_EQUIV (map->const_equiv_varray, i).rtx = 0;
break;
case CODE_LABEL:
/* If this is the loop start label, then we don't need to emit a
copy of this label since no one will use it. */
if (insn != start_label)
{
copy = emit_label (get_label_from_map (map,
CODE_LABEL_NUMBER (insn)));
map->const_age++;
}
break;
case BARRIER:
copy = emit_barrier ();
break;
case NOTE:
/* VTOP and CONT notes are valid only before the loop exit test.
If placed anywhere else, loop may generate bad code. */
/* BASIC_BLOCK notes exist to stabilize basic block structures with
the associated rtl. We do not want to share the structure in
this new block. */
if (NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
&& NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED_LABEL
&& NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
&& ((NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP
&& NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_CONT)
|| (last_iteration && unroll_type != UNROLL_COMPLETELY)))
copy = emit_note (NOTE_SOURCE_FILE (insn),
NOTE_LINE_NUMBER (insn));
else
copy = 0;
break;
default:
abort ();
}
map->insn_map[INSN_UID (insn)] = copy;
}
while (insn != copy_end);
/* Now finish coping the REG_NOTES. */
insn = copy_start;
do
{
insn = NEXT_INSN (insn);
if ((GET_CODE (insn) == INSN || GET_CODE (insn) == JUMP_INSN
|| GET_CODE (insn) == CALL_INSN)
&& map->insn_map[INSN_UID (insn)])
final_reg_note_copy (&REG_NOTES (map->insn_map[INSN_UID (insn)]), map);
}
while (insn != copy_end);
/* There may be notes between copy_notes_from and loop_end. Emit a copy of
each of these notes here, since there may be some important ones, such as
NOTE_INSN_BLOCK_END notes, in this group. We don't do this on the last
iteration, because the original notes won't be deleted.
We can't use insert_before here, because when from preconditioning,
insert_before points before the loop. We can't use copy_end, because
there may be insns already inserted after it (which we don't want to
copy) when not from preconditioning code. */
if (! last_iteration)
{
for (insn = copy_notes_from; insn != loop_end; insn = NEXT_INSN (insn))
{
/* VTOP notes are valid only before the loop exit test.
If placed anywhere else, loop may generate bad code.
Although COPY_NOTES_FROM will be at most one or two (for cc0)
instructions before the last insn in the loop, COPY_NOTES_FROM
can be a NOTE_INSN_LOOP_CONT note if there is no VTOP note,
as in a do .. while loop. */
if (GET_CODE (insn) == NOTE
&& NOTE_LINE_NUMBER (insn) != NOTE_INSN_DELETED
&& NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK
&& NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_VTOP
&& NOTE_LINE_NUMBER (insn) != NOTE_INSN_LOOP_CONT)
emit_note (NOTE_SOURCE_FILE (insn), NOTE_LINE_NUMBER (insn));
}
}
if (final_label && LABEL_NUSES (final_label) > 0)
emit_label (final_label);
tem = get_insns ();
end_sequence ();
loop_insn_emit_before (loop, 0, insert_before, tem);
}
/* Emit an insn, using the expand_binop to ensure that a valid insn is
emitted. This will correctly handle the case where the increment value
won't fit in the immediate field of a PLUS insns. */
void
emit_unrolled_add (dest_reg, src_reg, increment)
rtx dest_reg, src_reg, increment;
{
rtx result;
result = expand_simple_binop (GET_MODE (dest_reg), PLUS, src_reg, increment,
dest_reg, 0, OPTAB_LIB_WIDEN);
if (dest_reg != result)
emit_move_insn (dest_reg, result);
}
/* Searches the insns between INSN and LOOP->END. Returns 1 if there
is a backward branch in that range that branches to somewhere between
LOOP->START and INSN. Returns 0 otherwise. */
/* ??? This is quadratic algorithm. Could be rewritten to be linear.
In practice, this is not a problem, because this function is seldom called,
and uses a negligible amount of CPU time on average. */
int
back_branch_in_range_p (loop, insn)
const struct loop *loop;
rtx insn;
{
rtx p, q, target_insn;
rtx loop_start = loop->start;
rtx loop_end = loop->end;
rtx orig_loop_end = loop->end;
/* Stop before we get to the backward branch at the end of the loop. */
loop_end = prev_nonnote_insn (loop_end);
if (GET_CODE (loop_end) == BARRIER)
loop_end = PREV_INSN (loop_end);
/* Check in case insn has been deleted, search forward for first non
deleted insn following it. */
while (INSN_DELETED_P (insn))
insn = NEXT_INSN (insn);
/* Check for the case where insn is the last insn in the loop. Deal
with the case where INSN was a deleted loop test insn, in which case
it will now be the NOTE_LOOP_END. */
if (insn == loop_end || insn == orig_loop_end)
return 0;
for (p = NEXT_INSN (insn); p != loop_end; p = NEXT_INSN (p))
{
if (GET_CODE (p) == JUMP_INSN)
{
target_insn = JUMP_LABEL (p);
/* Search from loop_start to insn, to see if one of them is
the target_insn. We can't use INSN_LUID comparisons here,
since insn may not have an LUID entry. */
for (q = loop_start; q != insn; q = NEXT_INSN (q))
if (q == target_insn)
return 1;
}
}
return 0;
}
/* Try to generate the simplest rtx for the expression
(PLUS (MULT mult1 mult2) add1). This is used to calculate the initial
value of giv's. */
static rtx
fold_rtx_mult_add (mult1, mult2, add1, mode)
rtx mult1, mult2, add1;
enum machine_mode mode;
{
rtx temp, mult_res;
rtx result;
/* The modes must all be the same. This should always be true. For now,
check to make sure. */
if ((GET_MODE (mult1) != mode && GET_MODE (mult1) != VOIDmode)
|| (GET_MODE (mult2) != mode && GET_MODE (mult2) != VOIDmode)
|| (GET_MODE (add1) != mode && GET_MODE (add1) != VOIDmode))
abort ();
/* Ensure that if at least one of mult1/mult2 are constant, then mult2
will be a constant. */
if (GET_CODE (mult1) == CONST_INT)
{
temp = mult2;
mult2 = mult1;
mult1 = temp;
}
mult_res = simplify_binary_operation (MULT, mode, mult1, mult2);
if (! mult_res)
mult_res = gen_rtx_MULT (mode, mult1, mult2);
/* Again, put the constant second. */
if (GET_CODE (add1) == CONST_INT)
{
temp = add1;
add1 = mult_res;
mult_res = temp;
}
result = simplify_binary_operation (PLUS, mode, add1, mult_res);
if (! result)
result = gen_rtx_PLUS (mode, add1, mult_res);
return result;
}
/* Searches the list of induction struct's for the biv BL, to try to calculate
the total increment value for one iteration of the loop as a constant.
Returns the increment value as an rtx, simplified as much as possible,
if it can be calculated. Otherwise, returns 0. */
rtx
biv_total_increment (bl)
const struct iv_class *bl;
{
struct induction *v;
rtx result;
/* For increment, must check every instruction that sets it. Each
instruction must be executed only once each time through the loop.
To verify this, we check that the insn is always executed, and that
there are no backward branches after the insn that branch to before it.
Also, the insn must have a mult_val of one (to make sure it really is
an increment). */
result = const0_rtx;
for (v = bl->biv; v; v = v->next_iv)
{
if (v->always_computable && v->mult_val == const1_rtx
&& ! v->maybe_multiple
&& SCALAR_INT_MODE_P (v->mode))
result = fold_rtx_mult_add (result, const1_rtx, v->add_val, v->mode);
else
return 0;
}
return result;
}
/* For each biv and giv, determine whether it can be safely split into
a different variable for each unrolled copy of the loop body. If it
is safe to split, then indicate that by saving some useful info
in the splittable_regs array.
If the loop is being completely unrolled, then splittable_regs will hold
the current value of the induction variable while the loop is unrolled.
It must be set to the initial value of the induction variable here.
Otherwise, splittable_regs will hold the difference between the current
value of the induction variable and the value the induction variable had
at the top of the loop. It must be set to the value 0 here.
Returns the total number of instructions that set registers that are
splittable. */
/* ?? If the loop is only unrolled twice, then most of the restrictions to
constant values are unnecessary, since we can easily calculate increment
values in this case even if nothing is constant. The increment value
should not involve a multiply however. */
/* ?? Even if the biv/giv increment values aren't constant, it may still
be beneficial to split the variable if the loop is only unrolled a few
times, since multiplies by small integers (1,2,3,4) are very cheap. */
static int
find_splittable_regs (loop, unroll_type, unroll_number)
const struct loop *loop;
enum unroll_types unroll_type;
int unroll_number;
{
struct loop_ivs *ivs = LOOP_IVS (loop);
struct iv_class *bl;
struct induction *v;
rtx increment, tem;
rtx biv_final_value;
int biv_splittable;
int result = 0;
for (bl = ivs->list; bl; bl = bl->next)
{
/* Biv_total_increment must return a constant value,
otherwise we can not calculate the split values. */
increment = biv_total_increment (bl);
if (! increment || GET_CODE (increment) != CONST_INT)
continue;
/* The loop must be unrolled completely, or else have a known number
of iterations and only one exit, or else the biv must be dead
outside the loop, or else the final value must be known. Otherwise,
it is unsafe to split the biv since it may not have the proper
value on loop exit. */
/* loop_number_exit_count is nonzero if the loop has an exit other than
a fall through at the end. */
biv_splittable = 1;
biv_final_value = 0;
if (unroll_type != UNROLL_COMPLETELY
&& (loop->exit_count || unroll_type == UNROLL_NAIVE)
&& (REGNO_LAST_LUID (bl->regno) >= INSN_LUID (loop->end)
|| ! bl->init_insn
|| INSN_UID (bl->init_insn) >= max_uid_for_loop
|| (REGNO_FIRST_LUID (bl->regno)
< INSN_LUID (bl->init_insn))
|| reg_mentioned_p (bl->biv->dest_reg, SET_SRC (bl->init_set)))
&& ! (biv_final_value = final_biv_value (loop, bl)))
biv_splittable = 0;
/* If any of the insns setting the BIV don't do so with a simple
PLUS, we don't know how to split it. */
for (v = bl->biv; biv_splittable && v; v = v->next_iv)
if ((tem = single_set (v->insn)) == 0
|| GET_CODE (SET_DEST (tem)) != REG
|| REGNO (SET_DEST (tem)) != bl->regno
|| GET_CODE (SET_SRC (tem)) != PLUS)
biv_splittable = 0;
/* If final value is nonzero, then must emit an instruction which sets
the value of the biv to the proper value. This is done after
handling all of the givs, since some of them may need to use the
biv's value in their initialization code. */
/* This biv is splittable. If completely unrolling the loop, save
the biv's initial value. Otherwise, save the constant zero. */
if (biv_splittable == 1)
{
if (unroll_type == UNROLL_COMPLETELY)
{
/* If the initial value of the biv is itself (i.e. it is too
complicated for strength_reduce to compute), or is a hard
register, or it isn't invariant, then we must create a new
pseudo reg to hold the initial value of the biv. */
if (GET_CODE (bl->initial_value) == REG
&& (REGNO (bl->initial_value) == bl->regno
|| REGNO (bl->initial_value) < FIRST_PSEUDO_REGISTER
|| ! loop_invariant_p (loop, bl->initial_value)))
{
rtx tem = gen_reg_rtx (bl->biv->mode);
record_base_value (REGNO (tem), bl->biv->add_val, 0);
loop_insn_hoist (loop,
gen_move_insn (tem, bl->biv->src_reg));
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Biv %d initial value remapped to %d.\n",
bl->regno, REGNO (tem));
splittable_regs[bl->regno] = tem;
}
else
splittable_regs[bl->regno] = bl->initial_value;
}
else
splittable_regs[bl->regno] = const0_rtx;
/* Save the number of instructions that modify the biv, so that
we can treat the last one specially. */
splittable_regs_updates[bl->regno] = bl->biv_count;
result += bl->biv_count;
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Biv %d safe to split.\n", bl->regno);
}
/* Check every giv that depends on this biv to see whether it is
splittable also. Even if the biv isn't splittable, givs which
depend on it may be splittable if the biv is live outside the
loop, and the givs aren't. */
result += find_splittable_givs (loop, bl, unroll_type, increment,
unroll_number);
/* If final value is nonzero, then must emit an instruction which sets
the value of the biv to the proper value. This is done after
handling all of the givs, since some of them may need to use the
biv's value in their initialization code. */
if (biv_final_value)
{
/* If the loop has multiple exits, emit the insns before the
loop to ensure that it will always be executed no matter
how the loop exits. Otherwise emit the insn after the loop,
since this is slightly more efficient. */
if (! loop->exit_count)
loop_insn_sink (loop, gen_move_insn (bl->biv->src_reg,
biv_final_value));
else
{
/* Create a new register to hold the value of the biv, and then
set the biv to its final value before the loop start. The biv
is set to its final value before loop start to ensure that
this insn will always be executed, no matter how the loop
exits. */
rtx tem = gen_reg_rtx (bl->biv->mode);
record_base_value (REGNO (tem), bl->biv->add_val, 0);
loop_insn_hoist (loop, gen_move_insn (tem, bl->biv->src_reg));
loop_insn_hoist (loop, gen_move_insn (bl->biv->src_reg,
biv_final_value));
if (loop_dump_stream)
fprintf (loop_dump_stream, "Biv %d mapped to %d for split.\n",
REGNO (bl->biv->src_reg), REGNO (tem));
/* Set up the mapping from the original biv register to the new
register. */
bl->biv->src_reg = tem;
}
}
}
return result;
}
/* For every giv based on the biv BL, check to determine whether it is
splittable. This is a subroutine to find_splittable_regs ().
Return the number of instructions that set splittable registers. */
static int
find_splittable_givs (loop, bl, unroll_type, increment, unroll_number)
const struct loop *loop;
struct iv_class *bl;
enum unroll_types unroll_type;
rtx increment;
int unroll_number ATTRIBUTE_UNUSED;
{
struct loop_ivs *ivs = LOOP_IVS (loop);
struct induction *v, *v2;
rtx final_value;
rtx tem;
int result = 0;
/* Scan the list of givs, and set the same_insn field when there are
multiple identical givs in the same insn. */
for (v = bl->giv; v; v = v->next_iv)
for (v2 = v->next_iv; v2; v2 = v2->next_iv)
if (v->insn == v2->insn && rtx_equal_p (v->new_reg, v2->new_reg)
&& ! v2->same_insn)
v2->same_insn = v;
for (v = bl->giv; v; v = v->next_iv)
{
rtx giv_inc, value;
/* Only split the giv if it has already been reduced, or if the loop is
being completely unrolled. */
if (unroll_type != UNROLL_COMPLETELY && v->ignore)
continue;
/* The giv can be split if the insn that sets the giv is executed once
and only once on every iteration of the loop. */
/* An address giv can always be split. v->insn is just a use not a set,
and hence it does not matter whether it is always executed. All that
matters is that all the biv increments are always executed, and we
won't reach here if they aren't. */
if (v->giv_type != DEST_ADDR
&& (! v->always_computable
|| back_branch_in_range_p (loop, v->insn)))
continue;
/* The giv increment value must be a constant. */
giv_inc = fold_rtx_mult_add (v->mult_val, increment, const0_rtx,
v->mode);
if (! giv_inc || GET_CODE (giv_inc) != CONST_INT)
continue;
/* The loop must be unrolled completely, or else have a known number of
iterations and only one exit, or else the giv must be dead outside
the loop, or else the final value of the giv must be known.
Otherwise, it is not safe to split the giv since it may not have the
proper value on loop exit. */
/* The used outside loop test will fail for DEST_ADDR givs. They are
never used outside the loop anyways, so it is always safe to split a
DEST_ADDR giv. */
final_value = 0;
if (unroll_type != UNROLL_COMPLETELY
&& (loop->exit_count || unroll_type == UNROLL_NAIVE)
&& v->giv_type != DEST_ADDR
/* The next part is true if the pseudo is used outside the loop.
We assume that this is true for any pseudo created after loop
starts, because we don't have a reg_n_info entry for them. */
&& (REGNO (v->dest_reg) >= max_reg_before_loop
|| (REGNO_FIRST_UID (REGNO (v->dest_reg)) != INSN_UID (v->insn)
/* Check for the case where the pseudo is set by a shift/add
sequence, in which case the first insn setting the pseudo
is the first insn of the shift/add sequence. */
&& (! (tem = find_reg_note (v->insn, REG_RETVAL, NULL_RTX))
|| (REGNO_FIRST_UID (REGNO (v->dest_reg))
!= INSN_UID (XEXP (tem, 0)))))
/* Line above always fails if INSN was moved by loop opt. */
|| (REGNO_LAST_LUID (REGNO (v->dest_reg))
>= INSN_LUID (loop->end)))
&& ! (final_value = v->final_value))
continue;
#if 0
/* Currently, non-reduced/final-value givs are never split. */
/* Should emit insns after the loop if possible, as the biv final value
code below does. */
/* If the final value is nonzero, and the giv has not been reduced,
then must emit an instruction to set the final value. */
if (final_value && !v->new_reg)
{
/* Create a new register to hold the value of the giv, and then set
the giv to its final value before the loop start. The giv is set
to its final value before loop start to ensure that this insn
will always be executed, no matter how we exit. */
tem = gen_reg_rtx (v->mode);
loop_insn_hoist (loop, gen_move_insn (tem, v->dest_reg));
loop_insn_hoist (loop, gen_move_insn (v->dest_reg, final_value));
if (loop_dump_stream)
fprintf (loop_dump_stream, "Giv %d mapped to %d for split.\n",
REGNO (v->dest_reg), REGNO (tem));
v->src_reg = tem;
}
#endif
/* This giv is splittable. If completely unrolling the loop, save the
giv's initial value. Otherwise, save the constant zero for it. */
if (unroll_type == UNROLL_COMPLETELY)
{
/* It is not safe to use bl->initial_value here, because it may not
be invariant. It is safe to use the initial value stored in
the splittable_regs array if it is set. In rare cases, it won't
be set, so then we do exactly the same thing as
find_splittable_regs does to get a safe value. */
rtx biv_initial_value;
if (splittable_regs[bl->regno])
biv_initial_value = splittable_regs[bl->regno];
else if (GET_CODE (bl->initial_value) != REG
|| (REGNO (bl->initial_value) != bl->regno
&& REGNO (bl->initial_value) >= FIRST_PSEUDO_REGISTER))
biv_initial_value = bl->initial_value;
else
{
rtx tem = gen_reg_rtx (bl->biv->mode);
record_base_value (REGNO (tem), bl->biv->add_val, 0);
loop_insn_hoist (loop, gen_move_insn (tem, bl->biv->src_reg));
biv_initial_value = tem;
}
biv_initial_value = extend_value_for_giv (v, biv_initial_value);
value = fold_rtx_mult_add (v->mult_val, biv_initial_value,
v->add_val, v->mode);
}
else
value = const0_rtx;
if (v->new_reg)
{
/* If a giv was combined with another giv, then we can only split
this giv if the giv it was combined with was reduced. This
is because the value of v->new_reg is meaningless in this
case. */
if (v->same && ! v->same->new_reg)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"giv combined with unreduced giv not split.\n");
continue;
}
/* If the giv is an address destination, it could be something other
than a simple register, these have to be treated differently. */
else if (v->giv_type == DEST_REG)
{
/* If value is not a constant, register, or register plus
constant, then compute its value into a register before
loop start. This prevents invalid rtx sharing, and should
generate better code. We can use bl->initial_value here
instead of splittable_regs[bl->regno] because this code
is going before the loop start. */
if (unroll_type == UNROLL_COMPLETELY
&& GET_CODE (value) != CONST_INT
&& GET_CODE (value) != REG
&& (GET_CODE (value) != PLUS
|| GET_CODE (XEXP (value, 0)) != REG
|| GET_CODE (XEXP (value, 1)) != CONST_INT))
{
rtx tem = gen_reg_rtx (v->mode);
record_base_value (REGNO (tem), v->add_val, 0);
loop_iv_add_mult_hoist (loop, bl->initial_value, v->mult_val,
v->add_val, tem);
value = tem;
}
splittable_regs[reg_or_subregno (v->new_reg)] = value;
}
else
continue;
}
else
{
#if 0
/* Currently, unreduced giv's can't be split. This is not too much
of a problem since unreduced giv's are not live across loop
iterations anyways. When unrolling a loop completely though,
it makes sense to reduce&split givs when possible, as this will
result in simpler instructions, and will not require that a reg
be live across loop iterations. */
splittable_regs[REGNO (v->dest_reg)] = value;
fprintf (stderr, "Giv %d at insn %d not reduced\n",
REGNO (v->dest_reg), INSN_UID (v->insn));
#else
continue;
#endif
}
/* Unreduced givs are only updated once by definition. Reduced givs
are updated as many times as their biv is. Mark it so if this is
a splittable register. Don't need to do anything for address givs
where this may not be a register. */
if (GET_CODE (v->new_reg) == REG)
{
int count = 1;
if (! v->ignore)
count = REG_IV_CLASS (ivs, REGNO (v->src_reg))->biv_count;
splittable_regs_updates[reg_or_subregno (v->new_reg)] = count;
}
result++;
if (loop_dump_stream)
{
int regnum;
if (GET_CODE (v->dest_reg) == CONST_INT)
regnum = -1;
else if (GET_CODE (v->dest_reg) != REG)
regnum = REGNO (XEXP (v->dest_reg, 0));
else
regnum = REGNO (v->dest_reg);
fprintf (loop_dump_stream, "Giv %d at insn %d safe to split.\n",
regnum, INSN_UID (v->insn));
}
}
return result;
}
/* Try to prove that the register is dead after the loop exits. Trace every
loop exit looking for an insn that will always be executed, which sets
the register to some value, and appears before the first use of the register
is found. If successful, then return 1, otherwise return 0. */
/* ?? Could be made more intelligent in the handling of jumps, so that
it can search past if statements and other similar structures. */
static int
reg_dead_after_loop (loop, reg)
const struct loop *loop;
rtx reg;
{
rtx insn, label;
enum rtx_code code;
int jump_count = 0;
int label_count = 0;
/* In addition to checking all exits of this loop, we must also check
all exits of inner nested loops that would exit this loop. We don't
have any way to identify those, so we just give up if there are any
such inner loop exits. */
for (label = loop->exit_labels; label; label = LABEL_NEXTREF (label))
label_count++;
if (label_count != loop->exit_count)
return 0;
/* HACK: Must also search the loop fall through exit, create a label_ref
here which points to the loop->end, and append the loop_number_exit_labels
list to it. */
label = gen_rtx_LABEL_REF (VOIDmode, loop->end);
LABEL_NEXTREF (label) = loop->exit_labels;
for (; label; label = LABEL_NEXTREF (label))
{
/* Succeed if find an insn which sets the biv or if reach end of
function. Fail if find an insn that uses the biv, or if come to
a conditional jump. */
insn = NEXT_INSN (XEXP (label, 0));
while (insn)
{
code = GET_CODE (insn);
if (GET_RTX_CLASS (code) == 'i')
{
rtx set, note;
if (reg_referenced_p (reg, PATTERN (insn)))
return 0;
note = find_reg_equal_equiv_note (insn);
if (note && reg_overlap_mentioned_p (reg, XEXP (note, 0)))
return 0;
set = single_set (insn);
if (set && rtx_equal_p (SET_DEST (set), reg))
break;
}
if (code == JUMP_INSN)
{
if (GET_CODE (PATTERN (insn)) == RETURN)
break;
else if (!any_uncondjump_p (insn)
/* Prevent infinite loop following infinite loops. */
|| jump_count++ > 20)
return 0;
else
insn = JUMP_LABEL (insn);
}
insn = NEXT_INSN (insn);
}
}
/* Success, the register is dead on all loop exits. */
return 1;
}
/* Try to calculate the final value of the biv, the value it will have at
the end of the loop. If we can do it, return that value. */
rtx
final_biv_value (loop, bl)
const struct loop *loop;
struct iv_class *bl;
{
unsigned HOST_WIDE_INT n_iterations = LOOP_INFO (loop)->n_iterations;
rtx increment, tem;
/* ??? This only works for MODE_INT biv's. Reject all others for now. */
if (GET_MODE_CLASS (bl->biv->mode) != MODE_INT)
return 0;
/* The final value for reversed bivs must be calculated differently than
for ordinary bivs. In this case, there is already an insn after the
loop which sets this biv's final value (if necessary), and there are
no other loop exits, so we can return any value. */
if (bl->reversed)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Final biv value for %d, reversed biv.\n", bl->regno);
return const0_rtx;
}
/* Try to calculate the final value as initial value + (number of iterations
* increment). For this to work, increment must be invariant, the only
exit from the loop must be the fall through at the bottom (otherwise
it may not have its final value when the loop exits), and the initial
value of the biv must be invariant. */
if (n_iterations != 0
&& ! loop->exit_count
&& loop_invariant_p (loop, bl->initial_value))
{
increment = biv_total_increment (bl);
if (increment && loop_invariant_p (loop, increment))
{
/* Can calculate the loop exit value, emit insns after loop
end to calculate this value into a temporary register in
case it is needed later. */
tem = gen_reg_rtx (bl->biv->mode);
record_base_value (REGNO (tem), bl->biv->add_val, 0);
loop_iv_add_mult_sink (loop, increment, GEN_INT (n_iterations),
bl->initial_value, tem);
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Final biv value for %d, calculated.\n", bl->regno);
return tem;
}
}
/* Check to see if the biv is dead at all loop exits. */
if (reg_dead_after_loop (loop, bl->biv->src_reg))
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Final biv value for %d, biv dead after loop exit.\n",
bl->regno);
return const0_rtx;
}
return 0;
}
/* Try to calculate the final value of the giv, the value it will have at
the end of the loop. If we can do it, return that value. */
rtx
final_giv_value (loop, v)
const struct loop *loop;
struct induction *v;
{
struct loop_ivs *ivs = LOOP_IVS (loop);
struct iv_class *bl;
rtx insn;
rtx increment, tem;
rtx seq;
rtx loop_end = loop->end;
unsigned HOST_WIDE_INT n_iterations = LOOP_INFO (loop)->n_iterations;
bl = REG_IV_CLASS (ivs, REGNO (v->src_reg));
/* The final value for givs which depend on reversed bivs must be calculated
differently than for ordinary givs. In this case, there is already an
insn after the loop which sets this giv's final value (if necessary),
and there are no other loop exits, so we can return any value. */
if (bl->reversed)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Final giv value for %d, depends on reversed biv\n",
REGNO (v->dest_reg));
return const0_rtx;
}
/* Try to calculate the final value as a function of the biv it depends
upon. The only exit from the loop must be the fall through at the bottom
and the insn that sets the giv must be executed on every iteration
(otherwise the giv may not have its final value when the loop exits). */
/* ??? Can calculate the final giv value by subtracting off the
extra biv increments times the giv's mult_val. The loop must have
only one exit for this to work, but the loop iterations does not need
to be known. */
if (n_iterations != 0
&& ! loop->exit_count
&& v->always_executed)
{
/* ?? It is tempting to use the biv's value here since these insns will
be put after the loop, and hence the biv will have its final value
then. However, this fails if the biv is subsequently eliminated.
Perhaps determine whether biv's are eliminable before trying to
determine whether giv's are replaceable so that we can use the
biv value here if it is not eliminable. */
/* We are emitting code after the end of the loop, so we must make
sure that bl->initial_value is still valid then. It will still
be valid if it is invariant. */
increment = biv_total_increment (bl);
if (increment && loop_invariant_p (loop, increment)
&& loop_invariant_p (loop, bl->initial_value))
{
/* Can calculate the loop exit value of its biv as
(n_iterations * increment) + initial_value */
/* The loop exit value of the giv is then
(final_biv_value - extra increments) * mult_val + add_val.
The extra increments are any increments to the biv which
occur in the loop after the giv's value is calculated.
We must search from the insn that sets the giv to the end
of the loop to calculate this value. */
/* Put the final biv value in tem. */
tem = gen_reg_rtx (v->mode);
record_base_value (REGNO (tem), bl->biv->add_val, 0);
loop_iv_add_mult_sink (loop, extend_value_for_giv (v, increment),
GEN_INT (n_iterations),
extend_value_for_giv (v, bl->initial_value),
tem);
/* Subtract off extra increments as we find them. */
for (insn = NEXT_INSN (v->insn); insn != loop_end;
insn = NEXT_INSN (insn))
{
struct induction *biv;
for (biv = bl->biv; biv; biv = biv->next_iv)
if (biv->insn == insn)
{
start_sequence ();
tem = expand_simple_binop (GET_MODE (tem), MINUS, tem,
biv->add_val, NULL_RTX, 0,
OPTAB_LIB_WIDEN);
seq = get_insns ();
end_sequence ();
loop_insn_sink (loop, seq);
}
}
/* Now calculate the giv's final value. */
loop_iv_add_mult_sink (loop, tem, v->mult_val, v->add_val, tem);
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Final giv value for %d, calc from biv's value.\n",
REGNO (v->dest_reg));
return tem;
}
}
/* Replaceable giv's should never reach here. */
if (v->replaceable)
abort ();
/* Check to see if the biv is dead at all loop exits. */
if (reg_dead_after_loop (loop, v->dest_reg))
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Final giv value for %d, giv dead after loop exit.\n",
REGNO (v->dest_reg));
return const0_rtx;
}
return 0;
}
/* Look back before LOOP->START for the insn that sets REG and return
the equivalent constant if there is a REG_EQUAL note otherwise just
the SET_SRC of REG. */
static rtx
loop_find_equiv_value (loop, reg)
const struct loop *loop;
rtx reg;
{
rtx loop_start = loop->start;
rtx insn, set;
rtx ret;
ret = reg;
for (insn = PREV_INSN (loop_start); insn; insn = PREV_INSN (insn))
{
if (GET_CODE (insn) == CODE_LABEL)
break;
else if (INSN_P (insn) && reg_set_p (reg, insn))
{
/* We found the last insn before the loop that sets the register.
If it sets the entire register, and has a REG_EQUAL note,
then use the value of the REG_EQUAL note. */
if ((set = single_set (insn))
&& (SET_DEST (set) == reg))
{
rtx note = find_reg_note (insn, REG_EQUAL, NULL_RTX);
/* Only use the REG_EQUAL note if it is a constant.
Other things, divide in particular, will cause
problems later if we use them. */
if (note && GET_CODE (XEXP (note, 0)) != EXPR_LIST
&& CONSTANT_P (XEXP (note, 0)))
ret = XEXP (note, 0);
else
ret = SET_SRC (set);
/* We cannot do this if it changes between the
assignment and loop start though. */
if (modified_between_p (ret, insn, loop_start))
ret = reg;
}
break;
}
}
return ret;
}
/* Return a simplified rtx for the expression OP - REG.
REG must appear in OP, and OP must be a register or the sum of a register
and a second term.
Thus, the return value must be const0_rtx or the second term.
The caller is responsible for verifying that REG appears in OP and OP has
the proper form. */
static rtx
subtract_reg_term (op, reg)
rtx op, reg;
{
if (op == reg)
return const0_rtx;
if (GET_CODE (op) == PLUS)
{
if (XEXP (op, 0) == reg)
return XEXP (op, 1);
else if (XEXP (op, 1) == reg)
return XEXP (op, 0);
}
/* OP does not contain REG as a term. */
abort ();
}
/* Find and return register term common to both expressions OP0 and
OP1 or NULL_RTX if no such term exists. Each expression must be a
REG or a PLUS of a REG. */
static rtx
find_common_reg_term (op0, op1)
rtx op0, op1;
{
if ((GET_CODE (op0) == REG || GET_CODE (op0) == PLUS)
&& (GET_CODE (op1) == REG || GET_CODE (op1) == PLUS))
{
rtx op00;
rtx op01;
rtx op10;
rtx op11;
if (GET_CODE (op0) == PLUS)
op01 = XEXP (op0, 1), op00 = XEXP (op0, 0);
else
op01 = const0_rtx, op00 = op0;
if (GET_CODE (op1) == PLUS)
op11 = XEXP (op1, 1), op10 = XEXP (op1, 0);
else
op11 = const0_rtx, op10 = op1;
/* Find and return common register term if present. */
if (REG_P (op00) && (op00 == op10 || op00 == op11))
return op00;
else if (REG_P (op01) && (op01 == op10 || op01 == op11))
return op01;
}
/* No common register term found. */
return NULL_RTX;
}
/* Determine the loop iterator and calculate the number of loop
iterations. Returns the exact number of loop iterations if it can
be calculated, otherwise returns zero. */
unsigned HOST_WIDE_INT
loop_iterations (loop)
struct loop *loop;
{
struct loop_info *loop_info = LOOP_INFO (loop);
struct loop_ivs *ivs = LOOP_IVS (loop);
rtx comparison, comparison_value;
rtx iteration_var, initial_value, increment, final_value;
enum rtx_code comparison_code;
HOST_WIDE_INT inc;
unsigned HOST_WIDE_INT abs_inc;
unsigned HOST_WIDE_INT abs_diff;
int off_by_one;
int increment_dir;
int unsigned_p, compare_dir, final_larger;
rtx last_loop_insn;
rtx reg_term;
struct iv_class *bl;
loop_info->n_iterations = 0;
loop_info->initial_value = 0;
loop_info->initial_equiv_value = 0;
loop_info->comparison_value = 0;
loop_info->final_value = 0;
loop_info->final_equiv_value = 0;
loop_info->increment = 0;
loop_info->iteration_var = 0;
loop_info->unroll_number = 1;
loop_info->iv = 0;
/* We used to use prev_nonnote_insn here, but that fails because it might
accidentally get the branch for a contained loop if the branch for this
loop was deleted. We can only trust branches immediately before the
loop_end. */
last_loop_insn = PREV_INSN (loop->end);
/* ??? We should probably try harder to find the jump insn
at the end of the loop. The following code assumes that
the last loop insn is a jump to the top of the loop. */
if (GET_CODE (last_loop_insn) != JUMP_INSN)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: No final conditional branch found.\n");
return 0;
}
/* If there is a more than a single jump to the top of the loop
we cannot (easily) determine the iteration count. */
if (LABEL_NUSES (JUMP_LABEL (last_loop_insn)) > 1)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: Loop has multiple back edges.\n");
return 0;
}
/* If there are multiple conditionalized loop exit tests, they may jump
back to differing CODE_LABELs. */
if (loop->top && loop->cont)
{
rtx temp = PREV_INSN (last_loop_insn);
do
{
if (GET_CODE (temp) == JUMP_INSN)
{
/* There are some kinds of jumps we can't deal with easily. */
if (JUMP_LABEL (temp) == 0)
{
if (loop_dump_stream)
fprintf
(loop_dump_stream,
"Loop iterations: Jump insn has null JUMP_LABEL.\n");
return 0;
}
if (/* Previous unrolling may have generated new insns not
covered by the uid_luid array. */
INSN_UID (JUMP_LABEL (temp)) < max_uid_for_loop
/* Check if we jump back into the loop body. */
&& INSN_LUID (JUMP_LABEL (temp)) > INSN_LUID (loop->top)
&& INSN_LUID (JUMP_LABEL (temp)) < INSN_LUID (loop->cont))
{
if (loop_dump_stream)
fprintf
(loop_dump_stream,
"Loop iterations: Loop has multiple back edges.\n");
return 0;
}
}
}
while ((temp = PREV_INSN (temp)) != loop->cont);
}
/* Find the iteration variable. If the last insn is a conditional
branch, and the insn before tests a register value, make that the
iteration variable. */
comparison = get_condition_for_loop (loop, last_loop_insn);
if (comparison == 0)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: No final comparison found.\n");
return 0;
}
/* ??? Get_condition may switch position of induction variable and
invariant register when it canonicalizes the comparison. */
comparison_code = GET_CODE (comparison);
iteration_var = XEXP (comparison, 0);
comparison_value = XEXP (comparison, 1);
if (GET_CODE (iteration_var) != REG)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: Comparison not against register.\n");
return 0;
}
/* The only new registers that are created before loop iterations
are givs made from biv increments or registers created by
load_mems. In the latter case, it is possible that try_copy_prop
will propagate a new pseudo into the old iteration register but
this will be marked by having the REG_USERVAR_P bit set. */
if ((unsigned) REGNO (iteration_var) >= ivs->n_regs
&& ! REG_USERVAR_P (iteration_var))
abort ();
/* Determine the initial value of the iteration variable, and the amount
that it is incremented each loop. Use the tables constructed by
the strength reduction pass to calculate these values. */
/* Clear the result values, in case no answer can be found. */
initial_value = 0;
increment = 0;
/* The iteration variable can be either a giv or a biv. Check to see
which it is, and compute the variable's initial value, and increment
value if possible. */
/* If this is a new register, can't handle it since we don't have any
reg_iv_type entry for it. */
if ((unsigned) REGNO (iteration_var) >= ivs->n_regs)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: No reg_iv_type entry for iteration var.\n");
return 0;
}
/* Reject iteration variables larger than the host wide int size, since they
could result in a number of iterations greater than the range of our
`unsigned HOST_WIDE_INT' variable loop_info->n_iterations. */
else if ((GET_MODE_BITSIZE (GET_MODE (iteration_var))
> HOST_BITS_PER_WIDE_INT))
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: Iteration var rejected because mode too large.\n");
return 0;
}
else if (GET_MODE_CLASS (GET_MODE (iteration_var)) != MODE_INT)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: Iteration var not an integer.\n");
return 0;
}
else if (REG_IV_TYPE (ivs, REGNO (iteration_var)) == BASIC_INDUCT)
{
if (REGNO (iteration_var) >= ivs->n_regs)
abort ();
/* Grab initial value, only useful if it is a constant. */
bl = REG_IV_CLASS (ivs, REGNO (iteration_var));
initial_value = bl->initial_value;
if (!bl->biv->always_executed || bl->biv->maybe_multiple)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: Basic induction var not set once in each iteration.\n");
return 0;
}
increment = biv_total_increment (bl);
}
else if (REG_IV_TYPE (ivs, REGNO (iteration_var)) == GENERAL_INDUCT)
{
HOST_WIDE_INT offset = 0;
struct induction *v = REG_IV_INFO (ivs, REGNO (iteration_var));
rtx biv_initial_value;
if (REGNO (v->src_reg) >= ivs->n_regs)
abort ();
if (!v->always_executed || v->maybe_multiple)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: General induction var not set once in each iteration.\n");
return 0;
}
bl = REG_IV_CLASS (ivs, REGNO (v->src_reg));
/* Increment value is mult_val times the increment value of the biv. */
increment = biv_total_increment (bl);
if (increment)
{
struct induction *biv_inc;
increment = fold_rtx_mult_add (v->mult_val,
extend_value_for_giv (v, increment),
const0_rtx, v->mode);
/* The caller assumes that one full increment has occurred at the
first loop test. But that's not true when the biv is incremented
after the giv is set (which is the usual case), e.g.:
i = 6; do {;} while (i++ < 9) .
Therefore, we bias the initial value by subtracting the amount of
the increment that occurs between the giv set and the giv test. */
for (biv_inc = bl->biv; biv_inc; biv_inc = biv_inc->next_iv)
{
if (loop_insn_first_p (v->insn, biv_inc->insn))
{
if (REG_P (biv_inc->add_val))
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: Basic induction var add_val is REG %d.\n",
REGNO (biv_inc->add_val));
return 0;
}
offset -= INTVAL (biv_inc->add_val);
}
}
}
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: Giv iterator, initial value bias %ld.\n",
(long) offset);
/* Initial value is mult_val times the biv's initial value plus
add_val. Only useful if it is a constant. */
biv_initial_value = extend_value_for_giv (v, bl->initial_value);
initial_value
= fold_rtx_mult_add (v->mult_val,
plus_constant (biv_initial_value, offset),
v->add_val, v->mode);
}
else
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: Not basic or general induction var.\n");
return 0;
}
if (initial_value == 0)
return 0;
unsigned_p = 0;
off_by_one = 0;
switch (comparison_code)
{
case LEU:
unsigned_p = 1;
case LE:
compare_dir = 1;
off_by_one = 1;
break;
case GEU:
unsigned_p = 1;
case GE:
compare_dir = -1;
off_by_one = -1;
break;
case EQ:
/* Cannot determine loop iterations with this case. */
compare_dir = 0;
break;
case LTU:
unsigned_p = 1;
case LT:
compare_dir = 1;
break;
case GTU:
unsigned_p = 1;
case GT:
compare_dir = -1;
case NE:
compare_dir = 0;
break;
default:
abort ();
}
/* If the comparison value is an invariant register, then try to find
its value from the insns before the start of the loop. */
final_value = comparison_value;
if (GET_CODE (comparison_value) == REG
&& loop_invariant_p (loop, comparison_value))
{
final_value = loop_find_equiv_value (loop, comparison_value);
/* If we don't get an invariant final value, we are better
off with the original register. */
if (! loop_invariant_p (loop, final_value))
final_value = comparison_value;
}
/* Calculate the approximate final value of the induction variable
(on the last successful iteration). The exact final value
depends on the branch operator, and increment sign. It will be
wrong if the iteration variable is not incremented by one each
time through the loop and (comparison_value + off_by_one -
initial_value) % increment != 0.
??? Note that the final_value may overflow and thus final_larger
will be bogus. A potentially infinite loop will be classified
as immediate, e.g. for (i = 0x7ffffff0; i <= 0x7fffffff; i++) */
if (off_by_one)
final_value = plus_constant (final_value, off_by_one);
/* Save the calculated values describing this loop's bounds, in case
precondition_loop_p will need them later. These values can not be
recalculated inside precondition_loop_p because strength reduction
optimizations may obscure the loop's structure.
These values are only required by precondition_loop_p and insert_bct
whenever the number of iterations cannot be computed at compile time.
Only the difference between final_value and initial_value is
important. Note that final_value is only approximate. */
loop_info->initial_value = initial_value;
loop_info->comparison_value = comparison_value;
loop_info->final_value = plus_constant (comparison_value, off_by_one);
loop_info->increment = increment;
loop_info->iteration_var = iteration_var;
loop_info->comparison_code = comparison_code;
loop_info->iv = bl;
/* Try to determine the iteration count for loops such
as (for i = init; i < init + const; i++). When running the
loop optimization twice, the first pass often converts simple
loops into this form. */
if (REG_P (initial_value))
{
rtx reg1;
rtx reg2;
rtx const2;
reg1 = initial_value;
if (GET_CODE (final_value) == PLUS)
reg2 = XEXP (final_value, 0), const2 = XEXP (final_value, 1);
else
reg2 = final_value, const2 = const0_rtx;
/* Check for initial_value = reg1, final_value = reg2 + const2,
where reg1 != reg2. */
if (REG_P (reg2) && reg2 != reg1)
{
rtx temp;
/* Find what reg1 is equivalent to. Hopefully it will
either be reg2 or reg2 plus a constant. */
temp = loop_find_equiv_value (loop, reg1);
if (find_common_reg_term (temp, reg2))
initial_value = temp;
else if (loop_invariant_p (loop, reg2))
{
/* Find what reg2 is equivalent to. Hopefully it will
either be reg1 or reg1 plus a constant. Let's ignore
the latter case for now since it is not so common. */
temp = loop_find_equiv_value (loop, reg2);
if (temp == loop_info->iteration_var)
temp = initial_value;
if (temp == reg1)
final_value = (const2 == const0_rtx)
? reg1 : gen_rtx_PLUS (GET_MODE (reg1), reg1, const2);
}
}
else if (loop->vtop && GET_CODE (reg2) == CONST_INT)
{
rtx temp;
/* When running the loop optimizer twice, check_dbra_loop
further obfuscates reversible loops of the form:
for (i = init; i < init + const; i++). We often end up with
final_value = 0, initial_value = temp, temp = temp2 - init,
where temp2 = init + const. If the loop has a vtop we
can replace initial_value with const. */
temp = loop_find_equiv_value (loop, reg1);
if (GET_CODE (temp) == MINUS && REG_P (XEXP (temp, 0)))
{
rtx temp2 = loop_find_equiv_value (loop, XEXP (temp, 0));
if (GET_CODE (temp2) == PLUS
&& XEXP (temp2, 0) == XEXP (temp, 1))
initial_value = XEXP (temp2, 1);
}
}
}
/* If have initial_value = reg + const1 and final_value = reg +
const2, then replace initial_value with const1 and final_value
with const2. This should be safe since we are protected by the
initial comparison before entering the loop if we have a vtop.
For example, a + b < a + c is not equivalent to b < c for all a
when using modulo arithmetic.
??? Without a vtop we could still perform the optimization if we check
the initial and final values carefully. */
if (loop->vtop
&& (reg_term = find_common_reg_term (initial_value, final_value)))
{
initial_value = subtract_reg_term (initial_value, reg_term);
final_value = subtract_reg_term (final_value, reg_term);
}
loop_info->initial_equiv_value = initial_value;
loop_info->final_equiv_value = final_value;
/* For EQ comparison loops, we don't have a valid final value.
Check this now so that we won't leave an invalid value if we
return early for any other reason. */
if (comparison_code == EQ)
loop_info->final_equiv_value = loop_info->final_value = 0;
if (increment == 0)
{
if (loop_dump_stream)
fprintf (loop_dump_stream,
"Loop iterations: Increment value can't be calculated.\n");
return 0;
}
if (GET_CODE (increment) != CONST_INT)
{
/* If we have a REG, check to see if REG holds a constant value. */
/* ??? Other RTL, such as (neg (reg)) is possible here, but it isn't
clear if it is worthwhile to try to handle such RTL. */
if (GET_CODE (increment) == REG || GET_CODE (increment) == SUBREG)
increment = loop_find_equiv_value (loop, increment);
if (GET_CODE (increment) != CONST_INT)
{
if (loop_dump_stream)
{
fprintf (loop_dump_stream,
"Loop iterations: Increment value not constant ");
print_simple_rtl (loop_dump_stream, increment);
fprintf (loop_dump_stream, ".\n");
}
return 0;
}
loop_info->increment = increment;
}
if (GET_CODE (initial_value) != CONST_INT)
{
if (loop_dump_stream)
{
fprintf (loop_dump_stream,
"Loop iterations: Initial value not constant ");
print_simple_rtl (loop_dump_stream, initial_value);
fprintf (loop_dump_stream, ".\n");
}
return 0;
}
else if (GET_CODE (final_value) != CONST_INT)
{
if (loop_dump_stream)
{
fprintf (loop_dump_stream,
"Loop iterations: Final value not constant ");
print_simple_rtl (loop_dump_stream, final_value);
fprintf (loop_dump_stream, ".\n");
}
return 0;
}
else if (comparison_code == EQ)
{
rtx inc_once;
if (loop_dump_stream)
fprintf (loop_dump_stream, "Loop iterations: EQ comparison loop.\n");
inc_once = gen_int_mode (INTVAL (initial_value) + INTVAL (increment),
GET_MODE (iteration_var));
if (inc_once == final_value)
{
/* The iterator value once through the loop is equal to the
comparision value. Either we have an infinite loop, or
we'll loop twice. */
if (increment == const0_rtx)
return 0;
loop_info->n_iterations = 2;
}
else
loop_info->n_iterations = 1;
if (GET_CODE (loop_info->initial_value) == CONST_INT)
loop_info->final_value
= gen_int_mode ((INTVAL (loop_info->initial_value)
+ loop_info->n_iterations * INTVAL (increment)),
GET_MODE (iteration_var));
else
loop_info->final_value
= plus_constant (loop_info->initial_value,
loop_info->n_iterations * INTVAL (increment));
loop_info->final_equiv_value
= gen_int_mode ((INTVAL (initial_value)
+ loop_info->n_iterations * INTVAL (increment)),
GET_MODE (iteration_var));
return loop_info->n_iterations;
}
/* Final_larger is 1 if final larger, 0 if they are equal, otherwise -1. */
if (unsigned_p)
final_larger
= ((unsigned HOST_WIDE_INT) INTVAL (final_value)
> (unsigned HOST_WIDE_INT) INTVAL (initial_value))
- ((unsigned HOST_WIDE_INT) INTVAL (final_value)
< (unsigned HOST_WIDE_INT) INTVAL (initial_value));
else
final_larger = (INTVAL (final_value) > INTVAL (initial_value))
- (INTVAL (final_value) < INTVAL (initial_value));
if (INTVAL (increment) > 0)
increment_dir = 1;
else if (INTVAL (increment) == 0)
increment_dir = 0;
else
increment_dir = -1;
/* There are 27 different cases: compare_dir = -1, 0, 1;
final_larger = -1, 0, 1; increment_dir = -1, 0, 1.
There are 4 normal cases, 4 reverse cases (where the iteration variable
will overflow before the loop exits), 4 infinite loop cases, and 15
immediate exit (0 or 1 iteration depending on loop type) cases.
Only try to optimize the normal cases. */
/* (compare_dir/final_larger/increment_dir)
Normal cases: (0/-1/-1), (0/1/1), (-1/-1/-1), (1/1/1)
Reverse cases: (0/-1/1), (0/1/-1), (-1/-1/1), (1/1/-1)
Infinite loops: (0/-1/0), (0/1/0), (-1/-1/0), (1/1/0)
Immediate exit: (0/0/X), (-1/0/X), (-1/1/X), (1/0/X), (1/-1/X) */
/* ?? If the meaning of reverse loops (where the iteration variable
will overflow before the loop exits) is undefined, then could
eliminate all of these special checks, and just always assume
the loops are normal/immediate/infinite. Note that this means
the sign of increment_dir does not have to be known. Also,
since it does not really hurt if immediate exit loops or infinite loops
are optimized, then that case could be ignored also, and hence all
loops can be optimized.
According to ANSI Spec, the reverse loop case result is undefined,
because the action on overflow is undefined.
See also the special test for NE loops below. */
if (final_larger == increment_dir && final_larger != 0
&& (final_larger == compare_dir || compare_dir == 0))
/* Normal case. */
;
else
{
if (loop_dump_stream)
fprintf (loop_dump_stream, "Loop iterations: Not normal loop.\n");
return 0;
}
/* Calculate the number of iterations, final_value is only an approximation,
so correct for that. Note that abs_diff and n_iterations are
unsigned, because they can be as large as 2^n - 1. */
inc = INTVAL (increment);
if (inc > 0)
{
abs_diff = INTVAL (final_value) - INTVAL (initial_value);
abs_inc = inc;
}
else if (inc < 0)
{
abs_diff = INTVAL (initial_value) - INTVAL (final_value);
abs_inc = -inc;
}
else
abort ();
/* Given that iteration_var is going to iterate over its own mode,
not HOST_WIDE_INT, disregard higher bits that might have come
into the picture due to sign extension of initial and final
values. */
abs_diff &= ((unsigned HOST_WIDE_INT) 1
<< (GET_MODE_BITSIZE (GET_MODE (iteration_var)) - 1)
<< 1) - 1;
/* For NE tests, make sure that the iteration variable won't miss
the final value. If abs_diff mod abs_incr is not zero, then the
iteration variable will overflow before the loop exits, and we
can not calculate the number of iterations. */
if (compare_dir == 0 && (abs_diff % abs_inc) != 0)
return 0;
/* Note that the number of iterations could be calculated using
(abs_diff + abs_inc - 1) / abs_inc, provided care was taken to
handle potential overflow of the summation. */
loop_info->n_iterations = abs_diff / abs_inc + ((abs_diff % abs_inc) != 0);
return loop_info->n_iterations;
}
/* Replace uses of split bivs with their split pseudo register. This is
for original instructions which remain after loop unrolling without
copying. */
static rtx
remap_split_bivs (loop, x)
struct loop *loop;
rtx x;
{
struct loop_ivs *ivs = LOOP_IVS (loop);
enum rtx_code code;
int i;
const char *fmt;
if (x == 0)
return x;
code = GET_CODE (x);
switch (code)
{
case SCRATCH:
case PC:
case CC0:
case CONST_INT:
case CONST_DOUBLE:
case CONST:
case SYMBOL_REF:
case LABEL_REF:
return x;
case REG:
#if 0
/* If non-reduced/final-value givs were split, then this would also
have to remap those givs also. */
#endif
if (REGNO (x) < ivs->n_regs
&& REG_IV_TYPE (ivs, REGNO (x)) == BASIC_INDUCT)
return REG_IV_CLASS (ivs, REGNO (x))->biv->src_reg;
break;
default:
break;
}
fmt = GET_RTX_FORMAT (code);
for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
{
if (fmt[i] == 'e')
XEXP (x, i) = remap_split_bivs (loop, XEXP (x, i));
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
XVECEXP (x, i, j) = remap_split_bivs (loop, XVECEXP (x, i, j));
}
}
return x;
}
/* If FIRST_UID is a set of REGNO, and FIRST_UID dominates LAST_UID (e.g.
FIST_UID is always executed if LAST_UID is), then return 1. Otherwise
return 0. COPY_START is where we can start looking for the insns
FIRST_UID and LAST_UID. COPY_END is where we stop looking for these
insns.
If there is no JUMP_INSN between LOOP_START and FIRST_UID, then FIRST_UID
must dominate LAST_UID.
If there is a CODE_LABEL between FIRST_UID and LAST_UID, then FIRST_UID
may not dominate LAST_UID.
If there is no CODE_LABEL between FIRST_UID and LAST_UID, then FIRST_UID
must dominate LAST_UID. */
int
set_dominates_use (regno, first_uid, last_uid, copy_start, copy_end)
int regno;
int first_uid;
int last_uid;
rtx copy_start;
rtx copy_end;
{
int passed_jump = 0;
rtx p = NEXT_INSN (copy_start);
while (INSN_UID (p) != first_uid)
{
if (GET_CODE (p) == JUMP_INSN)
passed_jump = 1;
/* Could not find FIRST_UID. */
if (p == copy_end)
return 0;
p = NEXT_INSN (p);
}
/* Verify that FIRST_UID is an insn that entirely sets REGNO. */
if (! INSN_P (p) || ! dead_or_set_regno_p (p, regno))
return 0;
/* FIRST_UID is always executed. */
if (passed_jump == 0)
return 1;
while (INSN_UID (p) != last_uid)
{
/* If we see a CODE_LABEL between FIRST_UID and LAST_UID, then we
can not be sure that FIRST_UID dominates LAST_UID. */
if (GET_CODE (p) == CODE_LABEL)
return 0;
/* Could not find LAST_UID, but we reached the end of the loop, so
it must be safe. */
else if (p == copy_end)
return 1;
p = NEXT_INSN (p);
}
/* FIRST_UID is always executed if LAST_UID is executed. */
return 1;
}
/* This routine is called when the number of iterations for the unrolled
loop is one. The goal is to identify a loop that begins with an
unconditional branch to the loop continuation note (or a label just after).
In this case, the unconditional branch that starts the loop needs to be
deleted so that we execute the single iteration. */
static rtx
ujump_to_loop_cont (loop_start, loop_cont)
rtx loop_start;
rtx loop_cont;
{
rtx x, label, label_ref;
/* See if loop start, or the next insn is an unconditional jump. */
loop_start = next_nonnote_insn (loop_start);
x = pc_set (loop_start);
if (!x)
return NULL_RTX;
label_ref = SET_SRC (x);
if (!label_ref)
return NULL_RTX;
/* Examine insn after loop continuation note. Return if not a label. */
label = next_nonnote_insn (loop_cont);
if (label == 0 || GET_CODE (label) != CODE_LABEL)
return NULL_RTX;
/* Return the loop start if the branch label matches the code label. */
if (CODE_LABEL_NUMBER (label) == CODE_LABEL_NUMBER (XEXP (label_ref, 0)))
return loop_start;
else
return NULL_RTX;
}
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