427 lines
16 KiB
C
427 lines
16 KiB
C
/* Loop optimization definitions for GNU C-Compiler
|
|
Copyright (C) 1991, 1995, 1998, 1999, 2000, 2001, 2002
|
|
Free Software Foundation, Inc.
|
|
|
|
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. */
|
|
|
|
#include "bitmap.h"
|
|
#include "sbitmap.h"
|
|
#include "hard-reg-set.h"
|
|
#include "basic-block.h"
|
|
|
|
/* Flags passed to loop_optimize. */
|
|
#define LOOP_UNROLL 1
|
|
#define LOOP_BCT 2
|
|
#define LOOP_PREFETCH 4
|
|
#define LOOP_AUTO_UNROLL 8
|
|
|
|
/* Get the loop info pointer of a loop. */
|
|
#define LOOP_INFO(LOOP) ((struct loop_info *) (LOOP)->aux)
|
|
|
|
/* Get a pointer to the loop movables structure. */
|
|
#define LOOP_MOVABLES(LOOP) (&LOOP_INFO (LOOP)->movables)
|
|
|
|
/* Get a pointer to the loop registers structure. */
|
|
#define LOOP_REGS(LOOP) (&LOOP_INFO (LOOP)->regs)
|
|
|
|
/* Get a pointer to the loop induction variables structure. */
|
|
#define LOOP_IVS(LOOP) (&LOOP_INFO (LOOP)->ivs)
|
|
|
|
/* Get the luid of an insn. Catch the error of trying to reference the LUID
|
|
of an insn added during loop, since these don't have LUIDs. */
|
|
|
|
#define INSN_LUID(INSN) \
|
|
(INSN_UID (INSN) < max_uid_for_loop ? uid_luid[INSN_UID (INSN)] \
|
|
: (abort (), -1))
|
|
|
|
#define REGNO_FIRST_LUID(REGNO) uid_luid[REGNO_FIRST_UID (REGNO)]
|
|
#define REGNO_LAST_LUID(REGNO) uid_luid[REGNO_LAST_UID (REGNO)]
|
|
|
|
|
|
/* A "basic induction variable" or biv is a pseudo reg that is set
|
|
(within this loop) only by incrementing or decrementing it. */
|
|
/* A "general induction variable" or giv is a pseudo reg whose
|
|
value is a linear function of a biv. */
|
|
|
|
/* Bivs are recognized by `basic_induction_var';
|
|
Givs by `general_induction_var'. */
|
|
|
|
/* An enum for the two different types of givs, those that are used
|
|
as memory addresses and those that are calculated into registers. */
|
|
enum g_types
|
|
{
|
|
DEST_ADDR,
|
|
DEST_REG
|
|
};
|
|
|
|
|
|
/* A `struct induction' is created for every instruction that sets
|
|
an induction variable (either a biv or a giv). */
|
|
|
|
struct induction
|
|
{
|
|
rtx insn; /* The insn that sets a biv or giv */
|
|
rtx new_reg; /* New register, containing strength reduced
|
|
version of this giv. */
|
|
rtx src_reg; /* Biv from which this giv is computed.
|
|
(If this is a biv, then this is the biv.) */
|
|
enum g_types giv_type; /* Indicate whether DEST_ADDR or DEST_REG */
|
|
rtx dest_reg; /* Destination register for insn: this is the
|
|
register which was the biv or giv.
|
|
For a biv, this equals src_reg.
|
|
For a DEST_ADDR type giv, this is 0. */
|
|
rtx *location; /* Place in the insn where this giv occurs.
|
|
If GIV_TYPE is DEST_REG, this is 0. */
|
|
/* For a biv, this is the place where add_val
|
|
was found. */
|
|
enum machine_mode mode; /* The mode of this biv or giv */
|
|
rtx mem; /* For DEST_ADDR, the memory object. */
|
|
rtx mult_val; /* Multiplicative factor for src_reg. */
|
|
rtx add_val; /* Additive constant for that product. */
|
|
int benefit; /* Gain from eliminating this insn. */
|
|
rtx final_value; /* If the giv is used outside the loop, and its
|
|
final value could be calculated, it is put
|
|
here, and the giv is made replaceable. Set
|
|
the giv to this value before the loop. */
|
|
unsigned combined_with; /* The number of givs this giv has been
|
|
combined with. If nonzero, this giv
|
|
cannot combine with any other giv. */
|
|
unsigned replaceable : 1; /* 1 if we can substitute the strength-reduced
|
|
variable for the original variable.
|
|
0 means they must be kept separate and the
|
|
new one must be copied into the old pseudo
|
|
reg each time the old one is set. */
|
|
unsigned not_replaceable : 1; /* Used to prevent duplicating work. This is
|
|
1 if we know that the giv definitely can
|
|
not be made replaceable, in which case we
|
|
don't bother checking the variable again
|
|
even if further info is available.
|
|
Both this and the above can be zero. */
|
|
unsigned ignore : 1; /* 1 prohibits further processing of giv */
|
|
unsigned always_computable : 1;/* 1 if this value is computable every
|
|
iteration. */
|
|
unsigned always_executed : 1; /* 1 if this set occurs each iteration. */
|
|
unsigned maybe_multiple : 1; /* Only used for a biv and 1 if this biv
|
|
update may be done multiple times per
|
|
iteration. */
|
|
unsigned cant_derive : 1; /* For giv's, 1 if this giv cannot derive
|
|
another giv. This occurs in many cases
|
|
where a giv's lifetime spans an update to
|
|
a biv. */
|
|
unsigned maybe_dead : 1; /* 1 if this giv might be dead. In that case,
|
|
we won't use it to eliminate a biv, it
|
|
would probably lose. */
|
|
unsigned auto_inc_opt : 1; /* 1 if this giv had its increment output next
|
|
to it to try to form an auto-inc address. */
|
|
unsigned unrolled : 1; /* 1 if new register has been allocated and
|
|
initialized in unrolled loop. */
|
|
unsigned shared : 1;
|
|
unsigned no_const_addval : 1; /* 1 if add_val does not contain a const. */
|
|
int lifetime; /* Length of life of this giv */
|
|
rtx derive_adjustment; /* If nonzero, is an adjustment to be
|
|
subtracted from add_val when this giv
|
|
derives another. This occurs when the
|
|
giv spans a biv update by incrementation. */
|
|
rtx ext_dependent; /* If nonzero, is a sign or zero extension
|
|
if a biv on which this giv is dependent. */
|
|
struct induction *next_iv; /* For givs, links together all givs that are
|
|
based on the same biv. For bivs, links
|
|
together all biv entries that refer to the
|
|
same biv register. */
|
|
struct induction *same; /* If this giv has been combined with another
|
|
giv, this points to the base giv. The base
|
|
giv will have COMBINED_WITH nonzero. */
|
|
HOST_WIDE_INT const_adjust; /* Used by loop unrolling, when an address giv
|
|
is split, and a constant is eliminated from
|
|
the address, the -constant is stored here
|
|
for later use. */
|
|
struct induction *same_insn; /* If there are multiple identical givs in
|
|
the same insn, then all but one have this
|
|
field set, and they all point to the giv
|
|
that doesn't have this field set. */
|
|
rtx last_use; /* For a giv made from a biv increment, this is
|
|
a substitute for the lifetime information. */
|
|
};
|
|
|
|
|
|
/* A `struct iv_class' is created for each biv. */
|
|
|
|
struct iv_class
|
|
{
|
|
unsigned int regno; /* Pseudo reg which is the biv. */
|
|
int biv_count; /* Number of insns setting this reg. */
|
|
struct induction *biv; /* List of all insns that set this reg. */
|
|
int giv_count; /* Number of DEST_REG givs computed from this
|
|
biv. The resulting count is only used in
|
|
check_dbra_loop. */
|
|
struct induction *giv; /* List of all insns that compute a giv
|
|
from this reg. */
|
|
int total_benefit; /* Sum of BENEFITs of all those givs. */
|
|
rtx initial_value; /* Value of reg at loop start. */
|
|
rtx initial_test; /* Test performed on BIV before loop. */
|
|
rtx final_value; /* Value of reg at loop end, if known. */
|
|
struct iv_class *next; /* Links all class structures together. */
|
|
rtx init_insn; /* insn which initializes biv, 0 if none. */
|
|
rtx init_set; /* SET of INIT_INSN, if any. */
|
|
unsigned incremented : 1; /* 1 if somewhere incremented/decremented */
|
|
unsigned eliminable : 1; /* 1 if plausible candidate for
|
|
elimination. */
|
|
unsigned nonneg : 1; /* 1 if we added a REG_NONNEG note for
|
|
this. */
|
|
unsigned reversed : 1; /* 1 if we reversed the loop that this
|
|
biv controls. */
|
|
unsigned all_reduced : 1; /* 1 if all givs using this biv have
|
|
been reduced. */
|
|
};
|
|
|
|
|
|
/* Definitions used by the basic induction variable discovery code. */
|
|
enum iv_mode
|
|
{
|
|
UNKNOWN_INDUCT,
|
|
BASIC_INDUCT,
|
|
NOT_BASIC_INDUCT,
|
|
GENERAL_INDUCT
|
|
};
|
|
|
|
|
|
/* A `struct iv' is created for every register. */
|
|
|
|
struct iv
|
|
{
|
|
enum iv_mode type;
|
|
union
|
|
{
|
|
struct iv_class *class;
|
|
struct induction *info;
|
|
} iv;
|
|
};
|
|
|
|
|
|
#define REG_IV_TYPE(ivs, n) ivs->regs[n].type
|
|
#define REG_IV_INFO(ivs, n) ivs->regs[n].iv.info
|
|
#define REG_IV_CLASS(ivs, n) ivs->regs[n].iv.class
|
|
|
|
|
|
struct loop_ivs
|
|
{
|
|
/* Indexed by register number, contains pointer to `struct
|
|
iv' if register is an induction variable. */
|
|
struct iv *regs;
|
|
|
|
/* Size of regs array. */
|
|
unsigned int n_regs;
|
|
|
|
/* The head of a list which links together (via the next field)
|
|
every iv class for the current loop. */
|
|
struct iv_class *list;
|
|
};
|
|
|
|
|
|
typedef struct loop_mem_info
|
|
{
|
|
rtx mem; /* The MEM itself. */
|
|
rtx reg; /* Corresponding pseudo, if any. */
|
|
int optimize; /* Nonzero if we can optimize access to this MEM. */
|
|
} loop_mem_info;
|
|
|
|
|
|
|
|
struct loop_reg
|
|
{
|
|
/* Number of times the reg is set during the loop being scanned.
|
|
During code motion, a negative value indicates a reg that has
|
|
been made a candidate; in particular -2 means that it is an
|
|
candidate that we know is equal to a constant and -1 means that
|
|
it is a candidate not known equal to a constant. After code
|
|
motion, regs moved have 0 (which is accurate now) while the
|
|
failed candidates have the original number of times set.
|
|
|
|
Therefore, at all times, == 0 indicates an invariant register;
|
|
< 0 a conditionally invariant one. */
|
|
int set_in_loop;
|
|
|
|
/* Original value of set_in_loop; same except that this value
|
|
is not set negative for a reg whose sets have been made candidates
|
|
and not set to 0 for a reg that is moved. */
|
|
int n_times_set;
|
|
|
|
/* Contains the insn in which a register was used if it was used
|
|
exactly once; contains const0_rtx if it was used more than once. */
|
|
rtx single_usage;
|
|
|
|
/* Nonzero indicates that the register cannot be moved or strength
|
|
reduced. */
|
|
char may_not_optimize;
|
|
|
|
/* Nonzero means reg N has already been moved out of one loop.
|
|
This reduces the desire to move it out of another. */
|
|
char moved_once;
|
|
};
|
|
|
|
|
|
struct loop_regs
|
|
{
|
|
int num; /* Number of regs used in table. */
|
|
int size; /* Size of table. */
|
|
struct loop_reg *array; /* Register usage info. array. */
|
|
int multiple_uses; /* Nonzero if a reg has multiple uses. */
|
|
};
|
|
|
|
|
|
|
|
struct loop_movables
|
|
{
|
|
/* Head of movable chain. */
|
|
struct movable *head;
|
|
/* Last movable in chain. */
|
|
struct movable *last;
|
|
};
|
|
|
|
|
|
/* Information pertaining to a loop. */
|
|
|
|
struct loop_info
|
|
{
|
|
/* Nonzero if there is a subroutine call in the current loop. */
|
|
int has_call;
|
|
/* Nonzero if there is a libcall in the current loop. */
|
|
int has_libcall;
|
|
/* Nonzero if there is a non constant call in the current loop. */
|
|
int has_nonconst_call;
|
|
/* Nonzero if there is a prefetch instruction in the current loop. */
|
|
int has_prefetch;
|
|
/* Nonzero if there is a volatile memory reference in the current
|
|
loop. */
|
|
int has_volatile;
|
|
/* Nonzero if there is a tablejump in the current loop. */
|
|
int has_tablejump;
|
|
/* Nonzero if there are ways to leave the loop other than falling
|
|
off the end. */
|
|
int has_multiple_exit_targets;
|
|
/* Nonzero if there is an indirect jump in the current function. */
|
|
int has_indirect_jump;
|
|
/* Whether loop unrolling has emitted copies of the loop body so
|
|
that the main loop needs no exit tests. */
|
|
int preconditioned;
|
|
/* Register or constant initial loop value. */
|
|
rtx initial_value;
|
|
/* Register or constant value used for comparison test. */
|
|
rtx comparison_value;
|
|
/* Register or constant approximate final value. */
|
|
rtx final_value;
|
|
/* Register or constant initial loop value with term common to
|
|
final_value removed. */
|
|
rtx initial_equiv_value;
|
|
/* Register or constant final loop value with term common to
|
|
initial_value removed. */
|
|
rtx final_equiv_value;
|
|
/* Register corresponding to iteration variable. */
|
|
rtx iteration_var;
|
|
/* Constant loop increment. */
|
|
rtx increment;
|
|
enum rtx_code comparison_code;
|
|
/* Holds the number of loop iterations. It is zero if the number
|
|
could not be calculated. Must be unsigned since the number of
|
|
iterations can be as high as 2^wordsize - 1. For loops with a
|
|
wider iterator, this number will be zero if the number of loop
|
|
iterations is too large for an unsigned integer to hold. */
|
|
unsigned HOST_WIDE_INT n_iterations;
|
|
/* The number of times the loop body was unrolled. */
|
|
unsigned int unroll_number;
|
|
int used_count_register;
|
|
/* The loop iterator induction variable. */
|
|
struct iv_class *iv;
|
|
/* List of MEMs that are stored in this loop. */
|
|
rtx store_mems;
|
|
/* Array of MEMs that are used (read or written) in this loop, but
|
|
cannot be aliased by anything in this loop, except perhaps
|
|
themselves. In other words, if mems[i] is altered during
|
|
the loop, it is altered by an expression that is rtx_equal_p to
|
|
it. */
|
|
loop_mem_info *mems;
|
|
/* The index of the next available slot in MEMS. */
|
|
int mems_idx;
|
|
/* The number of elements allocated in MEMS. */
|
|
int mems_allocated;
|
|
/* Nonzero if we don't know what MEMs were changed in the current
|
|
loop. This happens if the loop contains a call (in which case
|
|
`has_call' will also be set) or if we store into more than
|
|
NUM_STORES MEMs. */
|
|
int unknown_address_altered;
|
|
/* The above doesn't count any readonly memory locations that are
|
|
stored. This does. */
|
|
int unknown_constant_address_altered;
|
|
/* Count of memory write instructions discovered in the loop. */
|
|
int num_mem_sets;
|
|
/* The insn where the first of these was found. */
|
|
rtx first_loop_store_insn;
|
|
/* The chain of movable insns in loop. */
|
|
struct loop_movables movables;
|
|
/* The registers used the in loop. */
|
|
struct loop_regs regs;
|
|
/* The induction variable information in loop. */
|
|
struct loop_ivs ivs;
|
|
/* Nonzero if call is in pre_header extended basic block. */
|
|
int pre_header_has_call;
|
|
};
|
|
|
|
|
|
/* Variables declared in loop.c, but also needed in unroll.c. */
|
|
|
|
extern int *uid_luid;
|
|
extern int max_uid_for_loop;
|
|
extern unsigned int max_reg_before_loop;
|
|
extern struct loop **uid_loop;
|
|
extern FILE *loop_dump_stream;
|
|
|
|
|
|
/* Forward declarations for non-static functions declared in loop.c and
|
|
unroll.c. */
|
|
int loop_invariant_p PARAMS ((const struct loop *, rtx));
|
|
rtx get_condition_for_loop PARAMS ((const struct loop *, rtx));
|
|
void loop_iv_add_mult_hoist PARAMS ((const struct loop *, rtx, rtx, rtx, rtx));
|
|
void loop_iv_add_mult_sink PARAMS ((const struct loop *, rtx, rtx, rtx, rtx));
|
|
void loop_iv_add_mult_emit_before PARAMS ((const struct loop *, rtx,
|
|
rtx, rtx, rtx,
|
|
basic_block, rtx));
|
|
rtx express_from PARAMS ((struct induction *, struct induction *));
|
|
rtx extend_value_for_giv PARAMS ((struct induction *, rtx));
|
|
|
|
void unroll_loop PARAMS ((struct loop *, int, int));
|
|
rtx biv_total_increment PARAMS ((const struct iv_class *));
|
|
unsigned HOST_WIDE_INT loop_iterations PARAMS ((struct loop *));
|
|
int precondition_loop_p PARAMS ((const struct loop *,
|
|
rtx *, rtx *, rtx *,
|
|
enum machine_mode *mode));
|
|
rtx final_biv_value PARAMS ((const struct loop *, struct iv_class *));
|
|
rtx final_giv_value PARAMS ((const struct loop *, struct induction *));
|
|
void emit_unrolled_add PARAMS ((rtx, rtx, rtx));
|
|
int back_branch_in_range_p PARAMS ((const struct loop *, rtx));
|
|
|
|
int loop_insn_first_p PARAMS ((rtx, rtx));
|
|
typedef rtx (*loop_insn_callback) PARAMS ((struct loop *, rtx, int, int));
|
|
void for_each_insn_in_loop PARAMS ((struct loop *, loop_insn_callback));
|
|
rtx loop_insn_emit_before PARAMS((const struct loop *, basic_block,
|
|
rtx, rtx));
|
|
rtx loop_insn_sink PARAMS((const struct loop *, rtx));
|
|
rtx loop_insn_hoist PARAMS((const struct loop *, rtx));
|
|
|
|
/* Forward declarations for non-static functions declared in doloop.c. */
|
|
int doloop_optimize PARAMS ((const struct loop *));
|