1233 lines
32 KiB
C
1233 lines
32 KiB
C
/* Control flow graph analysis code for GNU compiler.
|
||
Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
|
||
1999, 2000, 2001, 2003 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. */
|
||
|
||
/* This file contains various simple utilities to analyze the CFG. */
|
||
#include "config.h"
|
||
#include "system.h"
|
||
#include "rtl.h"
|
||
#include "hard-reg-set.h"
|
||
#include "basic-block.h"
|
||
#include "insn-config.h"
|
||
#include "recog.h"
|
||
#include "toplev.h"
|
||
#include "obstack.h"
|
||
#include "tm_p.h"
|
||
|
||
/* Store the data structures necessary for depth-first search. */
|
||
struct depth_first_search_dsS {
|
||
/* stack for backtracking during the algorithm */
|
||
basic_block *stack;
|
||
|
||
/* number of edges in the stack. That is, positions 0, ..., sp-1
|
||
have edges. */
|
||
unsigned int sp;
|
||
|
||
/* record of basic blocks already seen by depth-first search */
|
||
sbitmap visited_blocks;
|
||
};
|
||
typedef struct depth_first_search_dsS *depth_first_search_ds;
|
||
|
||
static void flow_dfs_compute_reverse_init
|
||
PARAMS ((depth_first_search_ds));
|
||
static void flow_dfs_compute_reverse_add_bb
|
||
PARAMS ((depth_first_search_ds, basic_block));
|
||
static basic_block flow_dfs_compute_reverse_execute
|
||
PARAMS ((depth_first_search_ds));
|
||
static void flow_dfs_compute_reverse_finish
|
||
PARAMS ((depth_first_search_ds));
|
||
static void remove_fake_successors PARAMS ((basic_block));
|
||
static bool need_fake_edge_p PARAMS ((rtx));
|
||
static bool keep_with_call_p PARAMS ((rtx));
|
||
static bool flow_active_insn_p PARAMS ((rtx));
|
||
|
||
/* Like active_insn_p, except keep the return value clobber around
|
||
even after reload. */
|
||
|
||
static bool
|
||
flow_active_insn_p (insn)
|
||
rtx insn;
|
||
{
|
||
if (active_insn_p (insn))
|
||
return true;
|
||
|
||
/* A clobber of the function return value exists for buggy
|
||
programs that fail to return a value. It's effect is to
|
||
keep the return value from being live across the entire
|
||
function. If we allow it to be skipped, we introduce the
|
||
possibility for register livetime aborts. */
|
||
if (GET_CODE (PATTERN (insn)) == CLOBBER
|
||
&& GET_CODE (XEXP (PATTERN (insn), 0)) == REG
|
||
&& REG_FUNCTION_VALUE_P (XEXP (PATTERN (insn), 0)))
|
||
return true;
|
||
|
||
return false;
|
||
}
|
||
|
||
/* Return true if the block has no effect and only forwards control flow to
|
||
its single destination. */
|
||
|
||
bool
|
||
forwarder_block_p (bb)
|
||
basic_block bb;
|
||
{
|
||
rtx insn;
|
||
|
||
if (bb == EXIT_BLOCK_PTR || bb == ENTRY_BLOCK_PTR
|
||
|| !bb->succ || bb->succ->succ_next)
|
||
return false;
|
||
|
||
for (insn = bb->head; insn != bb->end; insn = NEXT_INSN (insn))
|
||
if (INSN_P (insn) && flow_active_insn_p (insn))
|
||
return false;
|
||
|
||
return (!INSN_P (insn)
|
||
|| (GET_CODE (insn) == JUMP_INSN && simplejump_p (insn))
|
||
|| !flow_active_insn_p (insn));
|
||
}
|
||
|
||
/* Return nonzero if we can reach target from src by falling through. */
|
||
|
||
bool
|
||
can_fallthru (src, target)
|
||
basic_block src, target;
|
||
{
|
||
rtx insn = src->end;
|
||
rtx insn2 = target->head;
|
||
|
||
if (src->index + 1 == target->index && !active_insn_p (insn2))
|
||
insn2 = next_active_insn (insn2);
|
||
|
||
/* ??? Later we may add code to move jump tables offline. */
|
||
return next_active_insn (insn) == insn2;
|
||
}
|
||
|
||
/* Mark the back edges in DFS traversal.
|
||
Return non-zero if a loop (natural or otherwise) is present.
|
||
Inspired by Depth_First_Search_PP described in:
|
||
|
||
Advanced Compiler Design and Implementation
|
||
Steven Muchnick
|
||
Morgan Kaufmann, 1997
|
||
|
||
and heavily borrowed from flow_depth_first_order_compute. */
|
||
|
||
bool
|
||
mark_dfs_back_edges ()
|
||
{
|
||
edge *stack;
|
||
int *pre;
|
||
int *post;
|
||
int sp;
|
||
int prenum = 1;
|
||
int postnum = 1;
|
||
sbitmap visited;
|
||
bool found = false;
|
||
|
||
/* Allocate the preorder and postorder number arrays. */
|
||
pre = (int *) xcalloc (n_basic_blocks, sizeof (int));
|
||
post = (int *) xcalloc (n_basic_blocks, sizeof (int));
|
||
|
||
/* Allocate stack for back-tracking up CFG. */
|
||
stack = (edge *) xmalloc ((n_basic_blocks + 1) * sizeof (edge));
|
||
sp = 0;
|
||
|
||
/* Allocate bitmap to track nodes that have been visited. */
|
||
visited = sbitmap_alloc (n_basic_blocks);
|
||
|
||
/* None of the nodes in the CFG have been visited yet. */
|
||
sbitmap_zero (visited);
|
||
|
||
/* Push the first edge on to the stack. */
|
||
stack[sp++] = ENTRY_BLOCK_PTR->succ;
|
||
|
||
while (sp)
|
||
{
|
||
edge e;
|
||
basic_block src;
|
||
basic_block dest;
|
||
|
||
/* Look at the edge on the top of the stack. */
|
||
e = stack[sp - 1];
|
||
src = e->src;
|
||
dest = e->dest;
|
||
e->flags &= ~EDGE_DFS_BACK;
|
||
|
||
/* Check if the edge destination has been visited yet. */
|
||
if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
|
||
{
|
||
/* Mark that we have visited the destination. */
|
||
SET_BIT (visited, dest->index);
|
||
|
||
pre[dest->index] = prenum++;
|
||
if (dest->succ)
|
||
{
|
||
/* Since the DEST node has been visited for the first
|
||
time, check its successors. */
|
||
stack[sp++] = dest->succ;
|
||
}
|
||
else
|
||
post[dest->index] = postnum++;
|
||
}
|
||
else
|
||
{
|
||
if (dest != EXIT_BLOCK_PTR && src != ENTRY_BLOCK_PTR
|
||
&& pre[src->index] >= pre[dest->index]
|
||
&& post[dest->index] == 0)
|
||
e->flags |= EDGE_DFS_BACK, found = true;
|
||
|
||
if (! e->succ_next && src != ENTRY_BLOCK_PTR)
|
||
post[src->index] = postnum++;
|
||
|
||
if (e->succ_next)
|
||
stack[sp - 1] = e->succ_next;
|
||
else
|
||
sp--;
|
||
}
|
||
}
|
||
|
||
free (pre);
|
||
free (post);
|
||
free (stack);
|
||
sbitmap_free (visited);
|
||
|
||
return found;
|
||
}
|
||
|
||
/* Return true if we need to add fake edge to exit.
|
||
Helper function for the flow_call_edges_add. */
|
||
|
||
static bool
|
||
need_fake_edge_p (insn)
|
||
rtx insn;
|
||
{
|
||
if (!INSN_P (insn))
|
||
return false;
|
||
|
||
if ((GET_CODE (insn) == CALL_INSN
|
||
&& !SIBLING_CALL_P (insn)
|
||
&& !find_reg_note (insn, REG_NORETURN, NULL)
|
||
&& !find_reg_note (insn, REG_ALWAYS_RETURN, NULL)
|
||
&& !CONST_OR_PURE_CALL_P (insn)))
|
||
return true;
|
||
|
||
return ((GET_CODE (PATTERN (insn)) == ASM_OPERANDS
|
||
&& MEM_VOLATILE_P (PATTERN (insn)))
|
||
|| (GET_CODE (PATTERN (insn)) == PARALLEL
|
||
&& asm_noperands (insn) != -1
|
||
&& MEM_VOLATILE_P (XVECEXP (PATTERN (insn), 0, 0)))
|
||
|| GET_CODE (PATTERN (insn)) == ASM_INPUT);
|
||
}
|
||
|
||
/* Return true if INSN should be kept in the same block as a preceding call.
|
||
This is done for a single-set whose destination is a fixed register or
|
||
whose source is the function return value. This is a helper function for
|
||
flow_call_edges_add. */
|
||
|
||
static bool
|
||
keep_with_call_p (insn)
|
||
rtx insn;
|
||
{
|
||
rtx set;
|
||
|
||
if (INSN_P (insn) && (set = single_set (insn)) != NULL)
|
||
{
|
||
if (GET_CODE (SET_DEST (set)) == REG
|
||
&& fixed_regs[REGNO (SET_DEST (set))]
|
||
&& general_operand (SET_SRC (set), VOIDmode))
|
||
return true;
|
||
if (GET_CODE (SET_SRC (set)) == REG
|
||
&& FUNCTION_VALUE_REGNO_P (REGNO (SET_SRC (set)))
|
||
&& GET_CODE (SET_DEST (set)) == REG
|
||
&& REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
|
||
return true;
|
||
}
|
||
return false;
|
||
}
|
||
|
||
/* Add fake edges to the function exit for any non constant and non noreturn
|
||
calls, volatile inline assembly in the bitmap of blocks specified by
|
||
BLOCKS or to the whole CFG if BLOCKS is zero. Return the number of blocks
|
||
that were split.
|
||
|
||
The goal is to expose cases in which entering a basic block does not imply
|
||
that all subsequent instructions must be executed. */
|
||
|
||
int
|
||
flow_call_edges_add (blocks)
|
||
sbitmap blocks;
|
||
{
|
||
int i;
|
||
int blocks_split = 0;
|
||
int bb_num = 0;
|
||
basic_block *bbs;
|
||
bool check_last_block = false;
|
||
|
||
/* Map bb indices into basic block pointers since split_block
|
||
will renumber the basic blocks. */
|
||
|
||
bbs = xmalloc (n_basic_blocks * sizeof (*bbs));
|
||
|
||
if (! blocks)
|
||
{
|
||
for (i = 0; i < n_basic_blocks; i++)
|
||
bbs[bb_num++] = BASIC_BLOCK (i);
|
||
|
||
check_last_block = true;
|
||
}
|
||
else
|
||
EXECUTE_IF_SET_IN_SBITMAP (blocks, 0, i,
|
||
{
|
||
bbs[bb_num++] = BASIC_BLOCK (i);
|
||
if (i == n_basic_blocks - 1)
|
||
check_last_block = true;
|
||
});
|
||
|
||
/* In the last basic block, before epilogue generation, there will be
|
||
a fallthru edge to EXIT. Special care is required if the last insn
|
||
of the last basic block is a call because make_edge folds duplicate
|
||
edges, which would result in the fallthru edge also being marked
|
||
fake, which would result in the fallthru edge being removed by
|
||
remove_fake_edges, which would result in an invalid CFG.
|
||
|
||
Moreover, we can't elide the outgoing fake edge, since the block
|
||
profiler needs to take this into account in order to solve the minimal
|
||
spanning tree in the case that the call doesn't return.
|
||
|
||
Handle this by adding a dummy instruction in a new last basic block. */
|
||
if (check_last_block)
|
||
{
|
||
basic_block bb = BASIC_BLOCK (n_basic_blocks - 1);
|
||
rtx insn = bb->end;
|
||
|
||
/* Back up past insns that must be kept in the same block as a call. */
|
||
while (insn != bb->head
|
||
&& keep_with_call_p (insn))
|
||
insn = PREV_INSN (insn);
|
||
|
||
if (need_fake_edge_p (insn))
|
||
{
|
||
edge e;
|
||
|
||
for (e = bb->succ; e; e = e->succ_next)
|
||
if (e->dest == EXIT_BLOCK_PTR)
|
||
{
|
||
insert_insn_on_edge (gen_rtx_USE (VOIDmode, const0_rtx), e);
|
||
commit_edge_insertions ();
|
||
break;
|
||
}
|
||
}
|
||
}
|
||
|
||
/* Now add fake edges to the function exit for any non constant
|
||
calls since there is no way that we can determine if they will
|
||
return or not... */
|
||
|
||
for (i = 0; i < bb_num; i++)
|
||
{
|
||
basic_block bb = bbs[i];
|
||
rtx insn;
|
||
rtx prev_insn;
|
||
|
||
for (insn = bb->end; ; insn = prev_insn)
|
||
{
|
||
prev_insn = PREV_INSN (insn);
|
||
if (need_fake_edge_p (insn))
|
||
{
|
||
edge e;
|
||
rtx split_at_insn = insn;
|
||
|
||
/* Don't split the block between a call and an insn that should
|
||
remain in the same block as the call. */
|
||
if (GET_CODE (insn) == CALL_INSN)
|
||
while (split_at_insn != bb->end
|
||
&& keep_with_call_p (NEXT_INSN (split_at_insn)))
|
||
split_at_insn = NEXT_INSN (split_at_insn);
|
||
|
||
/* The handling above of the final block before the epilogue
|
||
should be enough to verify that there is no edge to the exit
|
||
block in CFG already. Calling make_edge in such case would
|
||
cause us to mark that edge as fake and remove it later. */
|
||
|
||
#ifdef ENABLE_CHECKING
|
||
if (split_at_insn == bb->end)
|
||
for (e = bb->succ; e; e = e->succ_next)
|
||
if (e->dest == EXIT_BLOCK_PTR)
|
||
abort ();
|
||
#endif
|
||
|
||
/* Note that the following may create a new basic block
|
||
and renumber the existing basic blocks. */
|
||
e = split_block (bb, split_at_insn);
|
||
if (e)
|
||
blocks_split++;
|
||
|
||
make_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
|
||
}
|
||
|
||
if (insn == bb->head)
|
||
break;
|
||
}
|
||
}
|
||
|
||
if (blocks_split)
|
||
verify_flow_info ();
|
||
|
||
free (bbs);
|
||
return blocks_split;
|
||
}
|
||
|
||
/* Find unreachable blocks. An unreachable block will have 0 in
|
||
the reachable bit in block->flags. A non-zero value indicates the
|
||
block is reachable. */
|
||
|
||
void
|
||
find_unreachable_blocks ()
|
||
{
|
||
edge e;
|
||
int i, n;
|
||
basic_block *tos, *worklist;
|
||
|
||
n = n_basic_blocks;
|
||
tos = worklist = (basic_block *) xmalloc (sizeof (basic_block) * n);
|
||
|
||
/* Clear all the reachability flags. */
|
||
|
||
for (i = 0; i < n; ++i)
|
||
BASIC_BLOCK (i)->flags &= ~BB_REACHABLE;
|
||
|
||
/* Add our starting points to the worklist. Almost always there will
|
||
be only one. It isn't inconceivable that we might one day directly
|
||
support Fortran alternate entry points. */
|
||
|
||
for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next)
|
||
{
|
||
*tos++ = e->dest;
|
||
|
||
/* Mark the block reachable. */
|
||
e->dest->flags |= BB_REACHABLE;
|
||
}
|
||
|
||
/* Iterate: find everything reachable from what we've already seen. */
|
||
|
||
while (tos != worklist)
|
||
{
|
||
basic_block b = *--tos;
|
||
|
||
for (e = b->succ; e; e = e->succ_next)
|
||
if (!(e->dest->flags & BB_REACHABLE))
|
||
{
|
||
*tos++ = e->dest;
|
||
e->dest->flags |= BB_REACHABLE;
|
||
}
|
||
}
|
||
|
||
free (worklist);
|
||
}
|
||
|
||
/* Functions to access an edge list with a vector representation.
|
||
Enough data is kept such that given an index number, the
|
||
pred and succ that edge represents can be determined, or
|
||
given a pred and a succ, its index number can be returned.
|
||
This allows algorithms which consume a lot of memory to
|
||
represent the normally full matrix of edge (pred,succ) with a
|
||
single indexed vector, edge (EDGE_INDEX (pred, succ)), with no
|
||
wasted space in the client code due to sparse flow graphs. */
|
||
|
||
/* This functions initializes the edge list. Basically the entire
|
||
flowgraph is processed, and all edges are assigned a number,
|
||
and the data structure is filled in. */
|
||
|
||
struct edge_list *
|
||
create_edge_list ()
|
||
{
|
||
struct edge_list *elist;
|
||
edge e;
|
||
int num_edges;
|
||
int x;
|
||
int block_count;
|
||
|
||
block_count = n_basic_blocks + 2; /* Include the entry and exit blocks. */
|
||
|
||
num_edges = 0;
|
||
|
||
/* Determine the number of edges in the flow graph by counting successor
|
||
edges on each basic block. */
|
||
for (x = 0; x < n_basic_blocks; x++)
|
||
{
|
||
basic_block bb = BASIC_BLOCK (x);
|
||
|
||
for (e = bb->succ; e; e = e->succ_next)
|
||
num_edges++;
|
||
}
|
||
|
||
/* Don't forget successors of the entry block. */
|
||
for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next)
|
||
num_edges++;
|
||
|
||
elist = (struct edge_list *) xmalloc (sizeof (struct edge_list));
|
||
elist->num_blocks = block_count;
|
||
elist->num_edges = num_edges;
|
||
elist->index_to_edge = (edge *) xmalloc (sizeof (edge) * num_edges);
|
||
|
||
num_edges = 0;
|
||
|
||
/* Follow successors of the entry block, and register these edges. */
|
||
for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next)
|
||
elist->index_to_edge[num_edges++] = e;
|
||
|
||
for (x = 0; x < n_basic_blocks; x++)
|
||
{
|
||
basic_block bb = BASIC_BLOCK (x);
|
||
|
||
/* Follow all successors of blocks, and register these edges. */
|
||
for (e = bb->succ; e; e = e->succ_next)
|
||
elist->index_to_edge[num_edges++] = e;
|
||
}
|
||
|
||
return elist;
|
||
}
|
||
|
||
/* This function free's memory associated with an edge list. */
|
||
|
||
void
|
||
free_edge_list (elist)
|
||
struct edge_list *elist;
|
||
{
|
||
if (elist)
|
||
{
|
||
free (elist->index_to_edge);
|
||
free (elist);
|
||
}
|
||
}
|
||
|
||
/* This function provides debug output showing an edge list. */
|
||
|
||
void
|
||
print_edge_list (f, elist)
|
||
FILE *f;
|
||
struct edge_list *elist;
|
||
{
|
||
int x;
|
||
|
||
fprintf (f, "Compressed edge list, %d BBs + entry & exit, and %d edges\n",
|
||
elist->num_blocks - 2, elist->num_edges);
|
||
|
||
for (x = 0; x < elist->num_edges; x++)
|
||
{
|
||
fprintf (f, " %-4d - edge(", x);
|
||
if (INDEX_EDGE_PRED_BB (elist, x) == ENTRY_BLOCK_PTR)
|
||
fprintf (f, "entry,");
|
||
else
|
||
fprintf (f, "%d,", INDEX_EDGE_PRED_BB (elist, x)->index);
|
||
|
||
if (INDEX_EDGE_SUCC_BB (elist, x) == EXIT_BLOCK_PTR)
|
||
fprintf (f, "exit)\n");
|
||
else
|
||
fprintf (f, "%d)\n", INDEX_EDGE_SUCC_BB (elist, x)->index);
|
||
}
|
||
}
|
||
|
||
/* This function provides an internal consistency check of an edge list,
|
||
verifying that all edges are present, and that there are no
|
||
extra edges. */
|
||
|
||
void
|
||
verify_edge_list (f, elist)
|
||
FILE *f;
|
||
struct edge_list *elist;
|
||
{
|
||
int x, pred, succ, index;
|
||
edge e;
|
||
|
||
for (x = 0; x < n_basic_blocks; x++)
|
||
{
|
||
basic_block bb = BASIC_BLOCK (x);
|
||
|
||
for (e = bb->succ; e; e = e->succ_next)
|
||
{
|
||
pred = e->src->index;
|
||
succ = e->dest->index;
|
||
index = EDGE_INDEX (elist, e->src, e->dest);
|
||
if (index == EDGE_INDEX_NO_EDGE)
|
||
{
|
||
fprintf (f, "*p* No index for edge from %d to %d\n", pred, succ);
|
||
continue;
|
||
}
|
||
|
||
if (INDEX_EDGE_PRED_BB (elist, index)->index != pred)
|
||
fprintf (f, "*p* Pred for index %d should be %d not %d\n",
|
||
index, pred, INDEX_EDGE_PRED_BB (elist, index)->index);
|
||
if (INDEX_EDGE_SUCC_BB (elist, index)->index != succ)
|
||
fprintf (f, "*p* Succ for index %d should be %d not %d\n",
|
||
index, succ, INDEX_EDGE_SUCC_BB (elist, index)->index);
|
||
}
|
||
}
|
||
|
||
for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next)
|
||
{
|
||
pred = e->src->index;
|
||
succ = e->dest->index;
|
||
index = EDGE_INDEX (elist, e->src, e->dest);
|
||
if (index == EDGE_INDEX_NO_EDGE)
|
||
{
|
||
fprintf (f, "*p* No index for edge from %d to %d\n", pred, succ);
|
||
continue;
|
||
}
|
||
|
||
if (INDEX_EDGE_PRED_BB (elist, index)->index != pred)
|
||
fprintf (f, "*p* Pred for index %d should be %d not %d\n",
|
||
index, pred, INDEX_EDGE_PRED_BB (elist, index)->index);
|
||
if (INDEX_EDGE_SUCC_BB (elist, index)->index != succ)
|
||
fprintf (f, "*p* Succ for index %d should be %d not %d\n",
|
||
index, succ, INDEX_EDGE_SUCC_BB (elist, index)->index);
|
||
}
|
||
|
||
/* We've verified that all the edges are in the list, no lets make sure
|
||
there are no spurious edges in the list. */
|
||
|
||
for (pred = 0; pred < n_basic_blocks; pred++)
|
||
for (succ = 0; succ < n_basic_blocks; succ++)
|
||
{
|
||
basic_block p = BASIC_BLOCK (pred);
|
||
basic_block s = BASIC_BLOCK (succ);
|
||
int found_edge = 0;
|
||
|
||
for (e = p->succ; e; e = e->succ_next)
|
||
if (e->dest == s)
|
||
{
|
||
found_edge = 1;
|
||
break;
|
||
}
|
||
|
||
for (e = s->pred; e; e = e->pred_next)
|
||
if (e->src == p)
|
||
{
|
||
found_edge = 1;
|
||
break;
|
||
}
|
||
|
||
if (EDGE_INDEX (elist, BASIC_BLOCK (pred), BASIC_BLOCK (succ))
|
||
== EDGE_INDEX_NO_EDGE && found_edge != 0)
|
||
fprintf (f, "*** Edge (%d, %d) appears to not have an index\n",
|
||
pred, succ);
|
||
if (EDGE_INDEX (elist, BASIC_BLOCK (pred), BASIC_BLOCK (succ))
|
||
!= EDGE_INDEX_NO_EDGE && found_edge == 0)
|
||
fprintf (f, "*** Edge (%d, %d) has index %d, but there is no edge\n",
|
||
pred, succ, EDGE_INDEX (elist, BASIC_BLOCK (pred),
|
||
BASIC_BLOCK (succ)));
|
||
}
|
||
|
||
for (succ = 0; succ < n_basic_blocks; succ++)
|
||
{
|
||
basic_block p = ENTRY_BLOCK_PTR;
|
||
basic_block s = BASIC_BLOCK (succ);
|
||
int found_edge = 0;
|
||
|
||
for (e = p->succ; e; e = e->succ_next)
|
||
if (e->dest == s)
|
||
{
|
||
found_edge = 1;
|
||
break;
|
||
}
|
||
|
||
for (e = s->pred; e; e = e->pred_next)
|
||
if (e->src == p)
|
||
{
|
||
found_edge = 1;
|
||
break;
|
||
}
|
||
|
||
if (EDGE_INDEX (elist, ENTRY_BLOCK_PTR, BASIC_BLOCK (succ))
|
||
== EDGE_INDEX_NO_EDGE && found_edge != 0)
|
||
fprintf (f, "*** Edge (entry, %d) appears to not have an index\n",
|
||
succ);
|
||
if (EDGE_INDEX (elist, ENTRY_BLOCK_PTR, BASIC_BLOCK (succ))
|
||
!= EDGE_INDEX_NO_EDGE && found_edge == 0)
|
||
fprintf (f, "*** Edge (entry, %d) has index %d, but no edge exists\n",
|
||
succ, EDGE_INDEX (elist, ENTRY_BLOCK_PTR,
|
||
BASIC_BLOCK (succ)));
|
||
}
|
||
|
||
for (pred = 0; pred < n_basic_blocks; pred++)
|
||
{
|
||
basic_block p = BASIC_BLOCK (pred);
|
||
basic_block s = EXIT_BLOCK_PTR;
|
||
int found_edge = 0;
|
||
|
||
for (e = p->succ; e; e = e->succ_next)
|
||
if (e->dest == s)
|
||
{
|
||
found_edge = 1;
|
||
break;
|
||
}
|
||
|
||
for (e = s->pred; e; e = e->pred_next)
|
||
if (e->src == p)
|
||
{
|
||
found_edge = 1;
|
||
break;
|
||
}
|
||
|
||
if (EDGE_INDEX (elist, BASIC_BLOCK (pred), EXIT_BLOCK_PTR)
|
||
== EDGE_INDEX_NO_EDGE && found_edge != 0)
|
||
fprintf (f, "*** Edge (%d, exit) appears to not have an index\n",
|
||
pred);
|
||
if (EDGE_INDEX (elist, BASIC_BLOCK (pred), EXIT_BLOCK_PTR)
|
||
!= EDGE_INDEX_NO_EDGE && found_edge == 0)
|
||
fprintf (f, "*** Edge (%d, exit) has index %d, but no edge exists\n",
|
||
pred, EDGE_INDEX (elist, BASIC_BLOCK (pred),
|
||
EXIT_BLOCK_PTR));
|
||
}
|
||
}
|
||
|
||
/* This routine will determine what, if any, edge there is between
|
||
a specified predecessor and successor. */
|
||
|
||
int
|
||
find_edge_index (edge_list, pred, succ)
|
||
struct edge_list *edge_list;
|
||
basic_block pred, succ;
|
||
{
|
||
int x;
|
||
|
||
for (x = 0; x < NUM_EDGES (edge_list); x++)
|
||
if (INDEX_EDGE_PRED_BB (edge_list, x) == pred
|
||
&& INDEX_EDGE_SUCC_BB (edge_list, x) == succ)
|
||
return x;
|
||
|
||
return (EDGE_INDEX_NO_EDGE);
|
||
}
|
||
|
||
/* Dump the list of basic blocks in the bitmap NODES. */
|
||
|
||
void
|
||
flow_nodes_print (str, nodes, file)
|
||
const char *str;
|
||
const sbitmap nodes;
|
||
FILE *file;
|
||
{
|
||
int node;
|
||
|
||
if (! nodes)
|
||
return;
|
||
|
||
fprintf (file, "%s { ", str);
|
||
EXECUTE_IF_SET_IN_SBITMAP (nodes, 0, node, {fprintf (file, "%d ", node);});
|
||
fputs ("}\n", file);
|
||
}
|
||
|
||
/* Dump the list of edges in the array EDGE_LIST. */
|
||
|
||
void
|
||
flow_edge_list_print (str, edge_list, num_edges, file)
|
||
const char *str;
|
||
const edge *edge_list;
|
||
int num_edges;
|
||
FILE *file;
|
||
{
|
||
int i;
|
||
|
||
if (! edge_list)
|
||
return;
|
||
|
||
fprintf (file, "%s { ", str);
|
||
for (i = 0; i < num_edges; i++)
|
||
fprintf (file, "%d->%d ", edge_list[i]->src->index,
|
||
edge_list[i]->dest->index);
|
||
|
||
fputs ("}\n", file);
|
||
}
|
||
|
||
|
||
/* This routine will remove any fake successor edges for a basic block.
|
||
When the edge is removed, it is also removed from whatever predecessor
|
||
list it is in. */
|
||
|
||
static void
|
||
remove_fake_successors (bb)
|
||
basic_block bb;
|
||
{
|
||
edge e;
|
||
|
||
for (e = bb->succ; e;)
|
||
{
|
||
edge tmp = e;
|
||
|
||
e = e->succ_next;
|
||
if ((tmp->flags & EDGE_FAKE) == EDGE_FAKE)
|
||
remove_edge (tmp);
|
||
}
|
||
}
|
||
|
||
/* This routine will remove all fake edges from the flow graph. If
|
||
we remove all fake successors, it will automatically remove all
|
||
fake predecessors. */
|
||
|
||
void
|
||
remove_fake_edges ()
|
||
{
|
||
int x;
|
||
|
||
for (x = 0; x < n_basic_blocks; x++)
|
||
remove_fake_successors (BASIC_BLOCK (x));
|
||
|
||
/* We've handled all successors except the entry block's. */
|
||
remove_fake_successors (ENTRY_BLOCK_PTR);
|
||
}
|
||
|
||
/* This function will add a fake edge between any block which has no
|
||
successors, and the exit block. Some data flow equations require these
|
||
edges to exist. */
|
||
|
||
void
|
||
add_noreturn_fake_exit_edges ()
|
||
{
|
||
int x;
|
||
|
||
for (x = 0; x < n_basic_blocks; x++)
|
||
if (BASIC_BLOCK (x)->succ == NULL)
|
||
make_single_succ_edge (BASIC_BLOCK (x), EXIT_BLOCK_PTR, EDGE_FAKE);
|
||
}
|
||
|
||
/* This function adds a fake edge between any infinite loops to the
|
||
exit block. Some optimizations require a path from each node to
|
||
the exit node.
|
||
|
||
See also Morgan, Figure 3.10, pp. 82-83.
|
||
|
||
The current implementation is ugly, not attempting to minimize the
|
||
number of inserted fake edges. To reduce the number of fake edges
|
||
to insert, add fake edges from _innermost_ loops containing only
|
||
nodes not reachable from the exit block. */
|
||
|
||
void
|
||
connect_infinite_loops_to_exit ()
|
||
{
|
||
basic_block unvisited_block;
|
||
struct depth_first_search_dsS dfs_ds;
|
||
|
||
/* Perform depth-first search in the reverse graph to find nodes
|
||
reachable from the exit block. */
|
||
flow_dfs_compute_reverse_init (&dfs_ds);
|
||
flow_dfs_compute_reverse_add_bb (&dfs_ds, EXIT_BLOCK_PTR);
|
||
|
||
/* Repeatedly add fake edges, updating the unreachable nodes. */
|
||
while (1)
|
||
{
|
||
unvisited_block = flow_dfs_compute_reverse_execute (&dfs_ds);
|
||
if (!unvisited_block)
|
||
break;
|
||
|
||
make_edge (unvisited_block, EXIT_BLOCK_PTR, EDGE_FAKE);
|
||
flow_dfs_compute_reverse_add_bb (&dfs_ds, unvisited_block);
|
||
}
|
||
|
||
flow_dfs_compute_reverse_finish (&dfs_ds);
|
||
return;
|
||
}
|
||
|
||
/* Compute reverse top sort order */
|
||
|
||
void
|
||
flow_reverse_top_sort_order_compute (rts_order)
|
||
int *rts_order;
|
||
{
|
||
edge *stack;
|
||
int sp;
|
||
int postnum = 0;
|
||
sbitmap visited;
|
||
|
||
/* Allocate stack for back-tracking up CFG. */
|
||
stack = (edge *) xmalloc ((n_basic_blocks + 1) * sizeof (edge));
|
||
sp = 0;
|
||
|
||
/* Allocate bitmap to track nodes that have been visited. */
|
||
visited = sbitmap_alloc (n_basic_blocks);
|
||
|
||
/* None of the nodes in the CFG have been visited yet. */
|
||
sbitmap_zero (visited);
|
||
|
||
/* Push the first edge on to the stack. */
|
||
stack[sp++] = ENTRY_BLOCK_PTR->succ;
|
||
|
||
while (sp)
|
||
{
|
||
edge e;
|
||
basic_block src;
|
||
basic_block dest;
|
||
|
||
/* Look at the edge on the top of the stack. */
|
||
e = stack[sp - 1];
|
||
src = e->src;
|
||
dest = e->dest;
|
||
|
||
/* Check if the edge destination has been visited yet. */
|
||
if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
|
||
{
|
||
/* Mark that we have visited the destination. */
|
||
SET_BIT (visited, dest->index);
|
||
|
||
if (dest->succ)
|
||
/* Since the DEST node has been visited for the first
|
||
time, check its successors. */
|
||
stack[sp++] = dest->succ;
|
||
else
|
||
rts_order[postnum++] = dest->index;
|
||
}
|
||
else
|
||
{
|
||
if (! e->succ_next && src != ENTRY_BLOCK_PTR)
|
||
rts_order[postnum++] = src->index;
|
||
|
||
if (e->succ_next)
|
||
stack[sp - 1] = e->succ_next;
|
||
else
|
||
sp--;
|
||
}
|
||
}
|
||
|
||
free (stack);
|
||
sbitmap_free (visited);
|
||
}
|
||
|
||
/* Compute the depth first search order and store in the array
|
||
DFS_ORDER if non-zero, marking the nodes visited in VISITED. If
|
||
RC_ORDER is non-zero, return the reverse completion number for each
|
||
node. Returns the number of nodes visited. A depth first search
|
||
tries to get as far away from the starting point as quickly as
|
||
possible. */
|
||
|
||
int
|
||
flow_depth_first_order_compute (dfs_order, rc_order)
|
||
int *dfs_order;
|
||
int *rc_order;
|
||
{
|
||
edge *stack;
|
||
int sp;
|
||
int dfsnum = 0;
|
||
int rcnum = n_basic_blocks - 1;
|
||
sbitmap visited;
|
||
|
||
/* Allocate stack for back-tracking up CFG. */
|
||
stack = (edge *) xmalloc ((n_basic_blocks + 1) * sizeof (edge));
|
||
sp = 0;
|
||
|
||
/* Allocate bitmap to track nodes that have been visited. */
|
||
visited = sbitmap_alloc (n_basic_blocks);
|
||
|
||
/* None of the nodes in the CFG have been visited yet. */
|
||
sbitmap_zero (visited);
|
||
|
||
/* Push the first edge on to the stack. */
|
||
stack[sp++] = ENTRY_BLOCK_PTR->succ;
|
||
|
||
while (sp)
|
||
{
|
||
edge e;
|
||
basic_block src;
|
||
basic_block dest;
|
||
|
||
/* Look at the edge on the top of the stack. */
|
||
e = stack[sp - 1];
|
||
src = e->src;
|
||
dest = e->dest;
|
||
|
||
/* Check if the edge destination has been visited yet. */
|
||
if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
|
||
{
|
||
/* Mark that we have visited the destination. */
|
||
SET_BIT (visited, dest->index);
|
||
|
||
if (dfs_order)
|
||
dfs_order[dfsnum] = dest->index;
|
||
|
||
dfsnum++;
|
||
|
||
if (dest->succ)
|
||
/* Since the DEST node has been visited for the first
|
||
time, check its successors. */
|
||
stack[sp++] = dest->succ;
|
||
else if (rc_order)
|
||
/* There are no successors for the DEST node so assign
|
||
its reverse completion number. */
|
||
rc_order[rcnum--] = dest->index;
|
||
}
|
||
else
|
||
{
|
||
if (! e->succ_next && src != ENTRY_BLOCK_PTR
|
||
&& rc_order)
|
||
/* There are no more successors for the SRC node
|
||
so assign its reverse completion number. */
|
||
rc_order[rcnum--] = src->index;
|
||
|
||
if (e->succ_next)
|
||
stack[sp - 1] = e->succ_next;
|
||
else
|
||
sp--;
|
||
}
|
||
}
|
||
|
||
free (stack);
|
||
sbitmap_free (visited);
|
||
|
||
/* The number of nodes visited should not be greater than
|
||
n_basic_blocks. */
|
||
if (dfsnum > n_basic_blocks)
|
||
abort ();
|
||
|
||
/* There are some nodes left in the CFG that are unreachable. */
|
||
if (dfsnum < n_basic_blocks)
|
||
abort ();
|
||
|
||
return dfsnum;
|
||
}
|
||
|
||
struct dfst_node
|
||
{
|
||
unsigned nnodes;
|
||
struct dfst_node **node;
|
||
struct dfst_node *up;
|
||
};
|
||
|
||
/* Compute a preorder transversal ordering such that a sub-tree which
|
||
is the source of a cross edge appears before the sub-tree which is
|
||
the destination of the cross edge. This allows for easy detection
|
||
of all the entry blocks for a loop.
|
||
|
||
The ordering is compute by:
|
||
|
||
1) Generating a depth first spanning tree.
|
||
|
||
2) Walking the resulting tree from right to left. */
|
||
|
||
void
|
||
flow_preorder_transversal_compute (pot_order)
|
||
int *pot_order;
|
||
{
|
||
edge e;
|
||
edge *stack;
|
||
int i;
|
||
int max_successors;
|
||
int sp;
|
||
sbitmap visited;
|
||
struct dfst_node *node;
|
||
struct dfst_node *dfst;
|
||
|
||
/* Allocate stack for back-tracking up CFG. */
|
||
stack = (edge *) xmalloc ((n_basic_blocks + 1) * sizeof (edge));
|
||
sp = 0;
|
||
|
||
/* Allocate the tree. */
|
||
dfst = (struct dfst_node *) xcalloc (n_basic_blocks,
|
||
sizeof (struct dfst_node));
|
||
|
||
for (i = 0; i < n_basic_blocks; i++)
|
||
{
|
||
max_successors = 0;
|
||
for (e = BASIC_BLOCK (i)->succ; e; e = e->succ_next)
|
||
max_successors++;
|
||
|
||
dfst[i].node
|
||
= (max_successors
|
||
? (struct dfst_node **) xcalloc (max_successors,
|
||
sizeof (struct dfst_node *))
|
||
: NULL);
|
||
}
|
||
|
||
/* Allocate bitmap to track nodes that have been visited. */
|
||
visited = sbitmap_alloc (n_basic_blocks);
|
||
|
||
/* None of the nodes in the CFG have been visited yet. */
|
||
sbitmap_zero (visited);
|
||
|
||
/* Push the first edge on to the stack. */
|
||
stack[sp++] = ENTRY_BLOCK_PTR->succ;
|
||
|
||
while (sp)
|
||
{
|
||
basic_block src;
|
||
basic_block dest;
|
||
|
||
/* Look at the edge on the top of the stack. */
|
||
e = stack[sp - 1];
|
||
src = e->src;
|
||
dest = e->dest;
|
||
|
||
/* Check if the edge destination has been visited yet. */
|
||
if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
|
||
{
|
||
/* Mark that we have visited the destination. */
|
||
SET_BIT (visited, dest->index);
|
||
|
||
/* Add the destination to the preorder tree. */
|
||
if (src != ENTRY_BLOCK_PTR)
|
||
{
|
||
dfst[src->index].node[dfst[src->index].nnodes++]
|
||
= &dfst[dest->index];
|
||
dfst[dest->index].up = &dfst[src->index];
|
||
}
|
||
|
||
if (dest->succ)
|
||
/* Since the DEST node has been visited for the first
|
||
time, check its successors. */
|
||
stack[sp++] = dest->succ;
|
||
}
|
||
|
||
else if (e->succ_next)
|
||
stack[sp - 1] = e->succ_next;
|
||
else
|
||
sp--;
|
||
}
|
||
|
||
free (stack);
|
||
sbitmap_free (visited);
|
||
|
||
/* Record the preorder transversal order by
|
||
walking the tree from right to left. */
|
||
|
||
i = 0;
|
||
node = &dfst[0];
|
||
pot_order[i++] = 0;
|
||
|
||
while (node)
|
||
{
|
||
if (node->nnodes)
|
||
{
|
||
node = node->node[--node->nnodes];
|
||
pot_order[i++] = node - dfst;
|
||
}
|
||
else
|
||
node = node->up;
|
||
}
|
||
|
||
/* Free the tree. */
|
||
|
||
for (i = 0; i < n_basic_blocks; i++)
|
||
if (dfst[i].node)
|
||
free (dfst[i].node);
|
||
|
||
free (dfst);
|
||
}
|
||
|
||
/* Compute the depth first search order on the _reverse_ graph and
|
||
store in the array DFS_ORDER, marking the nodes visited in VISITED.
|
||
Returns the number of nodes visited.
|
||
|
||
The computation is split into three pieces:
|
||
|
||
flow_dfs_compute_reverse_init () creates the necessary data
|
||
structures.
|
||
|
||
flow_dfs_compute_reverse_add_bb () adds a basic block to the data
|
||
structures. The block will start the search.
|
||
|
||
flow_dfs_compute_reverse_execute () continues (or starts) the
|
||
search using the block on the top of the stack, stopping when the
|
||
stack is empty.
|
||
|
||
flow_dfs_compute_reverse_finish () destroys the necessary data
|
||
structures.
|
||
|
||
Thus, the user will probably call ..._init(), call ..._add_bb() to
|
||
add a beginning basic block to the stack, call ..._execute(),
|
||
possibly add another bb to the stack and again call ..._execute(),
|
||
..., and finally call _finish(). */
|
||
|
||
/* Initialize the data structures used for depth-first search on the
|
||
reverse graph. If INITIALIZE_STACK is nonzero, the exit block is
|
||
added to the basic block stack. DATA is the current depth-first
|
||
search context. If INITIALIZE_STACK is non-zero, there is an
|
||
element on the stack. */
|
||
|
||
static void
|
||
flow_dfs_compute_reverse_init (data)
|
||
depth_first_search_ds data;
|
||
{
|
||
/* Allocate stack for back-tracking up CFG. */
|
||
data->stack = (basic_block *) xmalloc ((n_basic_blocks - (INVALID_BLOCK + 1))
|
||
* sizeof (basic_block));
|
||
data->sp = 0;
|
||
|
||
/* Allocate bitmap to track nodes that have been visited. */
|
||
data->visited_blocks = sbitmap_alloc (n_basic_blocks - (INVALID_BLOCK + 1));
|
||
|
||
/* None of the nodes in the CFG have been visited yet. */
|
||
sbitmap_zero (data->visited_blocks);
|
||
|
||
return;
|
||
}
|
||
|
||
/* Add the specified basic block to the top of the dfs data
|
||
structures. When the search continues, it will start at the
|
||
block. */
|
||
|
||
static void
|
||
flow_dfs_compute_reverse_add_bb (data, bb)
|
||
depth_first_search_ds data;
|
||
basic_block bb;
|
||
{
|
||
data->stack[data->sp++] = bb;
|
||
SET_BIT (data->visited_blocks, bb->index - (INVALID_BLOCK + 1));
|
||
}
|
||
|
||
/* Continue the depth-first search through the reverse graph starting with the
|
||
block at the stack's top and ending when the stack is empty. Visited nodes
|
||
are marked. Returns an unvisited basic block, or NULL if there is none
|
||
available. */
|
||
|
||
static basic_block
|
||
flow_dfs_compute_reverse_execute (data)
|
||
depth_first_search_ds data;
|
||
{
|
||
basic_block bb;
|
||
edge e;
|
||
int i;
|
||
|
||
while (data->sp > 0)
|
||
{
|
||
bb = data->stack[--data->sp];
|
||
|
||
/* Perform depth-first search on adjacent vertices. */
|
||
for (e = bb->pred; e; e = e->pred_next)
|
||
if (!TEST_BIT (data->visited_blocks,
|
||
e->src->index - (INVALID_BLOCK + 1)))
|
||
flow_dfs_compute_reverse_add_bb (data, e->src);
|
||
}
|
||
|
||
/* Determine if there are unvisited basic blocks. */
|
||
for (i = n_basic_blocks - (INVALID_BLOCK + 1); --i >= 0; )
|
||
if (!TEST_BIT (data->visited_blocks, i))
|
||
return BASIC_BLOCK (i + (INVALID_BLOCK + 1));
|
||
|
||
return NULL;
|
||
}
|
||
|
||
/* Destroy the data structures needed for depth-first search on the
|
||
reverse graph. */
|
||
|
||
static void
|
||
flow_dfs_compute_reverse_finish (data)
|
||
depth_first_search_ds data;
|
||
{
|
||
free (data->stack);
|
||
sbitmap_free (data->visited_blocks);
|
||
}
|