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tree-ssa-dce.c (cfg_altered): New global.

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* tree-ssa-dce.c (cfg_altered): New global.
        (tree_dce_init): Initialize cfg_altered.
        (remove_dead_stmt): If we remove an edge in the CFG, then set
        CFG_ALTERED.
        (perform_tree_ssa_dce): If we altered the CFG, then invalidate
        the dominators.

        * gcc.c-torture/compile/pr21356.c: New test.

From-SVN: r101652
This commit is contained in:
Jeff Law 2005-07-05 23:25:57 -06:00 committed by Jeff Law
parent 1538fc3c3e
commit 9da4058c14
4 changed files with 49 additions and 1 deletions
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9
gcc/ChangeLog
View File

@ -1,3 +1,12 @@
2005-07-06 Jeff Law <law@redhat.com>
* tree-ssa-dce.c (cfg_altered): New global.
(tree_dce_init): Initialize cfg_altered.
(remove_dead_stmt): If we remove an edge in the CFG, then set
CFG_ALTERED.
(perform_tree_ssa_dce): If we altered the CFG, then invalidate
the dominators.
2005-07-06 Kazu Hirata <kazu@codesourcery.com>
* Makefile.in (stamp-collect-ld): Use

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2005-07-06 Jeff Law <law@redhat.com>
* gcc.c-torture/compile/pr21356.c: New test.
2005-07-05 Joseph S. Myers <joseph@codesourcery.com>
PR c/22013

13
gcc/testsuite/gcc.c-torture/compile/pr21356.c Normal file
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@ -0,0 +1,13 @@
int a;
void* p;
void foo (void)
{
switch (a)
{
a0: case 0: p = &&a1;
a1: case 1: p = &&a2;
a2: default: p = &&a1;
}
goto *p;
}

24
gcc/tree-ssa-dce.c
View File

@ -96,6 +96,13 @@ static bitmap *control_dependence_map;
processed that it is control dependent on. */
static sbitmap visited_control_parents;
/* TRUE if this pass alters the CFG (by removing control statements).
FALSE otherwise.
If this pass alters the CFG, then it will arrange for the dominators
to be recomputed. */
static bool cfg_altered;
/* Execute CODE for each edge (given number EDGE_NUMBER within the CODE)
for which the block with index N is control dependent. */
#define EXECUTE_IF_CONTROL_DEPENDENT(N, EDGE_NUMBER, CODE) \
@ -774,7 +781,15 @@ remove_dead_stmt (block_stmt_iterator *i, basic_block bb)
/* Remove the remaining the outgoing edges. */
while (!single_succ_p (bb))
remove_edge (EDGE_SUCC (bb, 1));
{
/* FIXME. When we remove the edge, we modify the CFG, which
in turn modifies the dominator and post-dominator tree.
Is it safe to postpone recomputing the dominator and
post-dominator tree until the end of this pass given that
the post-dominators are used above? */
cfg_altered = true;
remove_edge (EDGE_SUCC (bb, 1));
}
}
FOR_EACH_SSA_DEF_OPERAND (def_p, t, iter, SSA_OP_VIRTUAL_DEFS)
@ -833,6 +848,7 @@ tree_dce_init (bool aggressive)
sbitmap_zero (processed);
worklist = VEC_alloc (tree, heap, 64);
cfg_altered = false;
}
/* Cleanup after this pass. */
@ -903,6 +919,12 @@ perform_tree_ssa_dce (bool aggressive)
if (aggressive)
free_dominance_info (CDI_POST_DOMINATORS);
/* If we removed paths in the CFG, then we need to update
dominators as well. I haven't investigated the possibility
of incrementally updating dominators. */
if (cfg_altered)
free_dominance_info (CDI_DOMINATORS);
/* Debugging dumps. */
if (dump_file)
print_stats ();