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store-merging: Fix up a -fcompare-debug bug in get_status_for_store_merging [PR104263]

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As mentioned in the PRthe following testcase fails, because the last
stmt of a bb with -g is a debug stmt and get_status_for_store_merging
uses gimple_seq_last_stmt (bb_seq (bb)) when testing if it is valid
for store merging.  The debug stmt isn't valid, while a stmt at that
position with -g0 is valid and so the divergence.

As we walk the whole bb already, this patch just remembers the last
non-debug stmt, so that we don't need to skip backwards debug stmts at the
end of the bb to find last real stmt.

2022-01-28  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/104263
	* gimple-ssa-store-merging.cc (get_status_for_store_merging): For
	cfun->can_throw_non_call_exceptions && cfun->eh test whether
	last non-debug stmt in the bb is store_valid_for_store_merging_p
	rather than last stmt.

	* gcc.dg/pr104263.c: New test.
This commit is contained in:
Jakub Jelinek 2022-01-28 19:02:26 +01:00
parent 90c31ff339
commit a591c71b41
2 changed files with 29 additions and 1 deletions
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5
gcc/gimple-ssa-store-merging.cc
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@ -5364,6 +5364,7 @@ get_status_for_store_merging (basic_block bb)
unsigned int num_constructors = 0;
gimple_stmt_iterator gsi;
edge e;
gimple *last_stmt = NULL;
for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
@ -5372,6 +5373,8 @@ get_status_for_store_merging (basic_block bb)
if (is_gimple_debug (stmt))
continue;
last_stmt = stmt;
if (store_valid_for_store_merging_p (stmt) && ++num_statements >= 2)
break;
@ -5398,7 +5401,7 @@ get_status_for_store_merging (basic_block bb)
return BB_INVALID;
if (cfun->can_throw_non_call_exceptions && cfun->eh
&& store_valid_for_store_merging_p (gimple_seq_last_stmt (bb_seq (bb)))
&& store_valid_for_store_merging_p (last_stmt)
&& (e = find_fallthru_edge (bb->succs))
&& e->dest == bb->next_bb)
return BB_EXTENDED_VALID;

25
gcc/testsuite/gcc.dg/pr104263.c Normal file
View File

@ -0,0 +1,25 @@
/* PR tree-optimization/104263 */
/* { dg-do compile } */
/* { dg-options "-O2 -fcompare-debug -fnon-call-exceptions -fno-inline-small-functions" } */
int n;
int
bar (void)
{
int a;
n = 0;
a = 0;
return n;
}
__attribute__ ((pure, returns_twice)) int
foo (void)
{
n = bar () + 1;
foo ();
return 0;
}