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tree-optimization/97559 - fix sinking in irreducible regions

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This fixes sinking of loads when irreducible regions are involved
and the heuristics to find stores on the path along the sink
breaks down since that uses dominator queries.

2020-12-08  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/97559
	* tree-ssa-sink.c (statement_sink_location): Never ignore
	PHIs on sink paths in irreducible regions.

	* gcc.dg/torture/pr97559-1.c: New testcase.
	* gcc.dg/torture/pr97559-2.c: Likewise.
This commit is contained in:
Richard Biener 2020-12-08 09:45:57 +01:00
parent 3a6e3ad38a
commit a294e6368f
3 changed files with 48 additions and 5 deletions
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21
gcc/testsuite/gcc.dg/torture/pr97559-1.c Normal file
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@ -0,0 +1,21 @@
/* { dg-do compile } */
int printf (char *, ...);
int a, b, c, d;
void e () {
int f = a;
if (b) {
L1:
b = 0;
L2:
if (c) {
if (f)
printf("0");
goto L1;
}
}
if (d)
goto L2;
}

18
gcc/testsuite/gcc.dg/torture/pr97559-2.c Normal file
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@ -0,0 +1,18 @@
/* { dg-do compile } */
int a, b, c, d;
void e() {
int f = b;
if (a) {
L1:
a = 0;
L2:
if (a) {
c = b;
goto L1;
}
}
if (d)
goto L2;
}

14
gcc/tree-ssa-sink.c
View File

@ -390,12 +390,15 @@ statement_sink_location (gimple *stmt, basic_block frombb,
with the use. */
if (gimple_code (use_stmt) == GIMPLE_PHI)
{
/* In case the PHI node post-dominates the current insert location
we can disregard it. But make sure it is not dominating
it as well as can happen in a CFG cycle. */
/* In case the PHI node post-dominates the current insert
location we can disregard it. But make sure it is not
dominating it as well as can happen in a CFG cycle. */
if (commondom != bb
&& !dominated_by_p (CDI_DOMINATORS, commondom, bb)
&& dominated_by_p (CDI_POST_DOMINATORS, commondom, bb))
&& dominated_by_p (CDI_POST_DOMINATORS, commondom, bb)
/* If the blocks are possibly within the same irreducible
cycle the above check breaks down. */
&& !(bb->flags & commondom->flags & BB_IRREDUCIBLE_LOOP))
continue;
bb = EDGE_PRED (bb, PHI_ARG_INDEX_FROM_USE (use_p))->src;
}
@ -407,7 +410,8 @@ statement_sink_location (gimple *stmt, basic_block frombb,
continue;
/* There is no easy way to disregard defs not on the path from
frombb to commondom so just consider them all. */
commondom = nearest_common_dominator (CDI_DOMINATORS, bb, commondom);
commondom = nearest_common_dominator (CDI_DOMINATORS,
bb, commondom);
if (commondom == frombb)
return false;
}