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tree-optimization/105618 - restore load sinking 

The PR97330 fix caused some missed sinking of loads out of loops
the following patch re-instantiates.

2022-05-17  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/105618
	* tree-ssa-sink.cc (statement_sink_location): For virtual
	PHI uses ignore those defining the used virtual operand.

	* gcc.dg/tree-ssa/ssa-sink-19.c: New testcase.

(cherry picked from commit ebce0e9bd8)
This commit is contained in:
Richard Biener 2022-05-17 09:45:02 +02:00
parent 25d7a73810
commit 374cee99d0
2 changed files with 24 additions and 0 deletions
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21
gcc/testsuite/gcc.dg/tree-ssa/ssa-sink-19.c Normal file
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@ -0,0 +1,21 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-sink1-details -fdump-tree-cddce2-details" } */
static int b=4;
int c;
int
main()
{
int e[5] = {1,1,1,1,1};
for (; b >= 0; b--) {
c = e[b];
}
return 0;
}
/* We should sink e[b] out of the loop which is possible after
applying store motion to c and b. */
/* { dg-final { scan-tree-dump "Sinking # VUSE" "sink1" } } */
/* And remove the loop after final value replacement. */
/* { dg-final { scan-tree-dump "fix_loop_structure: removing loop" "cddce2" } } */

3
gcc/tree-ssa-sink.cc
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@ -390,6 +390,9 @@ statement_sink_location (gimple *stmt, basic_block frombb,
with the use. */
if (gimple_code (use_stmt) == GIMPLE_PHI)
{
/* If the PHI defines the virtual operand, ignore it. */
if (gimple_phi_result (use_stmt) == gimple_vuse (stmt))
continue;
/* 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. */