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tree-optimization/117510 - fix guard hoisting validity check

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For the loop in the testcase we currently fail to hoist the guard
check of the inner loop (m > 0) out of the outer loop because
find_loop_guard checks all blocks of the outer loop for side-effects,
including those that are skipped by the guard.  This usually
is harmless as the guard does not skip any blocks in the outer loop
but in this case store-motion was applied to the inner loop and thus
there's now a skipped store in the outer loop.

The following properly skips blocks that are dominated by the
entry to the skipped region.

	PR tree-optimization/117510
	* tree-ssa-loop-unswitch.cc (find_loop_guard): Only check
	not skipped blocks for side-effects.

	* gcc.dg/vect/vect-outer-pr117510.c: New testcase.
This commit is contained in:
Richard Biener 2024-11-11 09:40:20 +01:00 committed by Richard Biener
parent 95960cd473
commit da64698159
2 changed files with 18 additions and 1 deletions
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13
gcc/testsuite/gcc.dg/vect/vect-outer-pr117510.c Normal file
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@ -0,0 +1,13 @@
/* { dg-do compile } */
/* { dg-require-effective-target vect_double } */
/* { dg-additional-options "-O3" } */
void f(int n, int m, double *a)
{
a = __builtin_assume_aligned (a, __BIGGEST_ALIGNMENT__);
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++)
a[i] += 2*a[i] + j;
}
/* { dg-final { scan-tree-dump "OUTER LOOP VECTORIZED" "vect" } } */

6
gcc/tree-ssa-loop-unswitch.cc
View File

@ -1256,7 +1256,11 @@ find_loop_guard (class loop *loop, vec<gimple *> &dbg_to_reset)
guard_edge = NULL;
goto end;
}
if (!empty_bb_without_guard_p (loop, bb, dbg_to_reset))
/* If any of the not skipped blocks has side-effects or defs with
uses outside of the loop we cannot hoist the guard. */
if (!dominated_by_p (CDI_DOMINATORS,
bb, guard_edge == te ? fe->dest : te->dest)
&& !empty_bb_without_guard_p (loop, bb, dbg_to_reset))
{
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, loc,