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tree-optimization/104543 - fix unroll-and-jam precondition

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We have to make sure that outer loop exits come after the inner
loop since we otherwise will put it into the fused loop body.

2022-02-15  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/104543
	* gimple-loop-jam.cc (unroll_jam_possible_p): Check outer loop exits
	come after the inner loop.

	* gcc.dg/torture/pr104543.c: New testcase.
This commit is contained in:
Richard Biener 2022-02-15 12:27:14 +01:00
parent 3939c1b112
commit d03a67dc69
2 changed files with 29 additions and 2 deletions
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10
gcc/gimple-loop-jam.cc
View file

@ -198,7 +198,8 @@ unroll_jam_possible_p (class loop *outer, class loop *loop)
if (!empty_block_p (loop->latch))
return false;
if (!single_exit (loop))
edge exit;
if (!(exit = single_exit (loop)))
return false;
/* We need a perfect nest. Quick check for adjacent inner loops. */
@ -259,7 +260,12 @@ unroll_jam_possible_p (class loop *outer, class loop *loop)
n = get_loop_body_with_size (outer, bbs, n_basic_blocks_for_fn (cfun));
for (i = 0; i < n; i++)
if (bbs[i]->loop_father == outer && bb_prevents_fusion_p (bbs[i]))
if (bbs[i]->loop_father == outer
&& (bb_prevents_fusion_p (bbs[i])
/* Outer loop exits must come after the inner loop, otherwise
we'll put the outer loop exit into the fused inner loop. */
|| (loop_exits_from_bb_p (outer, bbs[i])
&& !dominated_by_p (CDI_DOMINATORS, bbs[i], exit->src))))
break;
free (bbs);
if (i != n)

21
gcc/testsuite/gcc.dg/torture/pr104543.c Normal file
View file

@ -0,0 +1,21 @@
/* { dg-do run } */
/* { dg-additional-options "-floop-unroll-and-jam" } */
int a[3], b, c;
static int e()
{
if (!c) {
for (b = 0; b < 3; b++)
for (c = 0; c < 3; c++)
a[c] ^= 1;
return -1;
}
return 0;
}
int main()
{
e();
if (a[1] != 1)
__builtin_abort();
return 0;
}