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tree-vect-patterns: Don't create over widening patterns for stmts used in reductions [PR98848]

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As discussed in the PR, the reduction code isn't able to cope with type
promotions/demotions in the reduction computation, so if we recognize an
over-widening pattern that has vect_reduction_def type, we most likely make
it non-vectorizable.

2021-02-02  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/98848
	* tree-vect-patterns.c (vect_recog_over_widening_pattern): Punt if
	STMT_VINFO_DEF_TYPE (last_stmt_info) is vect_reduction_def.

	* gcc.dg/vect/pr98848.c: New test.
	* gcc.dg/vect/pr92205.c: Remove xfail.
This commit is contained in:
Jakub Jelinek 2021-02-02 10:32:23 +01:00
parent eedda4e160
commit 1592b74350
3 changed files with 23 additions and 1 deletions
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2
gcc/testsuite/gcc.dg/vect/pr92205.c
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@ -10,4 +10,4 @@ int b(int n, unsigned char *a)
return d;
}
/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" { xfail *-*-* } } } */
/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" { target { vect_unpack && { ! vect_no_bitwise } } } } } */

18
gcc/testsuite/gcc.dg/vect/pr98848.c Normal file
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@ -0,0 +1,18 @@
/* PR tree-optimization/98848 */
/* { dg-do compile } */
/* { dg-require-effective-target vect_int } */
short a[9000];
int
foo (void)
{
int b = a[0];
int i;
for (i = 1; i < 9000; i ++)
if (a[i] < b)
b = a[i];
return b;
}
/* { dg-final { scan-tree-dump-times "vectorized 1 loop" 1 "vect" { xfail { vect_no_int_add || vect_no_int_min_max } } } } */

4
gcc/tree-vect-patterns.c
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@ -1579,6 +1579,10 @@ vect_recog_over_widening_pattern (vec_info *vinfo,
tree type = TREE_TYPE (lhs);
tree_code code = gimple_assign_rhs_code (last_stmt);
/* Punt for reductions where we don't handle the type conversions. */
if (STMT_VINFO_DEF_TYPE (last_stmt_info) == vect_reduction_def)
return NULL;
/* Keep the first operand of a COND_EXPR as-is: only the other two
operands are interesting. */
unsigned int first_op = (code == COND_EXPR ? 2 : 1);