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tree-optimization/115669 - fix SLP reduction association

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The following avoids associating a reduction path as that might
get STMT_VINFO_REDUC_IDX out-of-sync with the SLP operand order.
This is a latent issue with SLP reductions but now easily exposed
as we're doing single-lane SLP reductions.

When we achieved SLP only we can move and update this meta-data.

	PR tree-optimization/115669
	* tree-vect-slp.cc (vect_build_slp_tree_2): Do not reassociate
	chains that participate in a reduction.

	* gcc.dg/vect/pr115669.c: New testcase.

(cherry picked from commit 7886830bb45c4f5dca0496d4deae9a45204d78f5)
This commit is contained in:
Richard Biener 2024-06-27 11:26:08 +02:00 • committed by Richard Biener
parent 078cdccc84
commit 03844a2a15
2 changed files with 25 additions and 0 deletions
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22
gcc/testsuite/gcc.dg/vect/pr115669.c Normal file
View file

@ -0,0 +1,22 @@
/* { dg-additional-options "-fwrapv" } */
#include "tree-vect.h"
int a = 10;
unsigned b;
long long c[100];
int foo()
{
long long *d = c;
for (short e = 0; e < a; e++)
b += ~(d ? d[e] : 0);
return b;
}
int main()
{
check_vect ();
if (foo () != -10)
abort ();
return 0;
}

3
gcc/tree-vect-slp.cc
View file

@ -2050,6 +2050,9 @@ vect_build_slp_tree_2 (vec_info *vinfo, slp_tree node,
else if (is_a <loop_vec_info> (vinfo)
/* ??? We don't handle !vect_internal_def defs below. */
&& STMT_VINFO_DEF_TYPE (stmt_info) == vect_internal_def
/* ??? Do not associate a reduction, this will wreck REDUC_IDX
mapping as long as that exists on the stmt_info level. */
&& STMT_VINFO_REDUC_IDX (stmt_info) == -1
&& is_gimple_assign (stmt_info->stmt)
&& (associative_tree_code (gimple_assign_rhs_code (stmt_info->stmt))
|| gimple_assign_rhs_code (stmt_info->stmt) == MINUS_EXPR)