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[SLP][VECT] Add check to fix 96837

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The following patch adds a simple check to prevent slp stmts from
vector constructors being rearranged. vect_attempt_slp_rearrange_stmts
tries to rearrange to avoid a load permutation.

This fixes PR target/96837
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96827

gcc/ChangeLog:

2020-09-29  Joel Hutton  <joel.hutton@arm.com>

	PR target/96837
	* tree-vect-slp.c (vect_analyze_slp): Do not call
	vect_attempt_slp_rearrange_stmts for vector constructors.

gcc/testsuite/ChangeLog:

2020-09-29  Joel Hutton  <joel.hutton@arm.com>

	PR target/96837
	* gcc.dg/vect/bb-slp-49.c: New test.
This commit is contained in:
Joel Hutton 2020-09-30 15:08:13 +01:00
parent aa248b8db9
commit 97b798d80b
2 changed files with 30 additions and 1 deletions
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28
gcc/testsuite/gcc.dg/vect/bb-slp-49.c Normal file
View file

@ -0,0 +1,28 @@
/* This checks that vectorized constructors have the correct ordering. */
/* { dg-require-effective-target vect_int } */
typedef int V __attribute__((__vector_size__(16)));
__attribute__((__noipa__)) void
foo (unsigned int x, V *y)
{
unsigned int a[4] = { x + 0, x + 2, x + 4, x + 6 };
for (unsigned int i = 0; i < 3; ++i)
if (a[i] == 1234)
a[i]--;
*y = (V) { a[3], a[2], a[1], a[0] };
}
int
main ()
{
V b;
foo (0, &b);
if (b[0] != 6 || b[1] != 4 || b[2] != 2 || b[3] != 0)
__builtin_abort ();
return 0;
}
/* See that we vectorize an SLP instance. */
/* { dg-final { scan-tree-dump "Analyzing vectorizable constructor" "slp1" } } */
/* { dg-final { scan-tree-dump "vectorizing stmts using SLP" "slp1" } } */

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

@ -2503,7 +2503,8 @@ vect_optimize_slp (vec_info *vinfo)
/* Reduction (there are no data-refs in the root).
In reduction chain the order of the loads is not important. */
if (!STMT_VINFO_DATA_REF (stmt_info)
&& !REDUC_GROUP_FIRST_ELEMENT (stmt_info))
&& !REDUC_GROUP_FIRST_ELEMENT (stmt_info)
&& !SLP_INSTANCE_ROOT_STMT (instance))
vect_attempt_slp_rearrange_stmts (instance);
}