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backport: re PR tree-optimization/81740 (wrong code at -O3 in both 32-bit and 64-bit modes on x86_64-linux-gnu)

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2019-09-04  Richard Biener  <rguenther@suse.de>

	Backport from mainline
	2019-03-26  Bin Cheng  <bin.cheng@linux.alibaba.com>

	PR tree-optimization/81740
	* tree-vect-data-refs.c (vect_analyze_data_ref_dependence):
	In case of outer loop vectorization, check for backward dependence
	at the inner loop if outer loop dependence is reversed.

	* gcc.dg/vect/pr81740-1.c: New testcase.
	* gcc.dg/vect/pr81740-2.c: Likewise.

From-SVN: r275372
This commit is contained in:
Richard Biener 2019-09-04 11:56:15 +00:00 committed by Richard Biener
parent f671f26a19
commit d586ffcdee
5 changed files with 77 additions and 1 deletions
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10
gcc/ChangeLog
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@ -1,3 +1,13 @@
2019-09-04 Richard Biener <rguenther@suse.de>
Backport from mainline
2019-03-26 Bin Cheng <bin.cheng@linux.alibaba.com>
PR tree-optimization/81740
* tree-vect-data-refs.c (vect_analyze_data_ref_dependence):
In case of outer loop vectorization, check for backward dependence
at the inner loop if outer loop dependence is reversed.
2019-09-04 Richard Biener <rguenther@suse.de>
Backport from mainline

9
gcc/testsuite/ChangeLog
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@ -1,3 +1,12 @@
2019-09-04 Richard Biener <rguenther@suse.de>
Backport from mainline
2019-03-26 Bin Cheng <bin.cheng@linux.alibaba.com>
PR tree-optimization/81740
* gcc.dg/vect/pr81740-1.c: New testcase.
* gcc.dg/vect/pr81740-2.c: Likewise.
2019-09-04 Richard Biener <rguenther@suse.de>
Backport from mainline

22
gcc/testsuite/gcc.dg/vect/pr81740-1.c Normal file
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@ -0,0 +1,22 @@
/* { dg-do run } */
/* { dg-require-effective-target vect_int } */
#include "tree-vect.h"
int a[8][10] = { [2][5] = 4 }, c;
int
main ()
{
short b;
int i, d;
check_vect ();
for (b = 4; b >= 0; b--)
for (c = 0; c <= 6; c++)
a[c + 1][b + 2] = a[c][b + 1];
for (i = 0; i < 8; i++)
for (d = 0; d < 10; d++)
if (a[i][d] != (i == 3 && d == 6) * 4)
__builtin_abort ();
return 0;
}

24
gcc/testsuite/gcc.dg/vect/pr81740-2.c Normal file
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@ -0,0 +1,24 @@
/* { dg-do run } */
/* { dg-require-effective-target vect_int } */
#include "tree-vect.h"
int a[8][10] = { [2][5] = 4 }, c;
int
main ()
{
short b;
int i, d;
check_vect ();
for (b = 4; b >= 0; b--)
for (c = 6; c >= 0; c--)
a[c + 1][b + 2] = a[c][b + 1];
for (i = 0; i < 8; i++)
for (d = 0; d < 10; d++)
if (a[i][d] != (i == 3 && d == 6) * 4)
__builtin_abort ();
return 0;
}
/* { dg-final { scan-tree-dump "OUTER LOOP VECTORIZED" "vect" } } */

13
gcc/tree-vect-data-refs.c
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@ -470,8 +470,19 @@ vect_analyze_data_ref_dependence (struct data_dependence_relation *ddr,
reversed (to make distance vector positive), and the actual
distance is negative. */
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
dump_printf_loc (MSG_NOTE, vect_location,
"dependence distance negative.\n");
/* When doing outer loop vectorization, we need to check if there is
a backward dependence at the inner loop level if the dependence
at the outer loop is reversed. See PR81740. */
if (nested_in_vect_loop_p (loop, DR_STMT (dra))
|| nested_in_vect_loop_p (loop, DR_STMT (drb)))
{
unsigned inner_depth = index_in_loop_nest (loop->inner->num,
DDR_LOOP_NEST (ddr));
if (dist_v[inner_depth] < 0)
return true;
}
/* Record a negative dependence distance to later limit the
amount of stmt copying / unrolling we can perform.
Only need to handle read-after-write dependence. */