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* [gcc r14-5626] tree-optimization/112281 - loop distribution and zero dependence distances
@ 2023-11-20 14:01 Richard Biener
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From: Richard Biener @ 2023-11-20 14:01 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:3b34902417259031823bff7f853f615a60464bbd
commit r14-5626-g3b34902417259031823bff7f853f615a60464bbd
Author: Richard Biener <rguenther@suse.de>
Date: Mon Nov 20 13:39:52 2023 +0100
tree-optimization/112281 - loop distribution and zero dependence distances
The following fixes an omission in dependence testing for loop
distribution. When the overall dependence distance is not zero but
the dependence direction in the innermost common loop is = there is
a conflict between the partitions and we have to merge them.
PR tree-optimization/112281
* tree-loop-distribution.cc
(loop_distribution::pg_add_dependence_edges): For = in the
innermost common loop record a partition conflict.
* gcc.dg/torture/pr112281-1.c: New testcase.
* gcc.dg/torture/pr112281-2.c: Likewise.
Diff:
---
gcc/testsuite/gcc.dg/torture/pr112281-1.c | 18 ++++++++++++++++++
gcc/testsuite/gcc.dg/torture/pr112281-2.c | 18 ++++++++++++++++++
gcc/tree-loop-distribution.cc | 18 ++++++++++++++----
3 files changed, 50 insertions(+), 4 deletions(-)
diff --git a/gcc/testsuite/gcc.dg/torture/pr112281-1.c b/gcc/testsuite/gcc.dg/torture/pr112281-1.c
new file mode 100644
index 00000000000..711f5663195
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr112281-1.c
@@ -0,0 +1,18 @@
+/* { dg-do run } */
+/* { dg-additional-options "-ftree-loop-distribution" } */
+
+struct {
+ int : 8;
+ int a;
+} b, d[4] = {{0}, {0}, {0}, {5}};
+int c, e;
+int main() {
+ for (c = 2; c; c--)
+ for (e = 0; e < 2; e++) {
+ d[c] = b = d[c + 1];
+ d[c + 1].a = 0;
+ }
+ if (b.a != 0)
+ __builtin_abort();
+ return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/torture/pr112281-2.c b/gcc/testsuite/gcc.dg/torture/pr112281-2.c
new file mode 100644
index 00000000000..d7671e3322b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr112281-2.c
@@ -0,0 +1,18 @@
+/* { dg-do run } */
+/* { dg-additional-options "-ftree-loop-distribution" } */
+
+struct {
+ int : 8;
+ int a;
+} b, d[4] = {{5}, {0}, {0}, {0}};
+int c, e;
+int main() {
+ for (c = 0; c < 2; c++)
+ for (e = 0; e < 2; e++) {
+ d[c + 1] = b = d[c];
+ d[c].a = 0;
+ }
+ if (b.a != 0)
+ __builtin_abort();
+ return 0;
+}
diff --git a/gcc/tree-loop-distribution.cc b/gcc/tree-loop-distribution.cc
index ffca535064b..95c1eea65be 100644
--- a/gcc/tree-loop-distribution.cc
+++ b/gcc/tree-loop-distribution.cc
@@ -2155,9 +2155,6 @@ loop_distribution::pg_add_dependence_edges (struct graph *rdg, int dir,
}
else if (DDR_ARE_DEPENDENT (ddr) == NULL_TREE)
{
- if (DDR_REVERSED_P (ddr))
- this_dir = -this_dir;
-
/* Known dependences can still be unordered througout the
iteration space, see gcc.dg/tree-ssa/ldist-16.c and
gcc.dg/tree-ssa/pr94969.c. */
@@ -2170,7 +2167,20 @@ loop_distribution::pg_add_dependence_edges (struct graph *rdg, int dir,
/* Else as the distance vector is lexicographic positive swap
the dependence direction. */
else
- this_dir = -this_dir;
+ {
+ if (DDR_REVERSED_P (ddr))
+ this_dir = -this_dir;
+ this_dir = -this_dir;
+
+ /* When then dependence distance of the innermost common
+ loop of the DRs is zero we have a conflict. */
+ auto l1 = gimple_bb (DR_STMT (dr1))->loop_father;
+ auto l2 = gimple_bb (DR_STMT (dr2))->loop_father;
+ int idx = index_in_loop_nest (find_common_loop (l1, l2)->num,
+ DDR_LOOP_NEST (ddr));
+ if (DDR_DIST_VECT (ddr, 0)[idx] == 0)
+ this_dir = 2;
+ }
}
else
this_dir = 0;
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