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author | Richard Biener <rguenther@suse.de> | 2023-11-14 11:37:13 +0100 |
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committer | Richard Biener <rguenther@suse.de> | 2023-11-14 13:44:56 +0100 |
commit | 5ea2965b499f9e491e45db19fedbccfccb75076a (patch) | |
tree | 099d234a5276bc4530d1bdcdc5fc57aab5818926 /gcc | |
parent | b9fd8399ec027ce42fd35a070ce38de8d69521b2 (diff) | |
download | gcc-5ea2965b499f9e491e45db19fedbccfccb75076a.zip gcc-5ea2965b499f9e491e45db19fedbccfccb75076a.tar.gz gcc-5ea2965b499f9e491e45db19fedbccfccb75076a.tar.bz2 |
tree-optimization/112281 - loop distribution and zero dependence distances
We currently distribute
for (c = 2; c; c--)
for (e = 0; e < 2; e++) {
d[c] = b = d[c + 1];
d[c + 1].a = 0;
}
in a wrong way where the inner loop zero dependence distance should
make us preserve stmt execution order. We fail to do so since we
only look for a fully zero distance vector rather than looking at
the innermost loop distance. This is somewhat similar to PR87022
where we instead looked at the outermost loop distance and changed
this to what we do now. The following switches us to look at the
innermost loop distance.
PR tree-optimization/112281
* tree-loop-distribution.cc (pg_add_dependence_edges):
Preserve stmt order when the innermost loop has exact
overlap.
* gcc.dg/torture/pr112281.c: New testcase.
Diffstat (limited to 'gcc')
-rw-r--r-- | gcc/testsuite/gcc.dg/torture/pr112281.c | 19 | ||||
-rw-r--r-- | gcc/tree-loop-distribution.cc | 7 |
2 files changed, 23 insertions, 3 deletions
diff --git a/gcc/testsuite/gcc.dg/torture/pr112281.c b/gcc/testsuite/gcc.dg/torture/pr112281.c new file mode 100644 index 0000000..3f0a61a --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr112281.c @@ -0,0 +1,19 @@ +/* { 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/tree-loop-distribution.cc b/gcc/tree-loop-distribution.cc index 8abfa99..8e92af6 100644 --- a/gcc/tree-loop-distribution.cc +++ b/gcc/tree-loop-distribution.cc @@ -2163,9 +2163,10 @@ loop_distribution::pg_add_dependence_edges (struct graph *rdg, int dir, gcc.dg/tree-ssa/pr94969.c. */ if (DDR_NUM_DIST_VECTS (ddr) != 1) this_dir = 2; - /* If the overlap is exact preserve stmt order. */ - else if (lambda_vector_zerop (DDR_DIST_VECT (ddr, 0), - DDR_NB_LOOPS (ddr))) + /* If the dependence distance is zero in the innermost + loop preserve stmt order. */ + else if (DDR_DIST_VECT (ddr, 0) + [DDR_LOOP_NEST (ddr).length () - 1] == 0) ; /* Else as the distance vector is lexicographic positive swap the dependence direction. */ |