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| author | Richard Biener <rguenther@suse.de> | 2021-05-10 11:37:27 +0200 |
|---|---|---|
| committer | Richard Biener <rguenther@suse.de> | 2021-05-10 13:05:58 +0200 |
| commit | 60af2db18013a0339302928ba98fee893ccc1957 (patch) | |
| tree | 88a9e0c0e46e838e441917a516385ce5a032ff33 | |
| parent | cc1d563887b1fe3183a21572b2ea63466b2bfa3a (diff) | |
| download | gcc-60af2db18013a0339302928ba98fee893ccc1957.zip gcc-60af2db18013a0339302928ba98fee893ccc1957.tar.gz gcc-60af2db18013a0339302928ba98fee893ccc1957.tar.bz2 | |
tree-optimization/100492 - avoid irreducible regions in loop distribution
When we distribute away a condition we rely on the ability to
change it to either 1 != 0 or 0 != 0 depending on the direction
of the exit branch in the respective loop. But when the loop
contains an irreducible sub-region then for the conditions inside
this this fails and can lead to infinite loops being generated.
Avoid distibuting loops with irreducible sub-regions.
2021-05-10 Richard Biener <rguenther@suse.de>
PR tree-optimization/100492
* tree-loop-distribution.c (find_seed_stmts_for_distribution):
Find nothing when the loop contains an irreducible region.
* gcc.dg/torture/pr100492.c: New testcase.
| -rw-r--r-- | gcc/testsuite/gcc.dg/torture/pr100492.c | 26 | ||||
| -rw-r--r-- | gcc/tree-loop-distribution.c | 10 |
2 files changed, 36 insertions, 0 deletions
diff --git a/gcc/testsuite/gcc.dg/torture/pr100492.c b/gcc/testsuite/gcc.dg/torture/pr100492.c new file mode 100644 index 0000000..75229c8 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr100492.c @@ -0,0 +1,26 @@ +/* { dg-do run } */ +/* { dg-additional-options "-ftree-loop-distribution" } */ + +extern void abort (void); + +signed char a, c; +int b, d, *e = &d, g; +signed static char f; +int main() { + int h = 0; + int a_ = a; + for (; a_ < 1; a = ++a_) { + int *i[5], **j = &i[4], ***k[3][2] = {{&j}}, ****l = &k[2][1], *****m = &l; + char *n = &c; + f = *e = g = 0; + for (; g < 2; g++) { + for (b = 0; b < 3; b++) + h = (h && (*n = 0)) == 0; + if (g) + break; + } + } + if (f != 0) + abort (); + return 0; +} diff --git a/gcc/tree-loop-distribution.c b/gcc/tree-loop-distribution.c index 8b91a30..65aa1df 100644 --- a/gcc/tree-loop-distribution.c +++ b/gcc/tree-loop-distribution.c @@ -3203,6 +3203,16 @@ find_seed_stmts_for_distribution (class loop *loop, vec<gimple *> *work_list) /* Initialize the worklist with stmts we seed the partitions with. */ for (unsigned i = 0; i < loop->num_nodes; ++i) { + /* In irreducible sub-regions we don't know how to redirect + conditions, so fail. See PR100492. */ + if (bbs[i]->flags & BB_IRREDUCIBLE_LOOP) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "loop %d contains an irreducible region.\n", + loop->num); + work_list->truncate (0); + break; + } for (gphi_iterator gsi = gsi_start_phis (bbs[i]); !gsi_end_p (gsi); gsi_next (&gsi)) { |