https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105198
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
So it's predictive commoning that triggers the miscompile, it works with
-fno-predictive-commoning. predcom does
--- a-t.c.167t.dce6 2022-04-08 10:59:28.824746581 +0200
+++ a-t.c.168t.pcom 2022-04-08 10:59:28.824746581 +0200
@@ -4,6 +4,7 @@
__attribute__((noipa, noinline, noclone, no_icf))
void next_set (int * x, int n, int k)
{
+ int D__lsm0.19;
vector(4) int * vectp.18;
vector(4) int * vectp.17;
vector(4) int vect_tmp_55.16;
@@ -117,6 +118,7 @@
[t.c:43:8] _13 = [t.c:43:8] *_12;
[t.c:43:11] _14 = _13 + 1;
[t.c:43:11] [t.c:43:8] *_12 = _14;
+ D__lsm0.19_72 = _14;
[t.c:40:17] if (j_49 > 0)
goto <bb 19>; [94.50%]
else
@@ -132,11 +134,12 @@
<bb 6> [local count: 1014686026]:
# j_73 = PHI <[t.c:42:8] j_49(19), [t.c:34:7] j_46(15)>
- # tmp_75 = PHI <[t.c:43:11] _14(19), [t.c:35:9] _8(15)>
+ # D__lsm0.19_77 = PHI <D__lsm0.19_72(19), _8(15)>
+ tmp_75 = D__lsm0.19_77;
[t.c:40:21] _16 = (long unsigned int) j_73;
[t.c:40:21] _17 = _16 * 4;
[t.c:40:21] _18 = x_47(D) + _17;
- [t.c:40:21] _19 = [t.c:40:21] *_18;
+ [t.c:40:21] _19 = D__lsm0.19_77;
[t.c:40:39] _21 = j_46 - j_73;
[t.c:40:30] _22 = n_41(D) - _21;
[t.c:40:17] if (_19 >= _22)
which at first doesn't look wrong, but when disabling PRE (which without
vectorization would do the same transform) the issue also shows up w/o
vectorization
-O2 -fno-tree-vectorize -fno-tree-pre -fpredictive-commoning
