https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94300
Bug ID: 94300
Summary: [10 Regression] memcpy vector load miscompiled during
const-prop
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: kretz at kde dot org
Target Milestone: ---
Target: x86_64-*-*, i?86-*-*
Test case `-O1 -march=skylake-avx512`:
int main()
{
double mem[16];
using V [[gnu::vector_size(64)]] = double;
const V a{0, 1, 2, 3, 4, 5, 6, 7};
const V b{8, 9, 10, 11, 12, 13, 14, 15};
__builtin_memcpy(mem, &a, 64);
__builtin_memcpy(mem + 8, &b, 64);
V c = {};
__builtin_memcpy(&c, mem + 4, 64);
if (c[5] != double(9))
__builtin_abort();
}
>From my extended test case, where c would be {4, 5, 6, 7, 8, 15, 9, 10}. If GCC
is made to forget the contents of mem (e.g. inline-asm), the test does not
fail. GCC9 does not do constant evaluation of the code above and therefore
doesn't fail.
