https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120799
Bug ID: 120799
Summary: Incorrect UBSan alignment requirements for
_mm_storeh_pd() and _mm_storel_pd()
Product: gcc
Version: 15.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: justus2510 at proton dot me
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org
Target Milestone: ---
UBSan shows warnings for _mm_storeh_pd() and _mm_storel_pd() when using
unaligned pointers. However, as far as I know, that's perfectly legal, similar
to _mm_storel_epi64() and _mm_loadl_epi64():
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70118
The Intel manual does not mention any alignment requirements for these
instructions, and Clang UBSan doesn't seem to complain about it either.
GCC version: 15.1.1 20250425
gcc -fsanitize=undefined ubsan.c
#include <emmintrin.h>
int main()
{
unsigned char buf[128];
_mm_storel_pd((double *)(buf+1), _mm_set1_pd(3.14));
}
/usr/lib/gcc/x86_64-pc-linux-gnu/15.1.1/include/emmintrin.h:203:8: runtime
error: store to misaligned address 0x7ffc80e8b5a1 for type 'double', which
requires 8 byte alignment
