https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91482
Bug ID: 91482
Summary: __builtin_assume_aligned should not break write
combining
Product: gcc
Version: 9.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: msharov at users dot sourceforge.net
Target Milestone: ---
void write64 (void* p)
{
unsigned* p1 = (unsigned*) __builtin_assume_aligned (p, 8);
*p1++ = 0;
unsigned* p2 = (unsigned*) __builtin_assume_aligned (p1, 4);
*p2++ = 1;
}
When the two stores are written without __builtin_assume_aligned, they are
coalesced into a single movq store. The code above, however, results in two
movl stores, even though the new information provided by
__builtin_assume_aligned does not prevent combination.
