https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114603
Bug ID: 114603
Summary: aarch64: Invalid SVE cnot optimisation
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: rsandifo at gcc dot gnu.org
Target Milestone: ---
Target: aarch64*-*-*
An overly lax condition on the cnot combine pattern means that we optimise:
#include <arm_sve.h>
svint32_t foo(svbool_t pg, svint32_t y)
{
return svsel(svcmpeq(pg, y, 0), svdup_s32(1), svdup_s32(0));
}
to a single cnot:
foo:
cnot z0.s, p0/m, z0.s
ret
The result must be 0 for inactive elements of pg, whereas the above would leave
the elements unchanged instead.
This seems to have been around since the SVE ACLE was first added.
