https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106324
Bug ID: 106324
Summary: ptrue not reused between vector instructions and
predicate instructions
Product: gcc
Version: 12.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: yyc1992 at gmail dot com
Target Milestone: ---
The following code has two use of `svptrue_b64()`s and none of the instructions
using them should be clearning it so only one `ptrue` instruction should be
needed.
```
svfloat64_t test(svbool_t pg, svfloat64_t a, svfloat64_t b)
{
auto d = svdiv_m(svptrue_b64(), a, b);
return svmul_m(svnot_z(svptrue_b64(), pg), d, d);
}
```
However, the code generated is,
```
ptrue p2.b, all
ptrue p1.d, all
fdiv z0.d, p2/m, z0.d, z1.d
not p0.b, p1/z, p0.b
fmul z0.d, p0/m, z0.d, z0.d
ret
```
which has an extra `ptrue`.
OTOH, clang generates,
```
ptrue p1.d
fdiv z0.d, p1/m, z0.d, z1.d
not p0.b, p1/z, p0.b
fmul z0.d, p0/m, z0.d, z0.d
ret
```
and the same `ptrue` is reused in both instructions.
This seems to be caused by gcc insisting on using `svptrue_b8` for the svnot
which does not seem necessary here especially since _b64 is explicitly
requested. Changing svptrue_b64 to svptrue_b8 in the code fixes the issue.
