d55a69e769
fold_imm starts with this check:
let SrcRef::Imm32(mut u) = self.src_ref else {
return *self;
};
For -rZ we thus return early and the matching in is_fneg_zero does not
find it. This MR adds a match for SrcRef::Zero + SrcMod::FNeg.
This lets copy propagation fold this:
r3 = shfl.bfly r2 0x2 0x1c03
r3 = fswzadd.ftz r3 r2 [sub, sub, subr, subr]
r3 = fadd.ftz -rZ |r3|
r16 = shfl.bfly r2 0x1 0x1c03
r16 = fswzadd.ftz r16 r2 [sub, subr, sub, subr]
r16 = fadd.ftz -rZ |r16|
r3 = fadd.ftz r16 r3
into:
r3 = shfl.bfly r2 0x2 0x1c03
r3 = fswzadd.ftz r3 r2 [sub, sub, subr, subr]
r16 = shfl.bfly r2 0x1 0x1c03
r16 = fswzadd.ftz r16 r2 [sub, subr, sub, subr]
r3 = fadd.ftz |r16| |r3|
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/12480
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33107>