https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117804
--- Comment #1 from Robin Dapp <rdapp at gcc dot gnu.org> ---
The problem is that at combine-time we don't know the range of cA, cB etc
anymore so we can't just combine those to the two-operand widening pattern.
I have a local patch that introduces a widening FMA operation at gimple-level
(we wanted to do this anyway for more of our widening ops). Once this is in
place, I just used a match.pd pattern that can access range information in
order to combine a single operand widening .FMA and the other operand with
range information into a WIDEN_FMA.
This is how it looks like locally:
.L5:
vsetvli a5,a2,e8,mf2,ta,ma
vle8.v v4,0(t4)
vle8.v v3,0(t3)
vmv1r.v v1,v2
vwmaccu.vv v1,v4,v8
vle8.v v4,0(t5)
vwmaccu.vv v1,v3,v7
vle8.v v3,0(t1)
vwmaccu.vv v1,v4,v6
vwmaccu.vv v1,v3,v5
vnsrl.wi v1,v1,6
vse8.v v1,0(a4)
