Looking at VOPD things, shifts are not very likely to get dual issued
but plain moves are. Looking at RDNA2 v_lshrrev_b64 are half the perf
of v_mov_b32 (but you need twice as many moves), so on GFX11 this likely
reaches the threshold where moves are faster.
Totals from 68400 (50.70% of 134906) affected shaders:
CodeSize: 275489516 -> 275459536 (-0.01%); split: -0.01%, +0.00%
Instrs: 51775474 -> 51991286 (+0.42%)
Latency: 589884847 -> 589066439 (-0.14%); split: -0.15%, +0.01%
InvThroughput: 127154986 -> 126037619 (-0.88%); split: -0.88%, +0.00%
Copies: 3756157 -> 3976193 (+5.86%)
Branches: 1259604 -> 1260072 (+0.04%)
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19633>
Bas Nieuwenhuizen
89663828ea