This becomes possible as long as we do
val = s_and_b32/64 exec, val
before any subgroup operations.
This precautional instruction can be removed by the
optimizer if 'val' was computed by a VOPC instruction
using the same exec mask.
Totals from 59 (0.04% of 146267) affected shaders (Navi10):
VGPRs: 2808 -> 2816 (+0.28%)
CodeSize: 340888 -> 340852 (-0.01%); split: -0.20%, +0.19%
Instrs: 61733 -> 61625 (-0.17%); split: -0.18%, +0.01%
Cycles: 470636 -> 469112 (-0.32%); split: -0.33%, +0.01%
VMEM: 8091 -> 7993 (-1.21%)
SMEM: 2736 -> 2719 (-0.62%); split: +0.29%, -0.91%
VClause: 1745 -> 1741 (-0.23%)
SClause: 2394 -> 2392 (-0.08%); split: -0.25%, +0.17%
Copies: 3249 -> 3253 (+0.12%); split: -0.62%, +0.74%
Branches: 1210 -> 1206 (-0.33%)
PreSGPRs: 3126 -> 3176 (+1.60%); split: -0.16%, +1.76%
Reviewed-by: Tony Wasserka <tony.wasserka@gmx.de>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9195>
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