Timothy Arceri
839818332c
This helps us avoid moving the movs outside if branches when there
src can't be scalarized.
For example it avoids:
vec4 32 ssa_7 = tex ssa_6 (coord), 0 (texture), 0 (sampler),
if ... {
r0 = imov ssa_7.z
r1 = imov ssa_7.y
r2 = imov ssa_7.x
r3 = imov ssa_7.w
...
} else {
...
if ... {
r0 = imov ssa_7.x
r1 = imov ssa_7.w
...
else {
r0 = imov ssa_7.z
r1 = imov ssa_7.y
...
}
r2 = imov ssa_7.x
r3 = imov ssa_7.w
}
...
vec4 32 ssa_36 = vec4 r0, r1, r2, r3
Becoming something like:
vec4 32 ssa_7 = tex ssa_6 (coord), 0 (texture), 0 (sampler),
r0 = imov ssa_7.z
r1 = imov ssa_7.y
r2 = imov ssa_7.x
r3 = imov ssa_7.w
if ... {
...
} else {
if ... {
r0 = imov r2
r1 = imov r3
...
else {
...
}
...
}
While this is has a smaller instruction count it requires more work
for the same result. With more complex examples we can also end up
shuffling the registers around in a way that requires more registers
to use as temps so that we don't overwrite our original values along
the way.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4636>
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