ac/nir/nggc: Don't reuse uniform values from divergent control flow.
With NGG culling, the shaders are split into two parts:
the top part that computes just the position output,
and the bottom part which produces the other outputs.
To reduce redundancy between the two, I added some code
to reuse uniform variables between them. However, there is
an edge case I didn't think about: because of vertex repacking,
it is possible for the bottom part to process a different vertex.
Therefore it can take a different divergent code path
(though it must still take the same uniform code path).
Due to this, when a uniform value comes from divergent control
flow, this may be undefined in the bottom part.
This commit stops reusing uniform variables from
divergent control flow, to fix issues that arise from this.
Fossil DB stats on Sienna Cichlid with NGGC on:
Totals from 1723 (1.34% of 128647) affected shaders:
VGPRs: 89312 -> 89184 (-0.14%); split: -0.15%, +0.01%
SpillSGPRs: 4575 -> 120 (-97.38%)
CodeSize: 10846424 -> 10873836 (+0.25%); split: -0.68%, +0.93%
MaxWaves: 34582 -> 34602 (+0.06%); split: +0.06%, -0.01%
Instrs: 2124471 -> 2128835 (+0.21%); split: -0.51%, +0.72%
Latency: 7274569 -> 7293899 (+0.27%); split: -0.22%, +0.48%
InvThroughput: 1637130 -> 1635490 (-0.10%); split: -0.17%, +0.07%
VClause: 25141 -> 25414 (+1.09%); split: -0.02%, +1.10%
SClause: 56367 -> 59503 (+5.56%); split: -1.36%, +6.93%
Copies: 230704 -> 219313 (-4.94%); split: -5.49%, +0.55%
Branches: 72781 -> 72681 (-0.14%); split: -0.21%, +0.07%
PreSGPRs: 118766 -> 100176 (-15.65%); split: -15.70%, +0.05%
PreVGPRs: 76876 -> 76833 (-0.06%)
Fixes: 0bb543bb60f93bea5b1c0ed6382ced49e659273e
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13001>
1 file changed
