[Mesa-dev] [PATCH 0/7] GLSL: Lowering small conditional branches

[Marek Olšák]

Hi,

this series enables lowering small branches for radeonsi, but other
drivers can enable it too. The GLSL compiler computes a cost per
branch and then either lowers the branch if the cost is low enough,
or keeps it.

It will take some time before LLVM learns to do this too and that
seems to be more involved, and we need a solution for Mesa now.

There are 4 piglit regressions, which could be an uncovered radeonsi
bug. Softpipe is unaffected. We might hold off pushing the last patch
depending on how serious the regressions are.

The reason why this is so important to us is that it reduces VGPR
spilling:
    Spilled VGPRs: 368 -> 96 (-73.91 %)
    Scratch VGPRs: 1344 -> 1060 (-21.13 %) dwords per thread

Please review.

Marek