llvm-project

3611c0b7 - [AMDGPU] SIWholeQuadMode: avoid execz effects in exact regions (#101157)

[AMDGPU] SIWholeQuadMode: avoid execz effects in exact regions (#101157) Exact mode regions within WQM may have EXEC=0 in divergent control flow. This occurs if a branch is only taken by helper lanes and an instruction requiring WQM disabling is encountered. The current code extends the exact region as far as possible; however, this can result in it including instructions with unwanted side effects at EXEC=0. In particular readfirstlane combined with scalar loads can produce invalid memory accesses in this circumstance. Workaround this by shrinking exact regions to only the instructions requiring WQM disabling when unwanted side effects are present. Eventually we should branch over these regions when EXEC=0, but this requires visibility of CFG/divergence information not currently available.