RISC-V EVL tail folding failure on SPEC CPU 2017 525.x264_r

[lukel97]

Split out from the discussion here: #122458 (comment)

On RISC-V with -march=rva22u64_v -O3 -flto -mllvm -force-tail-folding-style=data-with-evl -mllvm -prefer-predicate-over-epilogue=predicate-else-scalar-epilogue, the SPEC CPU 2017 525.x264_r benchmark fails in the train dataset, likely due to a miscompile.

It's been failing since at least 6ad0dcf, detected from this LNT run: https://lnt.lukelau.me/db_default/v4/nts/89

[llvmbot]

@llvm/issue-subscribers-backend-risc-v

Author: Luke Lau (lukel97)

Split out from the discussion here: https://github.com//pull/122458#issuecomment-2585713670

On RISC-V with -march=rva22u64_v -O3 -flto -mllvm -force-tail-folding-style=data-with-evl -mllvm -prefer-predicate-over-epilogue=predicate-else-scalar-epilogue, the SPEC CPU 2017 525.x264_r benchmark fails in the train dataset, likely due to a miscompile.

It's been failing since at least 6ad0dcf, detected from this LNT run: https://lnt.lukelau.me/db_default/v4/nts/89

[fhahn]

cc @Mel-Chen @LiqinWeng @alexey-bataev @ElvisWang123