[all-commits] [llvm/llvm-project] 35bf92: [RISCV] Delete dead COPYs to vmv0 during vmv0 elim...

[Luke Lau via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 35bf925f7ea95e71208a839cf4b02de2ee473f75
      https://github.com/llvm/llvm-project/commit/35bf925f7ea95e71208a839cf4b02de2ee473f75
  Author: Luke Lau <luke at igalia.com>
  Date:   2025-02-26 (Wed, 26 Feb 2025)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVVMV0Elimination.cpp
    M llvm/test/CodeGen/RISCV/rvv/expandload.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-ceil-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-cttz-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-floor-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-int.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-round-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-roundeven-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-roundtozero-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-trunc-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fmaximum-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fminimum-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/fshr-fshl-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/nearbyint-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/setcc-fp-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vector-deinterleave.ll
    M llvm/test/CodeGen/RISCV/rvv/vfadd-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfdiv-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfma-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfmax-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfmin-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfmul-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfptosi-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfptoui-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfptrunc-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vfsub-vp.ll
    A llvm/test/CodeGen/RISCV/rvv/vmv0-elimination.mir
    M llvm/test/CodeGen/RISCV/rvv/vsitofp-vp.ll
    M llvm/test/CodeGen/RISCV/rvv/vuitofp-vp.ll

  Log Message:
  -----------
  [RISCV] Delete dead COPYs to vmv0 during vmv0 elimination

This fixes a crash reported at
https://github.com/llvm/llvm-project/pull/126850#issuecomment-2685166388,
where we may leave around a COPY to vmv0 after peeking through it.
Even though the COPY is dead, there's no pass between vmv0 elimination
and regalloc that will delete it so regalloc will try to allocate
something for it.

The test showcasing this is added in vmv0-elimination.mir. Removing
the dead COPY results in changes in spills in the >= LMUL 16 VP tests,
but it's worth noting that these tests are very noisy and not
representative of real world code.



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