[all-commits] [llvm/llvm-project] dd8712: [DAGCombiner] Eliminate fp casts if we have the ri...

[John Brawn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: dd87127f4e579d9c13480b40a79860d19a5891f1
      https://github.com/llvm/llvm-project/commit/dd87127f4e579d9c13480b40a79860d19a5891f1
  Author: John Brawn <john.brawn at arm.com>
  Date:   2025-04-28 (Mon, 28 Apr 2025)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    A llvm/test/CodeGen/AArch64/bf16_fast_math.ll
    M llvm/test/CodeGen/AArch64/f16-instructions.ll
    M llvm/test/CodeGen/AArch64/fmla.ll
    M llvm/test/CodeGen/AArch64/fp16_fast_math.ll
    M llvm/test/CodeGen/AArch64/sve-streaming-mode-fixed-length-fp-reduce.ll
    M llvm/test/CodeGen/AArch64/vecreduce-fadd.ll
    M llvm/test/CodeGen/AArch64/vecreduce-fmul.ll
    M llvm/test/CodeGen/AMDGPU/llvm.exp.ll
    M llvm/test/CodeGen/AMDGPU/llvm.exp10.ll
    M llvm/test/CodeGen/AMDGPU/llvm.exp2.ll
    M llvm/test/CodeGen/AMDGPU/llvm.log.ll
    M llvm/test/CodeGen/AMDGPU/llvm.log10.ll
    M llvm/test/CodeGen/AMDGPU/llvm.log2.ll
    A llvm/test/CodeGen/ARM/bf16_fast_math.ll
    M llvm/test/CodeGen/ARM/fp16_fast_math.ll
    M llvm/test/CodeGen/Thumb2/bf16-instructions.ll

  Log Message:
  -----------
  [DAGCombiner] Eliminate fp casts if we have the right fast math flags (#131345)

When floating-point operations are legalized to operations of a higher
precision (e.g. f16 fadd being legalized to f32 fadd) then we get
narrowing then widening operations between each operation. With the
appropriate fast math flags (nnan ninf contract) we can eliminate these
casts.



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