[PATCH] D117687: [RISCV] Optimize lowering of floating-point -0.0

[Fraser Cormack via Phabricator via llvm-commits]

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This idea has come up in several reviews -- D115978 <https://reviews.llvm.org/D115978> and D105902 <https://reviews.llvm.org/D105902> -- so I
can't take any credit for the idea. Instead of using a constant pool to
lower -0.0, we can emit a sequence of two instructions:

  fmv.[hwd].x freg, zero
  fsgnjn.[hsd] freg, freg, freg

This is only done when the floating-point type is legal.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D117687

Files:
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp
  llvm/lib/Target/RISCV/RISCVInstrInfoD.td
  llvm/lib/Target/RISCV/RISCVInstrInfoF.td
  llvm/lib/Target/RISCV/RISCVInstrInfoZfh.td
  llvm/test/CodeGen/RISCV/fp-imm.ll
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-reduction-fp.ll
  llvm/test/CodeGen/RISCV/rvv/vreductions-fp-sdnode.ll
  llvm/test/CodeGen/RISCV/zfh-imm.ll

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