[PATCH] D157111: AMDGPU: Try to select fmul by power of 2 to ldexp

[Matt Arsenault via Phabricator via llvm-commits]

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For the f64 case, this gives us a cheaper to materialize 32-bit
constant. It's less obviously a win for f32 and f16. It forces us to
use a VOP3 encoding so it's a neutral code size change.

      

GlobalISel cases don't work because of the constant-is-copy-to-vgpr
problem.


https://reviews.llvm.org/D157111

Files:
  llvm/lib/Target/AMDGPU/AMDGPUGISel.td
  llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp
  llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.h
  llvm/lib/Target/AMDGPU/SIInstructions.td
  llvm/test/CodeGen/AMDGPU/GlobalISel/inst-select-fmul.mir
  llvm/test/CodeGen/AMDGPU/fmul-to-ldexp.ll
  llvm/test/CodeGen/AMDGPU/fp_to_sint.f64.ll
  llvm/test/CodeGen/AMDGPU/fp_to_uint.f64.ll

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