[PATCH] D111976: [DAG] Create fptosi.sat from clamped fptosi

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
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This adds a fold in DAGCombine to create fptosi_sat from sequences for smin(smax(fptosi(x))) nodes, where the min/max saturate the output of the fp convert to a specific bitwidth (say INT_MIN and INT_MAX). Because it is dealing with smin(/smax) in DAG they may currently be ISD::SMIN, ISD::SETCC/ISD::SELECT, ISD::VSELECT or ISD::SELECT_CC nodes which need to be handled similarly.

A shouldConvertFpToSat method was added to control when converting may be profitable. The original fptosi will have a less strict semantics than the fptosisat, with less values that need to produce defined behaviour.

This especially helps on ARM/AArch64 where the vcvt instructions naturally saturate the result.


https://reviews.llvm.org/D111976

Files:
  llvm/include/llvm/CodeGen/TargetLowering.h
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/lib/Target/ARM/ARMISelLowering.cpp
  llvm/lib/Target/ARM/ARMISelLowering.h
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp
  llvm/lib/Target/RISCV/RISCVISelLowering.h
  llvm/test/CodeGen/AArch64/fpclamptosat.ll
  llvm/test/CodeGen/AArch64/fpclamptosat_vec.ll
  llvm/test/CodeGen/ARM/fpclamptosat.ll
  llvm/test/CodeGen/RISCV/fpclamptosat.ll
  llvm/test/CodeGen/Thumb2/mve-fpclamptosat_vec.ll
  llvm/test/CodeGen/WebAssembly/fpclamptosat.ll
  llvm/test/CodeGen/WebAssembly/fpclamptosat_vec.ll
  llvm/test/CodeGen/X86/fpclamptosat.ll

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