[all-commits] [llvm/llvm-project] 9e8a71: [DAG] Create fptosi.sat from clamped fptosi

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 9e8a71caf02a503006eb08b5cd291adeaa20a9c2
      https://github.com/llvm/llvm-project/commit/9e8a71caf02a503006eb08b5cd291adeaa20a9c2
  Author: David Green <david.green at arm.com>
  Date:   2021-11-30 (Tue, 30 Nov 2021)

  Changed paths:
    M llvm/include/llvm/CodeGen/TargetLowering.h
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
    M llvm/lib/Target/AArch64/AArch64ISelLowering.h
    M llvm/lib/Target/ARM/ARMISelLowering.cpp
    M llvm/lib/Target/ARM/ARMISelLowering.h
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/lib/Target/RISCV/RISCVISelLowering.h
    M llvm/test/CodeGen/AArch64/fpclamptosat.ll
    M llvm/test/CodeGen/AArch64/fpclamptosat_vec.ll
    M llvm/test/CodeGen/ARM/fpclamptosat.ll
    M llvm/test/CodeGen/RISCV/fpclamptosat.ll
    M llvm/test/CodeGen/Thumb2/mve-fpclamptosat_vec.ll
    M llvm/test/CodeGen/WebAssembly/fpclamptosat.ll
    M llvm/test/CodeGen/WebAssembly/fpclamptosat_vec.ll
    M llvm/test/CodeGen/X86/fpclamptosat.ll

  Log Message:
  -----------
  [DAG] Create fptosi.sat from clamped fptosi

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.

Differential Revision: https://reviews.llvm.org/D111976