[all-commits] [llvm/llvm-project] 0d074b: [DAG] Support saturated truncate (#99418)

[hanbeom via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0d074ba197166b4f00cc3b1b1011625eb7be0a53
      https://github.com/llvm/llvm-project/commit/0d074ba197166b4f00cc3b1b1011625eb7be0a53
  Author: hanbeom <kese111 at gmail.com>
  Date:   2024-08-14 (Wed, 14 Aug 2024)

  Changed paths:
    M llvm/include/llvm/CodeGen/ISDOpcodes.h
    M llvm/include/llvm/Target/TargetSelectionDAG.td
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
    M llvm/lib/CodeGen/TargetLoweringBase.cpp
    M llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
    M llvm/lib/Target/AArch64/AArch64ISelLowering.h
    M llvm/lib/Target/AArch64/AArch64InstrInfo.td
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/test/CodeGen/AArch64/fpclamptosat_vec.ll
    M llvm/test/CodeGen/AArch64/qmovn.ll
    M llvm/test/CodeGen/RISCV/rvv/fixed-vectors-trunc-sat-clip.ll
    M llvm/test/CodeGen/RISCV/rvv/fpclamptosat_vec.ll
    M llvm/test/CodeGen/RISCV/rvv/trunc-sat-clip-sdnode.ll
    M llvm/test/CodeGen/RISCV/rvv/trunc-select-to-max-usat.ll

  Log Message:
  -----------
  [DAG] Support saturated truncate (#99418)

A truncate is considered saturated if no additional conversion is required between the target and return values. If the target is saturated when attempting to truncate from a vector, there is an opportunity to optimize it.

Previously, each architecture had its own attempt at optimization, leading to redundant code. This patch implements common logic by introducing three new ISDs:

`ISD::TRUNCATE_SSAT_S`: When the operand is a signed value and  the range of values matches the range of signed values of the  destination type.

`ISD::TRUNCATE_SSAT_U`: When the operand is a signed value and the range of values matches the range of unsigned values of the destination type.

`ISD::TRUNCATE_USAT_U`: When the operand is an unsigned value and the range of values matches the range of unsigned values of the destination type.

These ISDs indicate a saturated truncate.

Fixes https://github.com/llvm/llvm-project/issues/85903



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