llvm/lib/CodeGen/GlobalISel/CombinerHelperCasts.cpp

//===- CombinerHelperCasts.cpp---------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements CombinerHelper for G_ANYEXT, G_SEXT, G_TRUNC, and
// G_ZEXT
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/GlobalISel/CombinerHelper.h"
#include "llvm/CodeGen/GlobalISel/LegalizerHelper.h"
#include "llvm/CodeGen/GlobalISel/LegalizerInfo.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/GlobalISel/Utils.h"
#include "llvm/CodeGen/LowLevelTypeUtils.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/Support/Casting.h"

#define DEBUG_TYPE "gi-combiner"

using namespace llvm;

bool CombinerHelper::matchSextOfTrunc(const MachineOperand &MO,
                                      BuildFnTy &MatchInfo) {
  GSext *Sext = cast<GSext>(getDefIgnoringCopies(MO.getReg(), MRI));
  GTrunc *Trunc = cast<GTrunc>(getDefIgnoringCopies(Sext->getSrcReg(), MRI));

  Register Dst = Sext->getReg(0);
  Register Src = Trunc->getSrcReg();

  LLT DstTy = MRI.getType(Dst);
  LLT SrcTy = MRI.getType(Src);

  if (DstTy == SrcTy) {
    MatchInfo = [=](MachineIRBuilder &B) { B.buildCopy(Dst, Src); };
    return true;
  }

  if (DstTy.getScalarSizeInBits() < SrcTy.getScalarSizeInBits() &&
      isLegalOrBeforeLegalizer({TargetOpcode::G_TRUNC, {DstTy, SrcTy}})) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildTrunc(Dst, Src, MachineInstr::MIFlag::NoSWrap);
    };
    return true;
  }

  if (DstTy.getScalarSizeInBits() > SrcTy.getScalarSizeInBits() &&
      isLegalOrBeforeLegalizer({TargetOpcode::G_SEXT, {DstTy, SrcTy}})) {
    MatchInfo = [=](MachineIRBuilder &B) { B.buildSExt(Dst, Src); };
    return true;
  }

  return false;
}

bool CombinerHelper::matchZextOfTrunc(const MachineOperand &MO,
                                      BuildFnTy &MatchInfo) {
  GZext *Zext = cast<GZext>(getDefIgnoringCopies(MO.getReg(), MRI));
  GTrunc *Trunc = cast<GTrunc>(getDefIgnoringCopies(Zext->getSrcReg(), MRI));

  Register Dst = Zext->getReg(0);
  Register Src = Trunc->getSrcReg();

  LLT DstTy = MRI.getType(Dst);
  LLT SrcTy = MRI.getType(Src);

  if (DstTy == SrcTy) {
    MatchInfo = [=](MachineIRBuilder &B) { B.buildCopy(Dst, Src); };
    return true;
  }

  if (DstTy.getScalarSizeInBits() < SrcTy.getScalarSizeInBits() &&
      isLegalOrBeforeLegalizer({TargetOpcode::G_TRUNC, {DstTy, SrcTy}})) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildTrunc(Dst, Src, MachineInstr::MIFlag::NoUWrap);
    };
    return true;
  }

  if (DstTy.getScalarSizeInBits() > SrcTy.getScalarSizeInBits() &&
      isLegalOrBeforeLegalizer({TargetOpcode::G_ZEXT, {DstTy, SrcTy}})) {
    MatchInfo = [=](MachineIRBuilder &B) {
      B.buildZExt(Dst, Src, MachineInstr::MIFlag::NonNeg);
    };
    return true;
  }

  return false;
}

bool CombinerHelper::matchNonNegZext(const MachineOperand &MO,
                                     BuildFnTy &MatchInfo) {
  GZext *Zext = cast<GZext>(MRI.getVRegDef(MO.getReg()));

  Register Dst = Zext->getReg(0);
  Register Src = Zext->getSrcReg();

  LLT DstTy = MRI.getType(Dst);
  LLT SrcTy = MRI.getType(Src);
  const auto &TLI = getTargetLowering();

  // Convert zext nneg to sext if sext is the preferred form for the target.
  if (isLegalOrBeforeLegalizer({TargetOpcode::G_SEXT, {DstTy, SrcTy}}) &&
      TLI.isSExtCheaperThanZExt(getMVTForLLT(SrcTy), getMVTForLLT(DstTy))) {
    MatchInfo = [=](MachineIRBuilder &B) { B.buildSExt(Dst, Src); };
    return true;
  }

  return false;
}