RISCVPostLegalizerCombiner.cpp

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//=== RISCVPostLegalizerCombiner.cpp --------------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
///
/// \file
/// Post-legalization combines on generic MachineInstrs.
///
/// The combines here must preserve instruction legality.
///
/// Combines which don't rely on instruction legality should go in the
/// RISCVPreLegalizerCombiner.
///
//===----------------------------------------------------------------------===//
 
#include "RISCV.h"
#include "RISCVTargetMachine.h"
#include "llvm/CodeGen/GlobalISel/CSEInfo.h"
#include "llvm/CodeGen/GlobalISel/Combiner.h"
#include "llvm/CodeGen/GlobalISel/CombinerHelper.h"
#include "llvm/CodeGen/GlobalISel/CombinerInfo.h"
#include "llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h"
#include "llvm/CodeGen/GlobalISel/GISelValueTracking.h"
#include "llvm/CodeGen/GlobalISel/MIPatternMatch.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionAnalysisManager.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachinePassManager.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/IR/Analysis.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FormatVariadic.h"
 
#define GET_GICOMBINER_DEPS
#include "RISCVGenPostLegalizeGICombiner.inc"
#undef GET_GICOMBINER_DEPS
 
#define DEBUG_TYPE "riscv-postlegalizer-combiner"
 
using namespace llvm;
using namespace MIPatternMatch;
 
namespace {
 
#define GET_GICOMBINER_TYPES
#include "RISCVGenPostLegalizeGICombiner.inc"
#undef GET_GICOMBINER_TYPES
 
/// Match: G_STORE (G_FCONSTANT +0.0), addr
/// Return the source vreg in MatchInfo if matched.
bool matchFoldFPZeroStore(MachineInstr &MI, MachineRegisterInfo &MRI,
                          const RISCVSubtarget &STI, Register &MatchInfo) {
  if (MI.getOpcode() != TargetOpcode::G_STORE)
    return false;
 
  Register SrcReg = MI.getOperand(0).getReg();
  if (!SrcReg.isVirtual())
    return false;
 
  if (!mi_match(SrcReg, MRI, m_PosZeroFP()))
    return false;
 
  unsigned ValBits = MRI.getType(SrcReg).getSizeInBits();
  if ((ValBits == 16 && !STI.hasStdExtZfh()) ||
      (ValBits == 32 && !STI.hasStdExtF()) ||
      (ValBits == 64 && (!STI.hasStdExtD() || !STI.is64Bit())))
    return false;
 
  MatchInfo = SrcReg;
  return true;
}
 
/// Apply: rewrite to G_STORE (G_CONSTANT 0 [XLEN]), addr
void applyFoldFPZeroStore(MachineInstr &MI, MachineRegisterInfo &MRI,
                          MachineIRBuilder &B, const RISCVSubtarget &STI,
                          Register &MatchInfo) {
  const unsigned XLen = STI.getXLen();
 
  auto Zero = B.buildConstant(LLT::scalar(XLen), 0);
  MI.getOperand(0).setReg(Zero.getReg(0));
 
  MachineInstr *Def = MRI.getVRegDef(MatchInfo);
  if (Def && MRI.use_nodbg_empty(MatchInfo))
    Def->eraseFromParent();
 
#ifndef NDEBUG
  unsigned ValBits = MRI.getType(MatchInfo).getSizeInBits();
  LLVM_DEBUG(dbgs() << formatv("[{0}] Fold FP zero store -> int zero "
                               "(XLEN={1}, ValBits={2}):\n  {3}\n",
                               DEBUG_TYPE, XLen, ValBits, MI));
#endif
}
 
class RISCVPostLegalizerCombinerImpl : public Combiner {
protected:
  const CombinerHelper Helper;
  const RISCVPostLegalizerCombinerImplRuleConfig &RuleConfig;
  const RISCVSubtarget &STI;
 
public:
  RISCVPostLegalizerCombinerImpl(
      MachineFunction &MF, CombinerInfo &CInfo, GISelValueTracking &VT,
      GISelCSEInfo *CSEInfo,
      const RISCVPostLegalizerCombinerImplRuleConfig &RuleConfig,
      const RISCVSubtarget &STI, MachineDominatorTree *MDT,
      const LegalizerInfo *LI);
 
  static const char *getName() { return "RISCVPostLegalizerCombiner"; }
 
  bool tryCombineAll(MachineInstr &I) const override;
 
private:
#define GET_GICOMBINER_CLASS_MEMBERS
#include "RISCVGenPostLegalizeGICombiner.inc"
#undef GET_GICOMBINER_CLASS_MEMBERS
};
 
#define GET_GICOMBINER_IMPL
#include "RISCVGenPostLegalizeGICombiner.inc"
#undef GET_GICOMBINER_IMPL
 
RISCVPostLegalizerCombinerImpl::RISCVPostLegalizerCombinerImpl(
    MachineFunction &MF, CombinerInfo &CInfo, GISelValueTracking &VT,
    GISelCSEInfo *CSEInfo,
    const RISCVPostLegalizerCombinerImplRuleConfig &RuleConfig,
    const RISCVSubtarget &STI, MachineDominatorTree *MDT,
    const LegalizerInfo *LI)
    : Combiner(MF, CInfo, &VT, CSEInfo),
      Helper(Observer, B, /*IsPreLegalize*/ false, &VT, MDT, LI),
      RuleConfig(RuleConfig), STI(STI),
#define GET_GICOMBINER_CONSTRUCTOR_INITS
#include "RISCVGenPostLegalizeGICombiner.inc"
#undef GET_GICOMBINER_CONSTRUCTOR_INITS
{
}
 
class RISCVPostLegalizerCombinerLegacy : public MachineFunctionPass {
public:
  static char ID;
 
  RISCVPostLegalizerCombinerLegacy();
 
  StringRef getPassName() const override {
    return "RISCVPostLegalizerCombiner";
  }
 
  bool runOnMachineFunction(MachineFunction &MF) override;
  void getAnalysisUsage(AnalysisUsage &AU) const override;
};
} // end anonymous namespace
 
void RISCVPostLegalizerCombinerLegacy::getAnalysisUsage(
    AnalysisUsage &AU) const {
  AU.addRequired<TargetPassConfig>();
  AU.setPreservesCFG();
  getSelectionDAGFallbackAnalysisUsage(AU);
  AU.addRequired<GISelValueTrackingAnalysisLegacy>();
  AU.addPreserved<GISelValueTrackingAnalysisLegacy>();
  AU.addRequired<MachineDominatorTreeWrapperPass>();
  AU.addRequired<GISelCSEAnalysisWrapperPass>();
  AU.addPreserved<GISelCSEAnalysisWrapperPass>();
  MachineFunctionPass::getAnalysisUsage(AU);
}
 
RISCVPostLegalizerCombinerLegacy::RISCVPostLegalizerCombinerLegacy()
    : MachineFunctionPass(ID) {}
 
static bool
runCombinerOnMachineFunction(MachineFunction &MF,
                             function_ref<bool()> ShouldSkip,
                             function_ref<GISelValueTracking *()> GetVT,
                             function_ref<MachineDominatorTree *()> GetMDT,
                             function_ref<GISelCSEInfo *()> GetCSEInfo) {
  if (MF.getProperties().hasFailedISel())
    return false;
  assert(MF.getProperties().hasLegalized() && "Expected a legalized function?");
  const Function &F = MF.getFunction();
  bool EnableOpt =
      MF.getTarget().getOptLevel() != CodeGenOptLevel::None && !ShouldSkip();
 
  RISCVPostLegalizerCombinerImplRuleConfig RuleConfig;
  if (!RuleConfig.parseCommandLineOption())
    reportFatalUsageError("Invalid rule identifier");
 
  const RISCVSubtarget &ST = MF.getSubtarget<RISCVSubtarget>();
  const auto *LI = ST.getLegalizerInfo();
 
  GISelValueTracking *VT = GetVT();
  MachineDominatorTree *MDT = GetMDT();
  GISelCSEInfo *CSEInfo = GetCSEInfo();
 
  CombinerInfo CInfo(/*AllowIllegalOps*/ true, /*ShouldLegalizeIllegal*/ false,
                     /*LegalizerInfo*/ nullptr, EnableOpt, F.hasOptSize(),
                     F.hasMinSize());
  RISCVPostLegalizerCombinerImpl Impl(MF, CInfo, *VT, CSEInfo, RuleConfig, ST,
                                      MDT, LI);
  return Impl.combineMachineInstrs();
}
 
char RISCVPostLegalizerCombinerLegacy::ID = 0;
INITIALIZE_PASS_BEGIN(RISCVPostLegalizerCombinerLegacy, DEBUG_TYPE,
                      "Combine RISC-V MachineInstrs after legalization", false,
                      false)
INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
INITIALIZE_PASS_DEPENDENCY(GISelValueTrackingAnalysisLegacy)
INITIALIZE_PASS_END(RISCVPostLegalizerCombinerLegacy, DEBUG_TYPE,
                    "Combine RISC-V MachineInstrs after legalization", false,
                    false)
 
FunctionPass *llvm::createRISCVPostLegalizerCombinerLegacyPass() {
  return new RISCVPostLegalizerCombinerLegacy();
}
 
bool RISCVPostLegalizerCombinerLegacy::runOnMachineFunction(
    MachineFunction &MF) {
  return runCombinerOnMachineFunction(
      MF, [&]() { return skipFunction(MF.getFunction()); },
      [&]() {
        return &getAnalysis<GISelValueTrackingAnalysisLegacy>().get(MF);
      },
      [&]() {
        return &getAnalysis<MachineDominatorTreeWrapperPass>().getDomTree();
      },
      [&]() {
        TargetPassConfig *TPC = &getAnalysis<TargetPassConfig>();
        GISelCSEAnalysisWrapper &Wrapper =
            getAnalysis<GISelCSEAnalysisWrapperPass>().getCSEWrapper();
        return &Wrapper.get(TPC->getCSEConfig());
      });
}
 
PreservedAnalyses
RISCVPostLegalizerCombinerPass::run(MachineFunction &MF,
                                    MachineFunctionAnalysisManager &MFAM) {
  bool Changed = runCombinerOnMachineFunction(
      MF,
      [&]() {
        return MF.getFunction().hasOptNone() ||
               shouldSkipOptimizationForOptBisect(MF.getFunction());
      },
      [&]() { return &MFAM.getResult<GISelValueTrackingAnalysis>(MF); },
      [&]() { return &MFAM.getResult<MachineDominatorTreeAnalysis>(MF); },
      [&]() { return MFAM.getResult<GISelCSEAnalysis>(MF).get(); });
  return Changed ? getMachineFunctionPassPreservedAnalyses()
                       .preserveSet<CFGAnalyses>()
                       .preserve<GISelValueTrackingAnalysis>()
                       .preserve<GISelCSEAnalysis>()
                 : PreservedAnalyses::all();
}