MachineStableHash.cpp

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//===- lib/CodeGen/MachineStableHash.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
//
//===----------------------------------------------------------------------===//
//
// Stable hashing for MachineInstr and MachineOperand. Useful or getting a
// hash across runs, modules, etc.
//
//===----------------------------------------------------------------------===//
 
#include "llvm/CodeGen/MachineStableHash.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StableHashing.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/ilist_iterator.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBundleIterator.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Register.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/Constants.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/Alignment.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/xxhash.h"
 
#define DEBUG_TYPE "machine-stable-hash"
 
using namespace llvm;
 
STATISTIC(StableHashBailingMachineBasicBlock,
          "Number of encountered unsupported MachineOperands that were "
          "MachineBasicBlocks while computing stable hashes");
STATISTIC(StableHashBailingConstantPoolIndex,
          "Number of encountered unsupported MachineOperands that were "
          "ConstantPoolIndex while computing stable hashes");
STATISTIC(StableHashBailingTargetIndexNoName,
          "Number of encountered unsupported MachineOperands that were "
          "TargetIndex with no name");
STATISTIC(StableHashBailingGlobalAddress,
          "Number of encountered unsupported MachineOperands that were "
          "GlobalAddress while computing stable hashes");
STATISTIC(StableHashBailingBlockAddress,
          "Number of encountered unsupported MachineOperands that were "
          "BlockAddress while computing stable hashes");
STATISTIC(StableHashBailingMetadataUnsupported,
          "Number of encountered unsupported MachineOperands that were "
          "Metadata of an unsupported kind while computing stable hashes");
 
stable_hash llvm::stableHashValue(const MachineOperand &MO) {
  switch (MO.getType()) {
  case MachineOperand::MO_Register:
    if (MO.getReg().isVirtual()) {
      const MachineRegisterInfo &MRI = MO.getParent()->getMF()->getRegInfo();
      SmallVector<unsigned> DefOpcodes;
      for (auto &Def : MRI.def_instructions(MO.getReg()))
        DefOpcodes.push_back(Def.getOpcode());
      return hash_combine_range(DefOpcodes.begin(), DefOpcodes.end());
    }
 
    // Register operands don't have target flags.
    return stable_hash_combine(MO.getType(), MO.getReg(), MO.getSubReg(),
                               MO.isDef());
  case MachineOperand::MO_Immediate:
    return stable_hash_combine(MO.getType(), MO.getTargetFlags(), MO.getImm());
  case MachineOperand::MO_CImmediate:
  case MachineOperand::MO_FPImmediate: {
    auto Val = MO.isCImm() ? MO.getCImm()->getValue()
                           : MO.getFPImm()->getValueAPF().bitcastToAPInt();
    auto ValHash =
        stable_hash_combine_array(Val.getRawData(), Val.getNumWords());
    return hash_combine(MO.getType(), MO.getTargetFlags(), ValHash);
  }
 
  case MachineOperand::MO_MachineBasicBlock:
    StableHashBailingMachineBasicBlock++;
    return 0;
  case MachineOperand::MO_ConstantPoolIndex:
    StableHashBailingConstantPoolIndex++;
    return 0;
  case MachineOperand::MO_BlockAddress:
    StableHashBailingBlockAddress++;
    return 0;
  case MachineOperand::MO_Metadata:
    StableHashBailingMetadataUnsupported++;
    return 0;
  case MachineOperand::MO_GlobalAddress:
    StableHashBailingGlobalAddress++;
    return 0;
  case MachineOperand::MO_TargetIndex: {
    if (const char *Name = MO.getTargetIndexName())
      return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
                                 xxh3_64bits(Name), MO.getOffset());
    StableHashBailingTargetIndexNoName++;
    return 0;
  }
 
  case MachineOperand::MO_FrameIndex:
  case MachineOperand::MO_JumpTableIndex:
    return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
                               MO.getIndex());
 
  case MachineOperand::MO_ExternalSymbol:
    return hash_combine(MO.getType(), MO.getTargetFlags(), MO.getOffset(),
                        xxh3_64bits(MO.getSymbolName()));
 
  case MachineOperand::MO_RegisterMask:
  case MachineOperand::MO_RegisterLiveOut: {
    if (const MachineInstr *MI = MO.getParent()) {
      if (const MachineBasicBlock *MBB = MI->getParent()) {
        if (const MachineFunction *MF = MBB->getParent()) {
          const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
          unsigned RegMaskSize =
              MachineOperand::getRegMaskSize(TRI->getNumRegs());
          const uint32_t *RegMask = MO.getRegMask();
          std::vector<llvm::stable_hash> RegMaskHashes(RegMask,
                                                       RegMask + RegMaskSize);
          return hash_combine(MO.getType(), MO.getTargetFlags(),
                              stable_hash_combine_array(RegMaskHashes.data(),
                                                        RegMaskHashes.size()));
        }
      }
    }
 
    assert(0 && "MachineOperand not associated with any MachineFunction");
    return hash_combine(MO.getType(), MO.getTargetFlags());
  }
 
  case MachineOperand::MO_ShuffleMask: {
    std::vector<llvm::stable_hash> ShuffleMaskHashes;
 
    llvm::transform(
        MO.getShuffleMask(), std::back_inserter(ShuffleMaskHashes),
        [](int S) -> llvm::stable_hash { return llvm::stable_hash(S); });
 
    return hash_combine(MO.getType(), MO.getTargetFlags(),
                        stable_hash_combine_array(ShuffleMaskHashes.data(),
                                                  ShuffleMaskHashes.size()));
  }
  case MachineOperand::MO_MCSymbol: {
    auto SymbolName = MO.getMCSymbol()->getName();
    return hash_combine(MO.getType(), MO.getTargetFlags(),
                        xxh3_64bits(SymbolName));
  }
  case MachineOperand::MO_CFIIndex:
    return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
                               MO.getCFIIndex());
  case MachineOperand::MO_IntrinsicID:
    return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
                               MO.getIntrinsicID());
  case MachineOperand::MO_Predicate:
    return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
                               MO.getPredicate());
  case MachineOperand::MO_DbgInstrRef:
    return stable_hash_combine(MO.getType(), MO.getInstrRefInstrIndex(),
                               MO.getInstrRefOpIndex());
  }
  llvm_unreachable("Invalid machine operand type");
}
 
/// A stable hash value for machine instructions.
/// Returns 0 if no stable hash could be computed.
/// The hashing and equality testing functions ignore definitions so this is
/// useful for CSE, etc.
stable_hash llvm::stableHashValue(const MachineInstr &MI, bool HashVRegs,
                                  bool HashConstantPoolIndices,
                                  bool HashMemOperands) {
  // Build up a buffer of hash code components.
  SmallVector<stable_hash, 16> HashComponents;
  HashComponents.reserve(MI.getNumOperands() + MI.getNumMemOperands() + 2);
  HashComponents.push_back(MI.getOpcode());
  HashComponents.push_back(MI.getFlags());
  for (const MachineOperand &MO : MI.operands()) {
    if (!HashVRegs && MO.isReg() && MO.isDef() && MO.getReg().isVirtual())
      continue; // Skip virtual register defs.
 
    if (MO.isCPI()) {
      HashComponents.push_back(stable_hash_combine(
          MO.getType(), MO.getTargetFlags(), MO.getIndex()));
      continue;
    }
 
    stable_hash StableHash = stableHashValue(MO);
    if (!StableHash)
      return 0;
    HashComponents.push_back(StableHash);
  }
 
  for (const auto *Op : MI.memoperands()) {
    if (!HashMemOperands)
      break;
    HashComponents.push_back(static_cast<unsigned>(Op->getSize().getValue()));
    HashComponents.push_back(static_cast<unsigned>(Op->getFlags()));
    HashComponents.push_back(static_cast<unsigned>(Op->getOffset()));
    HashComponents.push_back(static_cast<unsigned>(Op->getSuccessOrdering()));
    HashComponents.push_back(static_cast<unsigned>(Op->getAddrSpace()));
    HashComponents.push_back(static_cast<unsigned>(Op->getSyncScopeID()));
    HashComponents.push_back(static_cast<unsigned>(Op->getBaseAlign().value()));
    HashComponents.push_back(static_cast<unsigned>(Op->getFailureOrdering()));
  }
 
  return stable_hash_combine_range(HashComponents.begin(),
                                   HashComponents.end());
}
 
stable_hash llvm::stableHashValue(const MachineBasicBlock &MBB) {
  SmallVector<stable_hash> HashComponents;
  // TODO: Hash more stuff like block alignment and branch probabilities.
  for (const auto &MI : MBB)
    HashComponents.push_back(stableHashValue(MI));
  return stable_hash_combine_range(HashComponents.begin(),
                                   HashComponents.end());
}
 
stable_hash llvm::stableHashValue(const MachineFunction &MF) {
  SmallVector<stable_hash> HashComponents;
  // TODO: Hash lots more stuff like function alignment and stack objects.
  for (const auto &MBB : MF)
    HashComponents.push_back(stableHashValue(MBB));
  return stable_hash_combine_range(HashComponents.begin(),
                                   HashComponents.end());
}