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https://github.com/llvm/llvm-project.git
synced 2026-10-26 13:53:31 +08:00
Zhaoxuan Jiang
cadc31b152
Global function merging and outliner compare hashes across modules. Some globals are hashed by name, so two modules that each define a same-named global with local linkage produce identical operand hashes although they denote different storage. The hash collision caused both GFM and GFO to make quite a few non-beneficial optimization decisions. Add a `SourceQualifyLocalGlobals` option to IR `StructuralHash` and MIR `stableHashValue`. When set, the name-based hash of a global with local linkage is combined with the source file name of its module. The module identifier itself is not suitable: the linker may name the module after an unstable temporary LTO object file, which would make the supposedly stable hash vary from run to run and between the generate and use rounds. Content-based hashes are unchanged, so equivalent literals still merge across modules. The option defaults to off, so other users of `stableHashValue` and `StructuralHash` keep their hashes.
249 lines
10 KiB
C++
249 lines
10 KiB
C++
//===- lib/CodeGen/MachineStableHash.cpp ----------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// Stable hashing for MachineInstr and MachineOperand. Useful or getting a
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// hash across runs, modules, etc.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/MachineStableHash.h"
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#include "llvm/ADT/APFloat.h"
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#include "llvm/ADT/APInt.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/StableHashing.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineMemOperand.h"
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#include "llvm/CodeGen/MachineOperand.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/CodeGen/Register.h"
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#include "llvm/Config/llvm-config.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/IR/StructuralHash.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/Support/Alignment.h"
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#include "llvm/Support/ErrorHandling.h"
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#define DEBUG_TYPE "machine-stable-hash"
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using namespace llvm;
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STATISTIC(StableHashBailingMachineBasicBlock,
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"Number of encountered unsupported MachineOperands that were "
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"MachineBasicBlocks while computing stable hashes");
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STATISTIC(StableHashBailingConstantPoolIndex,
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"Number of encountered unsupported MachineOperands that were "
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"ConstantPoolIndex while computing stable hashes");
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STATISTIC(StableHashBailingTargetIndexNoName,
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"Number of encountered unsupported MachineOperands that were "
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"TargetIndex with no name");
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STATISTIC(StableHashBailingGlobalAddress,
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"Number of encountered unsupported MachineOperands that were "
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"GlobalAddress while computing stable hashes");
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STATISTIC(StableHashBailingBlockAddress,
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"Number of encountered unsupported MachineOperands that were "
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"BlockAddress while computing stable hashes");
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STATISTIC(StableHashBailingMetadataUnsupported,
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"Number of encountered unsupported MachineOperands that were "
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"Metadata of an unsupported kind while computing stable hashes");
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stable_hash llvm::stableHashValue(const MachineOperand &MO,
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bool SourceQualifyLocalGlobals) {
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switch (MO.getType()) {
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case MachineOperand::MO_Register:
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if (MO.getReg().isVirtual()) {
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const MachineRegisterInfo &MRI = MO.getParent()->getMF()->getRegInfo();
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SmallVector<stable_hash> DefOpcodes;
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for (auto &Def : MRI.def_instructions(MO.getReg()))
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DefOpcodes.push_back(Def.getOpcode());
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return stable_hash_combine(DefOpcodes);
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}
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// Register operands don't have target flags.
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return stable_hash_combine(MO.getType(), MO.getReg().id(), MO.getSubReg(),
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MO.isDef());
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case MachineOperand::MO_Immediate:
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(), MO.getImm());
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case MachineOperand::MO_CImmediate:
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case MachineOperand::MO_FPImmediate: {
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auto Val = MO.isCImm() ? MO.getCImm()->getValue()
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: MO.getFPImm()->getValueAPF().bitcastToAPInt();
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auto ValHash = stable_hash_combine(
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ArrayRef<stable_hash>(Val.getRawData(), Val.getNumWords()));
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(), ValHash);
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}
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case MachineOperand::MO_MachineBasicBlock:
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++StableHashBailingMachineBasicBlock;
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return 0;
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case MachineOperand::MO_ConstantPoolIndex:
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++StableHashBailingConstantPoolIndex;
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return 0;
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case MachineOperand::MO_BlockAddress:
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++StableHashBailingBlockAddress;
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return 0;
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case MachineOperand::MO_Metadata:
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++StableHashBailingMetadataUnsupported;
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return 0;
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case MachineOperand::MO_GlobalAddress: {
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const GlobalValue *GV = MO.getGlobal();
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stable_hash GVHash = 0;
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if (auto *GVar = dyn_cast<GlobalVariable>(GV))
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GVHash = StructuralHash(*GVar, SourceQualifyLocalGlobals);
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if (!GVHash) {
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if (!GV->hasName()) {
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++StableHashBailingGlobalAddress;
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return 0;
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}
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GVHash = stable_hash_name(GV->getName());
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}
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(), GVHash,
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MO.getOffset());
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}
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case MachineOperand::MO_TargetIndex: {
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if (const char *Name = MO.getTargetIndexName())
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
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stable_hash_name(Name), MO.getOffset());
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++StableHashBailingTargetIndexNoName;
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return 0;
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}
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case MachineOperand::MO_FrameIndex:
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case MachineOperand::MO_JumpTableIndex:
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
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MO.getIndex());
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case MachineOperand::MO_ExternalSymbol:
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
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MO.getOffset(),
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stable_hash_name(MO.getSymbolName()));
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case MachineOperand::MO_RegisterMask:
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case MachineOperand::MO_RegisterLiveOut: {
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if (const MachineInstr *MI = MO.getParent()) {
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if (const MachineBasicBlock *MBB = MI->getParent()) {
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if (const MachineFunction *MF = MBB->getParent()) {
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const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
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unsigned RegMaskSize =
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MachineOperand::getRegMaskSize(TRI->getNumRegs());
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const uint32_t *RegMask =
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MO.isRegMask() ? MO.getRegMask() : MO.getRegLiveOut();
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std::vector<llvm::stable_hash> RegMaskHashes(RegMask,
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RegMask + RegMaskSize);
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
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stable_hash_combine(RegMaskHashes));
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}
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}
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}
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assert(0 && "MachineOperand not associated with any MachineFunction");
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return stable_hash_combine(MO.getType(), MO.getTargetFlags());
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}
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case MachineOperand::MO_ShuffleMask: {
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std::vector<llvm::stable_hash> ShuffleMaskHashes;
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llvm::transform(
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MO.getShuffleMask(), std::back_inserter(ShuffleMaskHashes),
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[](int S) -> llvm::stable_hash { return llvm::stable_hash(S); });
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
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stable_hash_combine(ShuffleMaskHashes));
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}
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case MachineOperand::MO_MCSymbol: {
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auto SymbolName = MO.getMCSymbol()->getName();
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
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stable_hash_name(SymbolName));
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}
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case MachineOperand::MO_LaneMask: {
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
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MO.getLaneMask().getAsInteger());
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}
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case MachineOperand::MO_CFIIndex:
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
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MO.getCFIIndex());
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case MachineOperand::MO_IntrinsicID:
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
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MO.getIntrinsicID());
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case MachineOperand::MO_Predicate:
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return stable_hash_combine(MO.getType(), MO.getTargetFlags(),
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MO.getPredicate());
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case MachineOperand::MO_DbgInstrRef:
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return stable_hash_combine(MO.getType(), MO.getInstrRefInstrIndex(),
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MO.getInstrRefOpIndex());
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}
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llvm_unreachable("Invalid machine operand type");
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}
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/// A stable hash value for machine instructions.
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/// Returns 0 if no stable hash could be computed.
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/// The hashing and equality testing functions ignore definitions so this is
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/// useful for CSE, etc.
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stable_hash llvm::stableHashValue(const MachineInstr &MI, bool HashVRegs,
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bool HashConstantPoolIndices,
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bool HashMemOperands,
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bool SourceQualifyLocalGlobals) {
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// Build up a buffer of hash code components.
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SmallVector<stable_hash, 16> HashComponents;
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HashComponents.reserve(MI.getNumOperands() + MI.getNumMemOperands() + 2);
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HashComponents.push_back(MI.getOpcode());
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HashComponents.push_back(MI.getFlags());
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for (const MachineOperand &MO : MI.operands()) {
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if (!HashVRegs && MO.isReg() && MO.isDef() && MO.getReg().isVirtual())
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continue; // Skip virtual register defs.
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if (MO.isCPI()) {
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HashComponents.push_back(stable_hash_combine(
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MO.getType(), MO.getTargetFlags(), MO.getIndex()));
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continue;
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}
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stable_hash StableHash = stableHashValue(MO, SourceQualifyLocalGlobals);
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if (!StableHash)
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return 0;
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HashComponents.push_back(StableHash);
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}
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for (const auto *Op : MI.memoperands()) {
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if (!HashMemOperands)
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break;
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HashComponents.push_back(static_cast<unsigned>(Op->getSize().getValue()));
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HashComponents.push_back(static_cast<unsigned>(Op->getFlags()));
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HashComponents.push_back(static_cast<unsigned>(Op->getOffset()));
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HashComponents.push_back(static_cast<unsigned>(Op->getSuccessOrdering()));
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HashComponents.push_back(static_cast<unsigned>(Op->getAddrSpace()));
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HashComponents.push_back(static_cast<unsigned>(Op->getSyncScopeID()));
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HashComponents.push_back(static_cast<unsigned>(Op->getBaseAlign().value()));
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HashComponents.push_back(static_cast<unsigned>(Op->getFailureOrdering()));
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}
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return stable_hash_combine(HashComponents);
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}
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stable_hash llvm::stableHashValue(const MachineBasicBlock &MBB) {
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SmallVector<stable_hash> HashComponents;
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// TODO: Hash more stuff like block alignment and branch probabilities.
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for (const auto &MI : MBB)
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HashComponents.push_back(stableHashValue(MI));
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return stable_hash_combine(HashComponents);
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}
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stable_hash llvm::stableHashValue(const MachineFunction &MF) {
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SmallVector<stable_hash> HashComponents;
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// TODO: Hash lots more stuff like function alignment and stack objects.
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for (const auto &MBB : MF)
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HashComponents.push_back(stableHashValue(MBB));
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return stable_hash_combine(HashComponents);
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}
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