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llvm-mirror/lib/CodeGen/GlobalISel/CSEInfo.cpp
Aditya Nandakumar 6daddf8fea [GlobalISel]: Fix some non determinism exposed in CSE due to not notifying observers about mutations + add verification for CSE
https://reviews.llvm.org/D67133

While investigating some non determinism (CSE doesn't produce wrong
code, it just doesn't CSE some times) in GISel CSE on an out of tree
target, I realized that the core issue was that there were lots of code
that mutates (setReg, setRegClass etc), but doesn't notify observers
(CSE in this case but this could be any other observer). In order to
make the Observer be available in various parts of code and to avoid
having to thread it through various API, the MachineFunction now has the
observer as field. This allows it to be easily used in helper functions
such as constrainOperandRegClass.
Also added some invariant verification method in CSEInfo which can
catch these issues (when CSE is enabled).
2020-02-18 14:54:57 -08:00

423 lines
12 KiB
C++

//===- CSEInfo.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
//
//===----------------------------------------------------------------------===//
//
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/GlobalISel/CSEInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/InitializePasses.h"
#define DEBUG_TYPE "cseinfo"
using namespace llvm;
char llvm::GISelCSEAnalysisWrapperPass::ID = 0;
GISelCSEAnalysisWrapperPass::GISelCSEAnalysisWrapperPass()
: MachineFunctionPass(ID) {
initializeGISelCSEAnalysisWrapperPassPass(*PassRegistry::getPassRegistry());
}
INITIALIZE_PASS_BEGIN(GISelCSEAnalysisWrapperPass, DEBUG_TYPE,
"Analysis containing CSE Info", false, true)
INITIALIZE_PASS_END(GISelCSEAnalysisWrapperPass, DEBUG_TYPE,
"Analysis containing CSE Info", false, true)
/// -------- UniqueMachineInstr -------------//
void UniqueMachineInstr::Profile(FoldingSetNodeID &ID) {
GISelInstProfileBuilder(ID, MI->getMF()->getRegInfo()).addNodeID(MI);
}
/// -----------------------------------------
/// --------- CSEConfigFull ---------- ///
bool CSEConfigFull::shouldCSEOpc(unsigned Opc) {
switch (Opc) {
default:
break;
case TargetOpcode::G_ADD:
case TargetOpcode::G_AND:
case TargetOpcode::G_ASHR:
case TargetOpcode::G_LSHR:
case TargetOpcode::G_MUL:
case TargetOpcode::G_OR:
case TargetOpcode::G_SHL:
case TargetOpcode::G_SUB:
case TargetOpcode::G_XOR:
case TargetOpcode::G_UDIV:
case TargetOpcode::G_SDIV:
case TargetOpcode::G_UREM:
case TargetOpcode::G_SREM:
case TargetOpcode::G_CONSTANT:
case TargetOpcode::G_FCONSTANT:
case TargetOpcode::G_IMPLICIT_DEF:
case TargetOpcode::G_ZEXT:
case TargetOpcode::G_SEXT:
case TargetOpcode::G_ANYEXT:
case TargetOpcode::G_UNMERGE_VALUES:
case TargetOpcode::G_TRUNC:
case TargetOpcode::G_PTR_ADD:
return true;
}
return false;
}
bool CSEConfigConstantOnly::shouldCSEOpc(unsigned Opc) {
return Opc == TargetOpcode::G_CONSTANT || Opc == TargetOpcode::G_IMPLICIT_DEF;
}
std::unique_ptr<CSEConfigBase>
llvm::getStandardCSEConfigForOpt(CodeGenOpt::Level Level) {
std::unique_ptr<CSEConfigBase> Config;
if (Level == CodeGenOpt::None)
Config = std::make_unique<CSEConfigConstantOnly>();
else
Config = std::make_unique<CSEConfigFull>();
return Config;
}
/// -----------------------------------------
/// -------- GISelCSEInfo -------------//
void GISelCSEInfo::setMF(MachineFunction &MF) {
this->MF = &MF;
this->MRI = &MF.getRegInfo();
}
GISelCSEInfo::~GISelCSEInfo() {}
bool GISelCSEInfo::isUniqueMachineInstValid(
const UniqueMachineInstr &UMI) const {
// Should we check here and assert that the instruction has been fully
// constructed?
// FIXME: Any other checks required to be done here? Remove this method if
// none.
return true;
}
void GISelCSEInfo::invalidateUniqueMachineInstr(UniqueMachineInstr *UMI) {
bool Removed = CSEMap.RemoveNode(UMI);
(void)Removed;
assert(Removed && "Invalidation called on invalid UMI");
// FIXME: Should UMI be deallocated/destroyed?
}
UniqueMachineInstr *GISelCSEInfo::getNodeIfExists(FoldingSetNodeID &ID,
MachineBasicBlock *MBB,
void *&InsertPos) {
auto *Node = CSEMap.FindNodeOrInsertPos(ID, InsertPos);
if (Node) {
if (!isUniqueMachineInstValid(*Node)) {
invalidateUniqueMachineInstr(Node);
return nullptr;
}
if (Node->MI->getParent() != MBB)
return nullptr;
}
return Node;
}
void GISelCSEInfo::insertNode(UniqueMachineInstr *UMI, void *InsertPos) {
handleRecordedInsts();
assert(UMI);
UniqueMachineInstr *MaybeNewNode = UMI;
if (InsertPos)
CSEMap.InsertNode(UMI, InsertPos);
else
MaybeNewNode = CSEMap.GetOrInsertNode(UMI);
if (MaybeNewNode != UMI) {
// A similar node exists in the folding set. Let's ignore this one.
return;
}
assert(InstrMapping.count(UMI->MI) == 0 &&
"This instruction should not be in the map");
InstrMapping[UMI->MI] = MaybeNewNode;
}
UniqueMachineInstr *GISelCSEInfo::getUniqueInstrForMI(const MachineInstr *MI) {
assert(shouldCSE(MI->getOpcode()) && "Trying to CSE an unsupported Node");
auto *Node = new (UniqueInstrAllocator) UniqueMachineInstr(MI);
return Node;
}
void GISelCSEInfo::insertInstr(MachineInstr *MI, void *InsertPos) {
assert(MI);
// If it exists in temporary insts, remove it.
TemporaryInsts.remove(MI);
auto *Node = getUniqueInstrForMI(MI);
insertNode(Node, InsertPos);
}
MachineInstr *GISelCSEInfo::getMachineInstrIfExists(FoldingSetNodeID &ID,
MachineBasicBlock *MBB,
void *&InsertPos) {
handleRecordedInsts();
if (auto *Inst = getNodeIfExists(ID, MBB, InsertPos)) {
LLVM_DEBUG(dbgs() << "CSEInfo::Found Instr " << *Inst->MI;);
return const_cast<MachineInstr *>(Inst->MI);
}
return nullptr;
}
void GISelCSEInfo::countOpcodeHit(unsigned Opc) {
#ifndef NDEBUG
if (OpcodeHitTable.count(Opc))
OpcodeHitTable[Opc] += 1;
else
OpcodeHitTable[Opc] = 1;
#endif
// Else do nothing.
}
void GISelCSEInfo::recordNewInstruction(MachineInstr *MI) {
if (shouldCSE(MI->getOpcode())) {
TemporaryInsts.insert(MI);
LLVM_DEBUG(dbgs() << "CSEInfo::Recording new MI " << *MI);
}
}
void GISelCSEInfo::handleRecordedInst(MachineInstr *MI) {
assert(shouldCSE(MI->getOpcode()) && "Invalid instruction for CSE");
auto *UMI = InstrMapping.lookup(MI);
LLVM_DEBUG(dbgs() << "CSEInfo::Handling recorded MI " << *MI);
if (UMI) {
// Invalidate this MI.
invalidateUniqueMachineInstr(UMI);
InstrMapping.erase(MI);
}
/// Now insert the new instruction.
if (UMI) {
/// We'll reuse the same UniqueMachineInstr to avoid the new
/// allocation.
*UMI = UniqueMachineInstr(MI);
insertNode(UMI, nullptr);
} else {
/// This is a new instruction. Allocate a new UniqueMachineInstr and
/// Insert.
insertInstr(MI);
}
}
void GISelCSEInfo::handleRemoveInst(MachineInstr *MI) {
if (auto *UMI = InstrMapping.lookup(MI)) {
invalidateUniqueMachineInstr(UMI);
InstrMapping.erase(MI);
}
TemporaryInsts.remove(MI);
}
void GISelCSEInfo::handleRecordedInsts() {
while (!TemporaryInsts.empty()) {
auto *MI = TemporaryInsts.pop_back_val();
handleRecordedInst(MI);
}
}
bool GISelCSEInfo::shouldCSE(unsigned Opc) const {
// Only GISel opcodes are CSEable
if (!isPreISelGenericOpcode(Opc))
return false;
assert(CSEOpt.get() && "CSEConfig not set");
return CSEOpt->shouldCSEOpc(Opc);
}
void GISelCSEInfo::erasingInstr(MachineInstr &MI) { handleRemoveInst(&MI); }
void GISelCSEInfo::createdInstr(MachineInstr &MI) { recordNewInstruction(&MI); }
void GISelCSEInfo::changingInstr(MachineInstr &MI) {
// For now, perform erase, followed by insert.
erasingInstr(MI);
createdInstr(MI);
}
void GISelCSEInfo::changedInstr(MachineInstr &MI) { changingInstr(MI); }
void GISelCSEInfo::analyze(MachineFunction &MF) {
setMF(MF);
for (auto &MBB : MF) {
if (MBB.empty())
continue;
for (MachineInstr &MI : MBB) {
if (!shouldCSE(MI.getOpcode()))
continue;
LLVM_DEBUG(dbgs() << "CSEInfo::Add MI: " << MI);
insertInstr(&MI);
}
}
}
void GISelCSEInfo::releaseMemory() {
print();
CSEMap.clear();
InstrMapping.clear();
UniqueInstrAllocator.Reset();
TemporaryInsts.clear();
CSEOpt.reset();
MRI = nullptr;
MF = nullptr;
#ifndef NDEBUG
OpcodeHitTable.clear();
#endif
}
Error GISelCSEInfo::verify() {
#ifndef NDEBUG
handleRecordedInsts();
// For each instruction in map from MI -> UMI,
// Profile(MI) and make sure UMI is found for that profile.
for (auto &It : InstrMapping) {
FoldingSetNodeID TmpID;
GISelInstProfileBuilder(TmpID, *MRI).addNodeID(It.first);
void *InsertPos;
UniqueMachineInstr *FoundNode =
CSEMap.FindNodeOrInsertPos(TmpID, InsertPos);
if (FoundNode != It.second)
return createStringError(std::errc::not_supported,
"CSEMap mismatch, InstrMapping has MIs without "
"corresponding Nodes in CSEMap");
}
// For every node in the CSEMap, make sure that the InstrMapping
// points to it.
for (auto It = CSEMap.begin(), End = CSEMap.end(); It != End; ++It) {
const UniqueMachineInstr &UMI = *It;
if (!InstrMapping.count(UMI.MI))
return createStringError(std::errc::not_supported,
"Node in CSE without InstrMapping", UMI.MI);
if (InstrMapping[UMI.MI] != &UMI)
return createStringError(std::make_error_code(std::errc::not_supported),
"Mismatch in CSE mapping");
}
#endif
return Error::success();
}
void GISelCSEInfo::print() {
LLVM_DEBUG(for (auto &It
: OpcodeHitTable) {
dbgs() << "CSEInfo::CSE Hit for Opc " << It.first << " : " << It.second
<< "\n";
};);
}
/// -----------------------------------------
// ---- Profiling methods for FoldingSetNode --- //
const GISelInstProfileBuilder &
GISelInstProfileBuilder::addNodeID(const MachineInstr *MI) const {
addNodeIDMBB(MI->getParent());
addNodeIDOpcode(MI->getOpcode());
for (auto &Op : MI->operands())
addNodeIDMachineOperand(Op);
addNodeIDFlag(MI->getFlags());
return *this;
}
const GISelInstProfileBuilder &
GISelInstProfileBuilder::addNodeIDOpcode(unsigned Opc) const {
ID.AddInteger(Opc);
return *this;
}
const GISelInstProfileBuilder &
GISelInstProfileBuilder::addNodeIDRegType(const LLT Ty) const {
uint64_t Val = Ty.getUniqueRAWLLTData();
ID.AddInteger(Val);
return *this;
}
const GISelInstProfileBuilder &
GISelInstProfileBuilder::addNodeIDRegType(const TargetRegisterClass *RC) const {
ID.AddPointer(RC);
return *this;
}
const GISelInstProfileBuilder &
GISelInstProfileBuilder::addNodeIDRegType(const RegisterBank *RB) const {
ID.AddPointer(RB);
return *this;
}
const GISelInstProfileBuilder &
GISelInstProfileBuilder::addNodeIDImmediate(int64_t Imm) const {
ID.AddInteger(Imm);
return *this;
}
const GISelInstProfileBuilder &
GISelInstProfileBuilder::addNodeIDRegNum(unsigned Reg) const {
ID.AddInteger(Reg);
return *this;
}
const GISelInstProfileBuilder &
GISelInstProfileBuilder::addNodeIDRegType(const unsigned Reg) const {
addNodeIDMachineOperand(MachineOperand::CreateReg(Reg, false));
return *this;
}
const GISelInstProfileBuilder &
GISelInstProfileBuilder::addNodeIDMBB(const MachineBasicBlock *MBB) const {
ID.AddPointer(MBB);
return *this;
}
const GISelInstProfileBuilder &
GISelInstProfileBuilder::addNodeIDFlag(unsigned Flag) const {
if (Flag)
ID.AddInteger(Flag);
return *this;
}
const GISelInstProfileBuilder &GISelInstProfileBuilder::addNodeIDMachineOperand(
const MachineOperand &MO) const {
if (MO.isReg()) {
Register Reg = MO.getReg();
if (!MO.isDef())
addNodeIDRegNum(Reg);
LLT Ty = MRI.getType(Reg);
if (Ty.isValid())
addNodeIDRegType(Ty);
auto *RB = MRI.getRegBankOrNull(Reg);
if (RB)
addNodeIDRegType(RB);
auto *RC = MRI.getRegClassOrNull(Reg);
if (RC)
addNodeIDRegType(RC);
assert(!MO.isImplicit() && "Unhandled case");
} else if (MO.isImm())
ID.AddInteger(MO.getImm());
else if (MO.isCImm())
ID.AddPointer(MO.getCImm());
else if (MO.isFPImm())
ID.AddPointer(MO.getFPImm());
else if (MO.isPredicate())
ID.AddInteger(MO.getPredicate());
else
llvm_unreachable("Unhandled operand type");
// Handle other types
return *this;
}
GISelCSEInfo &
GISelCSEAnalysisWrapper::get(std::unique_ptr<CSEConfigBase> CSEOpt,
bool Recompute) {
if (!AlreadyComputed || Recompute) {
Info.releaseMemory();
Info.setCSEConfig(std::move(CSEOpt));
Info.analyze(*MF);
AlreadyComputed = true;
}
return Info;
}
void GISelCSEAnalysisWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
MachineFunctionPass::getAnalysisUsage(AU);
}
bool GISelCSEAnalysisWrapperPass::runOnMachineFunction(MachineFunction &MF) {
releaseMemory();
Wrapper.setMF(MF);
return false;
}