maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/bolt/lib/Passes/FrameAnalysis.cpp

643 lines
20 KiB
C++
Raw Blame History

//===- bolt/Passes/FrameAnalysis.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 the FrameAnalysis class.
//
//===----------------------------------------------------------------------===//
#include "bolt/Passes/FrameAnalysis.h"
#include "bolt/Core/ParallelUtilities.h"
#include "bolt/Passes/CallGraphWalker.h"
#include "llvm/Support/Timer.h"
#include <fstream>
#include <stack>
#define DEBUG_TYPE "fa"
using namespace llvm;
namespace opts {
extern cl::OptionCategory BoltOptCategory;
extern cl::opt<unsigned> Verbosity;
static cl::list<std::string>
FrameOptFunctionNames("funcs-fop", cl::CommaSeparated,
cl::desc("list of functions to apply frame opts"),
cl::value_desc("func1,func2,func3,..."));
static cl::opt<std::string> FrameOptFunctionNamesFile(
"funcs-file-fop",
cl::desc("file with list of functions to frame optimize"));
static cl::opt<bool>
TimeFA("time-fa",
cl::desc("time frame analysis steps"),
cl::ReallyHidden,
cl::ZeroOrMore,
cl::cat(BoltOptCategory));
bool shouldFrameOptimize(const llvm::bolt::BinaryFunction &Function) {
if (Function.hasUnknownControlFlow())
return false;
if (!FrameOptFunctionNamesFile.empty()) {
assert(!FrameOptFunctionNamesFile.empty() && "unexpected empty file name");
std::ifstream FuncsFile(FrameOptFunctionNamesFile, std::ios::in);
std::string FuncName;
while (std::getline(FuncsFile, FuncName))
FrameOptFunctionNames.push_back(FuncName);
FrameOptFunctionNamesFile = "";
}
bool IsValid = true;
if (!FrameOptFunctionNames.empty()) {
IsValid = false;
for (std::string &Name : FrameOptFunctionNames) {
if (Function.hasName(Name)) {
IsValid = true;
break;
}
}
}
if (!IsValid)
return false;
return IsValid;
}
} // namespace opts
namespace llvm {
namespace bolt {
raw_ostream &operator<<(raw_ostream &OS, const FrameIndexEntry &FIE) {
OS << "FrameIndexEntry<IsLoad: " << FIE.IsLoad << ", IsStore: " << FIE.IsStore
<< ", IsStoreFromReg: " << FIE.IsStoreFromReg
<< ", RegOrImm: " << FIE.RegOrImm << ", StackOffset: ";
if (FIE.StackOffset < 0)
OS << "-" << Twine::utohexstr(-FIE.StackOffset);
else
OS << "+" << Twine::utohexstr(FIE.StackOffset);
OS << ", Size: " << static_cast<int>(FIE.Size)
<< ", IsSimple: " << FIE.IsSimple << ">";
return OS;
}
namespace {
/// This class should be used to iterate through basic blocks in layout order
/// to analyze instructions for frame accesses. The user should call
/// enterNewBB() whenever starting analyzing a new BB and doNext() for each
/// instruction. After doNext(), if isValidAccess() returns true, it means the
/// current instruction accesses the frame and getFIE() may be used to obtain
/// details about this access.
class FrameAccessAnalysis {
/// We depend on Stack Pointer Tracking to figure out the current SP offset
/// value at a given program point
StackPointerTracking &SPT;
/// Context vars
const BinaryContext &BC;
const BinaryFunction &BF;
// Vars used for storing useful CFI info to give us a hint about how the stack
// is used in this function
int SPOffset{0};
int FPOffset{0};
int64_t CfaOffset{-8};
uint16_t CfaReg{7};
std::stack<std::pair<int64_t, uint16_t>> CFIStack;
/// Our pointer to access SPT info
const MCInst *Prev{nullptr};
/// Info about the last frame access
bool IsValidAccess{false};
FrameIndexEntry FIE;
bool decodeFrameAccess(const MCInst &Inst) {
int32_t SrcImm = 0;
MCPhysReg Reg = 0;
int64_t StackOffset = 0;
bool IsIndexed = false;
if (!BC.MIB->isStackAccess(
Inst, FIE.IsLoad, FIE.IsStore, FIE.IsStoreFromReg, Reg, SrcImm,
FIE.StackPtrReg, StackOffset, FIE.Size, FIE.IsSimple, IsIndexed)) {
return true;
}
if (IsIndexed || FIE.Size == 0) {
LLVM_DEBUG(dbgs() << "Giving up on indexed memory access/unknown size\n");
LLVM_DEBUG(dbgs() << "Blame insn: ");
LLVM_DEBUG(Inst.dump());
return false;
}
assert(FIE.Size != 0);
FIE.RegOrImm = SrcImm;
if (FIE.IsLoad || FIE.IsStoreFromReg)
FIE.RegOrImm = Reg;
if (FIE.StackPtrReg == BC.MIB->getStackPointer() && SPOffset != SPT.EMPTY &&
SPOffset != SPT.SUPERPOSITION) {
LLVM_DEBUG(
dbgs() << "Adding access via SP while CFA reg is another one\n");
FIE.StackOffset = SPOffset + StackOffset;
} else if (FIE.StackPtrReg == BC.MIB->getFramePointer() &&
FPOffset != SPT.EMPTY && FPOffset != SPT.SUPERPOSITION) {
LLVM_DEBUG(
dbgs() << "Adding access via FP while CFA reg is another one\n");
FIE.StackOffset = FPOffset + StackOffset;
} else if (FIE.StackPtrReg ==
*BC.MRI->getLLVMRegNum(CfaReg, /*isEH=*/false)) {
FIE.StackOffset = CfaOffset + StackOffset;
} else {
LLVM_DEBUG(
dbgs() << "Found stack access with reg different than cfa reg.\n");
LLVM_DEBUG(dbgs() << "\tCurrent CFA reg: " << CfaReg
<< "\n\tStack access reg: " << FIE.StackPtrReg << "\n");
LLVM_DEBUG(dbgs() << "Blame insn: ");
LLVM_DEBUG(Inst.dump());
return false;
}
IsValidAccess = true;
return true;
}
public:
FrameAccessAnalysis(BinaryFunction &BF, StackPointerTracking &SPT)
: SPT(SPT), BC(BF.getBinaryContext()), BF(BF) {}
void enterNewBB() { Prev = nullptr; }
const FrameIndexEntry &getFIE() const { return FIE; }
int getSPOffset() const { return SPOffset; }
bool isValidAccess() const { return IsValidAccess; }
bool doNext(const BinaryBasicBlock &BB, const MCInst &Inst) {
IsValidAccess = false;
std::tie(SPOffset, FPOffset) =
Prev ? *SPT.getStateAt(*Prev) : *SPT.getStateAt(BB);
Prev = &Inst;
// Use CFI information to keep track of which register is being used to
// access the frame
if (BC.MIB->isCFI(Inst)) {
const MCCFIInstruction *CFI = BF.getCFIFor(Inst);
switch (CFI->getOperation()) {
case MCCFIInstruction::OpDefCfa:
CfaOffset = CFI->getOffset();
LLVM_FALLTHROUGH;
case MCCFIInstruction::OpDefCfaRegister:
CfaReg = CFI->getRegister();
break;
case MCCFIInstruction::OpDefCfaOffset:
CfaOffset = CFI->getOffset();
break;
case MCCFIInstruction::OpRememberState:
CFIStack.push(std::make_pair(CfaOffset, CfaReg));
break;
case MCCFIInstruction::OpRestoreState: {
if (CFIStack.empty())
dbgs() << "Assertion is about to fail: " << BF.getPrintName() << "\n";
assert(!CFIStack.empty() && "Corrupt CFI stack");
std::pair<int64_t, uint16_t> &Elem = CFIStack.top();
CFIStack.pop();
CfaOffset = Elem.first;
CfaReg = Elem.second;
break;
}
case MCCFIInstruction::OpAdjustCfaOffset:
llvm_unreachable("Unhandled AdjustCfaOffset");
break;
default:
break;
}
return true;
}
if (BC.MIB->escapesVariable(Inst, SPT.HasFramePointer)) {
LLVM_DEBUG(
dbgs() << "Leaked stack address, giving up on this function.\n");
LLVM_DEBUG(dbgs() << "Blame insn: ");
LLVM_DEBUG(Inst.dump());
return false;
}
return decodeFrameAccess(Inst);
}
};
} // end anonymous namespace
void FrameAnalysis::addArgAccessesFor(MCInst &Inst, ArgAccesses &&AA) {
if (ErrorOr<ArgAccesses &> OldAA = getArgAccessesFor(Inst)) {
if (OldAA->AssumeEverything)
return;
*OldAA = std::move(AA);
return;
}
if (AA.AssumeEverything) {
// Index 0 in ArgAccessesVector represents an "assumeeverything" entry
BC.MIB->addAnnotation(Inst, "ArgAccessEntry", 0U);
return;
}
BC.MIB->addAnnotation(Inst, "ArgAccessEntry",
(unsigned)ArgAccessesVector.size());
ArgAccessesVector.emplace_back(std::move(AA));
}
void FrameAnalysis::addArgInStackAccessFor(MCInst &Inst,
const ArgInStackAccess &Arg) {
ErrorOr<ArgAccesses &> AA = getArgAccessesFor(Inst);
if (!AA) {
addArgAccessesFor(Inst, ArgAccesses(false));
AA = getArgAccessesFor(Inst);
assert(AA && "Object setup failed");
}
std::set<ArgInStackAccess> &Set = AA->Set;
assert(!AA->AssumeEverything && "Adding arg to AssumeEverything set");
Set.emplace(Arg);
}
void FrameAnalysis::addFIEFor(MCInst &Inst, const FrameIndexEntry &FIE) {
BC.MIB->addAnnotation(Inst, "FrameAccessEntry", (unsigned)FIEVector.size());
FIEVector.emplace_back(FIE);
}
ErrorOr<ArgAccesses &> FrameAnalysis::getArgAccessesFor(const MCInst &Inst) {
if (auto Idx = BC.MIB->tryGetAnnotationAs<unsigned>(Inst, "ArgAccessEntry")) {
assert(ArgAccessesVector.size() > *Idx && "Out of bounds");
return ArgAccessesVector[*Idx];
}
return make_error_code(errc::result_out_of_range);
}
ErrorOr<const ArgAccesses &>
FrameAnalysis::getArgAccessesFor(const MCInst &Inst) const {
if (auto Idx = BC.MIB->tryGetAnnotationAs<unsigned>(Inst, "ArgAccessEntry")) {
assert(ArgAccessesVector.size() > *Idx && "Out of bounds");
return ArgAccessesVector[*Idx];
}
return make_error_code(errc::result_out_of_range);
}
ErrorOr<const FrameIndexEntry &>
FrameAnalysis::getFIEFor(const MCInst &Inst) const {
if (auto Idx =
BC.MIB->tryGetAnnotationAs<unsigned>(Inst, "FrameAccessEntry")) {
assert(FIEVector.size() > *Idx && "Out of bounds");
return FIEVector[*Idx];
}
return make_error_code(errc::result_out_of_range);
}
void FrameAnalysis::traverseCG(BinaryFunctionCallGraph &CG) {
CallGraphWalker CGWalker(CG);
CGWalker.registerVisitor(
[&](BinaryFunction *Func) -> bool { return computeArgsAccessed(*Func); });
CGWalker.walk();
DEBUG_WITH_TYPE("ra", {
for (auto &MapEntry : ArgsTouchedMap) {
const BinaryFunction *Func = MapEntry.first;
const auto &Set = MapEntry.second;
dbgs() << "Args accessed for " << Func->getPrintName() << ": ";
if (!Set.empty() && Set.count(std::make_pair(-1, 0)))
dbgs() << "assume everything";
else
for (const std::pair<int64_t, uint8_t> &Entry : Set)
dbgs() << "[" << Entry.first << ", " << (int)Entry.second << "] ";
dbgs() << "\n";
}
});
}
bool FrameAnalysis::updateArgsTouchedFor(const BinaryFunction &BF, MCInst &Inst,
int CurOffset) {
if (!BC.MIB->isCall(Inst))
return false;
std::set<int64_t> Res;
const MCSymbol *TargetSymbol = BC.MIB->getTargetSymbol(Inst);
// If indirect call, we conservatively assume it accesses all stack positions
if (TargetSymbol == nullptr) {
addArgAccessesFor(Inst, ArgAccesses(/*AssumeEverything=*/true));
if (!FunctionsRequireAlignment.count(&BF)) {
FunctionsRequireAlignment.insert(&BF);
return true;
}
return false;
}
const BinaryFunction *Function = BC.getFunctionForSymbol(TargetSymbol);
// Call to a function without a BinaryFunction object. Conservatively assume
// it accesses all stack positions
if (Function == nullptr) {
addArgAccessesFor(Inst, ArgAccesses(/*AssumeEverything=*/true));
if (!FunctionsRequireAlignment.count(&BF)) {
FunctionsRequireAlignment.insert(&BF);
return true;
}
return false;
}
auto Iter = ArgsTouchedMap.find(Function);
bool Changed = false;
if (BC.MIB->isTailCall(Inst) && Iter != ArgsTouchedMap.end()) {
// Ignore checking CurOffset because we can't always reliably determine the
// offset specially after an epilogue, where tailcalls happen. It should be
// -8.
for (std::pair<int64_t, uint8_t> Elem : Iter->second) {
if (ArgsTouchedMap[&BF].find(Elem) == ArgsTouchedMap[&BF].end()) {
ArgsTouchedMap[&BF].emplace(Elem);
Changed = true;
}
}
}
if (FunctionsRequireAlignment.count(Function) &&
!FunctionsRequireAlignment.count(&BF)) {
Changed = true;
FunctionsRequireAlignment.insert(&BF);
}
if (Iter == ArgsTouchedMap.end())
return Changed;
if (CurOffset == StackPointerTracking::EMPTY ||
CurOffset == StackPointerTracking::SUPERPOSITION) {
addArgAccessesFor(Inst, ArgAccesses(/*AssumeEverything=*/true));
return Changed;
}
for (std::pair<int64_t, uint8_t> Elem : Iter->second) {
if (Elem.first == -1) {
addArgAccessesFor(Inst, ArgAccesses(/*AssumeEverything=*/true));
break;
}
LLVM_DEBUG(dbgs() << "Added arg in stack access annotation "
<< CurOffset + Elem.first << "\n");
addArgInStackAccessFor(
Inst, ArgInStackAccess{/*StackOffset=*/CurOffset + Elem.first,
/*Size=*/Elem.second});
}
return Changed;
}
bool FrameAnalysis::computeArgsAccessed(BinaryFunction &BF) {
if (!BF.isSimple() || !BF.hasCFG()) {
LLVM_DEBUG(dbgs() << "Treating " << BF.getPrintName()
<< " conservatively.\n");
ArgsTouchedMap[&BF].emplace(std::make_pair(-1, 0));
if (!FunctionsRequireAlignment.count(&BF)) {
FunctionsRequireAlignment.insert(&BF);
return true;
}
return false;
}
LLVM_DEBUG(dbgs() << "Now computing args accessed for: " << BF.getPrintName()
<< "\n");
bool UpdatedArgsTouched = false;
bool NoInfo = false;
FrameAccessAnalysis FAA(BF, getSPT(BF));
for (BinaryBasicBlock *BB : BF.layout()) {
FAA.enterNewBB();
for (MCInst &Inst : *BB) {
if (!FAA.doNext(*BB, Inst)) {
ArgsTouchedMap[&BF].emplace(std::make_pair(-1, 0));
NoInfo = true;
break;
}
// Check for calls -- attach stack accessing info to them regarding their
// target
if (updateArgsTouchedFor(BF, Inst, FAA.getSPOffset()))
UpdatedArgsTouched = true;
// Check for stack accesses that affect callers
if (!FAA.isValidAccess())
continue;
const FrameIndexEntry &FIE = FAA.getFIE();
if (FIE.StackOffset < 0)
continue;
if (ArgsTouchedMap[&BF].find(std::make_pair(FIE.StackOffset, FIE.Size)) !=
ArgsTouchedMap[&BF].end())
continue;
// Record accesses to the previous stack frame
ArgsTouchedMap[&BF].emplace(std::make_pair(FIE.StackOffset, FIE.Size));
UpdatedArgsTouched = true;
LLVM_DEBUG({
dbgs() << "Arg access offset " << FIE.StackOffset << " added to:\n";
BC.printInstruction(dbgs(), Inst, 0, &BF, true);
});
}
if (NoInfo)
break;
}
if (FunctionsRequireAlignment.count(&BF))
return UpdatedArgsTouched;
if (NoInfo) {
FunctionsRequireAlignment.insert(&BF);
return true;
}
for (BinaryBasicBlock &BB : BF) {
for (MCInst &Inst : BB) {
if (BC.MIB->requiresAlignedAddress(Inst)) {
FunctionsRequireAlignment.insert(&BF);
return true;
}
}
}
return UpdatedArgsTouched;
}
bool FrameAnalysis::restoreFrameIndex(BinaryFunction &BF) {
FrameAccessAnalysis FAA(BF, getSPT(BF));
LLVM_DEBUG(dbgs() << "Restoring frame indices for \"" << BF.getPrintName()
<< "\"\n");
for (BinaryBasicBlock *BB : BF.layout()) {
LLVM_DEBUG(dbgs() << "\tNow at BB " << BB->getName() << "\n");
FAA.enterNewBB();
for (MCInst &Inst : *BB) {
if (!FAA.doNext(*BB, Inst))
return false;
LLVM_DEBUG({
dbgs() << "\t\tNow at ";
Inst.dump();
dbgs() << "\t\t\tSP offset is " << FAA.getSPOffset() << "\n";
});
if (!FAA.isValidAccess())
continue;
const FrameIndexEntry &FIE = FAA.getFIE();
addFIEFor(Inst, FIE);
LLVM_DEBUG({
dbgs() << "Frame index annotation " << FIE << " added to:\n";
BC.printInstruction(dbgs(), Inst, 0, &BF, true);
});
}
}
return true;
}
void FrameAnalysis::cleanAnnotations() {
NamedRegionTimer T("cleanannotations", "clean annotations", "FA",
"FA breakdown", opts::TimeFA);
ParallelUtilities::WorkFuncTy CleanFunction = [&](BinaryFunction &BF) {
for (BinaryBasicBlock &BB : BF) {
for (MCInst &Inst : BB) {
BC.MIB->removeAnnotation(Inst, "ArgAccessEntry");
BC.MIB->removeAnnotation(Inst, "FrameAccessEntry");
}
}
};
ParallelUtilities::runOnEachFunction(
BC, ParallelUtilities::SchedulingPolicy::SP_INST_LINEAR, CleanFunction,
ParallelUtilities::PredicateTy(nullptr), "cleanAnnotations");
}
FrameAnalysis::FrameAnalysis(BinaryContext &BC, BinaryFunctionCallGraph &CG)
: BC(BC) {
// Position 0 of the vector should be always associated with "assume access
// everything".
ArgAccessesVector.emplace_back(ArgAccesses(/*AssumeEverything*/ true));
if (!opts::NoThreads) {
NamedRegionTimer T1("precomputespt", "pre-compute spt", "FA",
"FA breakdown", opts::TimeFA);
preComputeSPT();
}
{
NamedRegionTimer T1("traversecg", "traverse call graph", "FA",
"FA breakdown", opts::TimeFA);
traverseCG(CG);
}
for (auto &I : BC.getBinaryFunctions()) {
uint64_t Count = I.second.getExecutionCount();
if (Count != BinaryFunction::COUNT_NO_PROFILE)
CountDenominator += Count;
// "shouldOptimize" for passes that run after finalize
if (!(I.second.isSimple() && I.second.hasCFG() && !I.second.isIgnored()) ||
!opts::shouldFrameOptimize(I.second)) {
++NumFunctionsNotOptimized;
if (Count != BinaryFunction::COUNT_NO_PROFILE)
CountFunctionsNotOptimized += Count;
continue;
}
{
NamedRegionTimer T1("restorefi", "restore frame index", "FA",
"FA breakdown", opts::TimeFA);
if (!restoreFrameIndex(I.second)) {
++NumFunctionsFailedRestoreFI;
uint64_t Count = I.second.getExecutionCount();
if (Count != BinaryFunction::COUNT_NO_PROFILE)
CountFunctionsFailedRestoreFI += Count;
continue;
}
}
AnalyzedFunctions.insert(&I.second);
}
{
NamedRegionTimer T1("clearspt", "clear spt", "FA", "FA breakdown",
opts::TimeFA);
clearSPTMap();
// Clean up memory allocated for annotation values
if (!opts::NoThreads)
for (MCPlusBuilder::AllocatorIdTy Id : SPTAllocatorsId)
BC.MIB->freeValuesAllocator(Id);
}
}
void FrameAnalysis::printStats() {
outs() << "BOLT-INFO: FRAME ANALYSIS: " << NumFunctionsNotOptimized
<< " function(s) "
<< format("(%.1lf%% dyn cov)",
(100.0 * CountFunctionsNotOptimized / CountDenominator))
<< " were not optimized.\n"
<< "BOLT-INFO: FRAME ANALYSIS: " << NumFunctionsFailedRestoreFI
<< " function(s) "
<< format("(%.1lf%% dyn cov)",
(100.0 * CountFunctionsFailedRestoreFI / CountDenominator))
<< " could not have its frame indices restored.\n";
}
void FrameAnalysis::clearSPTMap() {
if (opts::NoThreads) {
SPTMap.clear();
return;
}
ParallelUtilities::WorkFuncTy ClearFunctionSPT = [&](BinaryFunction &BF) {
std::unique_ptr<StackPointerTracking> &SPTPtr = SPTMap.find(&BF)->second;
SPTPtr.reset();
};
ParallelUtilities::PredicateTy SkipFunc = [&](const BinaryFunction &BF) {
return !BF.isSimple() || !BF.hasCFG();
};
ParallelUtilities::runOnEachFunction(
BC, ParallelUtilities::SchedulingPolicy::SP_INST_LINEAR, ClearFunctionSPT,
SkipFunc, "clearSPTMap");
SPTMap.clear();
}
void FrameAnalysis::preComputeSPT() {
// Make sure that the SPTMap is empty
assert(SPTMap.size() == 0);
// Create map entries to allow lock-free parallel execution
for (auto &BFI : BC.getBinaryFunctions()) {
BinaryFunction &BF = BFI.second;
if (!BF.isSimple() || !BF.hasCFG())
continue;
SPTMap.emplace(&BF, std::unique_ptr<StackPointerTracking>());
}
// Create an index for the SPT annotation to allow lock-free parallel
// execution
BC.MIB->getOrCreateAnnotationIndex("StackPointerTracking");
// Run SPT in parallel
ParallelUtilities::WorkFuncWithAllocTy ProcessFunction =
[&](BinaryFunction &BF, MCPlusBuilder::AllocatorIdTy AllocId) {
std::unique_ptr<StackPointerTracking> &SPTPtr =
SPTMap.find(&BF)->second;
SPTPtr = std::make_unique<StackPointerTracking>(BF, AllocId);
SPTPtr->run();
};
ParallelUtilities::PredicateTy SkipPredicate = [&](const BinaryFunction &BF) {
return !BF.isSimple() || !BF.hasCFG();
};
ParallelUtilities::runOnEachFunctionWithUniqueAllocId(
BC, ParallelUtilities::SchedulingPolicy::SP_BB_QUADRATIC, ProcessFunction,
SkipPredicate, "preComputeSPT");
}
} // namespace bolt
} // namespace llvm
Reference in New Issue View Git Blame Copy Permalink