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//===- EntryExitInstrumenter.cpp - Function Entry/Exit Instrumentation ----===//
//
// 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/Transforms/Utils/EntryExitInstrumenter.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/InitializePasses.h"
#include "llvm/TargetParser/Triple.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Utils.h"
using namespace llvm;
static void insertCall(Function &CurFn, StringRef Func,
BasicBlock::iterator InsertionPt, DebugLoc DL) {
Module &M = *InsertionPt->getParent()->getParent()->getParent();
LLVMContext &C = InsertionPt->getParent()->getContext();
if (Func == "mcount" ||
Func == ".mcount" ||
Func == "llvm.arm.gnu.eabi.mcount" ||
Func == "\01_mcount" ||
Func == "\01mcount" ||
Func == "__mcount" ||
Func == "_mcount" ||
Func == "__cyg_profile_func_enter_bare") {
Triple TargetTriple(M.getTargetTriple());
if (TargetTriple.isOSAIX() && Func == "__mcount") {
Type *SizeTy = M.getDataLayout().getIntPtrType(C);
Type *SizePtrTy = PointerType::getUnqual(C);
GlobalVariable *GV = new GlobalVariable(M, SizeTy, /*isConstant=*/false,
GlobalValue::InternalLinkage,
ConstantInt::get(SizeTy, 0));
CallInst *Call = CallInst::Create(
M.getOrInsertFunction(Func,
FunctionType::get(Type::getVoidTy(C), {SizePtrTy},
/*isVarArg=*/false)),
{GV}, "", InsertionPt);
Call->setDebugLoc(DL);
} else if (TargetTriple.isRISCV() || TargetTriple.isAArch64() ||
TargetTriple.isLoongArch()) {
// On RISC-V, AArch64, and LoongArch, the `_mcount` function takes
// `__builtin_return_address(0)` as an argument since
// `__builtin_return_address(1)` is not available on these platforms.
Instruction *RetAddr = CallInst::Create(
Intrinsic::getOrInsertDeclaration(&M, Intrinsic::returnaddress),
ConstantInt::get(Type::getInt32Ty(C), 0), "", InsertionPt);
RetAddr->setDebugLoc(DL);
FunctionCallee Fn = M.getOrInsertFunction(
Func, FunctionType::get(Type::getVoidTy(C), PointerType::getUnqual(C),
false));
CallInst *Call = CallInst::Create(Fn, RetAddr, "", InsertionPt);
Call->setDebugLoc(DL);
} else if (TargetTriple.isSystemZ()) {
// skip insertion for `mcount` on SystemZ. This will be handled later in
// `emitPrologue`. Add custom attribute to denote this.
CurFn.addFnAttr(
llvm::Attribute::get(C, "systemz-instrument-function-entry", Func));
} else {
FunctionCallee Fn = M.getOrInsertFunction(Func, Type::getVoidTy(C));
CallInst *Call = CallInst::Create(Fn, "", InsertionPt);
Call->setDebugLoc(DL);
}
return;
}
if (Func == "__cyg_profile_func_enter" || Func == "__cyg_profile_func_exit") {
Type *ArgTypes[] = {PointerType::getUnqual(C), PointerType::getUnqual(C)};
FunctionCallee Fn = M.getOrInsertFunction(
Func, FunctionType::get(Type::getVoidTy(C), ArgTypes, false));
Instruction *RetAddr = CallInst::Create(
Intrinsic::getOrInsertDeclaration(&M, Intrinsic::returnaddress),
ArrayRef<Value *>(ConstantInt::get(Type::getInt32Ty(C), 0)), "",
InsertionPt);
RetAddr->setDebugLoc(DL);
Value *Args[] = {&CurFn, RetAddr};
CallInst *Call =
CallInst::Create(Fn, ArrayRef<Value *>(Args), "", InsertionPt);
Call->setDebugLoc(DL);
return;
}
// We only know how to call a fixed set of instrumentation functions, because
// they all expect different arguments, etc.
report_fatal_error(Twine("Unknown instrumentation function: '") + Func + "'");
}
static bool runOnFunction(Function &F, bool PostInlining) {
// The asm in a naked function may reasonably expect the argument registers
// and the return address register (if present) to be live. An inserted
// function call will clobber these registers. Simply skip naked functions for
// all targets.
if (F.hasFnAttribute(Attribute::Naked))
return false;
// available_externally functions may not have definitions external to the
// module (e.g. gnu::always_inline). Instrumenting them might lead to linker
// errors if they are optimized out. Skip them like GCC.
if (F.hasAvailableExternallyLinkage())
return false;
StringRef EntryAttr = PostInlining ? "instrument-function-entry-inlined"
: "instrument-function-entry";
StringRef ExitAttr = PostInlining ? "instrument-function-exit-inlined"
: "instrument-function-exit";
StringRef EntryFunc = F.getFnAttribute(EntryAttr).getValueAsString();
StringRef ExitFunc = F.getFnAttribute(ExitAttr).getValueAsString();
bool Changed = false;
// If the attribute is specified, insert instrumentation and then "consume"
// the attribute so that it's not inserted again if the pass should happen to
// run later for some reason.
if (!EntryFunc.empty()) {
DebugLoc DL;
if (auto SP = F.getSubprogram())
DL = DILocation::get(SP->getContext(), SP->getScopeLine(), 0, SP);
insertCall(F, EntryFunc, F.begin()->getFirstInsertionPt(), DL);
Changed = true;
F.removeFnAttr(EntryAttr);
}
if (!ExitFunc.empty()) {
for (BasicBlock &BB : F) {
Instruction *T = BB.getTerminator();
if (!isa<ReturnInst>(T))
continue;
// If T is preceded by a musttail call, that's the real terminator.
if (CallInst *CI = BB.getTerminatingMustTailCall())
T = CI;
DebugLoc DL;
if (DebugLoc TerminatorDL = T->getDebugLoc())
DL = TerminatorDL;
else if (auto SP = F.getSubprogram())
DL = DILocation::get(SP->getContext(), 0, 0, SP);
insertCall(F, ExitFunc, T->getIterator(), DL);
Changed = true;
}
F.removeFnAttr(ExitAttr);
}
return Changed;
}
namespace {
struct PostInlineEntryExitInstrumenter : public FunctionPass {
static char ID;
PostInlineEntryExitInstrumenter() : FunctionPass(ID) {
initializePostInlineEntryExitInstrumenterPass(
*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addPreserved<GlobalsAAWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
}
bool runOnFunction(Function &F) override { return ::runOnFunction(F, true); }
};
char PostInlineEntryExitInstrumenter::ID = 0;
}
INITIALIZE_PASS_BEGIN(
PostInlineEntryExitInstrumenter, "post-inline-ee-instrument",
"Instrument function entry/exit with calls to e.g. mcount() "
"(post inlining)",
false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_END(
PostInlineEntryExitInstrumenter, "post-inline-ee-instrument",
"Instrument function entry/exit with calls to e.g. mcount() "
"(post inlining)",
false, false)
FunctionPass *llvm::createPostInlineEntryExitInstrumenterPass() {
return new PostInlineEntryExitInstrumenter();
}
PreservedAnalyses
llvm::EntryExitInstrumenterPass::run(Function &F, FunctionAnalysisManager &AM) {
if (!runOnFunction(F, PostInlining))
return PreservedAnalyses::all();
PreservedAnalyses PA;
PA.preserveSet<CFGAnalyses>();
return PA;
}
void llvm::EntryExitInstrumenterPass::printPipeline(
raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
static_cast<PassInfoMixin<llvm::EntryExitInstrumenterPass> *>(this)
->printPipeline(OS, MapClassName2PassName);
OS << '<';
if (PostInlining)
OS << "post-inline";
OS << '>';
}
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