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llvm-project/llvm/tools/bugpoint/ExtractFunction.cpp

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//===- ExtractFunction.cpp - Extract a function from Program --------------===//
//
// 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 several methods that are used to extract functions,
// loops, or portions of a module from the rest of the module.
//
//===----------------------------------------------------------------------===//
#include "BugDriver.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/FileUtilities.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/CodeExtractor.h"
#include <set>
using namespace llvm;
#define DEBUG_TYPE "bugpoint"
namespace llvm {
bool DisableSimplifyCFG = false;
extern cl::opt<std::string> OutputPrefix;
} // End llvm namespace
namespace {
cl::opt<bool> NoDCE("disable-dce",
cl::desc("Do not use the -dce pass to reduce testcases"));
cl::opt<bool, true>
NoSCFG("disable-simplifycfg", cl::location(DisableSimplifyCFG),
cl::desc("Do not use the -simplifycfg pass to reduce testcases"));
Function *globalInitUsesExternalBA(GlobalVariable *GV) {
if (!GV->hasInitializer())
return nullptr;
Constant *I = GV->getInitializer();
// walk the values used by the initializer
// (and recurse into things like ConstantExpr)
std::vector<Constant *> Todo;
std::set<Constant *> Done;
Todo.push_back(I);
while (!Todo.empty()) {
Constant *V = Todo.back();
Todo.pop_back();
Done.insert(V);
if (BlockAddress *BA = dyn_cast<BlockAddress>(V)) {
Function *F = BA->getFunction();
if (F->isDeclaration())
return F;
}
for (User::op_iterator i = V->op_begin(), e = V->op_end(); i != e; ++i) {
Constant *C = dyn_cast<Constant>(*i);
if (C && !isa<GlobalValue>(C) && !Done.count(C))
Todo.push_back(C);
}
}
return nullptr;
}
} // end anonymous namespace
std::unique_ptr<Module>
BugDriver::deleteInstructionFromProgram(const Instruction *I,
unsigned Simplification) {
// FIXME, use vmap?
std::unique_ptr<Module> Clone = CloneModule(*Program);
const BasicBlock *PBB = I->getParent();
const Function *PF = PBB->getParent();
Module::iterator RFI = Clone->begin(); // Get iterator to corresponding fn
std::advance(
RFI, std::distance(PF->getParent()->begin(), Module::const_iterator(PF)));
Function::iterator RBI = RFI->begin(); // Get iterator to corresponding BB
std::advance(RBI, std::distance(PF->begin(), Function::const_iterator(PBB)));
BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
std::advance(RI, std::distance(PBB->begin(), BasicBlock::const_iterator(I)));
Instruction *TheInst = &*RI; // Got the corresponding instruction!
// If this instruction produces a value, replace any users with null values
if (!TheInst->getType()->isVoidTy())
TheInst->replaceAllUsesWith(Constant::getNullValue(TheInst->getType()));
// Remove the instruction from the program.
TheInst->getParent()->getInstList().erase(TheInst);
// Spiff up the output a little bit.
std::vector<std::string> Passes;
/// Can we get rid of the -disable-* options?
if (Simplification > 1 && !NoDCE)
Passes.push_back("dce");
if (Simplification && !DisableSimplifyCFG)
Passes.push_back("simplifycfg"); // Delete dead control flow
Passes.push_back("verify");
std::unique_ptr<Module> New = runPassesOn(Clone.get(), Passes);
if (!New) {
errs() << "Instruction removal failed. Sorry. :( Please report a bug!\n";
exit(1);
}
return New;
}
std::unique_ptr<Module>
BugDriver::performFinalCleanups(std::unique_ptr<Module> M,
bool MayModifySemantics) {
// Make all functions external, so GlobalDCE doesn't delete them...
for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
I->setLinkage(GlobalValue::ExternalLinkage);
std::vector<std::string> CleanupPasses;
CleanupPasses.push_back("globaldce");
if (MayModifySemantics)
CleanupPasses.push_back("deadarghaX0r");
else
CleanupPasses.push_back("deadargelim");
std::unique_ptr<Module> New = runPassesOn(M.get(), CleanupPasses);
if (!New) {
errs() << "Final cleanups failed. Sorry. :( Please report a bug!\n";
return nullptr;
}
return New;
}
std::unique_ptr<Module> BugDriver::extractLoop(Module *M) {
std::vector<std::string> LoopExtractPasses;
LoopExtractPasses.push_back("loop-extract-single");
std::unique_ptr<Module> NewM = runPassesOn(M, LoopExtractPasses);
if (!NewM) {
outs() << "*** Loop extraction failed: ";
EmitProgressBitcode(*M, "loopextraction", true);
outs() << "*** Sorry. :( Please report a bug!\n";
return nullptr;
}
// Check to see if we created any new functions. If not, no loops were
// extracted and we should return null. Limit the number of loops we extract
// to avoid taking forever.
static unsigned NumExtracted = 32;
if (M->size() == NewM->size() || --NumExtracted == 0) {
return nullptr;
} else {
assert(M->size() < NewM->size() && "Loop extract removed functions?");
Module::iterator MI = NewM->begin();
for (unsigned i = 0, e = M->size(); i != e; ++i)
++MI;
}
return NewM;
}
static void eliminateAliases(GlobalValue *GV) {
// First, check whether a GlobalAlias references this definition.
// GlobalAlias MAY NOT reference declarations.
for (;;) {
// 1. Find aliases
SmallVector<GlobalAlias *, 1> aliases;
Module *M = GV->getParent();
for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end();
I != E; ++I)
if (I->getAliasee()->stripPointerCasts() == GV)
aliases.push_back(&*I);
if (aliases.empty())
break;
// 2. Resolve aliases
for (unsigned i = 0, e = aliases.size(); i < e; ++i) {
aliases[i]->replaceAllUsesWith(aliases[i]->getAliasee());
aliases[i]->eraseFromParent();
}
// 3. Repeat until no more aliases found; there might
// be an alias to an alias...
}
}
//
// DeleteGlobalInitializer - "Remove" the global variable by deleting its
// initializer,
// making it external.
//
void llvm::DeleteGlobalInitializer(GlobalVariable *GV) {
eliminateAliases(GV);
GV->setInitializer(nullptr);
GV->setComdat(nullptr);
}
// DeleteFunctionBody - "Remove" the function by deleting all of its basic
// blocks, making it external.
//
void llvm::DeleteFunctionBody(Function *F) {
eliminateAliases(F);
// Function declarations can't have comdats.
F->setComdat(nullptr);
// delete the body of the function...
F->deleteBody();
assert(F->isDeclaration() && "This didn't make the function external!");
}
/// GetTorInit - Given a list of entries for static ctors/dtors, return them
/// as a constant array.
static Constant *GetTorInit(std::vector<std::pair<Function *, int>> &TorList) {
assert(!TorList.empty() && "Don't create empty tor list!");
std::vector<Constant *> ArrayElts;
Type *Int32Ty = Type::getInt32Ty(TorList[0].first->getContext());
StructType *STy = StructType::get(Int32Ty, TorList[0].first->getType());
for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
Constant *Elts[] = {ConstantInt::get(Int32Ty, TorList[i].second),
TorList[i].first};
ArrayElts.push_back(ConstantStruct::get(STy, Elts));
}
return ConstantArray::get(
ArrayType::get(ArrayElts[0]->getType(), ArrayElts.size()), ArrayElts);
}
/// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
/// M1 has all of the global variables. If M2 contains any functions that are
/// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
/// prune appropriate entries out of M1s list.
static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
ValueToValueMapTy &VMap) {
GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() || !GV->use_empty())
return;
std::vector<std::pair<Function *, int>> M1Tors, M2Tors;
ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
if (!InitList)
return;
for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
if (ConstantStruct *CS =
dyn_cast<ConstantStruct>(InitList->getOperand(i))) {
if (CS->getNumOperands() != 2)
return; // Not array of 2-element structs.
if (CS->getOperand(1)->isNullValue())
break; // Found a null terminator, stop here.
ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
int Priority = CI ? CI->getSExtValue() : 0;
Constant *FP = CS->getOperand(1);
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
if (CE->isCast())
FP = CE->getOperand(0);
if (Function *F = dyn_cast<Function>(FP)) {
if (!F->isDeclaration())
M1Tors.push_back(std::make_pair(F, Priority));
else {
// Map to M2's version of the function.
F = cast<Function>(VMap[F]);
M2Tors.push_back(std::make_pair(F, Priority));
}
}
}
}
GV->eraseFromParent();
if (!M1Tors.empty()) {
Constant *M1Init = GetTorInit(M1Tors);
new GlobalVariable(*M1, M1Init->getType(), false,
GlobalValue::AppendingLinkage, M1Init, GlobalName);
}
GV = M2->getNamedGlobal(GlobalName);
assert(GV && "Not a clone of M1?");
assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
GV->eraseFromParent();
if (!M2Tors.empty()) {
Constant *M2Init = GetTorInit(M2Tors);
new GlobalVariable(*M2, M2Init->getType(), false,
GlobalValue::AppendingLinkage, M2Init, GlobalName);
}
}
std::unique_ptr<Module>
llvm::SplitFunctionsOutOfModule(Module *M, const std::vector<Function *> &F,
ValueToValueMapTy &VMap) {
// Make sure functions & globals are all external so that linkage
// between the two modules will work.
for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
I->setLinkage(GlobalValue::ExternalLinkage);
for (Module::global_iterator I = M->global_begin(), E = M->global_end();
I != E; ++I) {
if (I->hasName() && I->getName()[0] == '\01')
I->setName(I->getName().substr(1));
I->setLinkage(GlobalValue::ExternalLinkage);
}
ValueToValueMapTy NewVMap;
std::unique_ptr<Module> New = CloneModule(*M, NewVMap);
// Remove the Test functions from the Safe module
std::set<Function *> TestFunctions;
for (unsigned i = 0, e = F.size(); i != e; ++i) {
Function *TNOF = cast<Function>(VMap[F[i]]);
LLVM_DEBUG(errs() << "Removing function ");
LLVM_DEBUG(TNOF->printAsOperand(errs(), false));
LLVM_DEBUG(errs() << "\n");
TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
DeleteFunctionBody(TNOF); // Function is now external in this module!
}
// Remove the Safe functions from the Test module
for (Function &I : *New)
if (!TestFunctions.count(&I))
DeleteFunctionBody(&I);
// Try to split the global initializers evenly
for (GlobalVariable &I : M->globals()) {
GlobalVariable *GV = cast<GlobalVariable>(NewVMap[&I]);
if (Function *TestFn = globalInitUsesExternalBA(&I)) {
if (Function *SafeFn = globalInitUsesExternalBA(GV)) {
errs() << "*** Error: when reducing functions, encountered "
"the global '";
GV->printAsOperand(errs(), false);
errs() << "' with an initializer that references blockaddresses "
"from safe function '"
<< SafeFn->getName() << "' and from test function '"
<< TestFn->getName() << "'.\n";
exit(1);
}
DeleteGlobalInitializer(&I); // Delete the initializer to make it external
} else {
// If we keep it in the safe module, then delete it in the test module
DeleteGlobalInitializer(GV);
}
}
// Make sure that there is a global ctor/dtor array in both halves of the
// module if they both have static ctor/dtor functions.
SplitStaticCtorDtor("llvm.global_ctors", M, New.get(), NewVMap);
SplitStaticCtorDtor("llvm.global_dtors", M, New.get(), NewVMap);
return New;
}
//===----------------------------------------------------------------------===//
// Basic Block Extraction Code
//===----------------------------------------------------------------------===//
std::unique_ptr<Module>
BugDriver::extractMappedBlocksFromModule(const std::vector<BasicBlock *> &BBs,
Module *M) {
auto Temp = sys::fs::TempFile::create(OutputPrefix + "-extractblocks%%%%%%%");
if (!Temp) {
outs() << "*** Basic Block extraction failed!\n";
errs() << "Error creating temporary file: " << toString(Temp.takeError())
<< "\n";
EmitProgressBitcode(*M, "basicblockextractfail", true);
return nullptr;
}
DiscardTemp Discard{*Temp};
// Extract all of the blocks except the ones in BBs.
SmallVector<BasicBlock *, 32> BlocksToExtract;
for (Function &F : *M)
for (BasicBlock &BB : F)
// Check if this block is going to be extracted.
if (!llvm::is_contained(BBs, &BB))
BlocksToExtract.push_back(&BB);
raw_fd_ostream OS(Temp->FD, /*shouldClose*/ false);
for (BasicBlock *BB : BBs) {
// If the BB doesn't have a name, give it one so we have something to key
// off of.
if (!BB->hasName())
BB->setName("tmpbb");
OS << BB->getParent()->getName() << " " << BB->getName() << "\n";
}
OS.flush();
if (OS.has_error()) {
errs() << "Error writing list of blocks to not extract\n";
EmitProgressBitcode(*M, "basicblockextractfail", true);
OS.clear_error();
return nullptr;
}
std::string uniqueFN = "--extract-blocks-file=";
uniqueFN += Temp->TmpName;
std::vector<std::string> PI;
PI.push_back("extract-blocks");
std::unique_ptr<Module> Ret = runPassesOn(M, PI, {uniqueFN});
if (!Ret) {
outs() << "*** Basic Block extraction failed, please report a bug!\n";
EmitProgressBitcode(*M, "basicblockextractfail", true);
}
return Ret;
}
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