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//===- BlockExtractor.cpp - Extracts blocks into their own functions ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass extracts the specified basic blocks from the module into their
// own functions.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/CodeExtractor.h"
using namespace llvm;
#define DEBUG_TYPE "block-extractor"
STATISTIC(NumExtracted, "Number of basic blocks extracted");
static cl::opt<std::string> BlockExtractorFile(
"extract-blocks-file", cl::value_desc("filename"),
cl::desc("A file containing list of basic blocks to extract"), cl::Hidden);
cl::opt<bool> BlockExtractorEraseFuncs("extract-blocks-erase-funcs",
cl::desc("Erase the existing functions"),
cl::Hidden);
namespace {
class BlockExtractor : public ModulePass {
SmallVector<BasicBlock *, 16> Blocks;
bool EraseFunctions;
SmallVector<std::pair<std::string, std::string>, 32> BlocksByName;
public:
static char ID;
BlockExtractor(const SmallVectorImpl<BasicBlock *> &BlocksToExtract,
bool EraseFunctions)
: ModulePass(ID), Blocks(BlocksToExtract.begin(), BlocksToExtract.end()),
EraseFunctions(EraseFunctions) {
if (!BlockExtractorFile.empty())
loadFile();
}
BlockExtractor() : BlockExtractor(SmallVector<BasicBlock *, 0>(), false) {}
bool runOnModule(Module &M) override;
private:
void loadFile();
void splitLandingPadPreds(Function &F);
};
} // end anonymous namespace
char BlockExtractor::ID = 0;
INITIALIZE_PASS(BlockExtractor, "extract-blocks",
"Extract basic blocks from module", false, false)
ModulePass *llvm::createBlockExtractorPass() { return new BlockExtractor(); }
ModulePass *llvm::createBlockExtractorPass(
const SmallVectorImpl<BasicBlock *> &BlocksToExtract, bool EraseFunctions) {
return new BlockExtractor(BlocksToExtract, EraseFunctions);
}
/// Gets all of the blocks specified in the input file.
void BlockExtractor::loadFile() {
auto ErrOrBuf = MemoryBuffer::getFile(BlockExtractorFile);
if (ErrOrBuf.getError())
report_fatal_error("BlockExtractor couldn't load the file.");
// Read the file.
auto &Buf = *ErrOrBuf;
SmallVector<StringRef, 16> Lines;
Buf->getBuffer().split(Lines, '\n', /*MaxSplit=*/-1,
/*KeepEmpty=*/false);
for (const auto &Line : Lines) {
auto FBPair = Line.split(' ');
BlocksByName.push_back({FBPair.first, FBPair.second});
}
}
/// Extracts the landing pads to make sure all of them have only one
/// predecessor.
void BlockExtractor::splitLandingPadPreds(Function &F) {
for (BasicBlock &BB : F) {
for (Instruction &I : BB) {
if (!isa<InvokeInst>(&I))
continue;
InvokeInst *II = cast<InvokeInst>(&I);
BasicBlock *Parent = II->getParent();
BasicBlock *LPad = II->getUnwindDest();
// Look through the landing pad's predecessors. If one of them ends in an
// 'invoke', then we want to split the landing pad.
bool Split = false;
for (auto PredBB : predecessors(LPad)) {
if (PredBB->isLandingPad() && PredBB != Parent &&
isa<InvokeInst>(Parent->getTerminator())) {
Split = true;
break;
}
}
if (!Split)
continue;
SmallVector<BasicBlock *, 2> NewBBs;
SplitLandingPadPredecessors(LPad, Parent, ".1", ".2", NewBBs);
}
}
}
bool BlockExtractor::runOnModule(Module &M) {
bool Changed = false;
// Get all the functions.
SmallVector<Function *, 4> Functions;
for (Function &F : M) {
splitLandingPadPreds(F);
Functions.push_back(&F);
}
// Get all the blocks specified in the input file.
for (const auto &BInfo : BlocksByName) {
Function *F = M.getFunction(BInfo.first);
if (!F)
report_fatal_error("Invalid function name specified in the input file");
auto Res = llvm::find_if(*F, [&](const BasicBlock &BB) {
return BB.getName().equals(BInfo.second);
});
if (Res == F->end())
report_fatal_error("Invalid block name specified in the input file");
Blocks.push_back(&*Res);
}
// Extract basic blocks.
for (BasicBlock *BB : Blocks) {
// Check if the module contains BB.
if (BB->getParent()->getParent() != &M)
report_fatal_error("Invalid basic block");
LLVM_DEBUG(dbgs() << "BlockExtractor: Extracting "
<< BB->getParent()->getName() << ":" << BB->getName()
<< "\n");
SmallVector<BasicBlock *, 2> BlocksToExtractVec;
BlocksToExtractVec.push_back(BB);
if (const InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
BlocksToExtractVec.push_back(II->getUnwindDest());
CodeExtractor(BlocksToExtractVec).extractCodeRegion();
++NumExtracted;
Changed = true;
}
// Erase the functions.
if (EraseFunctions || BlockExtractorEraseFuncs) {
for (Function *F : Functions) {
LLVM_DEBUG(dbgs() << "BlockExtractor: Trying to delete " << F->getName()
<< "\n");
F->deleteBody();
}
// Set linkage as ExternalLinkage to avoid erasing unreachable functions.
for (Function &F : M)
F.setLinkage(GlobalValue::ExternalLinkage);
Changed = true;
}
return Changed;
}
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