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//===- BlockExtractor.cpp - Extracts blocks into their own functions ------===//
//
// 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 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<SmallVector<BasicBlock *, 16>, 4> GroupsOfBlocks;
bool EraseFunctions;
/// Map a function name to groups of blocks.
SmallVector<std::pair<std::string, SmallVector<std::string, 4>>, 4>
BlocksByName;
void init(const SmallVectorImpl<SmallVector<BasicBlock *, 16>>
&GroupsOfBlocksToExtract) {
for (const SmallVectorImpl<BasicBlock *> &GroupOfBlocks :
GroupsOfBlocksToExtract) {
SmallVector<BasicBlock *, 16> NewGroup;
NewGroup.append(GroupOfBlocks.begin(), GroupOfBlocks.end());
GroupsOfBlocks.emplace_back(NewGroup);
}
if (!BlockExtractorFile.empty())
loadFile();
}
public:
static char ID;
BlockExtractor(const SmallVectorImpl<BasicBlock *> &BlocksToExtract,
bool EraseFunctions)
: ModulePass(ID), EraseFunctions(EraseFunctions) {
// We want one group per element of the input list.
SmallVector<SmallVector<BasicBlock *, 16>, 4> MassagedGroupsOfBlocks;
for (BasicBlock *BB : BlocksToExtract) {
SmallVector<BasicBlock *, 16> NewGroup;
NewGroup.push_back(BB);
MassagedGroupsOfBlocks.push_back(NewGroup);
}
init(MassagedGroupsOfBlocks);
}
BlockExtractor(const SmallVectorImpl<SmallVector<BasicBlock *, 16>>
&GroupsOfBlocksToExtract,
bool EraseFunctions)
: ModulePass(ID), EraseFunctions(EraseFunctions) {
init(GroupsOfBlocksToExtract);
}
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);
}
ModulePass *llvm::createBlockExtractorPass(
const SmallVectorImpl<SmallVector<BasicBlock *, 16>>
&GroupsOfBlocksToExtract,
bool EraseFunctions) {
return new BlockExtractor(GroupsOfBlocksToExtract, 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) {
SmallVector<StringRef, 4> LineSplit;
Line.split(LineSplit, ' ', /*MaxSplit=*/-1,
/*KeepEmpty=*/false);
if (LineSplit.empty())
continue;
if (LineSplit.size()!=2)
report_fatal_error("Invalid line format, expecting lines like: 'funcname bb1[;bb2..]'");
SmallVector<StringRef, 4> BBNames;
LineSplit[1].split(BBNames, ';', /*MaxSplit=*/-1,
/*KeepEmpty=*/false);
if (BBNames.empty())
report_fatal_error("Missing bbs name");
BlocksByName.push_back({LineSplit[0], {BBNames.begin(), BBNames.end()}});
}
}
/// 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.
unsigned NextGroupIdx = GroupsOfBlocks.size();
GroupsOfBlocks.resize(NextGroupIdx + BlocksByName.size());
for (const auto &BInfo : BlocksByName) {
Function *F = M.getFunction(BInfo.first);
if (!F)
report_fatal_error("Invalid function name specified in the input file");
for (const auto &BBInfo : BInfo.second) {
auto Res = llvm::find_if(*F, [&](const BasicBlock &BB) {
return BB.getName().equals(BBInfo);
});
if (Res == F->end())
report_fatal_error("Invalid block name specified in the input file");
GroupsOfBlocks[NextGroupIdx].push_back(&*Res);
}
++NextGroupIdx;
}
// Extract each group of basic blocks.
for (auto &BBs : GroupsOfBlocks) {
SmallVector<BasicBlock *, 32> BlocksToExtractVec;
for (BasicBlock *BB : BBs) {
// 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");
BlocksToExtractVec.push_back(BB);
if (const InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
BlocksToExtractVec.push_back(II->getUnwindDest());
++NumExtracted;
Changed = true;
}
CodeExtractorAnalysisCache CEAC(*BBs[0]->getParent());
Function *F = CodeExtractor(BlocksToExtractVec).extractCodeRegion(CEAC);
if (F)
LLVM_DEBUG(dbgs() << "Extracted group '" << (*BBs.begin())->getName()
<< "' in: " << F->getName() << '\n');
else
LLVM_DEBUG(dbgs() << "Failed to extract for group '"
<< (*BBs.begin())->getName() << "'\n");
}
// 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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