UnifyFunctionExitNodes.cpp [plain text]
#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/BasicBlock.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/Type.h"
#include "llvm/ADT/StringExtras.h"
using namespace llvm;
char UnifyFunctionExitNodes::ID = 0;
INITIALIZE_PASS(UnifyFunctionExitNodes, "mergereturn",
"Unify function exit nodes", false, false)
Pass *llvm::createUnifyFunctionExitNodesPass() {
return new UnifyFunctionExitNodes();
}
void UnifyFunctionExitNodes::getAnalysisUsage(AnalysisUsage &AU) const{
AU.addPreservedID(BreakCriticalEdgesID);
AU.addPreserved("mem2reg");
AU.addPreservedID(LowerSwitchID);
}
bool UnifyFunctionExitNodes::runOnFunction(Function &F) {
std::vector<BasicBlock*> ReturningBlocks;
std::vector<BasicBlock*> UnwindingBlocks;
std::vector<BasicBlock*> UnreachableBlocks;
for(Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
if (isa<ReturnInst>(I->getTerminator()))
ReturningBlocks.push_back(I);
else if (isa<UnwindInst>(I->getTerminator()))
UnwindingBlocks.push_back(I);
else if (isa<UnreachableInst>(I->getTerminator()))
UnreachableBlocks.push_back(I);
if (UnwindingBlocks.empty()) {
UnwindBlock = 0;
} else if (UnwindingBlocks.size() == 1) {
UnwindBlock = UnwindingBlocks.front();
} else {
UnwindBlock = BasicBlock::Create(F.getContext(), "UnifiedUnwindBlock", &F);
new UnwindInst(F.getContext(), UnwindBlock);
for (std::vector<BasicBlock*>::iterator I = UnwindingBlocks.begin(),
E = UnwindingBlocks.end(); I != E; ++I) {
BasicBlock *BB = *I;
BB->getInstList().pop_back(); BranchInst::Create(UnwindBlock, BB);
}
}
if (UnreachableBlocks.empty()) {
UnreachableBlock = 0;
} else if (UnreachableBlocks.size() == 1) {
UnreachableBlock = UnreachableBlocks.front();
} else {
UnreachableBlock = BasicBlock::Create(F.getContext(),
"UnifiedUnreachableBlock", &F);
new UnreachableInst(F.getContext(), UnreachableBlock);
for (std::vector<BasicBlock*>::iterator I = UnreachableBlocks.begin(),
E = UnreachableBlocks.end(); I != E; ++I) {
BasicBlock *BB = *I;
BB->getInstList().pop_back(); BranchInst::Create(UnreachableBlock, BB);
}
}
if (ReturningBlocks.empty()) {
ReturnBlock = 0;
return false; } else if (ReturningBlocks.size() == 1) {
ReturnBlock = ReturningBlocks.front(); return false;
}
BasicBlock *NewRetBlock = BasicBlock::Create(F.getContext(),
"UnifiedReturnBlock", &F);
PHINode *PN = 0;
if (F.getReturnType()->isVoidTy()) {
ReturnInst::Create(F.getContext(), NULL, NewRetBlock);
} else {
PN = PHINode::Create(F.getReturnType(), ReturningBlocks.size(),
"UnifiedRetVal");
NewRetBlock->getInstList().push_back(PN);
ReturnInst::Create(F.getContext(), PN, NewRetBlock);
}
for (std::vector<BasicBlock*>::iterator I = ReturningBlocks.begin(),
E = ReturningBlocks.end(); I != E; ++I) {
BasicBlock *BB = *I;
if (PN)
PN->addIncoming(BB->getTerminator()->getOperand(0), BB);
BB->getInstList().pop_back(); BranchInst::Create(NewRetBlock, BB);
}
ReturnBlock = NewRetBlock;
return true;
}