//===- UnifyFunctionExitNodes.cpp - Make all functions have a single exit -===//
//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
// This pass is used to ensure that functions have at most one return
// instruction in them. Additionally, it keeps track of which node is the new
// exit node of the CFG. If there are no exit nodes in the CFG, the getExitNode
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
-#include "llvm/BasicBlock.h"
-#include "llvm/Function.h"
-#include "llvm/iTerminators.h"
-#include "llvm/iPHINode.h"
-#include "llvm/Type.h"
-using std::vector;
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Transforms/Scalar.h"
+using namespace llvm;
+
+char UnifyFunctionExitNodes::ID = 0;
+INITIALIZE_PASS(UnifyFunctionExitNodes, "mergereturn",
+ "Unify function exit nodes", false, false)
-static RegisterOpt<UnifyFunctionExitNodes>
-X("mergereturn", "Unify function exit nodes");
+Pass *llvm::createUnifyFunctionExitNodesPass() {
+ return new UnifyFunctionExitNodes();
+}
+
+void UnifyFunctionExitNodes::getAnalysisUsage(AnalysisUsage &AU) const{
+ // We preserve the non-critical-edgeness property
+ AU.addPreservedID(BreakCriticalEdgesID);
+ // This is a cluster of orthogonal Transforms
+ AU.addPreservedID(LowerSwitchID);
+}
// UnifyAllExitNodes - Unify all exit nodes of the CFG by creating a new
// BasicBlock, and converting all returns to unconditional branches to this
// Loop over all of the blocks in a function, tracking all of the blocks that
// return.
//
- vector<BasicBlock*> ReturningBlocks;
- for(Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
- if (isa<ReturnInst>(I->getTerminator()))
- ReturningBlocks.push_back(I);
+ std::vector<BasicBlock*> ReturningBlocks;
+ std::vector<BasicBlock*> UnreachableBlocks;
+ for (BasicBlock &I : F)
+ if (isa<ReturnInst>(I.getTerminator()))
+ ReturningBlocks.push_back(&I);
+ else if (isa<UnreachableInst>(I.getTerminator()))
+ UnreachableBlocks.push_back(&I);
+
+ // Then unreachable blocks.
+ if (UnreachableBlocks.empty()) {
+ UnreachableBlock = nullptr;
+ } 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(); // Remove the unreachable inst.
+ BranchInst::Create(UnreachableBlock, BB);
+ }
+ }
+ // Now handle return blocks.
if (ReturningBlocks.empty()) {
- ExitNode = 0;
+ ReturnBlock = nullptr;
return false; // No blocks return
} else if (ReturningBlocks.size() == 1) {
- ExitNode = ReturningBlocks.front(); // Already has a single return block
+ ReturnBlock = ReturningBlocks.front(); // Already has a single return block
return false;
}
// Otherwise, we need to insert a new basic block into the function, add a PHI
- // node (if the function returns a value), and convert all of the return
+ // nodes (if the function returns values), and convert all of the return
// instructions into unconditional branches.
//
- BasicBlock *NewRetBlock = new BasicBlock("UnifiedExitNode", &F);
+ BasicBlock *NewRetBlock = BasicBlock::Create(F.getContext(),
+ "UnifiedReturnBlock", &F);
- if (F.getReturnType() != Type::VoidTy) {
+ PHINode *PN = nullptr;
+ if (F.getReturnType()->isVoidTy()) {
+ ReturnInst::Create(F.getContext(), nullptr, NewRetBlock);
+ } else {
// If the function doesn't return void... add a PHI node to the block...
- PHINode *PN = new PHINode(F.getReturnType(), "UnifiedRetVal");
+ PN = PHINode::Create(F.getReturnType(), ReturningBlocks.size(),
+ "UnifiedRetVal");
NewRetBlock->getInstList().push_back(PN);
-
- // Add an incoming element to the PHI node for every return instruction that
- // is merging into this new block...
- for (vector<BasicBlock*>::iterator I = ReturningBlocks.begin(),
- E = ReturningBlocks.end(); I != E; ++I)
- PN->addIncoming((*I)->getTerminator()->getOperand(0), *I);
-
- // Add a return instruction to return the result of the PHI node...
- NewRetBlock->getInstList().push_back(new ReturnInst(PN));
- } else {
- // If it returns void, just add a return void instruction to the block
- new ReturnInst(0, NewRetBlock->end());
+ ReturnInst::Create(F.getContext(), PN, NewRetBlock);
}
// Loop over all of the blocks, replacing the return instruction with an
// unconditional branch.
//
- for (vector<BasicBlock*>::iterator I = ReturningBlocks.begin(),
- E = ReturningBlocks.end(); I != E; ++I) {
- (*I)->getInstList().pop_back(); // Remove the return insn
- (*I)->getInstList().push_back(new BranchInst(NewRetBlock));
+ for (std::vector<BasicBlock*>::iterator I = ReturningBlocks.begin(),
+ E = ReturningBlocks.end(); I != E; ++I) {
+ BasicBlock *BB = *I;
+
+ // Add an incoming element to the PHI node for every return instruction that
+ // is merging into this new block...
+ if (PN)
+ PN->addIncoming(BB->getTerminator()->getOperand(0), BB);
+
+ BB->getInstList().pop_back(); // Remove the return insn
+ BranchInst::Create(NewRetBlock, BB);
}
- ExitNode = NewRetBlock;
+ ReturnBlock = NewRetBlock;
return true;
}