| //===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This family of functions perform manipulations on basic blocks, and |
| // instructions contained within basic blocks. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Function.h" |
| #include "llvm/iTerminators.h" |
| #include "llvm/Constant.h" |
| #include "llvm/Type.h" |
| #include <algorithm> |
| |
| // ReplaceInstWithValue - Replace all uses of an instruction (specified by BI) |
| // with a value, then remove and delete the original instruction. |
| // |
| void ReplaceInstWithValue(BasicBlock::InstListType &BIL, |
| BasicBlock::iterator &BI, Value *V) { |
| Instruction &I = *BI; |
| // Replaces all of the uses of the instruction with uses of the value |
| I.replaceAllUsesWith(V); |
| |
| std::string OldName = I.getName(); |
| |
| // Delete the unnecessary instruction now... |
| BI = BIL.erase(BI); |
| |
| // Make sure to propagate a name if there is one already... |
| if (OldName.size() && !V->hasName()) |
| V->setName(OldName, &BIL.getParent()->getSymbolTable()); |
| } |
| |
| |
| // ReplaceInstWithInst - Replace the instruction specified by BI with the |
| // instruction specified by I. The original instruction is deleted and BI is |
| // updated to point to the new instruction. |
| // |
| void ReplaceInstWithInst(BasicBlock::InstListType &BIL, |
| BasicBlock::iterator &BI, Instruction *I) { |
| assert(I->getParent() == 0 && |
| "ReplaceInstWithInst: Instruction already inserted into basic block!"); |
| |
| // Insert the new instruction into the basic block... |
| BasicBlock::iterator New = BIL.insert(BI, I); |
| |
| // Replace all uses of the old instruction, and delete it. |
| ReplaceInstWithValue(BIL, BI, I); |
| |
| // Move BI back to point to the newly inserted instruction |
| BI = New; |
| } |
| |
| // ReplaceInstWithInst - Replace the instruction specified by From with the |
| // instruction specified by To. |
| // |
| void ReplaceInstWithInst(Instruction *From, Instruction *To) { |
| BasicBlock::iterator BI(From); |
| ReplaceInstWithInst(From->getParent()->getInstList(), BI, To); |
| } |
| |
| // RemoveSuccessor - Change the specified terminator instruction such that its |
| // successor #SuccNum no longer exists. Because this reduces the outgoing |
| // degree of the current basic block, the actual terminator instruction itself |
| // may have to be changed. In the case where the last successor of the block is |
| // deleted, a return instruction is inserted in its place which can cause a |
| // surprising change in program behavior if it is not expected. |
| // |
| void RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) { |
| assert(SuccNum < TI->getNumSuccessors() && |
| "Trying to remove a nonexistant successor!"); |
| |
| // If our old successor block contains any PHI nodes, remove the entry in the |
| // PHI nodes that comes from this branch... |
| // |
| BasicBlock *BB = TI->getParent(); |
| TI->getSuccessor(SuccNum)->removePredecessor(BB); |
| |
| TerminatorInst *NewTI = 0; |
| switch (TI->getOpcode()) { |
| case Instruction::Br: |
| // If this is a conditional branch... convert to unconditional branch. |
| if (TI->getNumSuccessors() == 2) { |
| cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum)); |
| } else { // Otherwise convert to a return instruction... |
| Value *RetVal = 0; |
| |
| // Create a value to return... if the function doesn't return null... |
| if (BB->getParent()->getReturnType() != Type::VoidTy) |
| RetVal = Constant::getNullValue(BB->getParent()->getReturnType()); |
| |
| // Create the return... |
| NewTI = new ReturnInst(RetVal); |
| } |
| break; |
| |
| case Instruction::Invoke: // Should convert to call |
| case Instruction::Switch: // Should remove entry |
| default: |
| case Instruction::Ret: // Cannot happen, has no successors! |
| assert(0 && "Unhandled terminator instruction type in RemoveSuccessor!"); |
| abort(); |
| } |
| |
| if (NewTI) // If it's a different instruction, replace. |
| ReplaceInstWithInst(TI, NewTI); |
| } |