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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45418 91177308-0d34-0410-b5e6-96231b3b80d8
189 lines
6.9 KiB
C++
189 lines
6.9 KiB
C++
//===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This family of functions perform manipulations on basic blocks, and
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// instructions contained within basic blocks.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Function.h"
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#include "llvm/Instructions.h"
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#include "llvm/Constant.h"
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#include "llvm/Type.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/Dominators.h"
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#include <algorithm>
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using namespace llvm;
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/// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
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/// with a value, then remove and delete the original instruction.
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///
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void llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL,
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BasicBlock::iterator &BI, Value *V) {
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Instruction &I = *BI;
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// Replaces all of the uses of the instruction with uses of the value
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I.replaceAllUsesWith(V);
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// Make sure to propagate a name if there is one already.
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if (I.hasName() && !V->hasName())
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V->takeName(&I);
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// Delete the unnecessary instruction now...
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BI = BIL.erase(BI);
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}
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/// ReplaceInstWithInst - Replace the instruction specified by BI with the
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/// instruction specified by I. The original instruction is deleted and BI is
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/// updated to point to the new instruction.
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///
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void llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL,
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BasicBlock::iterator &BI, Instruction *I) {
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assert(I->getParent() == 0 &&
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"ReplaceInstWithInst: Instruction already inserted into basic block!");
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// Insert the new instruction into the basic block...
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BasicBlock::iterator New = BIL.insert(BI, I);
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// Replace all uses of the old instruction, and delete it.
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ReplaceInstWithValue(BIL, BI, I);
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// Move BI back to point to the newly inserted instruction
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BI = New;
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}
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/// ReplaceInstWithInst - Replace the instruction specified by From with the
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/// instruction specified by To.
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///
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void llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) {
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BasicBlock::iterator BI(From);
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ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
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}
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/// RemoveSuccessor - Change the specified terminator instruction such that its
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/// successor SuccNum no longer exists. Because this reduces the outgoing
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/// degree of the current basic block, the actual terminator instruction itself
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/// may have to be changed. In the case where the last successor of the block
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/// is deleted, a return instruction is inserted in its place which can cause a
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/// surprising change in program behavior if it is not expected.
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///
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void llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) {
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assert(SuccNum < TI->getNumSuccessors() &&
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"Trying to remove a nonexistant successor!");
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// If our old successor block contains any PHI nodes, remove the entry in the
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// PHI nodes that comes from this branch...
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//
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BasicBlock *BB = TI->getParent();
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TI->getSuccessor(SuccNum)->removePredecessor(BB);
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TerminatorInst *NewTI = 0;
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switch (TI->getOpcode()) {
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case Instruction::Br:
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// If this is a conditional branch... convert to unconditional branch.
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if (TI->getNumSuccessors() == 2) {
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cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum));
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} else { // Otherwise convert to a return instruction...
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Value *RetVal = 0;
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// Create a value to return... if the function doesn't return null...
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if (BB->getParent()->getReturnType() != Type::VoidTy)
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RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
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// Create the return...
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NewTI = new ReturnInst(RetVal);
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}
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break;
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case Instruction::Invoke: // Should convert to call
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case Instruction::Switch: // Should remove entry
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default:
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case Instruction::Ret: // Cannot happen, has no successors!
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assert(0 && "Unhandled terminator instruction type in RemoveSuccessor!");
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abort();
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}
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if (NewTI) // If it's a different instruction, replace.
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ReplaceInstWithInst(TI, NewTI);
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}
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/// SplitEdge - Split the edge connecting specified block. Pass P must
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/// not be NULL.
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BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) {
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TerminatorInst *LatchTerm = BB->getTerminator();
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unsigned SuccNum = 0;
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for (unsigned i = 0, e = LatchTerm->getNumSuccessors(); ; ++i) {
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assert(i != e && "Didn't find edge?");
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if (LatchTerm->getSuccessor(i) == Succ) {
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SuccNum = i;
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break;
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}
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}
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// If this is a critical edge, let SplitCriticalEdge do it.
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if (SplitCriticalEdge(BB->getTerminator(), SuccNum, P))
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return LatchTerm->getSuccessor(SuccNum);
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// If the edge isn't critical, then BB has a single successor or Succ has a
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// single pred. Split the block.
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BasicBlock::iterator SplitPoint;
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if (BasicBlock *SP = Succ->getSinglePredecessor()) {
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// If the successor only has a single pred, split the top of the successor
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// block.
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assert(SP == BB && "CFG broken");
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return SplitBlock(Succ, Succ->begin(), P);
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} else {
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// Otherwise, if BB has a single successor, split it at the bottom of the
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// block.
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assert(BB->getTerminator()->getNumSuccessors() == 1 &&
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"Should have a single succ!");
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return SplitBlock(BB, BB->getTerminator(), P);
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}
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}
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/// SplitBlock - Split the specified block at the specified instruction - every
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/// thing before SplitPt stays in Old and everything starting with SplitPt moves
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/// to a new block. The two blocks are joined by an unconditional branch and
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/// the loop info is updated.
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///
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BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
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LoopInfo &LI = P->getAnalysis<LoopInfo>();
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BasicBlock::iterator SplitIt = SplitPt;
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while (isa<PHINode>(SplitIt))
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++SplitIt;
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BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
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// The new block lives in whichever loop the old one did.
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if (Loop *L = LI.getLoopFor(Old))
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L->addBasicBlockToLoop(New, LI.getBase());
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if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>())
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{
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// Old dominates New. New node domiantes all other nodes dominated by Old.
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DomTreeNode *OldNode = DT->getNode(Old);
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std::vector<DomTreeNode *> Children;
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for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
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I != E; ++I)
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Children.push_back(*I);
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DomTreeNode *NewNode = DT->addNewBlock(New,Old);
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for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
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E = Children.end(); I != E; ++I)
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DT->changeImmediateDominator(*I, NewNode);
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}
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if (DominanceFrontier *DF = P->getAnalysisToUpdate<DominanceFrontier>())
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DF->splitBlock(Old);
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return New;
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}
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