BasicBlockUtils.cpp revision e435a5d9374b61049b16ef69e6314542815fadb4
14d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner//===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==// 2fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman// 3b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// The LLVM Compiler Infrastructure 4b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 54ee451de366474b9c228b4e5fa573795a715216dChris Lattner// This file is distributed under the University of Illinois Open Source 64ee451de366474b9c228b4e5fa573795a715216dChris Lattner// License. See LICENSE.TXT for details. 7fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman// 8b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell//===----------------------------------------------------------------------===// 94d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner// 104d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner// This family of functions perform manipulations on basic blocks, and 114d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner// instructions contained within basic blocks. 124d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner// 134d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner//===----------------------------------------------------------------------===// 144d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 154d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner#include "llvm/Transforms/Utils/BasicBlockUtils.h" 164d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner#include "llvm/Function.h" 1747b14a4a6a455c7be169cfd312fcbe796f0ad426Misha Brukman#include "llvm/Instructions.h" 18b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner#include "llvm/Constant.h" 19b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner#include "llvm/Type.h" 2054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner#include "llvm/Analysis/AliasAnalysis.h" 218019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel#include "llvm/Analysis/LoopInfo.h" 228019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel#include "llvm/Analysis/Dominators.h" 234d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner#include <algorithm> 24f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnerusing namespace llvm; 25d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 26b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor, 27b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson/// if possible. The return value indicates success or failure. 28b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Andersonbool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) { 2911f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson pred_iterator PI(pred_begin(BB)), PE(pred_end(BB)); 30b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Can't merge the entry block. 31b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson if (pred_begin(BB) == pred_end(BB)) return false; 32b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 3311f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson BasicBlock *PredBB = *PI++; 3411f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson for (; PI != PE; ++PI) // Search all predecessors, see if they are all same 3511f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (*PI != PredBB) { 3611f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson PredBB = 0; // There are multiple different predecessors... 3711f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson break; 3811f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson } 39b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 4011f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson // Can't merge if there are multiple predecessors. 4111f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (!PredBB) return false; 423ecaf1b33940470d5bf554135778ba5a8bce9a79Owen Anderson // Don't break self-loops. 433ecaf1b33940470d5bf554135778ba5a8bce9a79Owen Anderson if (PredBB == BB) return false; 443ecaf1b33940470d5bf554135778ba5a8bce9a79Owen Anderson // Don't break invokes. 453ecaf1b33940470d5bf554135778ba5a8bce9a79Owen Anderson if (isa<InvokeInst>(PredBB->getTerminator())) return false; 4611f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson 4711f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB)); 4811f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson BasicBlock* OnlySucc = BB; 4911f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson for (; SI != SE; ++SI) 5011f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (*SI != OnlySucc) { 5111f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson OnlySucc = 0; // There are multiple distinct successors! 5211f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson break; 5311f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson } 5411f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson 5511f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson // Can't merge if there are multiple successors. 5611f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (!OnlySucc) return false; 57e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel 58e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel // Can't merge if there is PHI loop. 59e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) { 60e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel if (PHINode *PN = dyn_cast<PHINode>(BI)) { 61e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 62e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel if (PN->getIncomingValue(i) == PN) 63e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel return false; 64e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel } else 65e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel break; 66e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel } 67e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel 68b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Begin by getting rid of unneeded PHIs. 69b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) { 70b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson PN->replaceAllUsesWith(PN->getIncomingValue(0)); 71b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson BB->getInstList().pop_front(); // Delete the phi node... 72b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 73b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 74b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Delete the unconditional branch from the predecessor... 75b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson PredBB->getInstList().pop_back(); 76b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 77b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Move all definitions in the successor to the predecessor... 78b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson PredBB->getInstList().splice(PredBB->end(), BB->getInstList()); 79b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 80b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Make all PHI nodes that referred to BB now refer to Pred as their 81b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // source... 82b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson BB->replaceAllUsesWith(PredBB); 83b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 8411f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson // Inherit predecessors name if it exists. 8511f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (!PredBB->hasName()) 8611f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson PredBB->takeName(BB); 8711f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson 88b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Finally, erase the old block and update dominator info. 89b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson if (P) { 90b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson if (DominatorTree* DT = P->getAnalysisToUpdate<DominatorTree>()) { 91b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DomTreeNode* DTN = DT->getNode(BB); 92b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DomTreeNode* PredDTN = DT->getNode(PredBB); 93b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 94b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson if (DTN) { 95b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson SmallPtrSet<DomTreeNode*, 8> Children(DTN->begin(), DTN->end()); 96b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = Children.begin(), 97b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DE = Children.end(); DI != DE; ++DI) 98b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DT->changeImmediateDominator(*DI, PredDTN); 99b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 100b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DT->eraseNode(BB); 101b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 102b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 103b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 104b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 105b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson BB->eraseFromParent(); 106b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 107b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 108b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson return true; 109b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson} 110b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 1110f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI) 1120f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// with a value, then remove and delete the original instruction. 1130f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 114f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL, 115f7703df4968084c18c248c1feea9961c19a32e6aChris Lattner BasicBlock::iterator &BI, Value *V) { 11618961504fc2b299578dba817900a0696cf3ccc4dChris Lattner Instruction &I = *BI; 1174d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Replaces all of the uses of the instruction with uses of the value 11818961504fc2b299578dba817900a0696cf3ccc4dChris Lattner I.replaceAllUsesWith(V); 1194d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 12086cc42355593dd1689f7d58d56695c451215b02bChris Lattner // Make sure to propagate a name if there is one already. 12186cc42355593dd1689f7d58d56695c451215b02bChris Lattner if (I.hasName() && !V->hasName()) 12286cc42355593dd1689f7d58d56695c451215b02bChris Lattner V->takeName(&I); 123fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 1245560c9d49ccae132cabf1155f18aa0480dce3edaMisha Brukman // Delete the unnecessary instruction now... 12518961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BI = BIL.erase(BI); 1264d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner} 1274d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1284d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1290f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// ReplaceInstWithInst - Replace the instruction specified by BI with the 1300f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// instruction specified by I. The original instruction is deleted and BI is 1310f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// updated to point to the new instruction. 1320f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 133f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL, 134f7703df4968084c18c248c1feea9961c19a32e6aChris Lattner BasicBlock::iterator &BI, Instruction *I) { 1354d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner assert(I->getParent() == 0 && 1364d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner "ReplaceInstWithInst: Instruction already inserted into basic block!"); 1374d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1384d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Insert the new instruction into the basic block... 13918961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BasicBlock::iterator New = BIL.insert(BI, I); 1404d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1414d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Replace all uses of the old instruction, and delete it. 1424d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner ReplaceInstWithValue(BIL, BI, I); 1434d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1444d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Move BI back to point to the newly inserted instruction 14518961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BI = New; 1464d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner} 1474d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1480f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// ReplaceInstWithInst - Replace the instruction specified by From with the 1490f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// instruction specified by To. 1500f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 151f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) { 15218961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BasicBlock::iterator BI(From); 15318961504fc2b299578dba817900a0696cf3ccc4dChris Lattner ReplaceInstWithInst(From->getParent()->getInstList(), BI, To); 1544d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner} 155b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 1560f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// RemoveSuccessor - Change the specified terminator instruction such that its 157bc2eba1ca2d99836af6b5e12128c08e022930918Reid Spencer/// successor SuccNum no longer exists. Because this reduces the outgoing 1580f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// degree of the current basic block, the actual terminator instruction itself 159bc2eba1ca2d99836af6b5e12128c08e022930918Reid Spencer/// may have to be changed. In the case where the last successor of the block 160bc2eba1ca2d99836af6b5e12128c08e022930918Reid Spencer/// is deleted, a return instruction is inserted in its place which can cause a 1610f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// surprising change in program behavior if it is not expected. 1620f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 163f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) { 164b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner assert(SuccNum < TI->getNumSuccessors() && 165b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner "Trying to remove a nonexistant successor!"); 166b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 167b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // If our old successor block contains any PHI nodes, remove the entry in the 168b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // PHI nodes that comes from this branch... 169b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // 170b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner BasicBlock *BB = TI->getParent(); 171b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner TI->getSuccessor(SuccNum)->removePredecessor(BB); 172b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 173b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner TerminatorInst *NewTI = 0; 174b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner switch (TI->getOpcode()) { 175b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner case Instruction::Br: 176b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // If this is a conditional branch... convert to unconditional branch. 177b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner if (TI->getNumSuccessors() == 2) { 178b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum)); 179b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner } else { // Otherwise convert to a return instruction... 180b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner Value *RetVal = 0; 181fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 182b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // Create a value to return... if the function doesn't return null... 183b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner if (BB->getParent()->getReturnType() != Type::VoidTy) 184b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner RetVal = Constant::getNullValue(BB->getParent()->getReturnType()); 185b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 186b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // Create the return... 187051a950000e21935165db56695e35bade668193bGabor Greif NewTI = ReturnInst::Create(RetVal); 188b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner } 189fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman break; 190b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 191b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner case Instruction::Invoke: // Should convert to call 192b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner case Instruction::Switch: // Should remove entry 193b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner default: 194b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner case Instruction::Ret: // Cannot happen, has no successors! 195b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner assert(0 && "Unhandled terminator instruction type in RemoveSuccessor!"); 196b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner abort(); 197b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner } 198b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 199b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner if (NewTI) // If it's a different instruction, replace. 200b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner ReplaceInstWithInst(TI, NewTI); 201b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner} 202d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 2038019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// SplitEdge - Split the edge connecting specified block. Pass P must 2048019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// not be NULL. 2058019893c3f55a4bfe770888fe285d6dae57cf216Devang PatelBasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) { 2068019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel TerminatorInst *LatchTerm = BB->getTerminator(); 2078019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel unsigned SuccNum = 0; 2088019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel for (unsigned i = 0, e = LatchTerm->getNumSuccessors(); ; ++i) { 2098019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel assert(i != e && "Didn't find edge?"); 2108019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel if (LatchTerm->getSuccessor(i) == Succ) { 2118019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel SuccNum = i; 2128019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel break; 2138019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel } 2148019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel } 2158019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2168019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // If this is a critical edge, let SplitCriticalEdge do it. 2178019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel if (SplitCriticalEdge(BB->getTerminator(), SuccNum, P)) 2188019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return LatchTerm->getSuccessor(SuccNum); 2198019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2208019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // If the edge isn't critical, then BB has a single successor or Succ has a 2218019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // single pred. Split the block. 2228019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel BasicBlock::iterator SplitPoint; 2238019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel if (BasicBlock *SP = Succ->getSinglePredecessor()) { 2248019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // If the successor only has a single pred, split the top of the successor 2258019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // block. 2268019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel assert(SP == BB && "CFG broken"); 2278019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return SplitBlock(Succ, Succ->begin(), P); 2288019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel } else { 2298019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // Otherwise, if BB has a single successor, split it at the bottom of the 2308019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // block. 2318019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel assert(BB->getTerminator()->getNumSuccessors() == 1 && 2328019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel "Should have a single succ!"); 2338019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return SplitBlock(BB, BB->getTerminator(), P); 2348019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel } 2358019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel} 2368019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2378019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// SplitBlock - Split the specified block at the specified instruction - every 2388019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// thing before SplitPt stays in Old and everything starting with SplitPt moves 2398019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// to a new block. The two blocks are joined by an unconditional branch and 2408019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// the loop info is updated. 2418019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// 2428019893c3f55a4bfe770888fe285d6dae57cf216Devang PatelBasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) { 2438019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2448019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel LoopInfo &LI = P->getAnalysis<LoopInfo>(); 2458019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel BasicBlock::iterator SplitIt = SplitPt; 2468019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel while (isa<PHINode>(SplitIt)) 2478019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel ++SplitIt; 2488019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split"); 2498019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2508019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // The new block lives in whichever loop the old one did. 2518019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel if (Loop *L = LI.getLoopFor(Old)) 252d735ee85dbab8e4f66f9ec157f19956e0d11ec7aOwen Anderson L->addBasicBlockToLoop(New, LI.getBase()); 2538019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 254a8a8a366299863fe3711880add4c041c437b63cfDevang Patel if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>()) 255a8a8a366299863fe3711880add4c041c437b63cfDevang Patel { 256a8a8a366299863fe3711880add4c041c437b63cfDevang Patel // Old dominates New. New node domiantes all other nodes dominated by Old. 257a8a8a366299863fe3711880add4c041c437b63cfDevang Patel DomTreeNode *OldNode = DT->getNode(Old); 258a8a8a366299863fe3711880add4c041c437b63cfDevang Patel std::vector<DomTreeNode *> Children; 259a8a8a366299863fe3711880add4c041c437b63cfDevang Patel for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end(); 260a8a8a366299863fe3711880add4c041c437b63cfDevang Patel I != E; ++I) 261a8a8a366299863fe3711880add4c041c437b63cfDevang Patel Children.push_back(*I); 262a8a8a366299863fe3711880add4c041c437b63cfDevang Patel 263a8a8a366299863fe3711880add4c041c437b63cfDevang Patel DomTreeNode *NewNode = DT->addNewBlock(New,Old); 264a8a8a366299863fe3711880add4c041c437b63cfDevang Patel 265a8a8a366299863fe3711880add4c041c437b63cfDevang Patel for (std::vector<DomTreeNode *>::iterator I = Children.begin(), 266a8a8a366299863fe3711880add4c041c437b63cfDevang Patel E = Children.end(); I != E; ++I) 267a8a8a366299863fe3711880add4c041c437b63cfDevang Patel DT->changeImmediateDominator(*I, NewNode); 268a8a8a366299863fe3711880add4c041c437b63cfDevang Patel } 2698019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2708019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel if (DominanceFrontier *DF = P->getAnalysisToUpdate<DominanceFrontier>()) 2718019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel DF->splitBlock(Old); 2728019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2738019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return New; 2748019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel} 27554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 27654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 27754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// SplitBlockPredecessors - This method transforms BB by introducing a new 27854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// basic block into the function, and moving some of the predecessors of BB to 27954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// be predecessors of the new block. The new predecessors are indicated by the 28054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// Preds array, which has NumPreds elements in it. The new block is given a 28154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// suffix of 'Suffix'. 28254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// 28354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree and 28454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// DominanceFrontier, but no other analyses. 28554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris LattnerBasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB, 28654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner BasicBlock *const *Preds, 28754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner unsigned NumPreds, const char *Suffix, 28854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Pass *P) { 28954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Create new basic block, insert right before the original block. 29054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner BasicBlock *NewBB = 29154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner BasicBlock::Create(BB->getName()+Suffix, BB->getParent(), BB); 29254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 29354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // The new block unconditionally branches to the old block. 29454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner BranchInst *BI = BranchInst::Create(BB, NewBB); 29554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 29654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Move the edges from Preds to point to NewBB instead of BB. 297280a6e607d8eb7401749a92db624a82de47da777Nick Lewycky for (unsigned i = 0; i != NumPreds; ++i) 29854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB); 29954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 30054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Update dominator tree and dominator frontier if available. 30154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner DominatorTree *DT = P ? P->getAnalysisToUpdate<DominatorTree>() : 0; 30254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (DT) 30354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner DT->splitBlock(NewBB); 30454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (DominanceFrontier *DF = P ? P->getAnalysisToUpdate<DominanceFrontier>():0) 30554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner DF->splitBlock(NewBB); 30654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner AliasAnalysis *AA = P ? P->getAnalysisToUpdate<AliasAnalysis>() : 0; 30754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 30854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 30954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Insert a new PHI node into NewBB for every PHI node in BB and that new PHI 31054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // node becomes an incoming value for BB's phi node. However, if the Preds 31154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // list is empty, we need to insert dummy entries into the PHI nodes in BB to 31254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // account for the newly created predecessor. 31354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (NumPreds == 0) { 31454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Insert dummy values as the incoming value. 31554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I) 31654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB); 31754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner return NewBB; 31854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 31954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 32054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Otherwise, create a new PHI node in NewBB for each PHI node in BB. 32154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) { 32254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PHINode *PN = cast<PHINode>(I++); 32354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 32454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Check to see if all of the values coming in are the same. If so, we 32554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // don't need to create a new PHI node. 32654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Value *InVal = PN->getIncomingValueForBlock(Preds[0]); 32754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (unsigned i = 1; i != NumPreds; ++i) 32854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (InVal != PN->getIncomingValueForBlock(Preds[i])) { 32954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner InVal = 0; 33054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner break; 33154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 33254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 33354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (InVal) { 33454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // If all incoming values for the new PHI would be the same, just don't 33554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // make a new PHI. Instead, just remove the incoming values from the old 33654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // PHI. 33754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (unsigned i = 0; i != NumPreds; ++i) 33854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PN->removeIncomingValue(Preds[i], false); 33954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } else { 34054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // If the values coming into the block are not the same, we need a PHI. 34154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Create the new PHI node, insert it into NewBB at the end of the block 34254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PHINode *NewPHI = 34354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PHINode::Create(PN->getType(), PN->getName()+".ph", BI); 34454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (AA) AA->copyValue(PN, NewPHI); 34554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 34654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Move all of the PHI values for 'Preds' to the new PHI. 34754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (unsigned i = 0; i != NumPreds; ++i) { 34854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Value *V = PN->removeIncomingValue(Preds[i], false); 34954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner NewPHI->addIncoming(V, Preds[i]); 35054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 35154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner InVal = NewPHI; 35254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 35354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 35454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Add an incoming value to the PHI node in the loop for the preheader 35554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // edge. 35654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PN->addIncoming(InVal, NewBB); 35754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 35854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Check to see if we can eliminate this phi node. 35954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (Value *V = PN->hasConstantValue(DT != 0)) { 36054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Instruction *I = dyn_cast<Instruction>(V); 36154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (!I || DT == 0 || DT->dominates(I, PN)) { 36254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PN->replaceAllUsesWith(V); 36354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (AA) AA->deleteValue(PN); 36454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PN->eraseFromParent(); 36554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 36654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 36754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 36854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 36954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner return NewBB; 37054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner} 371