BasicBlockUtils.cpp revision 5622f07a21b799964dc172925b9ebc38191859f6
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" 23ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner#include "llvm/Target/TargetData.h" 244d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner#include <algorithm> 25f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnerusing namespace llvm; 26d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 2771af9b07a58a264064813545889cf6473ce23de6Chris Lattner/// DeleteDeadBlock - Delete the specified block, which must have no 2871af9b07a58a264064813545889cf6473ce23de6Chris Lattner/// predecessors. 2971af9b07a58a264064813545889cf6473ce23de6Chris Lattnervoid llvm::DeleteDeadBlock(BasicBlock *BB) { 302973a25dbc0ee1081e34421e53b8f4308b624854Chris Lattner assert((pred_begin(BB) == pred_end(BB) || 312973a25dbc0ee1081e34421e53b8f4308b624854Chris Lattner // Can delete self loop. 322973a25dbc0ee1081e34421e53b8f4308b624854Chris Lattner BB->getSinglePredecessor() == BB) && "Block is not dead!"); 332b1ba24fb75e633560846e551acadade92783bb3Chris Lattner TerminatorInst *BBTerm = BB->getTerminator(); 345622f07a21b799964dc172925b9ebc38191859f6Devang Patel 352b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // Loop through all of our successors and make sure they know that one 362b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // of their predecessors is going away. 372b1ba24fb75e633560846e551acadade92783bb3Chris Lattner for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i) 382b1ba24fb75e633560846e551acadade92783bb3Chris Lattner BBTerm->getSuccessor(i)->removePredecessor(BB); 392b1ba24fb75e633560846e551acadade92783bb3Chris Lattner 402b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // Zap all the instructions in the block. 412b1ba24fb75e633560846e551acadade92783bb3Chris Lattner while (!BB->empty()) { 422b1ba24fb75e633560846e551acadade92783bb3Chris Lattner Instruction &I = BB->back(); 432b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // If this instruction is used, replace uses with an arbitrary value. 442b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // Because control flow can't get here, we don't care what we replace the 452b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // value with. Note that since this block is unreachable, and all values 462b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // contained within it must dominate their uses, that all uses will 472b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // eventually be removed (they are themselves dead). 482b1ba24fb75e633560846e551acadade92783bb3Chris Lattner if (!I.use_empty()) 492b1ba24fb75e633560846e551acadade92783bb3Chris Lattner I.replaceAllUsesWith(UndefValue::get(I.getType())); 502b1ba24fb75e633560846e551acadade92783bb3Chris Lattner BB->getInstList().pop_back(); 512b1ba24fb75e633560846e551acadade92783bb3Chris Lattner } 525622f07a21b799964dc172925b9ebc38191859f6Devang Patel 532b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // Zap the block! 542b1ba24fb75e633560846e551acadade92783bb3Chris Lattner BB->eraseFromParent(); 552b1ba24fb75e633560846e551acadade92783bb3Chris Lattner} 562b1ba24fb75e633560846e551acadade92783bb3Chris Lattner 5729874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner/// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are 5829874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner/// any single-entry PHI nodes in it, fold them away. This handles the case 5929874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner/// when all entries to the PHI nodes in a block are guaranteed equal, such as 6029874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner/// when the block has exactly one predecessor. 6129874e0dc6c4e55bc384611273343bb358982cc3Chris Lattnervoid llvm::FoldSingleEntryPHINodes(BasicBlock *BB) { 6229874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner if (!isa<PHINode>(BB->begin())) 6329874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner return; 6429874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner 6529874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) { 6629874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner if (PN->getIncomingValue(0) != PN) 6729874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner PN->replaceAllUsesWith(PN->getIncomingValue(0)); 6829874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner else 6929874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner PN->replaceAllUsesWith(UndefValue::get(PN->getType())); 7029874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner PN->eraseFromParent(); 7129874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner } 7229874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner} 7329874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner 7429874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner 75b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor, 76b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson/// if possible. The return value indicates success or failure. 77b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Andersonbool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) { 7811f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson pred_iterator PI(pred_begin(BB)), PE(pred_end(BB)); 79b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Can't merge the entry block. 80b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson if (pred_begin(BB) == pred_end(BB)) return false; 81b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 8211f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson BasicBlock *PredBB = *PI++; 8311f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson for (; PI != PE; ++PI) // Search all predecessors, see if they are all same 8411f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (*PI != PredBB) { 8511f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson PredBB = 0; // There are multiple different predecessors... 8611f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson break; 8711f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson } 88b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 8911f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson // Can't merge if there are multiple predecessors. 9011f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (!PredBB) return false; 913ecaf1b33940470d5bf554135778ba5a8bce9a79Owen Anderson // Don't break self-loops. 923ecaf1b33940470d5bf554135778ba5a8bce9a79Owen Anderson if (PredBB == BB) return false; 933ecaf1b33940470d5bf554135778ba5a8bce9a79Owen Anderson // Don't break invokes. 943ecaf1b33940470d5bf554135778ba5a8bce9a79Owen Anderson if (isa<InvokeInst>(PredBB->getTerminator())) return false; 9511f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson 9611f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB)); 9711f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson BasicBlock* OnlySucc = BB; 9811f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson for (; SI != SE; ++SI) 9911f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (*SI != OnlySucc) { 10011f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson OnlySucc = 0; // There are multiple distinct successors! 10111f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson break; 10211f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson } 10311f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson 10411f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson // Can't merge if there are multiple successors. 10511f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (!OnlySucc) return false; 106e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel 107e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel // Can't merge if there is PHI loop. 108e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) { 109e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel if (PHINode *PN = dyn_cast<PHINode>(BI)) { 110e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 111e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel if (PN->getIncomingValue(i) == PN) 112e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel return false; 113e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel } else 114e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel break; 115e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel } 116e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel 117b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Begin by getting rid of unneeded PHIs. 118b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) { 119b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson PN->replaceAllUsesWith(PN->getIncomingValue(0)); 120b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson BB->getInstList().pop_front(); // Delete the phi node... 121b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 122b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 123b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Delete the unconditional branch from the predecessor... 124b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson PredBB->getInstList().pop_back(); 125b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 126b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Move all definitions in the successor to the predecessor... 127b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson PredBB->getInstList().splice(PredBB->end(), BB->getInstList()); 128b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 129b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Make all PHI nodes that referred to BB now refer to Pred as their 130b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // source... 131b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson BB->replaceAllUsesWith(PredBB); 132b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 13311f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson // Inherit predecessors name if it exists. 13411f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (!PredBB->hasName()) 13511f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson PredBB->takeName(BB); 13611f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson 137b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Finally, erase the old block and update dominator info. 138b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson if (P) { 1391465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands if (DominatorTree* DT = P->getAnalysisIfAvailable<DominatorTree>()) { 140b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DomTreeNode* DTN = DT->getNode(BB); 141b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DomTreeNode* PredDTN = DT->getNode(PredBB); 142b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 143b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson if (DTN) { 144b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson SmallPtrSet<DomTreeNode*, 8> Children(DTN->begin(), DTN->end()); 145b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = Children.begin(), 146b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DE = Children.end(); DI != DE; ++DI) 147b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DT->changeImmediateDominator(*DI, PredDTN); 148b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 149b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DT->eraseNode(BB); 150b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 151b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 152b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 153b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 154b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson BB->eraseFromParent(); 155b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 156b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 157b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson return true; 158b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson} 159b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 1600f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI) 1610f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// with a value, then remove and delete the original instruction. 1620f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 163f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL, 164f7703df4968084c18c248c1feea9961c19a32e6aChris Lattner BasicBlock::iterator &BI, Value *V) { 16518961504fc2b299578dba817900a0696cf3ccc4dChris Lattner Instruction &I = *BI; 1664d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Replaces all of the uses of the instruction with uses of the value 16718961504fc2b299578dba817900a0696cf3ccc4dChris Lattner I.replaceAllUsesWith(V); 1684d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 16986cc42355593dd1689f7d58d56695c451215b02bChris Lattner // Make sure to propagate a name if there is one already. 17086cc42355593dd1689f7d58d56695c451215b02bChris Lattner if (I.hasName() && !V->hasName()) 17186cc42355593dd1689f7d58d56695c451215b02bChris Lattner V->takeName(&I); 172fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 1735560c9d49ccae132cabf1155f18aa0480dce3edaMisha Brukman // Delete the unnecessary instruction now... 17418961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BI = BIL.erase(BI); 1754d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner} 1764d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1774d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1780f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// ReplaceInstWithInst - Replace the instruction specified by BI with the 1790f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// instruction specified by I. The original instruction is deleted and BI is 1800f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// updated to point to the new instruction. 1810f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 182f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL, 183f7703df4968084c18c248c1feea9961c19a32e6aChris Lattner BasicBlock::iterator &BI, Instruction *I) { 1844d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner assert(I->getParent() == 0 && 1854d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner "ReplaceInstWithInst: Instruction already inserted into basic block!"); 1864d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1874d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Insert the new instruction into the basic block... 18818961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BasicBlock::iterator New = BIL.insert(BI, I); 1894d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1904d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Replace all uses of the old instruction, and delete it. 1914d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner ReplaceInstWithValue(BIL, BI, I); 1924d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1934d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Move BI back to point to the newly inserted instruction 19418961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BI = New; 1954d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner} 1964d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 1970f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// ReplaceInstWithInst - Replace the instruction specified by From with the 1980f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// instruction specified by To. 1990f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 200f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) { 20118961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BasicBlock::iterator BI(From); 20218961504fc2b299578dba817900a0696cf3ccc4dChris Lattner ReplaceInstWithInst(From->getParent()->getInstList(), BI, To); 2034d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner} 204b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 2050f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// RemoveSuccessor - Change the specified terminator instruction such that its 206bc2eba1ca2d99836af6b5e12128c08e022930918Reid Spencer/// successor SuccNum no longer exists. Because this reduces the outgoing 2070f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// degree of the current basic block, the actual terminator instruction itself 208bc2eba1ca2d99836af6b5e12128c08e022930918Reid Spencer/// may have to be changed. In the case where the last successor of the block 209bc2eba1ca2d99836af6b5e12128c08e022930918Reid Spencer/// is deleted, a return instruction is inserted in its place which can cause a 2100f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// surprising change in program behavior if it is not expected. 2110f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 212f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) { 213b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner assert(SuccNum < TI->getNumSuccessors() && 214b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner "Trying to remove a nonexistant successor!"); 215b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 216b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // If our old successor block contains any PHI nodes, remove the entry in the 217b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // PHI nodes that comes from this branch... 218b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // 219b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner BasicBlock *BB = TI->getParent(); 220b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner TI->getSuccessor(SuccNum)->removePredecessor(BB); 221b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 222b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner TerminatorInst *NewTI = 0; 223b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner switch (TI->getOpcode()) { 224b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner case Instruction::Br: 225b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // If this is a conditional branch... convert to unconditional branch. 226b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner if (TI->getNumSuccessors() == 2) { 227b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum)); 228b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner } else { // Otherwise convert to a return instruction... 229b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner Value *RetVal = 0; 230fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 231b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // Create a value to return... if the function doesn't return null... 232b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner if (BB->getParent()->getReturnType() != Type::VoidTy) 233b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner RetVal = Constant::getNullValue(BB->getParent()->getReturnType()); 234b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 235b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner // Create the return... 236051a950000e21935165db56695e35bade668193bGabor Greif NewTI = ReturnInst::Create(RetVal); 237b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner } 238fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman break; 239b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 240b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner case Instruction::Invoke: // Should convert to call 241b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner case Instruction::Switch: // Should remove entry 242b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner default: 243b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner case Instruction::Ret: // Cannot happen, has no successors! 244b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner assert(0 && "Unhandled terminator instruction type in RemoveSuccessor!"); 245b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner abort(); 246b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner } 247b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 248b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner if (NewTI) // If it's a different instruction, replace. 249b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner ReplaceInstWithInst(TI, NewTI); 250b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner} 251d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 2528019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// SplitEdge - Split the edge connecting specified block. Pass P must 2538019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// not be NULL. 2548019893c3f55a4bfe770888fe285d6dae57cf216Devang PatelBasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) { 2558019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel TerminatorInst *LatchTerm = BB->getTerminator(); 2568019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel unsigned SuccNum = 0; 2578a88a14462db7e8ad96536c89b3ab948b89d0c2bDevang Patel#ifndef NDEBUG 2588a88a14462db7e8ad96536c89b3ab948b89d0c2bDevang Patel unsigned e = LatchTerm->getNumSuccessors(); 2598a88a14462db7e8ad96536c89b3ab948b89d0c2bDevang Patel#endif 2608a88a14462db7e8ad96536c89b3ab948b89d0c2bDevang Patel for (unsigned i = 0; ; ++i) { 2618019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel assert(i != e && "Didn't find edge?"); 2628019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel if (LatchTerm->getSuccessor(i) == Succ) { 2638019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel SuccNum = i; 2648019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel break; 2658019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel } 2668019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel } 2678019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2688019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // If this is a critical edge, let SplitCriticalEdge do it. 2698019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel if (SplitCriticalEdge(BB->getTerminator(), SuccNum, P)) 2708019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return LatchTerm->getSuccessor(SuccNum); 2718019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2728019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // If the edge isn't critical, then BB has a single successor or Succ has a 2738019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // single pred. Split the block. 2748019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel BasicBlock::iterator SplitPoint; 2758019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel if (BasicBlock *SP = Succ->getSinglePredecessor()) { 2768019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // If the successor only has a single pred, split the top of the successor 2778019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // block. 2788019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel assert(SP == BB && "CFG broken"); 2798a88a14462db7e8ad96536c89b3ab948b89d0c2bDevang Patel SP = NULL; 2808019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return SplitBlock(Succ, Succ->begin(), P); 2818019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel } else { 2828019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // Otherwise, if BB has a single successor, split it at the bottom of the 2838019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // block. 2848019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel assert(BB->getTerminator()->getNumSuccessors() == 1 && 2858019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel "Should have a single succ!"); 2868019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return SplitBlock(BB, BB->getTerminator(), P); 2878019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel } 2888019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel} 2898019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2908019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// SplitBlock - Split the specified block at the specified instruction - every 2918019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// thing before SplitPt stays in Old and everything starting with SplitPt moves 2928019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// to a new block. The two blocks are joined by an unconditional branch and 2938019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// the loop info is updated. 2948019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// 2958019893c3f55a4bfe770888fe285d6dae57cf216Devang PatelBasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) { 2968019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel BasicBlock::iterator SplitIt = SplitPt; 2978019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel while (isa<PHINode>(SplitIt)) 2988019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel ++SplitIt; 2998019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split"); 3008019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 3018019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // The new block lives in whichever loop the old one did. 3021465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands if (LoopInfo* LI = P->getAnalysisIfAvailable<LoopInfo>()) 303a90793b431458c1bac4c7267946738968c4cdf58Owen Anderson if (Loop *L = LI->getLoopFor(Old)) 304a90793b431458c1bac4c7267946738968c4cdf58Owen Anderson L->addBasicBlockToLoop(New, LI->getBase()); 3058019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 3061465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) 307a8a8a366299863fe3711880add4c041c437b63cfDevang Patel { 308a8a8a366299863fe3711880add4c041c437b63cfDevang Patel // Old dominates New. New node domiantes all other nodes dominated by Old. 309a8a8a366299863fe3711880add4c041c437b63cfDevang Patel DomTreeNode *OldNode = DT->getNode(Old); 310a8a8a366299863fe3711880add4c041c437b63cfDevang Patel std::vector<DomTreeNode *> Children; 311a8a8a366299863fe3711880add4c041c437b63cfDevang Patel for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end(); 312a8a8a366299863fe3711880add4c041c437b63cfDevang Patel I != E; ++I) 313a8a8a366299863fe3711880add4c041c437b63cfDevang Patel Children.push_back(*I); 314a8a8a366299863fe3711880add4c041c437b63cfDevang Patel 315a8a8a366299863fe3711880add4c041c437b63cfDevang Patel DomTreeNode *NewNode = DT->addNewBlock(New,Old); 316a8a8a366299863fe3711880add4c041c437b63cfDevang Patel 317a8a8a366299863fe3711880add4c041c437b63cfDevang Patel for (std::vector<DomTreeNode *>::iterator I = Children.begin(), 318a8a8a366299863fe3711880add4c041c437b63cfDevang Patel E = Children.end(); I != E; ++I) 319a8a8a366299863fe3711880add4c041c437b63cfDevang Patel DT->changeImmediateDominator(*I, NewNode); 320a8a8a366299863fe3711880add4c041c437b63cfDevang Patel } 3218019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 3221465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands if (DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>()) 3238019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel DF->splitBlock(Old); 3248019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 3258019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return New; 3268019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel} 32754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 32854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 32954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// SplitBlockPredecessors - This method transforms BB by introducing a new 33054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// basic block into the function, and moving some of the predecessors of BB to 33154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// be predecessors of the new block. The new predecessors are indicated by the 33254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// Preds array, which has NumPreds elements in it. The new block is given a 33354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// suffix of 'Suffix'. 33454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// 33554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree and 33654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// DominanceFrontier, but no other analyses. 33754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris LattnerBasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB, 33854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner BasicBlock *const *Preds, 33954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner unsigned NumPreds, const char *Suffix, 34054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Pass *P) { 34154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Create new basic block, insert right before the original block. 34254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner BasicBlock *NewBB = 34354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner BasicBlock::Create(BB->getName()+Suffix, BB->getParent(), BB); 34454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 34554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // The new block unconditionally branches to the old block. 34654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner BranchInst *BI = BranchInst::Create(BB, NewBB); 34754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 34854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Move the edges from Preds to point to NewBB instead of BB. 349280a6e607d8eb7401749a92db624a82de47da777Nick Lewycky for (unsigned i = 0; i != NumPreds; ++i) 35054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB); 35154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 35254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Update dominator tree and dominator frontier if available. 3531465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0; 35454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (DT) 35554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner DT->splitBlock(NewBB); 3561465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands if (DominanceFrontier *DF = P ? P->getAnalysisIfAvailable<DominanceFrontier>():0) 35754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner DF->splitBlock(NewBB); 3581465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0; 35954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 36054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 36154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Insert a new PHI node into NewBB for every PHI node in BB and that new PHI 36254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // node becomes an incoming value for BB's phi node. However, if the Preds 36354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // list is empty, we need to insert dummy entries into the PHI nodes in BB to 36454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // account for the newly created predecessor. 36554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (NumPreds == 0) { 36654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Insert dummy values as the incoming value. 36754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I) 36854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB); 36954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner return NewBB; 37054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 37154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 37254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Otherwise, create a new PHI node in NewBB for each PHI node in BB. 37354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) { 37454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PHINode *PN = cast<PHINode>(I++); 37554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 37654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Check to see if all of the values coming in are the same. If so, we 37754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // don't need to create a new PHI node. 37854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Value *InVal = PN->getIncomingValueForBlock(Preds[0]); 37954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (unsigned i = 1; i != NumPreds; ++i) 38054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (InVal != PN->getIncomingValueForBlock(Preds[i])) { 38154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner InVal = 0; 38254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner break; 38354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 38454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 38554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (InVal) { 38654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // If all incoming values for the new PHI would be the same, just don't 38754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // make a new PHI. Instead, just remove the incoming values from the old 38854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // PHI. 38954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (unsigned i = 0; i != NumPreds; ++i) 39054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PN->removeIncomingValue(Preds[i], false); 39154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } else { 39254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // If the values coming into the block are not the same, we need a PHI. 39354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Create the new PHI node, insert it into NewBB at the end of the block 39454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PHINode *NewPHI = 39554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PHINode::Create(PN->getType(), PN->getName()+".ph", BI); 39654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (AA) AA->copyValue(PN, NewPHI); 39754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 39854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Move all of the PHI values for 'Preds' to the new PHI. 39954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (unsigned i = 0; i != NumPreds; ++i) { 40054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Value *V = PN->removeIncomingValue(Preds[i], false); 40154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner NewPHI->addIncoming(V, Preds[i]); 40254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 40354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner InVal = NewPHI; 40454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 40554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 40654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Add an incoming value to the PHI node in the loop for the preheader 40754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // edge. 40854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PN->addIncoming(InVal, NewBB); 40954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 41054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Check to see if we can eliminate this phi node. 41154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (Value *V = PN->hasConstantValue(DT != 0)) { 41254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Instruction *I = dyn_cast<Instruction>(V); 41354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (!I || DT == 0 || DT->dominates(I, PN)) { 41454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PN->replaceAllUsesWith(V); 41554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (AA) AA->deleteValue(PN); 41654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PN->eraseFromParent(); 41754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 41854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 41954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 42054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 42154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner return NewBB; 42254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner} 42352c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner 4244aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner/// AreEquivalentAddressValues - Test if A and B will obviously have the same 4254aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner/// value. This includes recognizing that %t0 and %t1 will have the same 4264aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner/// value in code like this: 4274aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner/// %t0 = getelementptr @a, 0, 3 4284aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner/// store i32 0, i32* %t0 4294aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner/// %t1 = getelementptr @a, 0, 3 4304aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner/// %t2 = load i32* %t1 4314aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner/// 4324aebaee0e40f2457f1a6588679655a3c600a553bChris Lattnerstatic bool AreEquivalentAddressValues(const Value *A, const Value *B) { 4334aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner // Test if the values are trivially equivalent. 4344aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner if (A == B) return true; 4354aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner 4364aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner // Test if the values come form identical arithmetic instructions. 4374aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner if (isa<BinaryOperator>(A) || isa<CastInst>(A) || 4384aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner isa<PHINode>(A) || isa<GetElementPtrInst>(A)) 4394aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner if (const Instruction *BI = dyn_cast<Instruction>(B)) 4404aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner if (cast<Instruction>(A)->isIdenticalTo(BI)) 4414aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner return true; 4424aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner 4434aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner // Otherwise they may not be equivalent. 4444aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner return false; 4454aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner} 4464aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner 44752c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at the 44852c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// instruction before ScanFrom) checking to see if we have the value at the 44952c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// memory address *Ptr locally available within a small number of instructions. 45052c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// If the value is available, return it. 45152c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// 45252c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// If not, return the iterator for the last validated instruction that the 45352c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// value would be live through. If we scanned the entire block and didn't find 45452c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// something that invalidates *Ptr or provides it, ScanFrom would be left at 45552c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// begin() and this returns null. ScanFrom could also be left 45652c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// 45752c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// MaxInstsToScan specifies the maximum instructions to scan in the block. If 45852c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// it is set to 0, it will scan the whole block. You can also optionally 45952c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner/// specify an alias analysis implementation, which makes this more precise. 46052c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris LattnerValue *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB, 46152c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner BasicBlock::iterator &ScanFrom, 46252c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner unsigned MaxInstsToScan, 46352c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner AliasAnalysis *AA) { 46452c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner if (MaxInstsToScan == 0) MaxInstsToScan = ~0U; 465ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner 466ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner // If we're using alias analysis to disambiguate get the size of *Ptr. 467ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner unsigned AccessSize = 0; 468ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner if (AA) { 469ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner const Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType(); 470ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner AccessSize = AA->getTargetData().getTypeStoreSizeInBits(AccessTy); 471ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner } 47252c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner 47352c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner while (ScanFrom != ScanBB->begin()) { 47452c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // Don't scan huge blocks. 47552c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner if (MaxInstsToScan-- == 0) return 0; 47652c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner 47752c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner Instruction *Inst = --ScanFrom; 47852c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner 47952c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // If this is a load of Ptr, the loaded value is available. 48052c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) 4814aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner if (AreEquivalentAddressValues(LI->getOperand(0), Ptr)) 48252c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner return LI; 48352c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner 48452c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 48552c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // If this is a store through Ptr, the value is available! 4864aebaee0e40f2457f1a6588679655a3c600a553bChris Lattner if (AreEquivalentAddressValues(SI->getOperand(1), Ptr)) 48752c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner return SI->getOperand(0); 48852c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner 48952c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // If Ptr is an alloca and this is a store to a different alloca, ignore 49052c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // the store. This is a trivial form of alias analysis that is important 49152c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // for reg2mem'd code. 49252c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner if ((isa<AllocaInst>(Ptr) || isa<GlobalVariable>(Ptr)) && 49352c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner (isa<AllocaInst>(SI->getOperand(1)) || 49452c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner isa<GlobalVariable>(SI->getOperand(1)))) 49552c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner continue; 49652c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner 497ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner // If we have alias analysis and it says the store won't modify the loaded 498ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner // value, ignore the store. 499ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner if (AA && 500ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner (AA->getModRefInfo(SI, Ptr, AccessSize) & AliasAnalysis::Mod) == 0) 501ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner continue; 502ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner 50352c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // Otherwise the store that may or may not alias the pointer, bail out. 50452c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner ++ScanFrom; 50552c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner return 0; 50652c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner } 50752c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner 50852c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // If this is some other instruction that may clobber Ptr, bail out. 50952c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner if (Inst->mayWriteToMemory()) { 510ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner // If alias analysis claims that it really won't modify the load, 511ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner // ignore it. 512ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner if (AA && 513ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner (AA->getModRefInfo(Inst, Ptr, AccessSize) & AliasAnalysis::Mod) == 0) 514ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner continue; 515ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner 51652c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // May modify the pointer, bail out. 51752c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner ++ScanFrom; 51852c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner return 0; 51952c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner } 52052c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner } 52152c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner 52252c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // Got to the start of the block, we didn't find it, but are done for this 52352c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner // block. 52452c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner return 0; 52552c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner} 526