BasicBlockUtils.cpp revision fbbd4abfe5a89e432240d2c05201b44a5e2f2f78
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" 18bd8e650876cc93952dde3120938271dbda6cbbb7Dale Johannesen#include "llvm/IntrinsicInst.h" 19b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner#include "llvm/Constant.h" 20b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner#include "llvm/Type.h" 2154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner#include "llvm/Analysis/AliasAnalysis.h" 229fc5cdf77c812aaa80419036de27576d45894d0dChris Lattner#include "llvm/Analysis/DominanceFrontier.h" 23b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner#include "llvm/Analysis/LoopInfo.h" 24b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner#include "llvm/Analysis/MemoryDependenceAnalysis.h" 25ee6e10bc8e389ed1a09c33c8cec15b3aa13e813bChris Lattner#include "llvm/Target/TargetData.h" 26afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman#include "llvm/Transforms/Utils/Local.h" 275c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman#include "llvm/Transforms/Scalar.h" 287d696d80409aad20bb5da0fc4eccab941dd371d4Torok Edwin#include "llvm/Support/ErrorHandling.h" 29afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman#include "llvm/Support/ValueHandle.h" 304d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner#include <algorithm> 31f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnerusing namespace llvm; 32d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 3371af9b07a58a264064813545889cf6473ce23de6Chris Lattner/// DeleteDeadBlock - Delete the specified block, which must have no 3471af9b07a58a264064813545889cf6473ce23de6Chris Lattner/// predecessors. 3571af9b07a58a264064813545889cf6473ce23de6Chris Lattnervoid llvm::DeleteDeadBlock(BasicBlock *BB) { 362973a25dbc0ee1081e34421e53b8f4308b624854Chris Lattner assert((pred_begin(BB) == pred_end(BB) || 372973a25dbc0ee1081e34421e53b8f4308b624854Chris Lattner // Can delete self loop. 382973a25dbc0ee1081e34421e53b8f4308b624854Chris Lattner BB->getSinglePredecessor() == BB) && "Block is not dead!"); 392b1ba24fb75e633560846e551acadade92783bb3Chris Lattner TerminatorInst *BBTerm = BB->getTerminator(); 405622f07a21b799964dc172925b9ebc38191859f6Devang Patel 412b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // Loop through all of our successors and make sure they know that one 422b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // of their predecessors is going away. 432b1ba24fb75e633560846e551acadade92783bb3Chris Lattner for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i) 442b1ba24fb75e633560846e551acadade92783bb3Chris Lattner BBTerm->getSuccessor(i)->removePredecessor(BB); 452b1ba24fb75e633560846e551acadade92783bb3Chris Lattner 462b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // Zap all the instructions in the block. 472b1ba24fb75e633560846e551acadade92783bb3Chris Lattner while (!BB->empty()) { 482b1ba24fb75e633560846e551acadade92783bb3Chris Lattner Instruction &I = BB->back(); 492b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // If this instruction is used, replace uses with an arbitrary value. 502b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // Because control flow can't get here, we don't care what we replace the 512b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // value with. Note that since this block is unreachable, and all values 522b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // contained within it must dominate their uses, that all uses will 532b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // eventually be removed (they are themselves dead). 542b1ba24fb75e633560846e551acadade92783bb3Chris Lattner if (!I.use_empty()) 559e9a0d5fc26878e51a58a8b57900fcbf952c2691Owen Anderson I.replaceAllUsesWith(UndefValue::get(I.getType())); 562b1ba24fb75e633560846e551acadade92783bb3Chris Lattner BB->getInstList().pop_back(); 572b1ba24fb75e633560846e551acadade92783bb3Chris Lattner } 585622f07a21b799964dc172925b9ebc38191859f6Devang Patel 592b1ba24fb75e633560846e551acadade92783bb3Chris Lattner // Zap the block! 602b1ba24fb75e633560846e551acadade92783bb3Chris Lattner BB->eraseFromParent(); 612b1ba24fb75e633560846e551acadade92783bb3Chris Lattner} 622b1ba24fb75e633560846e551acadade92783bb3Chris Lattner 6329874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner/// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are 6429874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner/// any single-entry PHI nodes in it, fold them away. This handles the case 6529874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner/// when all entries to the PHI nodes in a block are guaranteed equal, such as 6629874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner/// when the block has exactly one predecessor. 67b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattnervoid llvm::FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P) { 68b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner if (!isa<PHINode>(BB->begin())) return; 69b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner 70b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner AliasAnalysis *AA = 0; 71b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner MemoryDependenceAnalysis *MemDep = 0; 72b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner if (P) { 73b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner AA = P->getAnalysisIfAvailable<AliasAnalysis>(); 74b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner MemDep = P->getAnalysisIfAvailable<MemoryDependenceAnalysis>(); 75b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner } 76b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner 7729874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) { 7829874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner if (PN->getIncomingValue(0) != PN) 7929874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner PN->replaceAllUsesWith(PN->getIncomingValue(0)); 8029874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner else 819e9a0d5fc26878e51a58a8b57900fcbf952c2691Owen Anderson PN->replaceAllUsesWith(UndefValue::get(PN->getType())); 82b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner 83b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner if (MemDep) 84b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner MemDep->removeInstruction(PN); // Memdep updates AA itself. 85b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner else if (AA && isa<PointerType>(PN->getType())) 86b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner AA->deleteValue(PN); 87b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner 8829874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner PN->eraseFromParent(); 8929874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner } 9029874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner} 9129874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner 9229874e0dc6c4e55bc384611273343bb358982cc3Chris Lattner 93afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman/// DeleteDeadPHIs - Examine each PHI in the given block and delete it if it 94afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman/// is dead. Also recursively delete any operands that become dead as 95afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman/// a result. This includes tracing the def-use list from the PHI to see if 9635738ac150afafe2359268d4b2169498c6c98c5fDan Gohman/// it is ultimately unused or if it reaches an unused cycle. 9790fe0bd68cdbeb980c08628c4992dffad0dc728fDan Gohmanbool llvm::DeleteDeadPHIs(BasicBlock *BB) { 98afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman // Recursively deleting a PHI may cause multiple PHIs to be deleted 99afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman // or RAUW'd undef, so use an array of WeakVH for the PHIs to delete. 100afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman SmallVector<WeakVH, 8> PHIs; 101afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman for (BasicBlock::iterator I = BB->begin(); 102afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman PHINode *PN = dyn_cast<PHINode>(I); ++I) 103afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman PHIs.push_back(PN); 104afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman 10590fe0bd68cdbeb980c08628c4992dffad0dc728fDan Gohman bool Changed = false; 106afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman for (unsigned i = 0, e = PHIs.size(); i != e; ++i) 107afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman if (PHINode *PN = dyn_cast_or_null<PHINode>(PHIs[i].operator Value*())) 10890fe0bd68cdbeb980c08628c4992dffad0dc728fDan Gohman Changed |= RecursivelyDeleteDeadPHINode(PN); 10990fe0bd68cdbeb980c08628c4992dffad0dc728fDan Gohman 11090fe0bd68cdbeb980c08628c4992dffad0dc728fDan Gohman return Changed; 111afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman} 112afc36a9520971832dfbebc0333593bf5d3098296Dan Gohman 113438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor, 114438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman/// if possible. The return value indicates success or failure. 115882029269e0cf4b497993b8e9a754429ef035facChris Lattnerbool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) { 1161c034dcbbc86674cc146340a877495f71d9a2569Dan Gohman // Don't merge away blocks who have their address taken. 1171c034dcbbc86674cc146340a877495f71d9a2569Dan Gohman if (BB->hasAddressTaken()) return false; 118438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman 1191c034dcbbc86674cc146340a877495f71d9a2569Dan Gohman // Can't merge if there are multiple predecessors, or no predecessors. 1201c034dcbbc86674cc146340a877495f71d9a2569Dan Gohman BasicBlock *PredBB = BB->getUniquePredecessor(); 121438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman if (!PredBB) return false; 1221c034dcbbc86674cc146340a877495f71d9a2569Dan Gohman 1233ecaf1b33940470d5bf554135778ba5a8bce9a79Owen Anderson // Don't break self-loops. 124438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman if (PredBB == BB) return false; 1253ecaf1b33940470d5bf554135778ba5a8bce9a79Owen Anderson // Don't break invokes. 126438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman if (isa<InvokeInst>(PredBB->getTerminator())) return false; 127438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman 128438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB)); 129dc85f8ab808aec2f673262f5145eda58538cfb26Chris Lattner BasicBlock *OnlySucc = BB; 130438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman for (; SI != SE; ++SI) 131438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman if (*SI != OnlySucc) { 132438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman OnlySucc = 0; // There are multiple distinct successors! 133438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman break; 134438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman } 135438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman 136438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman // Can't merge if there are multiple successors. 137438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman if (!OnlySucc) return false; 138e435a5d9374b61049b16ef69e6314542815fadb4Devang Patel 139438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman // Can't merge if there is PHI loop. 140438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) { 141438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman if (PHINode *PN = dyn_cast<PHINode>(BI)) { 142438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 143438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman if (PN->getIncomingValue(i) == PN) 144438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman return false; 145438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman } else 146438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman break; 147438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman } 148438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman 149438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman // Begin by getting rid of unneeded PHIs. 150dc85f8ab808aec2f673262f5145eda58538cfb26Chris Lattner if (isa<PHINode>(BB->front())) 151b5b7997fd0765f73b711ea4c72e4433ce3637794Chris Lattner FoldSingleEntryPHINodes(BB, P); 152438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman 153b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Delete the unconditional branch from the predecessor... 154b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson PredBB->getInstList().pop_back(); 155b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 156b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Move all definitions in the successor to the predecessor... 157b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson PredBB->getInstList().splice(PredBB->end(), BB->getInstList()); 158b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 159b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Make all PHI nodes that referred to BB now refer to Pred as their 160b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // source... 161b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson BB->replaceAllUsesWith(PredBB); 162b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 163438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman // Inherit predecessors name if it exists. 16411f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson if (!PredBB->hasName()) 16511f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson PredBB->takeName(BB); 16611f2ec8eb534502a0d5b7e3c13c1a38e877876b2Owen Anderson 167b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson // Finally, erase the old block and update dominator info. 168b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson if (P) { 169dc85f8ab808aec2f673262f5145eda58538cfb26Chris Lattner if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) { 170dc85f8ab808aec2f673262f5145eda58538cfb26Chris Lattner if (DomTreeNode *DTN = DT->getNode(BB)) { 171dc85f8ab808aec2f673262f5145eda58538cfb26Chris Lattner DomTreeNode *PredDTN = DT->getNode(PredBB); 172fbbd4abfe5a89e432240d2c05201b44a5e2f2f78Jakob Stoklund Olesen SmallVector<DomTreeNode*, 8> Children(DTN->begin(), DTN->end()); 173fbbd4abfe5a89e432240d2c05201b44a5e2f2f78Jakob Stoklund Olesen for (SmallVector<DomTreeNode*, 8>::iterator DI = Children.begin(), 174b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DE = Children.end(); DI != DE; ++DI) 175b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DT->changeImmediateDominator(*DI, PredDTN); 176b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 177b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson DT->eraseNode(BB); 178b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 179dc85f8ab808aec2f673262f5145eda58538cfb26Chris Lattner 180dc85f8ab808aec2f673262f5145eda58538cfb26Chris Lattner if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>()) 181dc85f8ab808aec2f673262f5145eda58538cfb26Chris Lattner LI->removeBlock(BB); 182b6810991a9648a40fe05162d744f42c3c178dba7Chris Lattner 183b6810991a9648a40fe05162d744f42c3c178dba7Chris Lattner if (MemoryDependenceAnalysis *MD = 184b6810991a9648a40fe05162d744f42c3c178dba7Chris Lattner P->getAnalysisIfAvailable<MemoryDependenceAnalysis>()) 185b6810991a9648a40fe05162d744f42c3c178dba7Chris Lattner MD->invalidateCachedPredecessors(); 186b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 187b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson } 188b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 189b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson BB->eraseFromParent(); 190438b583dbd20f63b70d0b5abb7780a50bf03dd83Dan Gohman return true; 191b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson} 192b31b06d04b81c5383e2fba0cd44d4ba3f324a794Owen Anderson 1930f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI) 1940f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// with a value, then remove and delete the original instruction. 1950f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 196f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL, 197f7703df4968084c18c248c1feea9961c19a32e6aChris Lattner BasicBlock::iterator &BI, Value *V) { 19818961504fc2b299578dba817900a0696cf3ccc4dChris Lattner Instruction &I = *BI; 1994d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Replaces all of the uses of the instruction with uses of the value 20018961504fc2b299578dba817900a0696cf3ccc4dChris Lattner I.replaceAllUsesWith(V); 2014d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 20286cc42355593dd1689f7d58d56695c451215b02bChris Lattner // Make sure to propagate a name if there is one already. 20386cc42355593dd1689f7d58d56695c451215b02bChris Lattner if (I.hasName() && !V->hasName()) 20486cc42355593dd1689f7d58d56695c451215b02bChris Lattner V->takeName(&I); 205fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 2065560c9d49ccae132cabf1155f18aa0480dce3edaMisha Brukman // Delete the unnecessary instruction now... 20718961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BI = BIL.erase(BI); 2084d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner} 2094d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 2104d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 2110f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// ReplaceInstWithInst - Replace the instruction specified by BI with the 2120f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// instruction specified by I. The original instruction is deleted and BI is 2130f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// updated to point to the new instruction. 2140f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 215f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL, 216f7703df4968084c18c248c1feea9961c19a32e6aChris Lattner BasicBlock::iterator &BI, Instruction *I) { 2174d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner assert(I->getParent() == 0 && 2184d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner "ReplaceInstWithInst: Instruction already inserted into basic block!"); 2194d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 2204d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Insert the new instruction into the basic block... 22118961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BasicBlock::iterator New = BIL.insert(BI, I); 2224d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 2234d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Replace all uses of the old instruction, and delete it. 2244d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner ReplaceInstWithValue(BIL, BI, I); 2254d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 2264d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner // Move BI back to point to the newly inserted instruction 22718961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BI = New; 2284d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner} 2294d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner 2300f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// ReplaceInstWithInst - Replace the instruction specified by From with the 2310f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// instruction specified by To. 2320f67dd6237eb7227aa58e9b77cd95f354989b891Chris Lattner/// 233f7703df4968084c18c248c1feea9961c19a32e6aChris Lattnervoid llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) { 23418961504fc2b299578dba817900a0696cf3ccc4dChris Lattner BasicBlock::iterator BI(From); 23518961504fc2b299578dba817900a0696cf3ccc4dChris Lattner ReplaceInstWithInst(From->getParent()->getInstList(), BI, To); 2364d1e46e7b06534cde262d32fad038135f406b6b7Chris Lattner} 237b0f0ef8f26eb8911ec1bb31380b5fe2d62e1c0ecChris Lattner 238ae23daf63afccd68be965ff4f7acafa818d76aaaBob Wilson/// GetSuccessorNumber - Search for the specified successor of basic block BB 239ae23daf63afccd68be965ff4f7acafa818d76aaaBob Wilson/// and return its position in the terminator instruction's list of 240ae23daf63afccd68be965ff4f7acafa818d76aaaBob Wilson/// successors. It is an error to call this with a block that is not a 241ae23daf63afccd68be965ff4f7acafa818d76aaaBob Wilson/// successor. 242ae23daf63afccd68be965ff4f7acafa818d76aaaBob Wilsonunsigned llvm::GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ) { 243adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson TerminatorInst *Term = BB->getTerminator(); 2448a88a14462db7e8ad96536c89b3ab948b89d0c2bDevang Patel#ifndef NDEBUG 245adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson unsigned e = Term->getNumSuccessors(); 2468a88a14462db7e8ad96536c89b3ab948b89d0c2bDevang Patel#endif 2478a88a14462db7e8ad96536c89b3ab948b89d0c2bDevang Patel for (unsigned i = 0; ; ++i) { 2488019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel assert(i != e && "Didn't find edge?"); 249adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson if (Term->getSuccessor(i) == Succ) 250adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson return i; 2518019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel } 252adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson return 0; 253adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson} 254adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson 255adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson/// SplitEdge - Split the edge connecting specified block. Pass P must 256adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson/// not be NULL. 257adb6f226714dcfae363f51b453c4590b0f42da5eBob WilsonBasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) { 258ae23daf63afccd68be965ff4f7acafa818d76aaaBob Wilson unsigned SuccNum = GetSuccessorNumber(BB, Succ); 2598019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2608019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // If this is a critical edge, let SplitCriticalEdge do it. 261adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson TerminatorInst *LatchTerm = BB->getTerminator(); 262adb6f226714dcfae363f51b453c4590b0f42da5eBob Wilson if (SplitCriticalEdge(LatchTerm, SuccNum, P)) 2638019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return LatchTerm->getSuccessor(SuccNum); 2648019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2658019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // If the edge isn't critical, then BB has a single successor or Succ has a 2668019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // single pred. Split the block. 2678019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel BasicBlock::iterator SplitPoint; 2688019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel if (BasicBlock *SP = Succ->getSinglePredecessor()) { 2698019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // If the successor only has a single pred, split the top of the successor 2708019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel // block. 2718019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel assert(SP == BB && "CFG broken"); 2728a88a14462db7e8ad96536c89b3ab948b89d0c2bDevang Patel SP = NULL; 2738019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return SplitBlock(Succ, Succ->begin(), P); 2748019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel } 275b0433d4b2fb66922fa3625871840ccb72c8a9decChris Lattner 276b0433d4b2fb66922fa3625871840ccb72c8a9decChris Lattner // Otherwise, if BB has a single successor, split it at the bottom of the 277b0433d4b2fb66922fa3625871840ccb72c8a9decChris Lattner // block. 278b0433d4b2fb66922fa3625871840ccb72c8a9decChris Lattner assert(BB->getTerminator()->getNumSuccessors() == 1 && 279b0433d4b2fb66922fa3625871840ccb72c8a9decChris Lattner "Should have a single succ!"); 280b0433d4b2fb66922fa3625871840ccb72c8a9decChris Lattner return SplitBlock(BB, BB->getTerminator(), P); 2818019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel} 2828019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2838019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// SplitBlock - Split the specified block at the specified instruction - every 2848019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// thing before SplitPt stays in Old and everything starting with SplitPt moves 2858019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// to a new block. The two blocks are joined by an unconditional branch and 2868019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// the loop info is updated. 2878019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel/// 2888019893c3f55a4bfe770888fe285d6dae57cf216Devang PatelBasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) { 2898019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel BasicBlock::iterator SplitIt = SplitPt; 2908019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel while (isa<PHINode>(SplitIt)) 2918019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel ++SplitIt; 2928019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split"); 2938019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 2945c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // The new block lives in whichever loop the old one did. This preserves 2955c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // LCSSA as well, because we force the split point to be after any PHI nodes. 296dc85f8ab808aec2f673262f5145eda58538cfb26Chris Lattner if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>()) 297a90793b431458c1bac4c7267946738968c4cdf58Owen Anderson if (Loop *L = LI->getLoopFor(Old)) 298a90793b431458c1bac4c7267946738968c4cdf58Owen Anderson L->addBasicBlockToLoop(New, LI->getBase()); 2998019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 3000f1666b480f7ac55af09fdd5ff09c3df7c20e2e4Evan Cheng if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) { 301e2d50046fd29cb3eb2483e080cb7c39b460fbb19Gabor Greif // Old dominates New. New node dominates all other nodes dominated by Old. 3020f1666b480f7ac55af09fdd5ff09c3df7c20e2e4Evan Cheng DomTreeNode *OldNode = DT->getNode(Old); 3030f1666b480f7ac55af09fdd5ff09c3df7c20e2e4Evan Cheng std::vector<DomTreeNode *> Children; 3040f1666b480f7ac55af09fdd5ff09c3df7c20e2e4Evan Cheng for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end(); 3050f1666b480f7ac55af09fdd5ff09c3df7c20e2e4Evan Cheng I != E; ++I) 3060f1666b480f7ac55af09fdd5ff09c3df7c20e2e4Evan Cheng Children.push_back(*I); 3070f1666b480f7ac55af09fdd5ff09c3df7c20e2e4Evan Cheng 3080f1666b480f7ac55af09fdd5ff09c3df7c20e2e4Evan Cheng DomTreeNode *NewNode = DT->addNewBlock(New,Old); 309a8a8a366299863fe3711880add4c041c437b63cfDevang Patel for (std::vector<DomTreeNode *>::iterator I = Children.begin(), 310a8a8a366299863fe3711880add4c041c437b63cfDevang Patel E = Children.end(); I != E; ++I) 311a8a8a366299863fe3711880add4c041c437b63cfDevang Patel DT->changeImmediateDominator(*I, NewNode); 3120f1666b480f7ac55af09fdd5ff09c3df7c20e2e4Evan Cheng } 3138019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 3141465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands if (DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>()) 3158019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel DF->splitBlock(Old); 3168019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel 3178019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel return New; 3188019893c3f55a4bfe770888fe285d6dae57cf216Devang Patel} 31954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 32054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 32154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// SplitBlockPredecessors - This method transforms BB by introducing a new 32254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// basic block into the function, and moving some of the predecessors of BB to 32354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// be predecessors of the new block. The new predecessors are indicated by the 32454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// Preds array, which has NumPreds elements in it. The new block is given a 32554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// suffix of 'Suffix'. 32654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner/// 3275c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree, 3285c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses. 3295c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman/// In particular, it does not preserve LoopSimplify (because it's 3305c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman/// complicated to handle the case where one of the edges being split 3315c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman/// is an exit of a loop with other exits). 3325c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman/// 33354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris LattnerBasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB, 33454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner BasicBlock *const *Preds, 33554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner unsigned NumPreds, const char *Suffix, 33654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Pass *P) { 33754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Create new basic block, insert right before the original block. 3381d0be15f89cb5056e20e2d24faa8d6afb1573bcaOwen Anderson BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), BB->getName()+Suffix, 3391d0be15f89cb5056e20e2d24faa8d6afb1573bcaOwen Anderson BB->getParent(), BB); 34054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 34154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // The new block unconditionally branches to the old block. 34254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner BranchInst *BI = BranchInst::Create(BB, NewBB); 34354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 3445c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman LoopInfo *LI = P ? P->getAnalysisIfAvailable<LoopInfo>() : 0; 3455c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman Loop *L = LI ? LI->getLoopFor(BB) : 0; 3465c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman bool PreserveLCSSA = P->mustPreserveAnalysisID(LCSSAID); 3475c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman 34854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Move the edges from Preds to point to NewBB instead of BB. 3495c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // While here, if we need to preserve loop analyses, collect 3505c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // some information about how this split will affect loops. 3515c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman bool HasLoopExit = false; 3525c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman bool IsLoopEntry = !!L; 3535c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman bool SplitMakesNewLoopHeader = false; 3545c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman for (unsigned i = 0; i != NumPreds; ++i) { 355b8eb17c80793c33368e3c3af6de4bd8c1b09ba5bDan Gohman // This is slightly more strict than necessary; the minimum requirement 356b8eb17c80793c33368e3c3af6de4bd8c1b09ba5bDan Gohman // is that there be no more than one indirectbr branching to BB. And 357b8eb17c80793c33368e3c3af6de4bd8c1b09ba5bDan Gohman // all BlockAddress uses would need to be updated. 358b8eb17c80793c33368e3c3af6de4bd8c1b09ba5bDan Gohman assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) && 359b8eb17c80793c33368e3c3af6de4bd8c1b09ba5bDan Gohman "Cannot split an edge from an IndirectBrInst"); 360b8eb17c80793c33368e3c3af6de4bd8c1b09ba5bDan Gohman 36154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB); 3625c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman 3635c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (LI) { 3645c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // If we need to preserve LCSSA, determine if any of 3655c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // the preds is a loop exit. 3665c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (PreserveLCSSA) 3675c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (Loop *PL = LI->getLoopFor(Preds[i])) 3685c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (!PL->contains(BB)) 3695c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman HasLoopExit = true; 3705c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // If we need to preserve LoopInfo, note whether any of the 3715c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // preds crosses an interesting loop boundary. 3725c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (L) { 3735c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (L->contains(Preds[i])) 3745c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman IsLoopEntry = false; 3755c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman else 3765c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman SplitMakesNewLoopHeader = true; 3775c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } 3785c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } 3795c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } 3805c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman 38154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Update dominator tree and dominator frontier if available. 3821465d61bdd36cfd6021036a527895f0dd358e97dDuncan Sands DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0; 38354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (DT) 38454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner DT->splitBlock(NewBB); 385c7e31fcf496e164cd6b45e6d15e06df54c3441a6Chris Lattner if (DominanceFrontier *DF = 386c7e31fcf496e164cd6b45e6d15e06df54c3441a6Chris Lattner P ? P->getAnalysisIfAvailable<DominanceFrontier>() : 0) 38754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner DF->splitBlock(NewBB); 3885c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman 38954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Insert a new PHI node into NewBB for every PHI node in BB and that new PHI 39054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // node becomes an incoming value for BB's phi node. However, if the Preds 39154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // list is empty, we need to insert dummy entries into the PHI nodes in BB to 39254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // account for the newly created predecessor. 39354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (NumPreds == 0) { 39454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Insert dummy values as the incoming value. 39554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I) 3969e9a0d5fc26878e51a58a8b57900fcbf952c2691Owen Anderson cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB); 39754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner return NewBB; 39854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 3995c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman 4005c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0; 4015c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman 4025c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (L) { 4035c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (IsLoopEntry) { 404841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman // Add the new block to the nearest enclosing loop (and not an 405841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman // adjacent loop). To find this, examine each of the predecessors and 406841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman // determine which loops enclose them, and select the most-nested loop 407841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman // which contains the loop containing the block being split. 408841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman Loop *InnermostPredLoop = 0; 409841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman for (unsigned i = 0; i != NumPreds; ++i) 410841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman if (Loop *PredLoop = LI->getLoopFor(Preds[i])) { 411841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman // Seek a loop which actually contains the block being split (to 412841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman // avoid adjacent loops). 413841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman while (PredLoop && !PredLoop->contains(BB)) 414841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman PredLoop = PredLoop->getParentLoop(); 415841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman // Select the most-nested of these loops which contains the block. 416841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman if (PredLoop && 417841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman PredLoop->contains(BB) && 418841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman (!InnermostPredLoop || 419841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth())) 420841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman InnermostPredLoop = PredLoop; 421841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman } 422841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman if (InnermostPredLoop) 423841a14753175bb9a02a8f5286ffe03d050b0da26Dan Gohman InnermostPredLoop->addBasicBlockToLoop(NewBB, LI->getBase()); 4245c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } else { 4255c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman L->addBasicBlockToLoop(NewBB, LI->getBase()); 4265c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (SplitMakesNewLoopHeader) 4275c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman L->moveToHeader(NewBB); 4285c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } 4295c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } 43054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 43154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Otherwise, create a new PHI node in NewBB for each PHI node in BB. 43254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) { 43354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PHINode *PN = cast<PHINode>(I++); 43454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 43554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Check to see if all of the values coming in are the same. If so, we 4365c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman // don't need to create a new PHI node, unless it's needed for LCSSA. 4375c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman Value *InVal = 0; 4385c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (!HasLoopExit) { 4395c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman InVal = PN->getIncomingValueForBlock(Preds[0]); 4405c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman for (unsigned i = 1; i != NumPreds; ++i) 4415c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman if (InVal != PN->getIncomingValueForBlock(Preds[i])) { 4425c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman InVal = 0; 4435c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman break; 4445c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } 4455c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman } 4465c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman 44754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (InVal) { 44854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // If all incoming values for the new PHI would be the same, just don't 44954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // make a new PHI. Instead, just remove the incoming values from the old 45054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // PHI. 45154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (unsigned i = 0; i != NumPreds; ++i) 45254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PN->removeIncomingValue(Preds[i], false); 45354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } else { 45454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // If the values coming into the block are not the same, we need a PHI. 45554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Create the new PHI node, insert it into NewBB at the end of the block 45654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PHINode *NewPHI = 45754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PHINode::Create(PN->getType(), PN->getName()+".ph", BI); 45854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner if (AA) AA->copyValue(PN, NewPHI); 45954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 46054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Move all of the PHI values for 'Preds' to the new PHI. 46154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner for (unsigned i = 0; i != NumPreds; ++i) { 46254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner Value *V = PN->removeIncomingValue(Preds[i], false); 46354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner NewPHI->addIncoming(V, Preds[i]); 46454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 46554b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner InVal = NewPHI; 46654b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 46754b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 46854b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // Add an incoming value to the PHI node in the loop for the preheader 46954b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner // edge. 47054b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner PN->addIncoming(InVal, NewBB); 47154b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner } 47254b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner 47354b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner return NewBB; 47454b9c3ba2a5b0aa8fda817bcc72c370040cfb3f8Chris Lattner} 47552c95856b4a40ccae6c4b0e13b2a04101e1f79c9Chris Lattner 476fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump/// FindFunctionBackedges - Analyze the specified function to find all of the 477fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump/// loop backedges in the function and return them. This is a relatively cheap 478fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump/// (compared to computing dominators and loop info) analysis. 479fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump/// 480fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump/// The output is added to Result, as pairs of <from,to> edge info. 481fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stumpvoid llvm::FindFunctionBackedges(const Function &F, 482fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result) { 483fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump const BasicBlock *BB = &F.getEntryBlock(); 484fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump if (succ_begin(BB) == succ_end(BB)) 485fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump return; 486fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump 487fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump SmallPtrSet<const BasicBlock*, 8> Visited; 488fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump SmallVector<std::pair<const BasicBlock*, succ_const_iterator>, 8> VisitStack; 489fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump SmallPtrSet<const BasicBlock*, 8> InStack; 490fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump 491fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump Visited.insert(BB); 492fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump VisitStack.push_back(std::make_pair(BB, succ_begin(BB))); 493fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump InStack.insert(BB); 494fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump do { 495fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump std::pair<const BasicBlock*, succ_const_iterator> &Top = VisitStack.back(); 496fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump const BasicBlock *ParentBB = Top.first; 497fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump succ_const_iterator &I = Top.second; 498fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump 499fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump bool FoundNew = false; 500fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump while (I != succ_end(ParentBB)) { 501fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump BB = *I++; 502fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump if (Visited.insert(BB)) { 503fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump FoundNew = true; 504fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump break; 505fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump } 506fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump // Successor is in VisitStack, it's a back edge. 507fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump if (InStack.count(BB)) 508fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump Result.push_back(std::make_pair(ParentBB, BB)); 509fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump } 510fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump 511fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump if (FoundNew) { 512fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump // Go down one level if there is a unvisited successor. 513fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump InStack.insert(BB); 514fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump VisitStack.push_back(std::make_pair(BB, succ_begin(BB))); 515fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump } else { 516fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump // Go up one level. 517fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump InStack.erase(VisitStack.pop_back_val().first); 518fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump } 519fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump } while (!VisitStack.empty()); 520fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump 521fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump 522fe095f39e7009c51d1c86769792ccbcad8cdd2ecMike Stump} 523