IndVarSimplify.cpp revision abaa8ca433a52dc522f6137c01a9552ebec44bb5
16148c02591bd83da7b957589c4bbf6f9720d503fChris Lattner//===- IndVarSimplify.cpp - Induction Variable Elimination ----------------===// 2fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman// 3b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// The LLVM Compiler Infrastructure 4b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 5b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// This file was developed by the LLVM research group and is distributed under 6b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// the University of Illinois Open Source License. See LICENSE.TXT for details. 7fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman// 8b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell//===----------------------------------------------------------------------===// 96148c02591bd83da7b957589c4bbf6f9720d503fChris Lattner// 1040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// This transformation analyzes and transforms the induction variables (and 1140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// computations derived from them) into simpler forms suitable for subsequent 1240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// analysis and transformation. 1340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// 1447a53ac726ceb1ac11bc1326be3fbe095f726b0dReid Spencer// This transformation makes the following changes to each loop with an 1540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// identifiable induction variable: 1640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// 1. All loops are transformed to have a SINGLE canonical induction variable 1740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// which starts at zero and steps by one. 1840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// 2. The canonical induction variable is guaranteed to be the first PHI node 1940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// in the loop header block. 2040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// 3. Any pointer arithmetic recurrences are raised to use array subscripts. 2140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// 2240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// If the trip count of a loop is computable, this pass also makes the following 2340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// changes: 2440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// 1. The exit condition for the loop is canonicalized to compare the 2540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// induction value against the exit value. This turns loops like: 2640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// 'for (i = 7; i*i < 1000; ++i)' into 'for (i = 0; i != 25; ++i)' 2740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// 2. Any use outside of the loop of an expression derived from the indvar 2840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// is changed to compute the derived value outside of the loop, eliminating 2940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// the dependence on the exit value of the induction variable. If the only 3040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// purpose of the loop is to compute the exit value of some derived 3140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// expression, this transformation will make the loop dead. 3240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// 3340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// This transformation should be followed by strength reduction after all of the 3440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// desired loop transformations have been performed. Additionally, on targets 3540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// where it is profitable, the loop could be transformed to count down to zero 3640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner// (the "do loop" optimization). 376148c02591bd83da7b957589c4bbf6f9720d503fChris Lattner// 386148c02591bd83da7b957589c4bbf6f9720d503fChris Lattner//===----------------------------------------------------------------------===// 396148c02591bd83da7b957589c4bbf6f9720d503fChris Lattner 400e5f499638c8d277b9dc4a4385712177c53b5681Chris Lattner#define DEBUG_TYPE "indvars" 41022103b3f33febb7e54b8fdf2c9bc461eea78cbaChris Lattner#include "llvm/Transforms/Scalar.h" 4240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner#include "llvm/BasicBlock.h" 4359fdaeeae8f183e18bb6ad5c382ca23e28e6aaf6Chris Lattner#include "llvm/Constants.h" 4418b3c97bc773b24a66eb779e85da1820b0f16b31Chris Lattner#include "llvm/Instructions.h" 4540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner#include "llvm/Type.h" 4636f891bdf6cf38fcc655a0930ca18664e18518d4Nate Begeman#include "llvm/Analysis/ScalarEvolutionExpander.h" 4747df12d80db90e125e9f2ff764286ee11665476dJohn Criswell#include "llvm/Analysis/LoopInfo.h" 48455889aa79e3463a4b0f2161e3d9d72a683268b6Chris Lattner#include "llvm/Support/CFG.h" 49ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner#include "llvm/Support/Debug.h" 50a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner#include "llvm/Support/GetElementPtrTypeIterator.h" 5147df12d80db90e125e9f2ff764286ee11665476dJohn Criswell#include "llvm/Transforms/Utils/Local.h" 52551ccae044b0ff658fe629dd67edd5ffe75d10e8Reid Spencer#include "llvm/Support/CommandLine.h" 53551ccae044b0ff658fe629dd67edd5ffe75d10e8Reid Spencer#include "llvm/ADT/Statistic.h" 5447df12d80db90e125e9f2ff764286ee11665476dJohn Criswellusing namespace llvm; 55d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 560e5f499638c8d277b9dc4a4385712177c53b5681Chris LattnerSTATISTIC(NumRemoved , "Number of aux indvars removed"); 570e5f499638c8d277b9dc4a4385712177c53b5681Chris LattnerSTATISTIC(NumPointer , "Number of pointer indvars promoted"); 580e5f499638c8d277b9dc4a4385712177c53b5681Chris LattnerSTATISTIC(NumInserted, "Number of canonical indvars added"); 590e5f499638c8d277b9dc4a4385712177c53b5681Chris LattnerSTATISTIC(NumReplaced, "Number of exit values replaced"); 600e5f499638c8d277b9dc4a4385712177c53b5681Chris LattnerSTATISTIC(NumLFTR , "Number of loop exit tests replaced"); 613324e718bc9ac2ede08a14c325848b576849542bChris Lattner 620e5f499638c8d277b9dc4a4385712177c53b5681Chris Lattnernamespace { 633324e718bc9ac2ede08a14c325848b576849542bChris Lattner class IndVarSimplify : public FunctionPass { 6440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner LoopInfo *LI; 6540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner ScalarEvolution *SE; 6615cad759fe2048ac5eb137c6bb0ab7287538677eChris Lattner bool Changed; 673324e718bc9ac2ede08a14c325848b576849542bChris Lattner public: 683324e718bc9ac2ede08a14c325848b576849542bChris Lattner virtual bool runOnFunction(Function &) { 6940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner LI = &getAnalysis<LoopInfo>(); 7040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner SE = &getAnalysis<ScalarEvolution>(); 7115cad759fe2048ac5eb137c6bb0ab7287538677eChris Lattner Changed = false; 7215cad759fe2048ac5eb137c6bb0ab7287538677eChris Lattner 733324e718bc9ac2ede08a14c325848b576849542bChris Lattner // Induction Variables live in the header nodes of loops 7440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) 75329c1c6c949d07e3fe9722ec633b4258217fd99dChris Lattner runOnLoop(*I); 763324e718bc9ac2ede08a14c325848b576849542bChris Lattner return Changed; 773324e718bc9ac2ede08a14c325848b576849542bChris Lattner } 783324e718bc9ac2ede08a14c325848b576849542bChris Lattner 793324e718bc9ac2ede08a14c325848b576849542bChris Lattner virtual void getAnalysisUsage(AnalysisUsage &AU) const { 803324e718bc9ac2ede08a14c325848b576849542bChris Lattner AU.addRequiredID(LoopSimplifyID); 8140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner AU.addRequired<ScalarEvolution>(); 8240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner AU.addRequired<LoopInfo>(); 833324e718bc9ac2ede08a14c325848b576849542bChris Lattner AU.addPreservedID(LoopSimplifyID); 84ac123227109303be313c3c4625b152246969e781Owen Anderson AU.addPreservedID(LCSSAID); 853324e718bc9ac2ede08a14c325848b576849542bChris Lattner AU.setPreservesCFG(); 863324e718bc9ac2ede08a14c325848b576849542bChris Lattner } 8740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner private: 8840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner void runOnLoop(Loop *L); 8940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner void EliminatePointerRecurrence(PHINode *PN, BasicBlock *Preheader, 9040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner std::set<Instruction*> &DeadInsts); 919ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner Instruction *LinearFunctionTestReplace(Loop *L, SCEV *IterationCount, 929ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner SCEVExpander &RW); 9340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner void RewriteLoopExitValues(Loop *L); 9440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 9540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner void DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts); 963324e718bc9ac2ede08a14c325848b576849542bChris Lattner }; 977f8897f22e88271cfa114998a4d6088e7c8e8e11Chris Lattner RegisterPass<IndVarSimplify> X("indvars", "Canonicalize Induction Variables"); 985e76140536ba66fadeced1cd892f79616f407e3cChris Lattner} 99394437ff7eaccfe1de92fe14d0022ca0addf3e41Chris Lattner 1004b5015604908e9296800991a7c538a255356428fChris LattnerFunctionPass *llvm::createIndVarSimplifyPass() { 1013324e718bc9ac2ede08a14c325848b576849542bChris Lattner return new IndVarSimplify(); 102394437ff7eaccfe1de92fe14d0022ca0addf3e41Chris Lattner} 103394437ff7eaccfe1de92fe14d0022ca0addf3e41Chris Lattner 10440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// DeleteTriviallyDeadInstructions - If any of the instructions is the 10540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// specified set are trivially dead, delete them and see if this makes any of 10640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// their operands subsequently dead. 10740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattnervoid IndVarSimplify:: 10840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris LattnerDeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts) { 10940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner while (!Insts.empty()) { 11040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Instruction *I = *Insts.begin(); 11140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Insts.erase(Insts.begin()); 11240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (isInstructionTriviallyDead(I)) { 11340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 11440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i))) 11540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Insts.insert(U); 11640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner SE->deleteInstructionFromRecords(I); 117ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner DOUT << "INDVARS: Deleting: " << *I; 118a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner I->eraseFromParent(); 11940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Changed = true; 12040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 12140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 12240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner} 1233324e718bc9ac2ede08a14c325848b576849542bChris Lattner 1246148c02591bd83da7b957589c4bbf6f9720d503fChris Lattner 12540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// EliminatePointerRecurrence - Check to see if this is a trivial GEP pointer 12640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// recurrence. If so, change it into an integer recurrence, permitting 12740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// analysis by the SCEV routines. 128fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukmanvoid IndVarSimplify::EliminatePointerRecurrence(PHINode *PN, 12940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock *Preheader, 13040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner std::set<Instruction*> &DeadInsts) { 13140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner assert(PN->getNumIncomingValues() == 2 && "Noncanonicalized loop!"); 13240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner unsigned PreheaderIdx = PN->getBasicBlockIndex(Preheader); 13340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner unsigned BackedgeIdx = PreheaderIdx^1; 13440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (GetElementPtrInst *GEPI = 135cda9ca5a4fed09ea3788b572dbddabf2a5a7a5d9Chris Lattner dyn_cast<GetElementPtrInst>(PN->getIncomingValue(BackedgeIdx))) 13640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (GEPI->getOperand(0) == PN) { 137cda9ca5a4fed09ea3788b572dbddabf2a5a7a5d9Chris Lattner assert(GEPI->getNumOperands() == 2 && "GEP types must match!"); 138ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner DOUT << "INDVARS: Eliminating pointer recurrence: " << *GEPI; 139ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner 14040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Okay, we found a pointer recurrence. Transform this pointer 14140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // recurrence into an integer recurrence. Compute the value that gets 14240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // added to the pointer at every iteration. 14340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Value *AddedVal = GEPI->getOperand(1); 14440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 14540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Insert a new integer PHI node into the top of the block. 14640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner PHINode *NewPhi = new PHINode(AddedVal->getType(), 14740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner PN->getName()+".rec", PN); 148c5c5e6afe584ffbd2bf2ce755e65bc89f170053aChris Lattner NewPhi->addIncoming(Constant::getNullValue(NewPhi->getType()), Preheader); 149c5c5e6afe584ffbd2bf2ce755e65bc89f170053aChris Lattner 15040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Create the new add instruction. 151c5c5e6afe584ffbd2bf2ce755e65bc89f170053aChris Lattner Value *NewAdd = BinaryOperator::createAdd(NewPhi, AddedVal, 152c5c5e6afe584ffbd2bf2ce755e65bc89f170053aChris Lattner GEPI->getName()+".rec", GEPI); 15340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner NewPhi->addIncoming(NewAdd, PN->getIncomingBlock(BackedgeIdx)); 154fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 15540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Update the existing GEP to use the recurrence. 15640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner GEPI->setOperand(0, PN->getIncomingValue(PreheaderIdx)); 157fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 15840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Update the GEP to use the new recurrence we just inserted. 15940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner GEPI->setOperand(1, NewAdd); 16040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 161a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner // If the incoming value is a constant expr GEP, try peeling out the array 162a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner // 0 index if possible to make things simpler. 163a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEPI->getOperand(0))) 164a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner if (CE->getOpcode() == Instruction::GetElementPtr) { 165a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner unsigned NumOps = CE->getNumOperands(); 166a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner assert(NumOps > 1 && "CE folding didn't work!"); 167a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner if (CE->getOperand(NumOps-1)->isNullValue()) { 168a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner // Check to make sure the last index really is an array index. 1691730078d5f553d7516a06e098e6c2089dc8bef9cChris Lattner gep_type_iterator GTI = gep_type_begin(CE); 170ceda605fd7d0e3532a22743538c6d118fe5e40c1Chris Lattner for (unsigned i = 1, e = CE->getNumOperands()-1; 171a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner i != e; ++i, ++GTI) 172a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner /*empty*/; 173a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner if (isa<SequentialType>(*GTI)) { 174a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner // Pull the last index out of the constant expr GEP. 175a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner std::vector<Value*> CEIdxs(CE->op_begin()+1, CE->op_end()-1); 176a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner Constant *NCE = ConstantExpr::getGetElementPtr(CE->getOperand(0), 177a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner CEIdxs); 178a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner GetElementPtrInst *NGEPI = 179c5b206b6be61d0d933b98b6af5e22f42edd48ad1Reid Spencer new GetElementPtrInst(NCE, Constant::getNullValue(Type::Int32Ty), 180a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner NewAdd, GEPI->getName(), GEPI); 181a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner GEPI->replaceAllUsesWith(NGEPI); 182a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner GEPI->eraseFromParent(); 183a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner GEPI = NGEPI; 184a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner } 185a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner } 186a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner } 187a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner 188a4b9c7841f94b6a3a2ba6c562b5dc4f4de02c637Chris Lattner 18940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Finally, if there are any other users of the PHI node, we must 19040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // insert a new GEP instruction that uses the pre-incremented version 19140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // of the induction amount. 19240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (!PN->use_empty()) { 19340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock::iterator InsertPos = PN; ++InsertPos; 19440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner while (isa<PHINode>(InsertPos)) ++InsertPos; 19540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner std::string Name = PN->getName(); PN->setName(""); 19640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Value *PreInc = 19740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner new GetElementPtrInst(PN->getIncomingValue(PreheaderIdx), 19840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner std::vector<Value*>(1, NewPhi), Name, 19940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner InsertPos); 20040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner PN->replaceAllUsesWith(PreInc); 20140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 20240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 20340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Delete the old PHI for sure, and the GEP if its otherwise unused. 20440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner DeadInsts.insert(PN); 2053324e718bc9ac2ede08a14c325848b576849542bChris Lattner 20640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner ++NumPointer; 20740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Changed = true; 20840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 20940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner} 2103324e718bc9ac2ede08a14c325848b576849542bChris Lattner 21140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// LinearFunctionTestReplace - This method rewrites the exit condition of the 21259fdaeeae8f183e18bb6ad5c382ca23e28e6aaf6Chris Lattner/// loop to be a canonical != comparison against the incremented loop induction 21359fdaeeae8f183e18bb6ad5c382ca23e28e6aaf6Chris Lattner/// variable. This pass is able to rewrite the exit tests of any loop where the 21459fdaeeae8f183e18bb6ad5c382ca23e28e6aaf6Chris Lattner/// SCEV analysis can determine a loop-invariant trip count of the loop, which 21559fdaeeae8f183e18bb6ad5c382ca23e28e6aaf6Chris Lattner/// is actually a much broader range than just linear tests. 2169ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner/// 2179ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner/// This method returns a "potentially dead" instruction whose computation chain 2189ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner/// should be deleted when convenient. 2199ba46c13bf3d49a5b697227c88ef987951e6b50dChris LattnerInstruction *IndVarSimplify::LinearFunctionTestReplace(Loop *L, 2209ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner SCEV *IterationCount, 2219ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner SCEVExpander &RW) { 22240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Find the exit block for the loop. We can currently only handle loops with 22340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // a single exit. 224f1ab4b4eac5603d19c20f4a508f93a118a52bdd5Chris Lattner std::vector<BasicBlock*> ExitBlocks; 225f1ab4b4eac5603d19c20f4a508f93a118a52bdd5Chris Lattner L->getExitBlocks(ExitBlocks); 2269ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner if (ExitBlocks.size() != 1) return 0; 227f1ab4b4eac5603d19c20f4a508f93a118a52bdd5Chris Lattner BasicBlock *ExitBlock = ExitBlocks[0]; 22840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 22940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Make sure there is only one predecessor block in the loop. 23040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock *ExitingBlock = 0; 23140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner for (pred_iterator PI = pred_begin(ExitBlock), PE = pred_end(ExitBlock); 23240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner PI != PE; ++PI) 23340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (L->contains(*PI)) { 23440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (ExitingBlock == 0) 23540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner ExitingBlock = *PI; 23640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner else 2379ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner return 0; // Multiple exits from loop to this block. 23840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 23940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner assert(ExitingBlock && "Loop info is broken"); 24040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 24140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (!isa<BranchInst>(ExitingBlock->getTerminator())) 2429ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner return 0; // Can't rewrite non-branch yet 24340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BranchInst *BI = cast<BranchInst>(ExitingBlock->getTerminator()); 24440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner assert(BI->isConditional() && "Must be conditional to be part of loop!"); 24540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 2469ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner Instruction *PotentiallyDeadInst = dyn_cast<Instruction>(BI->getCondition()); 2479ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner 248d244057a48660c3cd30d219118ece3f947947790Chris Lattner // If the exiting block is not the same as the backedge block, we must compare 249d244057a48660c3cd30d219118ece3f947947790Chris Lattner // against the preincremented value, otherwise we prefer to compare against 250d244057a48660c3cd30d219118ece3f947947790Chris Lattner // the post-incremented value. 251d244057a48660c3cd30d219118ece3f947947790Chris Lattner BasicBlock *Header = L->getHeader(); 252d244057a48660c3cd30d219118ece3f947947790Chris Lattner pred_iterator HPI = pred_begin(Header); 253d244057a48660c3cd30d219118ece3f947947790Chris Lattner assert(HPI != pred_end(Header) && "Loop with zero preds???"); 254d244057a48660c3cd30d219118ece3f947947790Chris Lattner if (!L->contains(*HPI)) ++HPI; 255d244057a48660c3cd30d219118ece3f947947790Chris Lattner assert(HPI != pred_end(Header) && L->contains(*HPI) && 256d244057a48660c3cd30d219118ece3f947947790Chris Lattner "No backedge in loop?"); 257d244057a48660c3cd30d219118ece3f947947790Chris Lattner 258d244057a48660c3cd30d219118ece3f947947790Chris Lattner SCEVHandle TripCount = IterationCount; 259d244057a48660c3cd30d219118ece3f947947790Chris Lattner Value *IndVar; 260d244057a48660c3cd30d219118ece3f947947790Chris Lattner if (*HPI == ExitingBlock) { 261d244057a48660c3cd30d219118ece3f947947790Chris Lattner // The IterationCount expression contains the number of times that the 262d244057a48660c3cd30d219118ece3f947947790Chris Lattner // backedge actually branches to the loop header. This is one less than the 263d244057a48660c3cd30d219118ece3f947947790Chris Lattner // number of times the loop executes, so add one to it. 264d244057a48660c3cd30d219118ece3f947947790Chris Lattner Constant *OneC = ConstantInt::get(IterationCount->getType(), 1); 265d244057a48660c3cd30d219118ece3f947947790Chris Lattner TripCount = SCEVAddExpr::get(IterationCount, SCEVUnknown::get(OneC)); 266d244057a48660c3cd30d219118ece3f947947790Chris Lattner IndVar = L->getCanonicalInductionVariableIncrement(); 267d244057a48660c3cd30d219118ece3f947947790Chris Lattner } else { 268d244057a48660c3cd30d219118ece3f947947790Chris Lattner // We have to use the preincremented value... 269d244057a48660c3cd30d219118ece3f947947790Chris Lattner IndVar = L->getCanonicalInductionVariable(); 270d244057a48660c3cd30d219118ece3f947947790Chris Lattner } 271ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner 272ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner DOUT << "INDVARS: LFTR: TripCount = " << *TripCount 273ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner << " IndVar = " << *IndVar << "\n"; 27459fdaeeae8f183e18bb6ad5c382ca23e28e6aaf6Chris Lattner 27540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Expand the code for the iteration count into the preheader of the loop. 27640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock *Preheader = L->getLoopPreheader(); 2774a7553e2da506a718f59869c03c5ce113eb40f7aChris Lattner Value *ExitCnt = RW.expandCodeFor(TripCount, Preheader->getTerminator(), 27840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner IndVar->getType()); 27940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 280e4d87aa2de6e52952dca73716386db09aad5a8fdReid Spencer // Insert a new icmp_ne or icmp_eq instruction before the branch. 281e4d87aa2de6e52952dca73716386db09aad5a8fdReid Spencer ICmpInst::Predicate Opcode; 28240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (L->contains(BI->getSuccessor(0))) 283e4d87aa2de6e52952dca73716386db09aad5a8fdReid Spencer Opcode = ICmpInst::ICMP_NE; 28440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner else 285e4d87aa2de6e52952dca73716386db09aad5a8fdReid Spencer Opcode = ICmpInst::ICMP_EQ; 28640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 287e4d87aa2de6e52952dca73716386db09aad5a8fdReid Spencer Value *Cond = new ICmpInst(Opcode, IndVar, ExitCnt, "exitcond", BI); 28840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BI->setCondition(Cond); 28940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner ++NumLFTR; 29040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Changed = true; 2919ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner return PotentiallyDeadInst; 29240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner} 2933324e718bc9ac2ede08a14c325848b576849542bChris Lattner 2943324e718bc9ac2ede08a14c325848b576849542bChris Lattner 29540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// RewriteLoopExitValues - Check to see if this loop has a computable 29640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// loop-invariant execution count. If so, this means that we can compute the 29740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// final value of any expressions that are recurrent in the loop, and 29840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// substitute the exit values from the loop into any instructions outside of 29940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner/// the loop that use the final values of the current expressions. 30040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattnervoid IndVarSimplify::RewriteLoopExitValues(Loop *L) { 30140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock *Preheader = L->getLoopPreheader(); 30240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 30340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Scan all of the instructions in the loop, looking at those that have 30440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // extra-loop users and which are recurrences. 3054a7553e2da506a718f59869c03c5ce113eb40f7aChris Lattner SCEVExpander Rewriter(*SE, *LI); 30640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 30740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // We insert the code into the preheader of the loop if the loop contains 30840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // multiple exit blocks, or in the exit block if there is exactly one. 30940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock *BlockToInsertInto; 310f1ab4b4eac5603d19c20f4a508f93a118a52bdd5Chris Lattner std::vector<BasicBlock*> ExitBlocks; 311f1ab4b4eac5603d19c20f4a508f93a118a52bdd5Chris Lattner L->getExitBlocks(ExitBlocks); 312f1ab4b4eac5603d19c20f4a508f93a118a52bdd5Chris Lattner if (ExitBlocks.size() == 1) 313f1ab4b4eac5603d19c20f4a508f93a118a52bdd5Chris Lattner BlockToInsertInto = ExitBlocks[0]; 31440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner else 31540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BlockToInsertInto = Preheader; 31640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock::iterator InsertPt = BlockToInsertInto->begin(); 31740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner while (isa<PHINode>(InsertPt)) ++InsertPt; 31840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 31920aa098ba694aa7e3f5fb5a52d22dba7c1e857aeChris Lattner bool HasConstantItCount = isa<SCEVConstant>(SE->getIterationCount(L)); 32020aa098ba694aa7e3f5fb5a52d22dba7c1e857aeChris Lattner 32140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner std::set<Instruction*> InstructionsToDelete; 322fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 32340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) 32440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop... 32540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock *BB = L->getBlocks()[i]; 3264bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) { 32740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (I->getType()->isInteger()) { // Is an integer instruction 32840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner SCEVHandle SH = SE->getSCEV(I); 32920aa098ba694aa7e3f5fb5a52d22dba7c1e857aeChris Lattner if (SH->hasComputableLoopEvolution(L) || // Varies predictably 33020aa098ba694aa7e3f5fb5a52d22dba7c1e857aeChris Lattner HasConstantItCount) { 33140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Find out if this predictably varying value is actually used 33240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // outside of the loop. "extra" as opposed to "intra". 333eb83f4e6cd00c50989f14ba41857f6b9e42b9e5eChris Lattner std::vector<Instruction*> ExtraLoopUsers; 33440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); 335eb83f4e6cd00c50989f14ba41857f6b9e42b9e5eChris Lattner UI != E; ++UI) { 336eb83f4e6cd00c50989f14ba41857f6b9e42b9e5eChris Lattner Instruction *User = cast<Instruction>(*UI); 337262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner if (!L->contains(User->getParent())) { 338262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner // If this is a PHI node in the exit block and we're inserting, 339262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner // into the exit block, it must have a single entry. In this 340262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner // case, we can't insert the code after the PHI and have the PHI 341262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner // still use it. Instead, don't insert the the PHI. 342262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner if (PHINode *PN = dyn_cast<PHINode>(User)) { 343262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner // FIXME: This is a case where LCSSA pessimizes code, this 344262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner // should be fixed better. 345262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner if (PN->getNumOperands() == 2 && 346262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner PN->getParent() == BlockToInsertInto) 347262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner continue; 348262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner } 349eb83f4e6cd00c50989f14ba41857f6b9e42b9e5eChris Lattner ExtraLoopUsers.push_back(User); 350262041892d7f821a86ea96c0282ff1e53aac1888Chris Lattner } 351eb83f4e6cd00c50989f14ba41857f6b9e42b9e5eChris Lattner } 352eb83f4e6cd00c50989f14ba41857f6b9e42b9e5eChris Lattner 35340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (!ExtraLoopUsers.empty()) { 35440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Okay, this instruction has a user outside of the current loop 35540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // and varies predictably in this loop. Evaluate the value it 35640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // contains when the loop exits, and insert code for it. 35720aa098ba694aa7e3f5fb5a52d22dba7c1e857aeChris Lattner SCEVHandle ExitValue = SE->getSCEVAtScope(I, L->getParentLoop()); 35840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (!isa<SCEVCouldNotCompute>(ExitValue)) { 35940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Changed = true; 36040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner ++NumReplaced; 3614bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner // Remember the next instruction. The rewriter can move code 3624bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner // around in some cases. 3634bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner BasicBlock::iterator NextI = I; ++NextI; 3644bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner 3654a7553e2da506a718f59869c03c5ce113eb40f7aChris Lattner Value *NewVal = Rewriter.expandCodeFor(ExitValue, InsertPt, 36640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner I->getType()); 36740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 368ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner DOUT << "INDVARS: RLEV: AfterLoopVal = " << *NewVal 369ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner << " LoopVal = " << *I << "\n"; 370ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner 37140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Rewrite any users of the computed value outside of the loop 37240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // with the newly computed value. 373c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson for (unsigned i = 0, e = ExtraLoopUsers.size(); i != e; ++i) { 374c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson PHINode* PN = dyn_cast<PHINode>(ExtraLoopUsers[i]); 375c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson if (PN && PN->getNumOperands() == 2 && 376c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson !L->contains(PN->getParent())) { 377c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson // We're dealing with an LCSSA Phi. Handle it specially. 378c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson Instruction* LCSSAInsertPt = BlockToInsertInto->begin(); 379c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson 380c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson Instruction* NewInstr = dyn_cast<Instruction>(NewVal); 381c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson if (NewInstr && !isa<PHINode>(NewInstr) && 382c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson !L->contains(NewInstr->getParent())) 383c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson for (unsigned j = 0; j < NewInstr->getNumOperands(); ++j){ 384c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson Instruction* PredI = 385c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson dyn_cast<Instruction>(NewInstr->getOperand(j)); 386c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson if (PredI && L->contains(PredI->getParent())) { 387c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson PHINode* NewLCSSA = new PHINode(PredI->getType(), 388c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson PredI->getName() + ".lcssa", 389c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson LCSSAInsertPt); 390c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson NewLCSSA->addIncoming(PredI, 391c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson BlockToInsertInto->getSinglePredecessor()); 392c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson 393c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson NewInstr->replaceUsesOfWith(PredI, NewLCSSA); 394c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson } 395c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson } 396c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson 397c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson PN->replaceAllUsesWith(NewVal); 398c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson PN->eraseFromParent(); 399c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson } else { 400c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson ExtraLoopUsers[i]->replaceUsesOfWith(I, NewVal); 401c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson } 402c1be492f94da7e53eef408c346b25c551c6bdf07Owen Anderson } 40340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 40440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // If this instruction is dead now, schedule it to be removed. 40540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (I->use_empty()) 40640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner InstructionsToDelete.insert(I); 4074bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner I = NextI; 4084bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner continue; // Skip the ++I 40940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 41040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 41140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 41240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 4134bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner 4144bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner // Next instruction. Continue instruction skips this. 4154bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner ++I; 4164bd09d70cceb3851f7eb1c2f98338b3071d405f3Chris Lattner } 4173324e718bc9ac2ede08a14c325848b576849542bChris Lattner } 4186148c02591bd83da7b957589c4bbf6f9720d503fChris Lattner 41940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner DeleteTriviallyDeadInstructions(InstructionsToDelete); 42040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner} 42115cad759fe2048ac5eb137c6bb0ab7287538677eChris Lattner 42215cad759fe2048ac5eb137c6bb0ab7287538677eChris Lattner 42340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattnervoid IndVarSimplify::runOnLoop(Loop *L) { 42440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // First step. Check to see if there are any trivial GEP pointer recurrences. 42540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // If there are, change them into integer recurrences, permitting analysis by 42640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // the SCEV routines. 42715cad759fe2048ac5eb137c6bb0ab7287538677eChris Lattner // 42840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock *Header = L->getHeader(); 42940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock *Preheader = L->getLoopPreheader(); 430fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 43140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner std::set<Instruction*> DeadInsts; 4322da5c3dda6f5b9c4ec6d55008d33327764364bd4Reid Spencer for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) { 4332da5c3dda6f5b9c4ec6d55008d33327764364bd4Reid Spencer PHINode *PN = cast<PHINode>(I); 43440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (isa<PointerType>(PN->getType())) 43540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner EliminatePointerRecurrence(PN, Preheader, DeadInsts); 4362da5c3dda6f5b9c4ec6d55008d33327764364bd4Reid Spencer } 43715cad759fe2048ac5eb137c6bb0ab7287538677eChris Lattner 43840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (!DeadInsts.empty()) 43940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner DeleteTriviallyDeadInstructions(DeadInsts); 440394437ff7eaccfe1de92fe14d0022ca0addf3e41Chris Lattner 441394437ff7eaccfe1de92fe14d0022ca0addf3e41Chris Lattner 44240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Next, transform all loops nesting inside of this loop. 44340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner for (LoopInfo::iterator I = L->begin(), E = L->end(); I != E; ++I) 44440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner runOnLoop(*I); 445394437ff7eaccfe1de92fe14d0022ca0addf3e41Chris Lattner 44640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Check to see if this loop has a computable loop-invariant execution count. 44740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // If so, this means that we can compute the final value of any expressions 44840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // that are recurrent in the loop, and substitute the exit values from the 44940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // loop into any instructions outside of the loop that use the final values of 45040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // the current expressions. 451394437ff7eaccfe1de92fe14d0022ca0addf3e41Chris Lattner // 45240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner SCEVHandle IterationCount = SE->getIterationCount(L); 45340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (!isa<SCEVCouldNotCompute>(IterationCount)) 45440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner RewriteLoopExitValues(L); 45540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 45640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Next, analyze all of the induction variables in the loop, canonicalizing 45740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // auxillary induction variables. 45840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner std::vector<std::pair<PHINode*, SCEVHandle> > IndVars; 45940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 4602da5c3dda6f5b9c4ec6d55008d33327764364bd4Reid Spencer for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) { 4612da5c3dda6f5b9c4ec6d55008d33327764364bd4Reid Spencer PHINode *PN = cast<PHINode>(I); 46240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (PN->getType()->isInteger()) { // FIXME: when we have fast-math, enable! 46340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner SCEVHandle SCEV = SE->getSCEV(PN); 46440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (SCEV->hasComputableLoopEvolution(L)) 465cda9ca5a4fed09ea3788b572dbddabf2a5a7a5d9Chris Lattner // FIXME: It is an extremely bad idea to indvar substitute anything more 466cda9ca5a4fed09ea3788b572dbddabf2a5a7a5d9Chris Lattner // complex than affine induction variables. Doing so will put expensive 467cda9ca5a4fed09ea3788b572dbddabf2a5a7a5d9Chris Lattner // polynomial evaluations inside of the loop, and the str reduction pass 468cda9ca5a4fed09ea3788b572dbddabf2a5a7a5d9Chris Lattner // currently can only reduce affine polynomials. For now just disable 469cda9ca5a4fed09ea3788b572dbddabf2a5a7a5d9Chris Lattner // indvar subst on anything more complex than an affine addrec. 470595ee7ec26432e4804f1e71817d9cf9b1f86318dChris Lattner if (SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SCEV)) 471cda9ca5a4fed09ea3788b572dbddabf2a5a7a5d9Chris Lattner if (AR->isAffine()) 472595ee7ec26432e4804f1e71817d9cf9b1f86318dChris Lattner IndVars.push_back(std::make_pair(PN, SCEV)); 47340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 4742da5c3dda6f5b9c4ec6d55008d33327764364bd4Reid Spencer } 475f016ea4ff80c56c467247a90567dd07bddb590f3Chris Lattner 47640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // If there are no induction variables in the loop, there is nothing more to 47740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // do. 478f50af088f19f525f3d1026eb61db77e0037a9f43Chris Lattner if (IndVars.empty()) { 479f50af088f19f525f3d1026eb61db77e0037a9f43Chris Lattner // Actually, if we know how many times the loop iterates, lets insert a 480f50af088f19f525f3d1026eb61db77e0037a9f43Chris Lattner // canonical induction variable to help subsequent passes. 481f50af088f19f525f3d1026eb61db77e0037a9f43Chris Lattner if (!isa<SCEVCouldNotCompute>(IterationCount)) { 4824a7553e2da506a718f59869c03c5ce113eb40f7aChris Lattner SCEVExpander Rewriter(*SE, *LI); 4834a7553e2da506a718f59869c03c5ce113eb40f7aChris Lattner Rewriter.getOrInsertCanonicalInductionVariable(L, 484f50af088f19f525f3d1026eb61db77e0037a9f43Chris Lattner IterationCount->getType()); 4859ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner if (Instruction *I = LinearFunctionTestReplace(L, IterationCount, 4869ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner Rewriter)) { 4879ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner std::set<Instruction*> InstructionsToDelete; 4889ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner InstructionsToDelete.insert(I); 4899ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner DeleteTriviallyDeadInstructions(InstructionsToDelete); 4909ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner } 491f50af088f19f525f3d1026eb61db77e0037a9f43Chris Lattner } 492f50af088f19f525f3d1026eb61db77e0037a9f43Chris Lattner return; 493f50af088f19f525f3d1026eb61db77e0037a9f43Chris Lattner } 494f016ea4ff80c56c467247a90567dd07bddb590f3Chris Lattner 49540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Compute the type of the largest recurrence expression. 49640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // 49740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner const Type *LargestType = IndVars[0].first->getType(); 498fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner bool DifferingSizes = false; 49940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner for (unsigned i = 1, e = IndVars.size(); i != e; ++i) { 50040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner const Type *Ty = IndVars[i].first->getType(); 501abaa8ca433a52dc522f6137c01a9552ebec44bb5Reid Spencer DifferingSizes |= 502abaa8ca433a52dc522f6137c01a9552ebec44bb5Reid Spencer Ty->getPrimitiveSizeInBits() != LargestType->getPrimitiveSizeInBits(); 503abaa8ca433a52dc522f6137c01a9552ebec44bb5Reid Spencer if (Ty->getPrimitiveSizeInBits() > LargestType->getPrimitiveSizeInBits()) 50440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner LargestType = Ty; 505500597a1c39e91a3020587318ed61e737b6c613aChris Lattner } 506394437ff7eaccfe1de92fe14d0022ca0addf3e41Chris Lattner 50740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Create a rewriter object which we'll use to transform the code with. 5084a7553e2da506a718f59869c03c5ce113eb40f7aChris Lattner SCEVExpander Rewriter(*SE, *LI); 50940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 51040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Now that we know the largest of of the induction variables in this loop, 51140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // insert a canonical induction variable of the largest size. 5124a7553e2da506a718f59869c03c5ce113eb40f7aChris Lattner Value *IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L,LargestType); 51340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner ++NumInserted; 51440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Changed = true; 515ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner DOUT << "INDVARS: New CanIV: " << *IndVar; 51640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 51740bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (!isa<SCEVCouldNotCompute>(IterationCount)) 5189ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner if (Instruction *DI = LinearFunctionTestReplace(L, IterationCount,Rewriter)) 5199ba46c13bf3d49a5b697227c88ef987951e6b50dChris Lattner DeadInsts.insert(DI); 52040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 52140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Now that we have a canonical induction variable, we can rewrite any 52240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // recurrences in terms of the induction variable. Start with the auxillary 52340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // induction variables, and recursively rewrite any of their uses. 52440bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock::iterator InsertPt = Header->begin(); 52540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner while (isa<PHINode>(InsertPt)) ++InsertPt; 52640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner 5275d461d20aea308471f2a31b718a274bfee28b60cChris Lattner // If there were induction variables of other sizes, cast the primary 5285d461d20aea308471f2a31b718a274bfee28b60cChris Lattner // induction variable to the right size for them, avoiding the need for the 5295d461d20aea308471f2a31b718a274bfee28b60cChris Lattner // code evaluation methods to insert induction variables of different sizes. 530fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner if (DifferingSizes) { 531fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner bool InsertedSizes[17] = { false }; 532fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner InsertedSizes[LargestType->getPrimitiveSize()] = true; 533fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner for (unsigned i = 0, e = IndVars.size(); i != e; ++i) 534fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner if (!InsertedSizes[IndVars[i].first->getType()->getPrimitiveSize()]) { 535fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner PHINode *PN = IndVars[i].first; 536fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner InsertedSizes[PN->getType()->getPrimitiveSize()] = true; 537ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner Instruction *New = new TruncInst(IndVar, PN->getType(), "indvar", 538ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner InsertPt); 539fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner Rewriter.addInsertedValue(New, SE->getSCEV(New)); 540ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner DOUT << "INDVARS: Made trunc IV for " << *PN 541ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner << " NewVal = " << *New << "\n"; 542fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner } 543fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner } 544fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner 545ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner // Rewrite all induction variables in terms of the canonical induction 546ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner // variable. 5475d461d20aea308471f2a31b718a274bfee28b60cChris Lattner std::map<unsigned, Value*> InsertedSizes; 54840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner while (!IndVars.empty()) { 54940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner PHINode *PN = IndVars.back().first; 5504a7553e2da506a718f59869c03c5ce113eb40f7aChris Lattner Value *NewVal = Rewriter.expandCodeFor(IndVars.back().second, InsertPt, 551fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner PN->getType()); 552ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner DOUT << "INDVARS: Rewrote IV '" << *IndVars.back().second << "' " << *PN 553ee4f13a9046c380725cdeab62d57722db375c473Chris Lattner << " into = " << *NewVal << "\n"; 554fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner std::string Name = PN->getName(); 555fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner PN->setName(""); 556fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner NewVal->setName(Name); 5575d461d20aea308471f2a31b718a274bfee28b60cChris Lattner 55840bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner // Replace the old PHI Node with the inserted computation. 559fcb81f5f4cbac61851b7dec403961cf88e614aa1Chris Lattner PN->replaceAllUsesWith(NewVal); 56040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner DeadInsts.insert(PN); 56140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner IndVars.pop_back(); 56240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner ++NumRemoved; 56340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner Changed = true; 564500597a1c39e91a3020587318ed61e737b6c613aChris Lattner } 565ba4f3f6a419326df190599421fa149c90235cb72Chris Lattner 566b4782d13d1444d9d18c0a681292cf0d0a32cf3efChris Lattner#if 0 5671363e85df74627530ceede53280613c62a4cdbe3Chris Lattner // Now replace all derived expressions in the loop body with simpler 5681363e85df74627530ceede53280613c62a4cdbe3Chris Lattner // expressions. 56940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner for (unsigned i = 0, e = L->getBlocks().size(); i != e; ++i) 57040bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (LI->getLoopFor(L->getBlocks()[i]) == L) { // Not in a subloop... 57140bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner BasicBlock *BB = L->getBlocks()[i]; 57240bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 57340bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner if (I->getType()->isInteger() && // Is an integer instruction 5741363e85df74627530ceede53280613c62a4cdbe3Chris Lattner !I->use_empty() && 57540bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner !Rewriter.isInsertedInstruction(I)) { 57640bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner SCEVHandle SH = SE->getSCEV(I); 5774a7553e2da506a718f59869c03c5ce113eb40f7aChris Lattner Value *V = Rewriter.expandCodeFor(SH, I, I->getType()); 5781363e85df74627530ceede53280613c62a4cdbe3Chris Lattner if (V != I) { 5791363e85df74627530ceede53280613c62a4cdbe3Chris Lattner if (isa<Instruction>(V)) { 5801363e85df74627530ceede53280613c62a4cdbe3Chris Lattner std::string Name = I->getName(); 5811363e85df74627530ceede53280613c62a4cdbe3Chris Lattner I->setName(""); 5821363e85df74627530ceede53280613c62a4cdbe3Chris Lattner V->setName(Name); 5831363e85df74627530ceede53280613c62a4cdbe3Chris Lattner } 5841363e85df74627530ceede53280613c62a4cdbe3Chris Lattner I->replaceAllUsesWith(V); 5851363e85df74627530ceede53280613c62a4cdbe3Chris Lattner DeadInsts.insert(I); 5861363e85df74627530ceede53280613c62a4cdbe3Chris Lattner ++NumRemoved; 5871363e85df74627530ceede53280613c62a4cdbe3Chris Lattner Changed = true; 588fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman } 58940bf8b48cdb9961898dba1bc67320be1e49e3da1Chris Lattner } 590394437ff7eaccfe1de92fe14d0022ca0addf3e41Chris Lattner } 591b4782d13d1444d9d18c0a681292cf0d0a32cf3efChris Lattner#endif 5921363e85df74627530ceede53280613c62a4cdbe3Chris Lattner 5931363e85df74627530ceede53280613c62a4cdbe3Chris Lattner DeleteTriviallyDeadInstructions(DeadInsts); 594eb705914924865201f8b8018977d94594b258142Owen Anderson 595eb705914924865201f8b8018977d94594b258142Owen Anderson if (mustPreserveAnalysisID(LCSSAID)) assert(L->isLCSSAForm()); 5966148c02591bd83da7b957589c4bbf6f9720d503fChris Lattner} 597