LICM.cpp revision c955d212a8c060d7082fe975fd65fcbc9263853a
1e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner//===-- LICM.cpp - Loop Invariant Code Motion Pass ------------------------===// 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//===----------------------------------------------------------------------===// 9e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner// 1092094b4d928119eceac1484331acffe950f4651cChris Lattner// This pass performs loop invariant code motion, attempting to remove as much 1192094b4d928119eceac1484331acffe950f4651cChris Lattner// code from the body of a loop as possible. It does this by either hoisting 1292094b4d928119eceac1484331acffe950f4651cChris Lattner// code into the preheader block, or by sinking code to the exit blocks if it is 1392094b4d928119eceac1484331acffe950f4651cChris Lattner// safe. This pass also promotes must-aliased memory locations in the loop to 14e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner// live in registers, thus hoisting and sinking "invariant" loads and stores. 1592094b4d928119eceac1484331acffe950f4651cChris Lattner// 1692094b4d928119eceac1484331acffe950f4651cChris Lattner// This pass uses alias analysis for two purposes: 172e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// 182741c971044d2165be572749b94398043caccfebChris Lattner// 1. Moving loop invariant loads and calls out of loops. If we can determine 192741c971044d2165be572749b94398043caccfebChris Lattner// that a load or call inside of a loop never aliases anything stored to, 202741c971044d2165be572749b94398043caccfebChris Lattner// we can hoist it or sink it like any other instruction. 212e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// 2. Scalar Promotion of Memory - If there is a store instruction inside of 222e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// the loop, we try to move the store to happen AFTER the loop instead of 232e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// inside of the loop. This can only happen if a few conditions are true: 242e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// A. The pointer stored through is loop invariant 252e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// B. There are no stores or loads in the loop which _may_ alias the 262e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// pointer. There are no calls in the loop which mod/ref the pointer. 272e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// If these conditions are true, we can promote the loads and stores in the 282e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// loop of the pointer to use a temporary alloca'd variable. We then use 29e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner// the SSAUpdater to construct the appropriate SSA form for the value. 30e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner// 31e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner//===----------------------------------------------------------------------===// 32e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 331f309c1a4e8068a64627c612a895d9b403dbcb26Chris Lattner#define DEBUG_TYPE "licm" 34e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner#include "llvm/Transforms/Scalar.h" 3579066fa6acce02c97c714a5a6e151ed8a249721cChris Lattner#include "llvm/Constants.h" 362741c971044d2165be572749b94398043caccfebChris Lattner#include "llvm/DerivedTypes.h" 379289ae85b41eef62ae1fadb93e99d33f723fb682Torok Edwin#include "llvm/IntrinsicInst.h" 382741c971044d2165be572749b94398043caccfebChris Lattner#include "llvm/Instructions.h" 39a8702eaf78e70e1eef8a63882ce97ae6d60edf5bDan Gohman#include "llvm/LLVMContext.h" 40f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner#include "llvm/Analysis/AliasAnalysis.h" 410252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner#include "llvm/Analysis/AliasSetTracker.h" 422ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner#include "llvm/Analysis/ConstantFolding.h" 432ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner#include "llvm/Analysis/LoopInfo.h" 442ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner#include "llvm/Analysis/LoopPass.h" 45952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner#include "llvm/Analysis/Dominators.h" 460de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner#include "llvm/Transforms/Utils/Local.h" 47a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner#include "llvm/Transforms/Utils/SSAUpdater.h" 489133fe28954d498fc4de13064c7d65bd811de02cReid Spencer#include "llvm/Support/CFG.h" 49551ccae044b0ff658fe629dd67edd5ffe75d10e8Reid Spencer#include "llvm/Support/CommandLine.h" 50ce63ffb52f249b62cdf2d250c128007b13f27e71Daniel Dunbar#include "llvm/Support/raw_ostream.h" 51551ccae044b0ff658fe629dd67edd5ffe75d10e8Reid Spencer#include "llvm/Support/Debug.h" 52551ccae044b0ff658fe629dd67edd5ffe75d10e8Reid Spencer#include "llvm/ADT/Statistic.h" 53e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner#include <algorithm> 5492094b4d928119eceac1484331acffe950f4651cChris Lattnerusing namespace llvm; 55d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 560e5f499638c8d277b9dc4a4385712177c53b5681Chris LattnerSTATISTIC(NumSunk , "Number of instructions sunk out of loop"); 570e5f499638c8d277b9dc4a4385712177c53b5681Chris LattnerSTATISTIC(NumHoisted , "Number of instructions hoisted out of loop"); 580e5f499638c8d277b9dc4a4385712177c53b5681Chris LattnerSTATISTIC(NumMovedLoads, "Number of load insts hoisted or sunk"); 590e5f499638c8d277b9dc4a4385712177c53b5681Chris LattnerSTATISTIC(NumMovedCalls, "Number of call insts hoisted or sunk"); 600e5f499638c8d277b9dc4a4385712177c53b5681Chris LattnerSTATISTIC(NumPromoted , "Number of memory locations promoted to registers"); 610e5f499638c8d277b9dc4a4385712177c53b5681Chris Lattner 62844731a7f1909f55935e3514c9e713a62d67662eDan Gohmanstatic cl::opt<bool> 63844731a7f1909f55935e3514c9e713a62d67662eDan GohmanDisablePromotion("disable-licm-promotion", cl::Hidden, 64844731a7f1909f55935e3514c9e713a62d67662eDan Gohman cl::desc("Disable memory promotion in LICM pass")); 652e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 66844731a7f1909f55935e3514c9e713a62d67662eDan Gohmannamespace { 673e8b6631e67e01e4960a7ba4668a50c596607473Chris Lattner struct LICM : public LoopPass { 68ecd94c804a563f2a86572dcf1d2e81f397e19daaNick Lewycky static char ID; // Pass identification, replacement for typeid 69081c34b725980f995be9080eaec24cd3dfaaf065Owen Anderson LICM() : LoopPass(ID) { 70081c34b725980f995be9080eaec24cd3dfaaf065Owen Anderson initializeLICMPass(*PassRegistry::getPassRegistry()); 71081c34b725980f995be9080eaec24cd3dfaaf065Owen Anderson } 72794fd75c67a2cdc128d67342c6d88a504d186896Devang Patel 7354959d6cf68a9b575c98c074babe9867682a7271Devang Patel virtual bool runOnLoop(Loop *L, LPPassManager &LPM); 74e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 7594170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// This transformation requires natural loop information & requires that 7694170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// loop preheaders be inserted into the CFG... 7794170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 78e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner virtual void getAnalysisUsage(AnalysisUsage &AU) const { 79cb2610ea037a17115ef3a01a6bdaab4e3cfdca27Chris Lattner AU.setPreservesCFG(); 803a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson AU.addRequired<DominatorTree>(); 811e381fcd553a3955a10338fd305efc023d7d22e1Dan Gohman AU.addRequired<LoopInfo>(); 821e381fcd553a3955a10338fd305efc023d7d22e1Dan Gohman AU.addRequiredID(LoopSimplifyID); 83f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner AU.addRequired<AliasAnalysis>(); 84e418ac832c1a2813736c44f6ec5c646b4c89c339Chris Lattner AU.addPreserved<AliasAnalysis>(); 85a9b61e7f7b1ab3a7344bbdc31c3e254c189fafccDan Gohman AU.addPreserved("scalar-evolution"); 865c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman AU.addPreservedID(LoopSimplifyID); 87e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner } 88e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 89747603e39ea3f29add9ba6c07bbefcc5c2432612Dan Gohman bool doFinalization() { 904282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner assert(LoopToAliasSetMap.empty() && "Didn't free loop alias sets"); 9154959d6cf68a9b575c98c074babe9867682a7271Devang Patel return false; 9254959d6cf68a9b575c98c074babe9867682a7271Devang Patel } 9354959d6cf68a9b575c98c074babe9867682a7271Devang Patel 94e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner private: 952e6e741b737960ecd0b68610875050019aac0f07Chris Lattner AliasAnalysis *AA; // Current AliasAnalysis information 9692094b4d928119eceac1484331acffe950f4651cChris Lattner LoopInfo *LI; // Current LoopInfo 9744e2bd31f13da68bca451e4210560db3644b8208Chris Lattner DominatorTree *DT; // Dominator Tree for the current Loop. 9892094b4d928119eceac1484331acffe950f4651cChris Lattner 994282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // State that is updated as we process loops. 1002e6e741b737960ecd0b68610875050019aac0f07Chris Lattner bool Changed; // Set to true when we change anything. 1012e6e741b737960ecd0b68610875050019aac0f07Chris Lattner BasicBlock *Preheader; // The preheader block of the current loop... 1022e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Loop *CurLoop; // The current loop we are working on... 1030252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AliasSetTracker *CurAST; // AliasSet information for the current loop... 1044282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner DenseMap<Loop*, AliasSetTracker*> LoopToAliasSetMap; 105e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 10691d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel /// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info. 10791d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel void cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, Loop *L); 10891d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 10991d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel /// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias 11091d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel /// set. 11191d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel void deleteAnalysisValue(Value *V, Loop *L); 11291d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 113e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// SinkRegion - Walk the specified region of the CFG (defined by all blocks 114e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// dominated by the specified block, and that are in the current loop) in 1153a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson /// reverse depth first order w.r.t the DominatorTree. This allows us to 116e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// visit uses before definitions, allowing us to sink a loop body in one 117e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// pass without iteration. 118e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// 11926042420d642e810f5cdfb2da6156b74aaf80945Devang Patel void SinkRegion(DomTreeNode *N); 120e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 121952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// HoistRegion - Walk the specified region of the CFG (defined by all 122952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// blocks dominated by the specified block, and that are in the current 1233a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson /// loop) in depth first order w.r.t the DominatorTree. This allows us to 124cf00c4ab3ba308d45d98c5ccab87362cf802facbMisha Brukman /// visit definitions before uses, allowing us to hoist a loop body in one 125952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// pass without iteration. 126952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// 12726042420d642e810f5cdfb2da6156b74aaf80945Devang Patel void HoistRegion(DomTreeNode *N); 128952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 129b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner /// inSubLoop - Little predicate that returns true if the specified basic 130b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner /// block is in a subloop of the current one, not the current one itself. 13194170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 132b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner bool inSubLoop(BasicBlock *BB) { 133b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop"); 13481a866d615d6e4ee8dcbd49268d2cfb174f5155bChris Lattner return LI->getLoopFor(BB) != CurLoop; 135e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner } 136e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 137a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// sink - When an instruction is found to only be used outside of the loop, 138a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// this function moves it to the exit blocks and patches up SSA form as 139a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// needed. 140a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// 141a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner void sink(Instruction &I); 142a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 14394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// hoist - When an instruction is found to only use loop invariant operands 14494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// that is safe to hoist, this instruction is called to do the dirty work. 14594170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 1467e70829632f82de15db187845666aaca6e04b792Chris Lattner void hoist(Instruction &I); 147e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 148a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it 149a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// is not a trapping instruction or if it is a trapping instruction and is 150a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// guaranteed to execute. 1519966c03aad031f738718bed3bc00371e358beb5dTanya Lattner /// 152a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isSafeToExecuteUnconditionally(Instruction &I); 1539966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 15494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// pointerInvalidatedByLoop - Return true if the body of this loop may 15594170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// store into the memory location pointed to by V. 156fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman /// 1573da848bbda62b25c12335998aaa44ab361f0bf15Dan Gohman bool pointerInvalidatedByLoop(Value *V, uint64_t Size, 158a8702eaf78e70e1eef8a63882ce97ae6d60edf5bDan Gohman const MDNode *TBAAInfo) { 1590252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Check to see if any of the basic blocks in CurLoop invalidate *V. 160a8702eaf78e70e1eef8a63882ce97ae6d60edf5bDan Gohman return CurAST->getAliasSetForPointer(V, Size, TBAAInfo).isMod(); 1612e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 162f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner 163a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool canSinkOrHoistInst(Instruction &I); 164a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isNotUsedInLoop(Instruction &I); 165e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 166e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner void PromoteAliasSet(AliasSet &AS); 167e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner }; 168e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 169e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 170844731a7f1909f55935e3514c9e713a62d67662eDan Gohmanchar LICM::ID = 0; 1712ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_BEGIN(LICM, "licm", "Loop Invariant Code Motion", false, false) 1722ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_DEPENDENCY(DominatorTree) 1732ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_DEPENDENCY(LoopInfo) 1742ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_DEPENDENCY(LoopSimplify) 1752ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_AG_DEPENDENCY(AliasAnalysis) 1762ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_END(LICM, "licm", "Loop Invariant Code Motion", false, false) 177844731a7f1909f55935e3514c9e713a62d67662eDan Gohman 178394f0441e06dafca29f0752cf400990a5b8fe4b1Daniel DunbarPass *llvm::createLICMPass() { return new LICM(); } 179e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 1808d246f09cb46fe38aa71d2a4edcd84f30c4bf80eDevang Patel/// Hoist expressions out of the specified loop. Note, alias info for inner 1818d246f09cb46fe38aa71d2a4edcd84f30c4bf80eDevang Patel/// loop is not preserved so it is not a good idea to run LICM multiple 1828d246f09cb46fe38aa71d2a4edcd84f30c4bf80eDevang Patel/// times on one loop. 18394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 18454959d6cf68a9b575c98c074babe9867682a7271Devang Patelbool LICM::runOnLoop(Loop *L, LPPassManager &LPM) { 1852e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Changed = false; 186e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 1872e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Get our Loop and Alias Analysis information... 1882e6e741b737960ecd0b68610875050019aac0f07Chris Lattner LI = &getAnalysis<LoopInfo>(); 189f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner AA = &getAnalysis<AliasAnalysis>(); 1903a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson DT = &getAnalysis<DominatorTree>(); 191f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner 19254959d6cf68a9b575c98c074babe9867682a7271Devang Patel CurAST = new AliasSetTracker(*AA); 1934282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // Collect Alias info from subloops. 19454959d6cf68a9b575c98c074babe9867682a7271Devang Patel for (Loop::iterator LoopItr = L->begin(), LoopItrE = L->end(); 19554959d6cf68a9b575c98c074babe9867682a7271Devang Patel LoopItr != LoopItrE; ++LoopItr) { 19654959d6cf68a9b575c98c074babe9867682a7271Devang Patel Loop *InnerL = *LoopItr; 1974282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner AliasSetTracker *InnerAST = LoopToAliasSetMap[InnerL]; 1984282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner assert(InnerAST && "Where is my AST?"); 19994170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner 20054959d6cf68a9b575c98c074babe9867682a7271Devang Patel // What if InnerLoop was modified by other passes ? 20154959d6cf68a9b575c98c074babe9867682a7271Devang Patel CurAST->add(*InnerAST); 2024282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner 2034282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // Once we've incorporated the inner loop's AST into ours, we don't need the 2044282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // subloop's anymore. 2054282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner delete InnerAST; 2064282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner LoopToAliasSetMap.erase(InnerL); 2072e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 20854959d6cf68a9b575c98c074babe9867682a7271Devang Patel 209e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner CurLoop = L; 210e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 21199a57216a935a512c418032f590a4660bad9d846Chris Lattner // Get the preheader block to move instructions into... 21299a57216a935a512c418032f590a4660bad9d846Chris Lattner Preheader = L->getLoopPreheader(); 21399a57216a935a512c418032f590a4660bad9d846Chris Lattner 2142e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Loop over the body of this loop, looking for calls, invokes, and stores. 2150252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Because subloops have already been incorporated into AST, we skip blocks in 2162e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // subloops. 2172e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 2189b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 2199b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman I != E; ++I) { 2209b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman BasicBlock *BB = *I; 2214282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner if (LI->getLoopFor(BB) == L) // Ignore blocks in subloops. 2229b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman CurAST->add(*BB); // Incorporate the specified basic block 2239b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman } 2242e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 225e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // We want to visit all of the instructions in this loop... that are not parts 226e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // of our subloops (they have already had their invariants hoisted out of 227e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // their loop, into this loop, so there is no need to process the BODIES of 228e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // the subloops). 229e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // 230952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // Traverse the body of the loop in depth first order on the dominator tree so 231952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // that we are guaranteed to see definitions before we see uses. This allows 232af5cbc82bb6410129425c98bbfc1ffc4c3d0f411Nick Lewycky // us to sink instructions in one pass, without iteration. After sinking 233e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // instructions, we perform another pass to hoist them out of the loop. 234952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // 23503e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman if (L->hasDedicatedExits()) 23603e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman SinkRegion(DT->getNode(L->getHeader())); 23703e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman if (Preheader) 23803e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman HoistRegion(DT->getNode(L->getHeader())); 239e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2402e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Now that all loop invariants have been removed from the loop, promote any 241e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // memory references to scalars that we can. 242e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!DisablePromotion && Preheader && L->hasDedicatedExits()) { 243e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Loop over all of the alias sets in the tracker object. 244e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end(); 245e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner I != E; ++I) 246e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner PromoteAliasSet(*I); 247e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 248e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 249e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // Clear out loops state information for the next iteration 250e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner CurLoop = 0; 25199a57216a935a512c418032f590a4660bad9d846Chris Lattner Preheader = 0; 25254959d6cf68a9b575c98c074babe9867682a7271Devang Patel 2534282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // If this loop is nested inside of another one, save the alias information 2544282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // for when we process the outer loop. 2554282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner if (L->getParentLoop()) 2564282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner LoopToAliasSetMap[L] = CurAST; 2574282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner else 2584282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner delete CurAST; 25954959d6cf68a9b575c98c074babe9867682a7271Devang Patel return Changed; 260e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 261e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 262e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// SinkRegion - Walk the specified region of the CFG (defined by all blocks 263e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// dominated by the specified block, and that are in the current loop) in 2643a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson/// reverse depth first order w.r.t the DominatorTree. This allows us to visit 265e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// uses before definitions, allowing us to sink a loop body in one pass without 266e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// iteration. 267e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// 26826042420d642e810f5cdfb2da6156b74aaf80945Devang Patelvoid LICM::SinkRegion(DomTreeNode *N) { 2693a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson assert(N != 0 && "Null dominator tree node?"); 2703a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson BasicBlock *BB = N->getBlock(); 271e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 272e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // If this subregion is not in the top level loop at all, exit. 273e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner if (!CurLoop->contains(BB)) return; 274e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 2750de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner // We are processing blocks in reverse dfo, so process children first. 27626042420d642e810f5cdfb2da6156b74aaf80945Devang Patel const std::vector<DomTreeNode*> &Children = N->getChildren(); 277e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner for (unsigned i = 0, e = Children.size(); i != e; ++i) 278e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner SinkRegion(Children[i]); 279e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 280e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Only need to process the contents of this block if it is not part of a 281e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // subloop (which would already have been processed). 282e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner if (inSubLoop(BB)) return; 283e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 284a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner for (BasicBlock::iterator II = BB->end(); II != BB->begin(); ) { 285a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner Instruction &I = *--II; 2860de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner 2870de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner // If the instruction is dead, we would try to sink it because it isn't used 2880de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner // in the loop, instead, just delete it. 2890de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner if (isInstructionTriviallyDead(&I)) { 290cb7f65342291caa3636cb50c0ee04b383cd79f8dChris Lattner DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n'); 2910de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner ++II; 2920de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner CurAST->deleteValue(&I); 2930de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner I.eraseFromParent(); 2940de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner Changed = true; 2950de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner continue; 2960de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner } 297fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 298e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Check to see if we can sink this instruction to the exit blocks 299e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // of the loop. We can do this if the all users of the instruction are 300e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // outside of the loop. In this case, it doesn't even matter if the 301e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // operands of the instruction are loop invariant. 302e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // 30370ac2dcb841dc62f08e16f0b0e2cefbf01baa4c5Chris Lattner if (isNotUsedInLoop(I) && canSinkOrHoistInst(I)) { 304a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner ++II; 305e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner sink(I); 306a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner } 307e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner } 308e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner} 309e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 310952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// HoistRegion - Walk the specified region of the CFG (defined by all blocks 311952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// dominated by the specified block, and that are in the current loop) in depth 3123a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson/// first order w.r.t the DominatorTree. This allows us to visit definitions 313952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// before uses, allowing us to hoist a loop body in one pass without iteration. 314952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// 31526042420d642e810f5cdfb2da6156b74aaf80945Devang Patelvoid LICM::HoistRegion(DomTreeNode *N) { 3163a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson assert(N != 0 && "Null dominator tree node?"); 3173a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson BasicBlock *BB = N->getBlock(); 318952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 319b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner // If this subregion is not in the top level loop at all, exit. 320ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (!CurLoop->contains(BB)) return; 321952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 322a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Only need to process the contents of this block if it is not part of a 323a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // subloop (which would already have been processed). 324ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (!inSubLoop(BB)) 325a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ) { 326a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Instruction &I = *II++; 327fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 3282ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner // Try constant folding this instruction. If all the operands are 3292ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner // constants, it is technically hoistable, but it would be better to just 3302ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner // fold it. 3312ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner if (Constant *C = ConstantFoldInstruction(&I)) { 3322ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner DEBUG(dbgs() << "LICM folding inst: " << I << " --> " << *C << '\n'); 3332ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner CurAST->copyValue(&I, C); 3342ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner CurAST->deleteValue(&I); 3352ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner I.replaceAllUsesWith(C); 3362ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner I.eraseFromParent(); 3372ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner continue; 3382ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner } 3392ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner 340e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Try hoisting the instruction out to the preheader. We can only do this 341e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // if all of the operands of the instruction are loop invariant and if it 342e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // is safe to hoist the instruction. 343e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // 344adc799112dc180b3cd099038c05101b85d217716Chris Lattner if (CurLoop->hasLoopInvariantOperands(&I) && canSinkOrHoistInst(I) && 345e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner isSafeToExecuteUnconditionally(I)) 3463c80a51cfd5e7187439ce4c051da77ee46e0ff9aChris Lattner hoist(I); 3472ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner } 348952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 34926042420d642e810f5cdfb2da6156b74aaf80945Devang Patel const std::vector<DomTreeNode*> &Children = N->getChildren(); 350952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner for (unsigned i = 0, e = Children.size(); i != e; ++i) 35156b7ee20dad7160a117ea0d102fc5432074ce2d0Chris Lattner HoistRegion(Children[i]); 352952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner} 353952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 354a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// canSinkOrHoistInst - Return true if the hoister and sinker can handle this 355a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// instruction. 356a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 357a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::canSinkOrHoistInst(Instruction &I) { 358ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // Loads have extra constraints we have to verify before we can hoist them. 359ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { 360ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (LI->isVolatile()) 361ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner return false; // Don't hoist volatile loads! 362ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 363967948b4e25cae3de68f38fddaa75d838e676decChris Lattner // Loads from constant memory are always safe to move, even if they end up 364967948b4e25cae3de68f38fddaa75d838e676decChris Lattner // in the same alias set as something that ends up being modified. 365dab249b3b762cff0ff16069b3233e4c885e75347Dan Gohman if (AA->pointsToConstantMemory(LI->getOperand(0))) 366967948b4e25cae3de68f38fddaa75d838e676decChris Lattner return true; 367967948b4e25cae3de68f38fddaa75d838e676decChris Lattner 368ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // Don't hoist loads which have may-aliased stores in loop. 3693da848bbda62b25c12335998aaa44ab361f0bf15Dan Gohman uint64_t Size = 0; 370f3e1d6977ee5fb6b66df314d65e28e2c35d6e244Chris Lattner if (LI->getType()->isSized()) 371fc2a3ed0c9e32cf7edaf5030fa0972b916cc5f0bDan Gohman Size = AA->getTypeStoreSize(LI->getType()); 372a8702eaf78e70e1eef8a63882ce97ae6d60edf5bDan Gohman return !pointerInvalidatedByLoop(LI->getOperand(0), Size, 373a8702eaf78e70e1eef8a63882ce97ae6d60edf5bDan Gohman LI->getMetadata(LLVMContext::MD_tbaa)); 374118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } else if (CallInst *CI = dyn_cast<CallInst>(&I)) { 375c955d212a8c060d7082fe975fd65fcbc9263853aEli Friedman // Handle obvious cases efficiently. 376dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands AliasAnalysis::ModRefBehavior Behavior = AA->getModRefBehavior(CI); 377dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands if (Behavior == AliasAnalysis::DoesNotAccessMemory) 378dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands return true; 379cd93f3bbb9cf209aff3ffdff9d7c7d05d935b292Dan Gohman if (AliasAnalysis::onlyReadsMemory(Behavior)) { 380dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands // If this call only reads from memory and there are no writes to memory 381dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands // in the loop, we can hoist or sink the call as appropriate. 382dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands bool FoundMod = false; 383dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end(); 384dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands I != E; ++I) { 385dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands AliasSet &AS = *I; 386dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands if (!AS.isForwardingAliasSet() && AS.isMod()) { 387dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands FoundMod = true; 388dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands break; 389118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 390118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 391dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands if (!FoundMod) return true; 392118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 393118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner 394118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // FIXME: This should use mod/ref information to see if we can hoist or sink 395118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // the call. 396fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 397118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner return false; 398ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner } 399ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 4003da59db637a887474c1b1346c1f3ccf53b6c4663Reid Spencer // Otherwise these instructions are hoistable/sinkable 401832254e1c2387c0cbeb0a820b8315fbe85cb003aReid Spencer return isa<BinaryOperator>(I) || isa<CastInst>(I) || 402d8af90c1da64b81a7aa167b5adcc1e81b0741252Dan Gohman isa<SelectInst>(I) || isa<GetElementPtrInst>(I) || isa<CmpInst>(I) || 403d8af90c1da64b81a7aa167b5adcc1e81b0741252Dan Gohman isa<InsertElementInst>(I) || isa<ExtractElementInst>(I) || 404d8af90c1da64b81a7aa167b5adcc1e81b0741252Dan Gohman isa<ShuffleVectorInst>(I); 405a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 406a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 407a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isNotUsedInLoop - Return true if the only users of this instruction are 408a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// outside of the loop. If this is true, we can sink the instruction to the 409a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// exit blocks of the loop. 410a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 411a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isNotUsedInLoop(Instruction &I) { 412ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner for (Value::use_iterator UI = I.use_begin(), E = I.use_end(); UI != E; ++UI) { 413ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner Instruction *User = cast<Instruction>(*UI); 414ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (PHINode *PN = dyn_cast<PHINode>(User)) { 415ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner // PHI node uses occur in predecessor blocks! 416ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 417ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (PN->getIncomingValue(i) == &I) 418ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (CurLoop->contains(PN->getIncomingBlock(i))) 419ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner return false; 42092329c7fbe572892c17aa2d2542a10e3ea16132fDan Gohman } else if (CurLoop->contains(User)) { 421a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 422ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } 423ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } 424a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 425a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 426a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 427a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 428a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// sink - When an instruction is found to only be used outside of the loop, 429a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// this function moves it to the exit blocks and patches up SSA form as needed. 430a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// This method is guaranteed to remove the original instruction from its 431a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// position, and may either delete it or move it to outside of the loop. 432a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 433a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnervoid LICM::sink(Instruction &I) { 43439a383124b70dda1fea18288235114029ede76cfNick Lewycky DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n"); 435a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 436b7211a2ce13a0365e0e1dd2f27adda2ee3d1288bDevang Patel SmallVector<BasicBlock*, 8> ExitBlocks; 437d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner CurLoop->getUniqueExitBlocks(ExitBlocks); 438df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner 439df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner if (isa<LoadInst>(I)) ++NumMovedLoads; 440118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner else if (isa<CallInst>(I)) ++NumMovedCalls; 441df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner ++NumSunk; 442df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner Changed = true; 443df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner 444a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The case where there is only a single exit node of this loop is common 445a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // enough that we handle it as a special (more efficient) case. It is more 446a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // efficient to handle because there are no PHI nodes that need to be placed. 447a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (ExitBlocks.size() == 1) { 448290342a15755e9f128916eb66ec88812d6cee569Devang Patel if (!isa<DbgInfoIntrinsic>(I) && 449290342a15755e9f128916eb66ec88812d6cee569Devang Patel !DT->dominates(I.getParent(), ExitBlocks[0])) { 450a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Instruction is not used, just delete it. 4512741c971044d2165be572749b94398043caccfebChris Lattner CurAST->deleteValue(&I); 4521bf5ebc7be0d5b05e4175c7adb767b38896adef1Devang Patel // If I has users in unreachable blocks, eliminate. 453228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // If I is not void type then replaceAllUsesWith undef. 454228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // This allows ValueHandlers and custom metadata to adjust itself. 455a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 456228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel I.replaceAllUsesWith(UndefValue::get(I.getType())); 4573c80a51cfd5e7187439ce4c051da77ee46e0ff9aChris Lattner I.eraseFromParent(); 458a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 459a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Move the instruction to the start of the exit block, after any PHI 460a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // nodes in it. 461d9a5daeb7719c83136c0dc43d6ef732402d1a1b5Chris Lattner I.moveBefore(ExitBlocks[0]->getFirstNonPHI()); 4624282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner 4634282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // This instruction is no longer in the AST for the current loop, because 4644282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // we just sunk it out of the loop. If we just sunk it into an outer 4654282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // loop, we will rediscover the operation when we process it. 4664282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner CurAST->deleteValue(&I); 467a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 468d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner return; 469d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 470d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 471d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner if (ExitBlocks.empty()) { 472a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The instruction is actually dead if there ARE NO exit blocks. 4732741c971044d2165be572749b94398043caccfebChris Lattner CurAST->deleteValue(&I); 4741bf5ebc7be0d5b05e4175c7adb767b38896adef1Devang Patel // If I has users in unreachable blocks, eliminate. 475228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // If I is not void type then replaceAllUsesWith undef. 476228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // This allows ValueHandlers and custom metadata to adjust itself. 477a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 478228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel I.replaceAllUsesWith(UndefValue::get(I.getType())); 4793c80a51cfd5e7187439ce4c051da77ee46e0ff9aChris Lattner I.eraseFromParent(); 480d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner return; 481d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 482d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 483a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Otherwise, if we have multiple exits, use the SSAUpdater to do all of the 484a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // hard work of inserting PHI nodes as necessary. 485a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SmallVector<PHINode*, 8> NewPHIs; 486a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SSAUpdater SSA(&NewPHIs); 487a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 488a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 489fc6e29d4ab52b7d3efd83846ed495a9ca7e51e49Duncan Sands SSA.Initialize(I.getType(), I.getName()); 490d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 491a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Insert a copy of the instruction in each exit block of the loop that is 492a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // dominated by the instruction. Each exit block is known to only be in the 493a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // ExitBlocks list once. 494a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner BasicBlock *InstOrigBB = I.getParent(); 495d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner unsigned NumInserted = 0; 496a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 497d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 498d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner BasicBlock *ExitBlock = ExitBlocks[i]; 499a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 50083fc584ea811aca780d965258c49db72a3ee8b1dChris Lattner if (!DT->dominates(InstOrigBB, ExitBlock)) 501d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner continue; 502d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 503a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Insert the code after the last PHI node. 504d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner BasicBlock::iterator InsertPt = ExitBlock->getFirstNonPHI(); 505a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 506d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // If this is the first exit block processed, just move the original 507d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // instruction, otherwise clone the original instruction and insert 508d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // the copy. 509d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner Instruction *New; 510a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (NumInserted++ == 0) { 511a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner I.moveBefore(InsertPt); 512d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner New = &I; 513d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } else { 514d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner New = I.clone(); 515d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner if (!I.getName().empty()) 516d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner New->setName(I.getName()+".le"); 517d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner ExitBlock->getInstList().insert(InsertPt, New); 518a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 519d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 520a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Now that we have inserted the instruction, inform SSAUpdater. 521a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 522a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SSA.AddAvailableValue(ExitBlock, New); 523d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 524a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 525c955d212a8c060d7082fe975fd65fcbc9263853aEli Friedman // If the instruction doesn't dominate any exit blocks, it must be dead. 526c955d212a8c060d7082fe975fd65fcbc9263853aEli Friedman if (NumInserted == 0) { 527c955d212a8c060d7082fe975fd65fcbc9263853aEli Friedman CurAST->deleteValue(&I); 528c955d212a8c060d7082fe975fd65fcbc9263853aEli Friedman if (!I.use_empty()) 529c955d212a8c060d7082fe975fd65fcbc9263853aEli Friedman I.replaceAllUsesWith(UndefValue::get(I.getType())); 530c955d212a8c060d7082fe975fd65fcbc9263853aEli Friedman I.eraseFromParent(); 531c955d212a8c060d7082fe975fd65fcbc9263853aEli Friedman return; 532c955d212a8c060d7082fe975fd65fcbc9263853aEli Friedman } 533a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 534a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Next, rewrite uses of the instruction, inserting PHI nodes as needed. 535a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; ) { 536a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Grab the use before incrementing the iterator. 537a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner Use &U = UI.getUse(); 538a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Increment the iterator before removing the use from the list. 539a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner ++UI; 540a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SSA.RewriteUseAfterInsertions(U); 541a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 542a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 543a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Update CurAST for NewPHIs if I had pointer type. 544a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (I.getType()->isPointerTy()) 545a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i) 5469c282011e6b7a6e23a3a163ec9c865890449e8dcChris Lattner CurAST->copyValue(&I, NewPHIs[i]); 54798917503c702e16f35ccdec3f6b4c48e5c4759acChris Lattner 54898917503c702e16f35ccdec3f6b4c48e5c4759acChris Lattner // Finally, remove the instruction from CurAST. It is no longer in the loop. 54998917503c702e16f35ccdec3f6b4c48e5c4759acChris Lattner CurAST->deleteValue(&I); 550a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 551952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 55294170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// hoist - When an instruction is found to only use loop invariant operands 55394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// that is safe to hoist, this instruction is called to do the dirty work. 55494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 555a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnervoid LICM::hoist(Instruction &I) { 556f15826999bc560ee6f67cff5ecd71bf9cce7a7aaDavid Greene DEBUG(dbgs() << "LICM hoisting to " << Preheader->getName() << ": " 55767d1d1f8322bdc460158888cd233be8d1cb1d4abEvan Cheng << I << "\n"); 558ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 559d9a5daeb7719c83136c0dc43d6ef732402d1a1b5Chris Lattner // Move the new node to the Preheader, before its terminator. 560d9a5daeb7719c83136c0dc43d6ef732402d1a1b5Chris Lattner I.moveBefore(Preheader->getTerminator()); 561fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 562a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (isa<LoadInst>(I)) ++NumMovedLoads; 563118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner else if (isa<CallInst>(I)) ++NumMovedCalls; 5649646e6b6af1f924f9366a2bffc6dde102f84d231Chris Lattner ++NumHoisted; 565e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner Changed = true; 566e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 567e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 568a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it is 569a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// not a trapping instruction or if it is a trapping instruction and is 570a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// guaranteed to execute. 5719966c03aad031f738718bed3bc00371e358beb5dTanya Lattner/// 572a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) { 57392094b4d928119eceac1484331acffe950f4651cChris Lattner // If it is not a trapping instruction, it is always safe to hoist. 5740b79a7727d68a507837e827803859424cf3d997bEli Friedman if (Inst.isSafeToSpeculativelyExecute()) 5750b79a7727d68a507837e827803859424cf3d997bEli Friedman return true; 576fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 57792094b4d928119eceac1484331acffe950f4651cChris Lattner // Otherwise we have to check to make sure that the instruction dominates all 57892094b4d928119eceac1484331acffe950f4651cChris Lattner // of the exit blocks. If it doesn't, then there is a path out of the loop 57992094b4d928119eceac1484331acffe950f4651cChris Lattner // which does not execute this instruction, so we can't hoist it. 58092094b4d928119eceac1484331acffe950f4651cChris Lattner 58192094b4d928119eceac1484331acffe950f4651cChris Lattner // If the instruction is in the header block for the loop (which is very 58292094b4d928119eceac1484331acffe950f4651cChris Lattner // common), it is always guaranteed to dominate the exit blocks. Since this 58392094b4d928119eceac1484331acffe950f4651cChris Lattner // is a common case, and can save some work, check it now. 584a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (Inst.getParent() == CurLoop->getHeader()) 58592094b4d928119eceac1484331acffe950f4651cChris Lattner return true; 58692094b4d928119eceac1484331acffe950f4651cChris Lattner 58792094b4d928119eceac1484331acffe950f4651cChris Lattner // Get the exit blocks for the current loop. 588b7211a2ce13a0365e0e1dd2f27adda2ee3d1288bDevang Patel SmallVector<BasicBlock*, 8> ExitBlocks; 5895fa802fe279f10f402e039bc931aa57c0e424bf5Chris Lattner CurLoop->getExitBlocks(ExitBlocks); 5909966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 59183fc584ea811aca780d965258c49db72a3ee8b1dChris Lattner // Verify that the block dominates each of the exit blocks of the loop. 592a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 59383fc584ea811aca780d965258c49db72a3ee8b1dChris Lattner if (!DT->dominates(Inst.getParent(), ExitBlocks[i])) 594a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 595fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 5969966c03aad031f738718bed3bc00371e358beb5dTanya Lattner return true; 5979966c03aad031f738718bed3bc00371e358beb5dTanya Lattner} 5989966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 599deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattnernamespace { 600deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner class LoopPromoter : public LoadAndStorePromoter { 601deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner Value *SomePtr; // Designated pointer to store to. 602deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner SmallPtrSet<Value*, 4> &PointerMustAliases; 603deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner SmallVectorImpl<BasicBlock*> &LoopExitBlocks; 604deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner AliasSetTracker &AST; 605deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner public: 606deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner LoopPromoter(Value *SP, 607deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S, 608deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner SmallPtrSet<Value*, 4> &PMA, 609deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner SmallVectorImpl<BasicBlock*> &LEB, AliasSetTracker &ast) 61013a16083abcdacf2ee44ae95b084f87937ea9aceCameron Zwarich : LoadAndStorePromoter(Insts, S, 0, 0), SomePtr(SP), 611c827939046670a9800659b83e2048f1d3a79a531Cameron Zwarich PointerMustAliases(PMA), LoopExitBlocks(LEB), AST(ast) {} 612deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner 613deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner virtual bool isInstInList(Instruction *I, 614deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner const SmallVectorImpl<Instruction*> &) const { 615deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner Value *Ptr; 616deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(I)) 617deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner Ptr = LI->getOperand(0); 618deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner else 619deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner Ptr = cast<StoreInst>(I)->getPointerOperand(); 620deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner return PointerMustAliases.count(Ptr); 621deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner } 622deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner 623deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner virtual void doExtraRewritesBeforeFinalDeletion() const { 624deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner // Insert stores after in the loop exit blocks. Each exit block gets a 625deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner // store of the live-out values that feed them. Since we've already told 626deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner // the SSA updater about the defs in the loop and the preheader 627deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner // definition, it is all set and we can start using it. 628deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) { 629deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner BasicBlock *ExitBlock = LoopExitBlocks[i]; 630deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock); 631deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner Instruction *InsertPos = ExitBlock->getFirstNonPHI(); 632deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner new StoreInst(LiveInValue, SomePtr, InsertPos); 633deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner } 634deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner } 635deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner 636deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner virtual void replaceLoadWithValue(LoadInst *LI, Value *V) const { 637deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner // Update alias analysis. 638deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner AST.copyValue(LI, V); 639deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner } 640deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner virtual void instructionDeleted(Instruction *I) const { 641deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner AST.deleteValue(I); 642deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner } 643deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner }; 644deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner} // end anon namespace 645deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner 646e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner/// PromoteAliasSet - Try to promote memory values to scalars by sinking 6472e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// stores out of the loop and moving loads to before the loop. We do this by 6482e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// looping over the stores in the loop, looking for stores to Must pointers 649e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner/// which are loop invariant. 6502e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// 651e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattnervoid LICM::PromoteAliasSet(AliasSet &AS) { 652e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // We can promote this alias set if it has a store, if it is a "Must" alias 653e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // set, if the pointer is loop invariant, and if we are not eliminating any 654e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // volatile loads or stores. 655e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() || 656e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner AS.isVolatile() || !CurLoop->isLoopInvariant(AS.begin()->getValue())) 657e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; 658e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 659e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner assert(!AS.empty() && 660e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner "Must alias set should have at least one pointer element in it!"); 661e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *SomePtr = AS.begin()->getValue(); 662fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 663e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // It isn't safe to promote a load/store from the loop if the load/store is 664e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // conditional. For example, turning: 6652e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 666e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // for () { if (c) *P += 1; } 6672e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 668e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // into: 669e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // 670e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // tmp = *P; for () { if (c) tmp +=1; } *P = tmp; 671e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // 672e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // is not safe, because *P may only be valid to access if 'c' is true. 673e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // 674e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // It is safe to promote P if all uses are direct load/stores and if at 675e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // least one is guaranteed to be executed. 676e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner bool GuaranteedToExecute = false; 677e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 678e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallVector<Instruction*, 64> LoopUses; 679e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallPtrSet<Value*, 4> PointerMustAliases; 680e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 681e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Check that all of the pointers in the alias set have the same type. We 682e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // cannot (yet) promote a memory location that is loaded and stored in 683e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // different sizes. 684e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) { 685e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *ASIV = ASI->getValue(); 686e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner PointerMustAliases.insert(ASIV); 68729d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner 68829d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner // Check that all of the pointers in the alias set have the same type. We 68929d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner // cannot (yet) promote a memory location that is loaded and stored in 69029d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner // different sizes. 691e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (SomePtr->getType() != ASIV->getType()) 692e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; 693e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 694e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (Value::use_iterator UI = ASIV->use_begin(), UE = ASIV->use_end(); 69519d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner UI != UE; ++UI) { 696e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Ignore instructions that are outside the loop. 69729d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner Instruction *Use = dyn_cast<Instruction>(*UI); 69892329c7fbe572892c17aa2d2542a10e3ea16132fDan Gohman if (!Use || !CurLoop->contains(Use)) 69929d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner continue; 700e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 701e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If there is an non-load/store instruction in the loop, we can't promote 702e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // it. 703e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (isa<LoadInst>(Use)) 704e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner assert(!cast<LoadInst>(Use)->isVolatile() && "AST broken"); 7050cccd7633e4a0ba36b5ff9a3dfda2a09d16dc337Chris Lattner else if (isa<StoreInst>(Use)) { 7061dec0d27048725cf73f73ce4f0bb97ca78255f97Chris Lattner // Stores *of* the pointer are not interesting, only stores *to* the 7071dec0d27048725cf73f73ce4f0bb97ca78255f97Chris Lattner // pointer. 7081dec0d27048725cf73f73ce4f0bb97ca78255f97Chris Lattner if (Use->getOperand(1) != ASIV) 7091dec0d27048725cf73f73ce4f0bb97ca78255f97Chris Lattner continue; 7101c0af0ed251af3d2ef795903133513656e5c369dChris Lattner assert(!cast<StoreInst>(Use)->isVolatile() && "AST broken"); 7110cccd7633e4a0ba36b5ff9a3dfda2a09d16dc337Chris Lattner } else 712e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; // Not a load or store. 71319d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner 71419d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner if (!GuaranteedToExecute) 71519d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner GuaranteedToExecute = isSafeToExecuteUnconditionally(*Use); 716e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 717e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LoopUses.push_back(Use); 71829d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner } 719e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 720e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 721e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If there isn't a guaranteed-to-execute instruction, we can't promote. 722e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!GuaranteedToExecute) 723e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; 724e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 725e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Otherwise, this is safe to promote, lets do it! 726e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " <<*SomePtr<<'\n'); 727e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Changed = true; 728e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner ++NumPromoted; 729bc2265abe1d1b830995bb2f6322409bc7d7c5740Devang Patel 730deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner SmallVector<BasicBlock*, 8> ExitBlocks; 731deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner CurLoop->getUniqueExitBlocks(ExitBlocks); 732deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner 733e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // We use the SSAUpdater interface to insert phi nodes as required. 734e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallVector<PHINode*, 16> NewPHIs; 735e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SSAUpdater SSA(&NewPHIs); 736deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks, 737deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner *CurAST); 738e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 739deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner // Set up the preheader to have a definition of the value. It is the live-out 740deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner // value from the preheader that uses in the loop will use. 741deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner LoadInst *PreheaderLoad = 742deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner new LoadInst(SomePtr, SomePtr->getName()+".promoted", 743deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner Preheader->getTerminator()); 744e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SSA.AddAvailableValue(Preheader, PreheaderLoad); 745e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 746deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner // Rewrite all the loads in the loop and remember all the definitions from 747deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner // stores in the loop. 748deaf55f69865bbc997a569c2a689ec5b0fbdefefChris Lattner Promoter.run(LoopUses); 7490e382192c1a7750a157e470f749645ac2266d317Eli Friedman 7500e382192c1a7750a157e470f749645ac2266d317Eli Friedman // If the SSAUpdater didn't use the load in the preheader, just zap it now. 7510e382192c1a7750a157e470f749645ac2266d317Eli Friedman if (PreheaderLoad->use_empty()) 7520e382192c1a7750a157e470f749645ac2266d317Eli Friedman PreheaderLoad->eraseFromParent(); 753f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner} 75491d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 755e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 75691d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel/// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info. 75791d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patelvoid LICM::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, Loop *L) { 7584282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner AliasSetTracker *AST = LoopToAliasSetMap.lookup(L); 75991d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel if (!AST) 76091d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel return; 76191d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 76291d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel AST->copyValue(From, To); 76391d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel} 76491d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 76591d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel/// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias 76691d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel/// set. 76791d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patelvoid LICM::deleteAnalysisValue(Value *V, Loop *L) { 7684282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner AliasSetTracker *AST = LoopToAliasSetMap.lookup(L); 76991d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel if (!AST) 77091d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel return; 77191d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 77291d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel AST->deleteValue(V); 77391d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel} 774