LICM.cpp revision 2ab36d350293c77fc8941ce1023e4899df7e3a82
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" 39f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner#include "llvm/Analysis/AliasAnalysis.h" 400252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner#include "llvm/Analysis/AliasSetTracker.h" 412ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner#include "llvm/Analysis/ConstantFolding.h" 422ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner#include "llvm/Analysis/LoopInfo.h" 432ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner#include "llvm/Analysis/LoopPass.h" 44952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner#include "llvm/Analysis/Dominators.h" 4596b651c627160e1ea0f1bb86d352d697e6c1972dDevang Patel#include "llvm/Analysis/ScalarEvolution.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 6990c579de5a383cee278acc3f7e7b9d0a656e6a35Owen Anderson LICM() : LoopPass(ID) {} 70794fd75c67a2cdc128d67342c6d88a504d186896Devang Patel 7154959d6cf68a9b575c98c074babe9867682a7271Devang Patel virtual bool runOnLoop(Loop *L, LPPassManager &LPM); 72e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 7394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// This transformation requires natural loop information & requires that 7494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// loop preheaders be inserted into the CFG... 7594170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 76e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner virtual void getAnalysisUsage(AnalysisUsage &AU) const { 77cb2610ea037a17115ef3a01a6bdaab4e3cfdca27Chris Lattner AU.setPreservesCFG(); 783a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson AU.addRequired<DominatorTree>(); 791e381fcd553a3955a10338fd305efc023d7d22e1Dan Gohman AU.addRequired<LoopInfo>(); 801e381fcd553a3955a10338fd305efc023d7d22e1Dan Gohman AU.addRequiredID(LoopSimplifyID); 81f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner AU.addRequired<AliasAnalysis>(); 82e418ac832c1a2813736c44f6ec5c646b4c89c339Chris Lattner AU.addPreserved<AliasAnalysis>(); 8396b651c627160e1ea0f1bb86d352d697e6c1972dDevang Patel AU.addPreserved<ScalarEvolution>(); 845c89b5240c90eb8171f999e5f06f815502d0321cDan Gohman AU.addPreservedID(LoopSimplifyID); 85e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner } 86e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 87747603e39ea3f29add9ba6c07bbefcc5c2432612Dan Gohman bool doFinalization() { 884282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner assert(LoopToAliasSetMap.empty() && "Didn't free loop alias sets"); 8954959d6cf68a9b575c98c074babe9867682a7271Devang Patel return false; 9054959d6cf68a9b575c98c074babe9867682a7271Devang Patel } 9154959d6cf68a9b575c98c074babe9867682a7271Devang Patel 92e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner private: 932e6e741b737960ecd0b68610875050019aac0f07Chris Lattner AliasAnalysis *AA; // Current AliasAnalysis information 9492094b4d928119eceac1484331acffe950f4651cChris Lattner LoopInfo *LI; // Current LoopInfo 9544e2bd31f13da68bca451e4210560db3644b8208Chris Lattner DominatorTree *DT; // Dominator Tree for the current Loop. 9692094b4d928119eceac1484331acffe950f4651cChris Lattner 974282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // State that is updated as we process loops. 982e6e741b737960ecd0b68610875050019aac0f07Chris Lattner bool Changed; // Set to true when we change anything. 992e6e741b737960ecd0b68610875050019aac0f07Chris Lattner BasicBlock *Preheader; // The preheader block of the current loop... 1002e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Loop *CurLoop; // The current loop we are working on... 1010252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AliasSetTracker *CurAST; // AliasSet information for the current loop... 1024282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner DenseMap<Loop*, AliasSetTracker*> LoopToAliasSetMap; 103e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 10491d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel /// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info. 10591d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel void cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, Loop *L); 10691d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 10791d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel /// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias 10891d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel /// set. 10991d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel void deleteAnalysisValue(Value *V, Loop *L); 11091d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 111e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// SinkRegion - Walk the specified region of the CFG (defined by all blocks 112e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// dominated by the specified block, and that are in the current loop) in 1133a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson /// reverse depth first order w.r.t the DominatorTree. This allows us to 114e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// visit uses before definitions, allowing us to sink a loop body in one 115e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// pass without iteration. 116e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// 11726042420d642e810f5cdfb2da6156b74aaf80945Devang Patel void SinkRegion(DomTreeNode *N); 118e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 119952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// HoistRegion - Walk the specified region of the CFG (defined by all 120952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// blocks dominated by the specified block, and that are in the current 1213a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson /// loop) in depth first order w.r.t the DominatorTree. This allows us to 122cf00c4ab3ba308d45d98c5ccab87362cf802facbMisha Brukman /// visit definitions before uses, allowing us to hoist a loop body in one 123952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// pass without iteration. 124952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// 12526042420d642e810f5cdfb2da6156b74aaf80945Devang Patel void HoistRegion(DomTreeNode *N); 126952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 127b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner /// inSubLoop - Little predicate that returns true if the specified basic 128b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner /// block is in a subloop of the current one, not the current one itself. 12994170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 130b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner bool inSubLoop(BasicBlock *BB) { 131b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop"); 132329c1c6c949d07e3fe9722ec633b4258217fd99dChris Lattner for (Loop::iterator I = CurLoop->begin(), E = CurLoop->end(); I != E; ++I) 133329c1c6c949d07e3fe9722ec633b4258217fd99dChris Lattner if ((*I)->contains(BB)) 134b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner return true; // A subloop actually contains this block! 135b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner return false; 136e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner } 137e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 138a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// isExitBlockDominatedByBlockInLoop - This method checks to see if the 139a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// specified exit block of the loop is dominated by the specified block 140a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// that is in the body of the loop. We use these constraints to 141a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// dramatically limit the amount of the dominator tree that needs to be 142a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// searched. 143a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isExitBlockDominatedByBlockInLoop(BasicBlock *ExitBlock, 144a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *BlockInLoop) const { 145a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If the block in the loop is the loop header, it must be dominated! 146a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *LoopHeader = CurLoop->getHeader(); 147a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (BlockInLoop == LoopHeader) 148a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 149fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 15026042420d642e810f5cdfb2da6156b74aaf80945Devang Patel DomTreeNode *BlockInLoopNode = DT->getNode(BlockInLoop); 15126042420d642e810f5cdfb2da6156b74aaf80945Devang Patel DomTreeNode *IDom = DT->getNode(ExitBlock); 152fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 153a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Because the exit block is not in the loop, we know we have to get _at 1542741c971044d2165be572749b94398043caccfebChris Lattner // least_ its immediate dominator. 1553472ae1e7b0f38c4ac0802ffc2900f71a5470c3bEric Christopher IDom = IDom->getIDom(); 1563472ae1e7b0f38c4ac0802ffc2900f71a5470c3bEric Christopher 1573472ae1e7b0f38c4ac0802ffc2900f71a5470c3bEric Christopher while (IDom && IDom != BlockInLoopNode) { 158a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If we have got to the header of the loop, then the instructions block 159a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // did not dominate the exit node, so we can't hoist it. 1603a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson if (IDom->getBlock() == LoopHeader) 161a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 162fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 1633472ae1e7b0f38c4ac0802ffc2900f71a5470c3bEric Christopher // Get next Immediate Dominator. 1643472ae1e7b0f38c4ac0802ffc2900f71a5470c3bEric Christopher IDom = IDom->getIDom(); 1653472ae1e7b0f38c4ac0802ffc2900f71a5470c3bEric Christopher }; 166a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 167a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 168a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 169a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 170a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// sink - When an instruction is found to only be used outside of the loop, 171a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// this function moves it to the exit blocks and patches up SSA form as 172a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// needed. 173a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// 174a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner void sink(Instruction &I); 175a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 17694170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// hoist - When an instruction is found to only use loop invariant operands 17794170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// that is safe to hoist, this instruction is called to do the dirty work. 17894170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 1797e70829632f82de15db187845666aaca6e04b792Chris Lattner void hoist(Instruction &I); 180e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 181a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it 182a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// is not a trapping instruction or if it is a trapping instruction and is 183a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// guaranteed to execute. 1849966c03aad031f738718bed3bc00371e358beb5dTanya Lattner /// 185a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isSafeToExecuteUnconditionally(Instruction &I); 1869966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 18794170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// pointerInvalidatedByLoop - Return true if the body of this loop may 18894170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// store into the memory location pointed to by V. 189fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman /// 190f3e1d6977ee5fb6b66df314d65e28e2c35d6e244Chris Lattner bool pointerInvalidatedByLoop(Value *V, unsigned Size) { 1910252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Check to see if any of the basic blocks in CurLoop invalidate *V. 192f3e1d6977ee5fb6b66df314d65e28e2c35d6e244Chris Lattner return CurAST->getAliasSetForPointer(V, Size).isMod(); 1932e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 194f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner 195a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool canSinkOrHoistInst(Instruction &I); 196a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isNotUsedInLoop(Instruction &I); 197e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 198e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner void PromoteAliasSet(AliasSet &AS); 199e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner }; 200e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 201e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 202844731a7f1909f55935e3514c9e713a62d67662eDan Gohmanchar LICM::ID = 0; 2032ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_BEGIN(LICM, "licm", "Loop Invariant Code Motion", false, false) 2042ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_DEPENDENCY(DominatorTree) 2052ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_DEPENDENCY(LoopInfo) 2062ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_DEPENDENCY(ScalarEvolution) 2072ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_DEPENDENCY(LoopSimplify) 2082ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_AG_DEPENDENCY(AliasAnalysis) 2092ab36d350293c77fc8941ce1023e4899df7e3a82Owen AndersonINITIALIZE_PASS_END(LICM, "licm", "Loop Invariant Code Motion", false, false) 210844731a7f1909f55935e3514c9e713a62d67662eDan Gohman 211394f0441e06dafca29f0752cf400990a5b8fe4b1Daniel DunbarPass *llvm::createLICMPass() { return new LICM(); } 212e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2138d246f09cb46fe38aa71d2a4edcd84f30c4bf80eDevang Patel/// Hoist expressions out of the specified loop. Note, alias info for inner 2148d246f09cb46fe38aa71d2a4edcd84f30c4bf80eDevang Patel/// loop is not preserved so it is not a good idea to run LICM multiple 2158d246f09cb46fe38aa71d2a4edcd84f30c4bf80eDevang Patel/// times on one loop. 21694170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 21754959d6cf68a9b575c98c074babe9867682a7271Devang Patelbool LICM::runOnLoop(Loop *L, LPPassManager &LPM) { 2182e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Changed = false; 219e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2202e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Get our Loop and Alias Analysis information... 2212e6e741b737960ecd0b68610875050019aac0f07Chris Lattner LI = &getAnalysis<LoopInfo>(); 222f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner AA = &getAnalysis<AliasAnalysis>(); 2233a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson DT = &getAnalysis<DominatorTree>(); 224f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner 22554959d6cf68a9b575c98c074babe9867682a7271Devang Patel CurAST = new AliasSetTracker(*AA); 2264282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // Collect Alias info from subloops. 22754959d6cf68a9b575c98c074babe9867682a7271Devang Patel for (Loop::iterator LoopItr = L->begin(), LoopItrE = L->end(); 22854959d6cf68a9b575c98c074babe9867682a7271Devang Patel LoopItr != LoopItrE; ++LoopItr) { 22954959d6cf68a9b575c98c074babe9867682a7271Devang Patel Loop *InnerL = *LoopItr; 2304282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner AliasSetTracker *InnerAST = LoopToAliasSetMap[InnerL]; 2314282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner assert(InnerAST && "Where is my AST?"); 23294170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner 23354959d6cf68a9b575c98c074babe9867682a7271Devang Patel // What if InnerLoop was modified by other passes ? 23454959d6cf68a9b575c98c074babe9867682a7271Devang Patel CurAST->add(*InnerAST); 2354282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner 2364282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // Once we've incorporated the inner loop's AST into ours, we don't need the 2374282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // subloop's anymore. 2384282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner delete InnerAST; 2394282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner LoopToAliasSetMap.erase(InnerL); 2402e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 24154959d6cf68a9b575c98c074babe9867682a7271Devang Patel 242e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner CurLoop = L; 243e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 24499a57216a935a512c418032f590a4660bad9d846Chris Lattner // Get the preheader block to move instructions into... 24599a57216a935a512c418032f590a4660bad9d846Chris Lattner Preheader = L->getLoopPreheader(); 24699a57216a935a512c418032f590a4660bad9d846Chris Lattner 2472e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Loop over the body of this loop, looking for calls, invokes, and stores. 2480252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Because subloops have already been incorporated into AST, we skip blocks in 2492e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // subloops. 2502e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 2519b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 2529b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman I != E; ++I) { 2539b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman BasicBlock *BB = *I; 2544282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner if (LI->getLoopFor(BB) == L) // Ignore blocks in subloops. 2559b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman CurAST->add(*BB); // Incorporate the specified basic block 2569b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman } 2572e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 258e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // We want to visit all of the instructions in this loop... that are not parts 259e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // of our subloops (they have already had their invariants hoisted out of 260e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // their loop, into this loop, so there is no need to process the BODIES of 261e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // the subloops). 262e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // 263952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // Traverse the body of the loop in depth first order on the dominator tree so 264952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // that we are guaranteed to see definitions before we see uses. This allows 265af5cbc82bb6410129425c98bbfc1ffc4c3d0f411Nick Lewycky // us to sink instructions in one pass, without iteration. After sinking 266e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // instructions, we perform another pass to hoist them out of the loop. 267952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // 26803e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman if (L->hasDedicatedExits()) 26903e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman SinkRegion(DT->getNode(L->getHeader())); 27003e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman if (Preheader) 27103e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman HoistRegion(DT->getNode(L->getHeader())); 272e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2732e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Now that all loop invariants have been removed from the loop, promote any 274e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // memory references to scalars that we can. 275e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!DisablePromotion && Preheader && L->hasDedicatedExits()) { 276e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Loop over all of the alias sets in the tracker object. 277e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end(); 278e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner I != E; ++I) 279e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner PromoteAliasSet(*I); 280e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 281e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 282e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // Clear out loops state information for the next iteration 283e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner CurLoop = 0; 28499a57216a935a512c418032f590a4660bad9d846Chris Lattner Preheader = 0; 28554959d6cf68a9b575c98c074babe9867682a7271Devang Patel 2864282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // If this loop is nested inside of another one, save the alias information 2874282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // for when we process the outer loop. 2884282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner if (L->getParentLoop()) 2894282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner LoopToAliasSetMap[L] = CurAST; 2904282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner else 2914282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner delete CurAST; 29254959d6cf68a9b575c98c074babe9867682a7271Devang Patel return Changed; 293e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 294e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 295e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// SinkRegion - Walk the specified region of the CFG (defined by all blocks 296e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// dominated by the specified block, and that are in the current loop) in 2973a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson/// reverse depth first order w.r.t the DominatorTree. This allows us to visit 298e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// uses before definitions, allowing us to sink a loop body in one pass without 299e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// iteration. 300e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// 30126042420d642e810f5cdfb2da6156b74aaf80945Devang Patelvoid LICM::SinkRegion(DomTreeNode *N) { 3023a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson assert(N != 0 && "Null dominator tree node?"); 3033a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson BasicBlock *BB = N->getBlock(); 304e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 305e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // If this subregion is not in the top level loop at all, exit. 306e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner if (!CurLoop->contains(BB)) return; 307e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 3080de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner // We are processing blocks in reverse dfo, so process children first. 30926042420d642e810f5cdfb2da6156b74aaf80945Devang Patel const std::vector<DomTreeNode*> &Children = N->getChildren(); 310e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner for (unsigned i = 0, e = Children.size(); i != e; ++i) 311e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner SinkRegion(Children[i]); 312e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 313e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Only need to process the contents of this block if it is not part of a 314e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // subloop (which would already have been processed). 315e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner if (inSubLoop(BB)) return; 316e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 317a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner for (BasicBlock::iterator II = BB->end(); II != BB->begin(); ) { 318a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner Instruction &I = *--II; 3190de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner 3200de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner // If the instruction is dead, we would try to sink it because it isn't used 3210de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner // in the loop, instead, just delete it. 3220de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner if (isInstructionTriviallyDead(&I)) { 323cb7f65342291caa3636cb50c0ee04b383cd79f8dChris Lattner DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n'); 3240de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner ++II; 3250de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner CurAST->deleteValue(&I); 3260de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner I.eraseFromParent(); 3270de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner Changed = true; 3280de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner continue; 3290de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner } 330fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 331e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Check to see if we can sink this instruction to the exit blocks 332e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // of the loop. We can do this if the all users of the instruction are 333e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // outside of the loop. In this case, it doesn't even matter if the 334e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // operands of the instruction are loop invariant. 335e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // 33670ac2dcb841dc62f08e16f0b0e2cefbf01baa4c5Chris Lattner if (isNotUsedInLoop(I) && canSinkOrHoistInst(I)) { 337a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner ++II; 338e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner sink(I); 339a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner } 340e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner } 341e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner} 342e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 343952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// HoistRegion - Walk the specified region of the CFG (defined by all blocks 344952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// dominated by the specified block, and that are in the current loop) in depth 3453a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson/// first order w.r.t the DominatorTree. This allows us to visit definitions 346952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// before uses, allowing us to hoist a loop body in one pass without iteration. 347952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// 34826042420d642e810f5cdfb2da6156b74aaf80945Devang Patelvoid LICM::HoistRegion(DomTreeNode *N) { 3493a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson assert(N != 0 && "Null dominator tree node?"); 3503a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson BasicBlock *BB = N->getBlock(); 351952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 352b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner // If this subregion is not in the top level loop at all, exit. 353ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (!CurLoop->contains(BB)) return; 354952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 355a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Only need to process the contents of this block if it is not part of a 356a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // subloop (which would already have been processed). 357ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (!inSubLoop(BB)) 358a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ) { 359a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Instruction &I = *II++; 360fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 3612ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner // Try constant folding this instruction. If all the operands are 3622ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner // constants, it is technically hoistable, but it would be better to just 3632ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner // fold it. 3642ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner if (Constant *C = ConstantFoldInstruction(&I)) { 3652ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner DEBUG(dbgs() << "LICM folding inst: " << I << " --> " << *C << '\n'); 3662ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner CurAST->copyValue(&I, C); 3672ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner CurAST->deleteValue(&I); 3682ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner I.replaceAllUsesWith(C); 3692ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner I.eraseFromParent(); 3702ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner continue; 3712ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner } 3722ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner 373e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Try hoisting the instruction out to the preheader. We can only do this 374e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // if all of the operands of the instruction are loop invariant and if it 375e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // is safe to hoist the instruction. 376e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // 377adc799112dc180b3cd099038c05101b85d217716Chris Lattner if (CurLoop->hasLoopInvariantOperands(&I) && canSinkOrHoistInst(I) && 378e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner isSafeToExecuteUnconditionally(I)) 3793c80a51cfd5e7187439ce4c051da77ee46e0ff9aChris Lattner hoist(I); 3802ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner } 381952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 38226042420d642e810f5cdfb2da6156b74aaf80945Devang Patel const std::vector<DomTreeNode*> &Children = N->getChildren(); 383952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner for (unsigned i = 0, e = Children.size(); i != e; ++i) 38456b7ee20dad7160a117ea0d102fc5432074ce2d0Chris Lattner HoistRegion(Children[i]); 385952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner} 386952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 387a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// canSinkOrHoistInst - Return true if the hoister and sinker can handle this 388a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// instruction. 389a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 390a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::canSinkOrHoistInst(Instruction &I) { 391ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // Loads have extra constraints we have to verify before we can hoist them. 392ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { 393ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (LI->isVolatile()) 394ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner return false; // Don't hoist volatile loads! 395ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 396967948b4e25cae3de68f38fddaa75d838e676decChris Lattner // Loads from constant memory are always safe to move, even if they end up 397967948b4e25cae3de68f38fddaa75d838e676decChris Lattner // in the same alias set as something that ends up being modified. 398dab249b3b762cff0ff16069b3233e4c885e75347Dan Gohman if (AA->pointsToConstantMemory(LI->getOperand(0))) 399967948b4e25cae3de68f38fddaa75d838e676decChris Lattner return true; 400967948b4e25cae3de68f38fddaa75d838e676decChris Lattner 401ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // Don't hoist loads which have may-aliased stores in loop. 402f3e1d6977ee5fb6b66df314d65e28e2c35d6e244Chris Lattner unsigned Size = 0; 403f3e1d6977ee5fb6b66df314d65e28e2c35d6e244Chris Lattner if (LI->getType()->isSized()) 404fc2a3ed0c9e32cf7edaf5030fa0972b916cc5f0bDan Gohman Size = AA->getTypeStoreSize(LI->getType()); 405f3e1d6977ee5fb6b66df314d65e28e2c35d6e244Chris Lattner return !pointerInvalidatedByLoop(LI->getOperand(0), Size); 406118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } else if (CallInst *CI = dyn_cast<CallInst>(&I)) { 407118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // Handle obvious cases efficiently. 408dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands AliasAnalysis::ModRefBehavior Behavior = AA->getModRefBehavior(CI); 409dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands if (Behavior == AliasAnalysis::DoesNotAccessMemory) 410dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands return true; 411dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands else if (Behavior == AliasAnalysis::OnlyReadsMemory) { 412dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands // If this call only reads from memory and there are no writes to memory 413dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands // in the loop, we can hoist or sink the call as appropriate. 414dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands bool FoundMod = false; 415dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end(); 416dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands I != E; ++I) { 417dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands AliasSet &AS = *I; 418dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands if (!AS.isForwardingAliasSet() && AS.isMod()) { 419dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands FoundMod = true; 420dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands break; 421118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 422118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 423dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands if (!FoundMod) return true; 424118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 425118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner 426118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // FIXME: This should use mod/ref information to see if we can hoist or sink 427118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // the call. 428fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 429118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner return false; 430ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner } 431ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 4323da59db637a887474c1b1346c1f3ccf53b6c4663Reid Spencer // Otherwise these instructions are hoistable/sinkable 433832254e1c2387c0cbeb0a820b8315fbe85cb003aReid Spencer return isa<BinaryOperator>(I) || isa<CastInst>(I) || 434d8af90c1da64b81a7aa167b5adcc1e81b0741252Dan Gohman isa<SelectInst>(I) || isa<GetElementPtrInst>(I) || isa<CmpInst>(I) || 435d8af90c1da64b81a7aa167b5adcc1e81b0741252Dan Gohman isa<InsertElementInst>(I) || isa<ExtractElementInst>(I) || 436d8af90c1da64b81a7aa167b5adcc1e81b0741252Dan Gohman isa<ShuffleVectorInst>(I); 437a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 438a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 439a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isNotUsedInLoop - Return true if the only users of this instruction are 440a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// outside of the loop. If this is true, we can sink the instruction to the 441a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// exit blocks of the loop. 442a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 443a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isNotUsedInLoop(Instruction &I) { 444ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner for (Value::use_iterator UI = I.use_begin(), E = I.use_end(); UI != E; ++UI) { 445ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner Instruction *User = cast<Instruction>(*UI); 446ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (PHINode *PN = dyn_cast<PHINode>(User)) { 447ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner // PHI node uses occur in predecessor blocks! 448ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 449ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (PN->getIncomingValue(i) == &I) 450ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (CurLoop->contains(PN->getIncomingBlock(i))) 451ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner return false; 45292329c7fbe572892c17aa2d2542a10e3ea16132fDan Gohman } else if (CurLoop->contains(User)) { 453a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 454ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } 455ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } 456a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 457a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 458a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 459a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 460a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// sink - When an instruction is found to only be used outside of the loop, 461a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// this function moves it to the exit blocks and patches up SSA form as needed. 462a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// This method is guaranteed to remove the original instruction from its 463a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// position, and may either delete it or move it to outside of the loop. 464a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 465a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnervoid LICM::sink(Instruction &I) { 46639a383124b70dda1fea18288235114029ede76cfNick Lewycky DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n"); 467a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 468b7211a2ce13a0365e0e1dd2f27adda2ee3d1288bDevang Patel SmallVector<BasicBlock*, 8> ExitBlocks; 469d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner CurLoop->getUniqueExitBlocks(ExitBlocks); 470df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner 471df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner if (isa<LoadInst>(I)) ++NumMovedLoads; 472118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner else if (isa<CallInst>(I)) ++NumMovedCalls; 473df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner ++NumSunk; 474df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner Changed = true; 475df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner 476a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The case where there is only a single exit node of this loop is common 477a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // enough that we handle it as a special (more efficient) case. It is more 478a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // efficient to handle because there are no PHI nodes that need to be placed. 479a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (ExitBlocks.size() == 1) { 480a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[0], I.getParent())) { 481a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Instruction is not used, just delete it. 4822741c971044d2165be572749b94398043caccfebChris Lattner CurAST->deleteValue(&I); 4831bf5ebc7be0d5b05e4175c7adb767b38896adef1Devang Patel // If I has users in unreachable blocks, eliminate. 484228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // If I is not void type then replaceAllUsesWith undef. 485228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // This allows ValueHandlers and custom metadata to adjust itself. 486a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 487228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel I.replaceAllUsesWith(UndefValue::get(I.getType())); 4883c80a51cfd5e7187439ce4c051da77ee46e0ff9aChris Lattner I.eraseFromParent(); 489a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 490a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Move the instruction to the start of the exit block, after any PHI 491a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // nodes in it. 492d9a5daeb7719c83136c0dc43d6ef732402d1a1b5Chris Lattner I.moveBefore(ExitBlocks[0]->getFirstNonPHI()); 4934282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner 4944282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // This instruction is no longer in the AST for the current loop, because 4954282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // we just sunk it out of the loop. If we just sunk it into an outer 4964282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // loop, we will rediscover the operation when we process it. 4974282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner CurAST->deleteValue(&I); 498a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 499d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner return; 500d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 501d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 502d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner if (ExitBlocks.empty()) { 503a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The instruction is actually dead if there ARE NO exit blocks. 5042741c971044d2165be572749b94398043caccfebChris Lattner CurAST->deleteValue(&I); 5051bf5ebc7be0d5b05e4175c7adb767b38896adef1Devang Patel // If I has users in unreachable blocks, eliminate. 506228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // If I is not void type then replaceAllUsesWith undef. 507228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // This allows ValueHandlers and custom metadata to adjust itself. 508a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 509228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel I.replaceAllUsesWith(UndefValue::get(I.getType())); 5103c80a51cfd5e7187439ce4c051da77ee46e0ff9aChris Lattner I.eraseFromParent(); 511d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner return; 512d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 513d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 514a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Otherwise, if we have multiple exits, use the SSAUpdater to do all of the 515a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // hard work of inserting PHI nodes as necessary. 516a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SmallVector<PHINode*, 8> NewPHIs; 517a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SSAUpdater SSA(&NewPHIs); 518a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 519a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 520fc6e29d4ab52b7d3efd83846ed495a9ca7e51e49Duncan Sands SSA.Initialize(I.getType(), I.getName()); 521d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 522a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Insert a copy of the instruction in each exit block of the loop that is 523a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // dominated by the instruction. Each exit block is known to only be in the 524a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // ExitBlocks list once. 525a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner BasicBlock *InstOrigBB = I.getParent(); 526d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner unsigned NumInserted = 0; 527a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 528d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 529d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner BasicBlock *ExitBlock = ExitBlocks[i]; 530a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 531d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner if (!isExitBlockDominatedByBlockInLoop(ExitBlock, InstOrigBB)) 532d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner continue; 533d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 534a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Insert the code after the last PHI node. 535d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner BasicBlock::iterator InsertPt = ExitBlock->getFirstNonPHI(); 536a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 537d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // If this is the first exit block processed, just move the original 538d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // instruction, otherwise clone the original instruction and insert 539d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // the copy. 540d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner Instruction *New; 541a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (NumInserted++ == 0) { 542a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner I.moveBefore(InsertPt); 543d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner New = &I; 544d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } else { 545d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner New = I.clone(); 546d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner if (!I.getName().empty()) 547d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner New->setName(I.getName()+".le"); 548d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner ExitBlock->getInstList().insert(InsertPt, New); 549a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 550d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 551a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Now that we have inserted the instruction, inform SSAUpdater. 552a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 553a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SSA.AddAvailableValue(ExitBlock, New); 554d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 555a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 556d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // If the instruction doesn't dominate any exit blocks, it must be dead. 557d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner if (NumInserted == 0) { 558d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner CurAST->deleteValue(&I); 559a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 560a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner I.replaceAllUsesWith(UndefValue::get(I.getType())); 561d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner I.eraseFromParent(); 562a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner return; 563d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 564a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 565a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Next, rewrite uses of the instruction, inserting PHI nodes as needed. 566a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; ) { 567a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Grab the use before incrementing the iterator. 568a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner Use &U = UI.getUse(); 569a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Increment the iterator before removing the use from the list. 570a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner ++UI; 571a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SSA.RewriteUseAfterInsertions(U); 572a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 573a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 574a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Update CurAST for NewPHIs if I had pointer type. 575a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (I.getType()->isPointerTy()) 576a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i) 5779c282011e6b7a6e23a3a163ec9c865890449e8dcChris Lattner CurAST->copyValue(&I, NewPHIs[i]); 57898917503c702e16f35ccdec3f6b4c48e5c4759acChris Lattner 57998917503c702e16f35ccdec3f6b4c48e5c4759acChris Lattner // Finally, remove the instruction from CurAST. It is no longer in the loop. 58098917503c702e16f35ccdec3f6b4c48e5c4759acChris Lattner CurAST->deleteValue(&I); 581a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 582952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 58394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// hoist - When an instruction is found to only use loop invariant operands 58494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// that is safe to hoist, this instruction is called to do the dirty work. 58594170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 586a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnervoid LICM::hoist(Instruction &I) { 587f15826999bc560ee6f67cff5ecd71bf9cce7a7aaDavid Greene DEBUG(dbgs() << "LICM hoisting to " << Preheader->getName() << ": " 58867d1d1f8322bdc460158888cd233be8d1cb1d4abEvan Cheng << I << "\n"); 589ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 590d9a5daeb7719c83136c0dc43d6ef732402d1a1b5Chris Lattner // Move the new node to the Preheader, before its terminator. 591d9a5daeb7719c83136c0dc43d6ef732402d1a1b5Chris Lattner I.moveBefore(Preheader->getTerminator()); 592fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 593a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (isa<LoadInst>(I)) ++NumMovedLoads; 594118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner else if (isa<CallInst>(I)) ++NumMovedCalls; 5959646e6b6af1f924f9366a2bffc6dde102f84d231Chris Lattner ++NumHoisted; 596e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner Changed = true; 597e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 598e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 599a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it is 600a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// not a trapping instruction or if it is a trapping instruction and is 601a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// guaranteed to execute. 6029966c03aad031f738718bed3bc00371e358beb5dTanya Lattner/// 603a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) { 60492094b4d928119eceac1484331acffe950f4651cChris Lattner // If it is not a trapping instruction, it is always safe to hoist. 6050b79a7727d68a507837e827803859424cf3d997bEli Friedman if (Inst.isSafeToSpeculativelyExecute()) 6060b79a7727d68a507837e827803859424cf3d997bEli Friedman return true; 607fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 60892094b4d928119eceac1484331acffe950f4651cChris Lattner // Otherwise we have to check to make sure that the instruction dominates all 60992094b4d928119eceac1484331acffe950f4651cChris Lattner // of the exit blocks. If it doesn't, then there is a path out of the loop 61092094b4d928119eceac1484331acffe950f4651cChris Lattner // which does not execute this instruction, so we can't hoist it. 61192094b4d928119eceac1484331acffe950f4651cChris Lattner 61292094b4d928119eceac1484331acffe950f4651cChris Lattner // If the instruction is in the header block for the loop (which is very 61392094b4d928119eceac1484331acffe950f4651cChris Lattner // common), it is always guaranteed to dominate the exit blocks. Since this 61492094b4d928119eceac1484331acffe950f4651cChris Lattner // is a common case, and can save some work, check it now. 615a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (Inst.getParent() == CurLoop->getHeader()) 61692094b4d928119eceac1484331acffe950f4651cChris Lattner return true; 61792094b4d928119eceac1484331acffe950f4651cChris Lattner 61892094b4d928119eceac1484331acffe950f4651cChris Lattner // Get the exit blocks for the current loop. 619b7211a2ce13a0365e0e1dd2f27adda2ee3d1288bDevang Patel SmallVector<BasicBlock*, 8> ExitBlocks; 6205fa802fe279f10f402e039bc931aa57c0e424bf5Chris Lattner CurLoop->getExitBlocks(ExitBlocks); 6219966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 6223a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson // For each exit block, get the DT node and walk up the DT until the 62392094b4d928119eceac1484331acffe950f4651cChris Lattner // instruction's basic block is found or we exit the loop. 624a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 625a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[i], Inst.getParent())) 626a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 627fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 6289966c03aad031f738718bed3bc00371e358beb5dTanya Lattner return true; 6299966c03aad031f738718bed3bc00371e358beb5dTanya Lattner} 6309966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 631e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner/// PromoteAliasSet - Try to promote memory values to scalars by sinking 6322e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// stores out of the loop and moving loads to before the loop. We do this by 6332e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// looping over the stores in the loop, looking for stores to Must pointers 634e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner/// which are loop invariant. 6352e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// 636e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattnervoid LICM::PromoteAliasSet(AliasSet &AS) { 637e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // We can promote this alias set if it has a store, if it is a "Must" alias 638e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // set, if the pointer is loop invariant, and if we are not eliminating any 639e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // volatile loads or stores. 640e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() || 641e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner AS.isVolatile() || !CurLoop->isLoopInvariant(AS.begin()->getValue())) 642e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; 643e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 644e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner assert(!AS.empty() && 645e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner "Must alias set should have at least one pointer element in it!"); 646e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *SomePtr = AS.begin()->getValue(); 647fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 648e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // It isn't safe to promote a load/store from the loop if the load/store is 649e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // conditional. For example, turning: 6502e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 651e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // for () { if (c) *P += 1; } 6522e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 653e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // into: 654e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // 655e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // tmp = *P; for () { if (c) tmp +=1; } *P = tmp; 656e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // 657e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // is not safe, because *P may only be valid to access if 'c' is true. 658e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // 659e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // It is safe to promote P if all uses are direct load/stores and if at 660e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // least one is guaranteed to be executed. 661e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner bool GuaranteedToExecute = false; 662e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 663e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallVector<Instruction*, 64> LoopUses; 664e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallPtrSet<Value*, 4> PointerMustAliases; 665e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 666e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Check that all of the pointers in the alias set have the same type. We 667e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // cannot (yet) promote a memory location that is loaded and stored in 668e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // different sizes. 669e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) { 670e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *ASIV = ASI->getValue(); 671e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner PointerMustAliases.insert(ASIV); 67229d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner 67329d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner // Check that all of the pointers in the alias set have the same type. We 67429d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner // cannot (yet) promote a memory location that is loaded and stored in 67529d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner // different sizes. 676e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (SomePtr->getType() != ASIV->getType()) 677e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; 678e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 679e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (Value::use_iterator UI = ASIV->use_begin(), UE = ASIV->use_end(); 68019d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner UI != UE; ++UI) { 681e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Ignore instructions that are outside the loop. 68229d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner Instruction *Use = dyn_cast<Instruction>(*UI); 68392329c7fbe572892c17aa2d2542a10e3ea16132fDan Gohman if (!Use || !CurLoop->contains(Use)) 68429d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner continue; 685e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 686e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If there is an non-load/store instruction in the loop, we can't promote 687e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // it. 688e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (isa<LoadInst>(Use)) 689e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner assert(!cast<LoadInst>(Use)->isVolatile() && "AST broken"); 6900cccd7633e4a0ba36b5ff9a3dfda2a09d16dc337Chris Lattner else if (isa<StoreInst>(Use)) { 6910cccd7633e4a0ba36b5ff9a3dfda2a09d16dc337Chris Lattner assert(!cast<StoreInst>(Use)->isVolatile() && "AST broken"); 6920cccd7633e4a0ba36b5ff9a3dfda2a09d16dc337Chris Lattner if (Use->getOperand(0) == ASIV) return; 6930cccd7633e4a0ba36b5ff9a3dfda2a09d16dc337Chris Lattner } else 694e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; // Not a load or store. 69519d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner 69619d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner if (!GuaranteedToExecute) 69719d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner GuaranteedToExecute = isSafeToExecuteUnconditionally(*Use); 698e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 699e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LoopUses.push_back(Use); 70029d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner } 701e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 702e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 703e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If there isn't a guaranteed-to-execute instruction, we can't promote. 704e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!GuaranteedToExecute) 705e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; 706e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 707e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Otherwise, this is safe to promote, lets do it! 708e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " <<*SomePtr<<'\n'); 709e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Changed = true; 710e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner ++NumPromoted; 711bc2265abe1d1b830995bb2f6322409bc7d7c5740Devang Patel 712e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // We use the SSAUpdater interface to insert phi nodes as required. 713e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallVector<PHINode*, 16> NewPHIs; 714e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SSAUpdater SSA(&NewPHIs); 715e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 716e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // It wants to know some value of the same type as what we'll be inserting. 717e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *SomeValue; 718e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (isa<LoadInst>(LoopUses[0])) 719e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SomeValue = LoopUses[0]; 720e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner else 721e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SomeValue = cast<StoreInst>(LoopUses[0])->getOperand(0); 722fc6e29d4ab52b7d3efd83846ed495a9ca7e51e49Duncan Sands SSA.Initialize(SomeValue->getType(), SomeValue->getName()); 723e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 724e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // First step: bucket up uses of the pointers by the block they occur in. 725e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // This is important because we have to handle multiple defs/uses in a block 726e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // ourselves: SSAUpdater is purely for cross-block references. 727e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // FIXME: Want a TinyVector<Instruction*> since there is usually 0/1 element. 728e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner DenseMap<BasicBlock*, std::vector<Instruction*> > UsesByBlock; 729e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = LoopUses.size(); i != e; ++i) { 730e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Instruction *User = LoopUses[i]; 731e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner UsesByBlock[User->getParent()].push_back(User); 732e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 733e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 734e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Okay, now we can iterate over all the blocks in the loop with uses, 735e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // processing them. Keep track of which loads are loading a live-in value. 736e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallVector<LoadInst*, 32> LiveInLoads; 737469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner DenseMap<Value*, Value*> ReplacedLoads; 738e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 739e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned LoopUse = 0, e = LoopUses.size(); LoopUse != e; ++LoopUse) { 740e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Instruction *User = LoopUses[LoopUse]; 741e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner std::vector<Instruction*> &BlockUses = UsesByBlock[User->getParent()]; 742e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 743e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If this block has already been processed, ignore this repeat use. 744e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (BlockUses.empty()) continue; 745e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 746e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Okay, this is the first use in the block. If this block just has a 747e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // single user in it, we can rewrite it trivially. 748e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (BlockUses.size() == 1) { 749e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If it is a store, it is a trivial def of the value in the block. 750e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (isa<StoreInst>(User)) { 751e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SSA.AddAvailableValue(User->getParent(), 752e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner cast<StoreInst>(User)->getOperand(0)); 753e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } else { 754e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Otherwise it is a load, queue it to rewrite as a live-in load. 755e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LiveInLoads.push_back(cast<LoadInst>(User)); 756e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 757e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner BlockUses.clear(); 75829d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner continue; 759e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 760e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 761e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Otherwise, check to see if this block is all loads. If so, we can queue 762e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // them all as live in loads. 763e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner bool HasStore = false; 764e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = BlockUses.size(); i != e; ++i) { 765e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (isa<StoreInst>(BlockUses[i])) { 766e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner HasStore = true; 767e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner break; 768e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 769e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 77029d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner 771e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!HasStore) { 772e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = BlockUses.size(); i != e; ++i) 773e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LiveInLoads.push_back(cast<LoadInst>(BlockUses[i])); 774e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner BlockUses.clear(); 775e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner continue; 776e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 777e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 778e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Otherwise, we have mixed loads and stores (or just a bunch of stores). 779e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Since SSAUpdater is purely for cross-block values, we need to determine 780e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // the order of these instructions in the block. If the first use in the 781e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // block is a load, then it uses the live in value. The last store defines 782e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // the live out value. We handle this by doing a linear scan of the block. 783e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner BasicBlock *BB = User->getParent(); 784e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *StoredValue = 0; 785e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) { 786e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (LoadInst *L = dyn_cast<LoadInst>(II)) { 787469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // If this is a load from an unrelated pointer, ignore it. 788e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!PointerMustAliases.count(L->getOperand(0))) continue; 789e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 790e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If we haven't seen a store yet, this is a live in use, otherwise 791e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // use the stored value. 792469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner if (StoredValue) { 793e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner L->replaceAllUsesWith(StoredValue); 794469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner ReplacedLoads[L] = StoredValue; 795469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner } else { 796e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LiveInLoads.push_back(L); 797469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner } 798e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner continue; 799e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 800e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 801e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (StoreInst *S = dyn_cast<StoreInst>(II)) { 802445560881898fe212c185bd4c0485140d7b4fc88Chris Lattner // If this is a store to an unrelated pointer, ignore it. 803e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!PointerMustAliases.count(S->getOperand(1))) continue; 804fb3ee1930bfd0902f5fa3e6526775e3791e38d3cChris Lattner 805e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Remember that this is the active value in the block. 806e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner StoredValue = S->getOperand(0); 807e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 808e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 809e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 810e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // The last stored value that happened is the live-out for the block. 811e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner assert(StoredValue && "Already checked that there is a store in block"); 812e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SSA.AddAvailableValue(BB, StoredValue); 813e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner BlockUses.clear(); 814e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 815e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 816e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Now that all the intra-loop values are classified, set up the preheader. 817e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // It gets a load of the pointer we're promoting, and it is the live-out value 818e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // from the preheader. 819e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LoadInst *PreheaderLoad = new LoadInst(SomePtr,SomePtr->getName()+".promoted", 820e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Preheader->getTerminator()); 821e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SSA.AddAvailableValue(Preheader, PreheaderLoad); 822e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 823e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Now that the preheader is good to go, set up the exit blocks. Each exit 824e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // block gets a store of the live-out values that feed them. Since we've 825e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // already told the SSA updater about the defs in the loop and the preheader 826e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // definition, it is all set and we can start using it. 827e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallVector<BasicBlock*, 8> ExitBlocks; 828e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner CurLoop->getUniqueExitBlocks(ExitBlocks); 829e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 830e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner BasicBlock *ExitBlock = ExitBlocks[i]; 831e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock); 832e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Instruction *InsertPos = ExitBlock->getFirstNonPHI(); 833e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner new StoreInst(LiveInValue, SomePtr, InsertPos); 834e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 835fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 836e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Okay, now we rewrite all loads that use live-in values in the loop, 837e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // inserting PHI nodes as necessary. 838e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = LiveInLoads.size(); i != e; ++i) { 839e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LoadInst *ALoad = LiveInLoads[i]; 8409c282011e6b7a6e23a3a163ec9c865890449e8dcChris Lattner Value *NewVal = SSA.GetValueInMiddleOfBlock(ALoad->getParent()); 8419c282011e6b7a6e23a3a163ec9c865890449e8dcChris Lattner ALoad->replaceAllUsesWith(NewVal); 8429c282011e6b7a6e23a3a163ec9c865890449e8dcChris Lattner CurAST->copyValue(ALoad, NewVal); 843469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner ReplacedLoads[ALoad] = NewVal; 844e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 845e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 8467abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner // If the preheader load is itself a pointer, we need to tell alias analysis 8477abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner // about the new pointer we created in the preheader block and about any PHI 8487abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner // nodes that just got inserted. 8497abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner if (PreheaderLoad->getType()->isPointerTy()) { 8507abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner // Copy any value stored to or loaded from a must-alias of the pointer. 8517abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner CurAST->copyValue(SomeValue, PreheaderLoad); 8527abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner 8537abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i) 8547abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner CurAST->copyValue(SomeValue, NewPHIs[i]); 8557abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner } 8567abdb22e52e2122cb04479a1129dc68916dece4cChris Lattner 857e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Now that everything is rewritten, delete the old instructions from the body 858e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // of the loop. They should all be dead now. 859e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = LoopUses.size(); i != e; ++i) { 860e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Instruction *User = LoopUses[i]; 861469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner 862469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // If this is a load that still has uses, then the load must have been added 863469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // as a live value in the SSAUpdate data structure for a block (e.g. because 864469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // the loaded value was stored later). In this case, we need to recursively 865469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // propagate the updates until we get to the real value. 866469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner if (!User->use_empty()) { 867469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner Value *NewVal = ReplacedLoads[User]; 868469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner assert(NewVal && "not a replaced load?"); 869469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner 870469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // Propagate down to the ultimate replacee. The intermediately loads 871469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // could theoretically already have been deleted, so we don't want to 872469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // dereference the Value*'s. 873469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner DenseMap<Value*, Value*>::iterator RLI = ReplacedLoads.find(NewVal); 874469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner while (RLI != ReplacedLoads.end()) { 875469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner NewVal = RLI->second; 876469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner RLI = ReplacedLoads.find(NewVal); 877469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner } 878469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner 879469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner User->replaceAllUsesWith(NewVal); 880469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner CurAST->copyValue(User, NewVal); 881469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner } 882469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner 883e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner CurAST->deleteValue(User); 884e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner User->eraseFromParent(); 885e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 886e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 887e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // fwew, we're done! 888f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner} 88991d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 890e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 89191d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel/// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info. 89291d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patelvoid LICM::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, Loop *L) { 8934282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner AliasSetTracker *AST = LoopToAliasSetMap.lookup(L); 89491d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel if (!AST) 89591d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel return; 89691d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 89791d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel AST->copyValue(From, To); 89891d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel} 89991d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 90091d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel/// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias 90191d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel/// set. 90291d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patelvoid LICM::deleteAnalysisValue(Value *V, Loop *L) { 9034282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner AliasSetTracker *AST = LoopToAliasSetMap.lookup(L); 90491d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel if (!AST) 90591d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel return; 90691d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 90791d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel AST->deleteValue(V); 90891d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel} 909