LICM.cpp revision adc799112dc180b3cd099038c05101b85d217716
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; 203d13db2c59cc94162d6cf0a04187d408bfef6d4a7Owen AndersonINITIALIZE_PASS(LICM, "licm", "Loop Invariant Code Motion", false, false); 204844731a7f1909f55935e3514c9e713a62d67662eDan Gohman 205394f0441e06dafca29f0752cf400990a5b8fe4b1Daniel DunbarPass *llvm::createLICMPass() { return new LICM(); } 206e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2078d246f09cb46fe38aa71d2a4edcd84f30c4bf80eDevang Patel/// Hoist expressions out of the specified loop. Note, alias info for inner 2088d246f09cb46fe38aa71d2a4edcd84f30c4bf80eDevang Patel/// loop is not preserved so it is not a good idea to run LICM multiple 2098d246f09cb46fe38aa71d2a4edcd84f30c4bf80eDevang Patel/// times on one loop. 21094170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 21154959d6cf68a9b575c98c074babe9867682a7271Devang Patelbool LICM::runOnLoop(Loop *L, LPPassManager &LPM) { 2122e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Changed = false; 213e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2142e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Get our Loop and Alias Analysis information... 2152e6e741b737960ecd0b68610875050019aac0f07Chris Lattner LI = &getAnalysis<LoopInfo>(); 216f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner AA = &getAnalysis<AliasAnalysis>(); 2173a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson DT = &getAnalysis<DominatorTree>(); 218f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner 21954959d6cf68a9b575c98c074babe9867682a7271Devang Patel CurAST = new AliasSetTracker(*AA); 2204282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // Collect Alias info from subloops. 22154959d6cf68a9b575c98c074babe9867682a7271Devang Patel for (Loop::iterator LoopItr = L->begin(), LoopItrE = L->end(); 22254959d6cf68a9b575c98c074babe9867682a7271Devang Patel LoopItr != LoopItrE; ++LoopItr) { 22354959d6cf68a9b575c98c074babe9867682a7271Devang Patel Loop *InnerL = *LoopItr; 2244282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner AliasSetTracker *InnerAST = LoopToAliasSetMap[InnerL]; 2254282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner assert(InnerAST && "Where is my AST?"); 22694170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner 22754959d6cf68a9b575c98c074babe9867682a7271Devang Patel // What if InnerLoop was modified by other passes ? 22854959d6cf68a9b575c98c074babe9867682a7271Devang Patel CurAST->add(*InnerAST); 2294282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner 2304282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // Once we've incorporated the inner loop's AST into ours, we don't need the 2314282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // subloop's anymore. 2324282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner delete InnerAST; 2334282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner LoopToAliasSetMap.erase(InnerL); 2342e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 23554959d6cf68a9b575c98c074babe9867682a7271Devang Patel 236e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner CurLoop = L; 237e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 23899a57216a935a512c418032f590a4660bad9d846Chris Lattner // Get the preheader block to move instructions into... 23999a57216a935a512c418032f590a4660bad9d846Chris Lattner Preheader = L->getLoopPreheader(); 24099a57216a935a512c418032f590a4660bad9d846Chris Lattner 2412e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Loop over the body of this loop, looking for calls, invokes, and stores. 2420252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Because subloops have already been incorporated into AST, we skip blocks in 2432e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // subloops. 2442e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 2459b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 2469b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman I != E; ++I) { 2479b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman BasicBlock *BB = *I; 2484282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner if (LI->getLoopFor(BB) == L) // Ignore blocks in subloops. 2499b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman CurAST->add(*BB); // Incorporate the specified basic block 2509b78763fce4cb418e7a2e672efb84bac25559b79Dan Gohman } 2512e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 252e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // We want to visit all of the instructions in this loop... that are not parts 253e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // of our subloops (they have already had their invariants hoisted out of 254e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // their loop, into this loop, so there is no need to process the BODIES of 255e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // the subloops). 256e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // 257952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // Traverse the body of the loop in depth first order on the dominator tree so 258952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // that we are guaranteed to see definitions before we see uses. This allows 259af5cbc82bb6410129425c98bbfc1ffc4c3d0f411Nick Lewycky // us to sink instructions in one pass, without iteration. After sinking 260e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // instructions, we perform another pass to hoist them out of the loop. 261952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // 26203e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman if (L->hasDedicatedExits()) 26303e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman SinkRegion(DT->getNode(L->getHeader())); 26403e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman if (Preheader) 26503e896bd6073efc4523d8bcd0239d6ed62126db7Dan Gohman HoistRegion(DT->getNode(L->getHeader())); 266e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2672e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Now that all loop invariants have been removed from the loop, promote any 268e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // memory references to scalars that we can. 269e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!DisablePromotion && Preheader && L->hasDedicatedExits()) { 270e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Loop over all of the alias sets in the tracker object. 271e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end(); 272e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner I != E; ++I) 273e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner PromoteAliasSet(*I); 274e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 275e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 276e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // Clear out loops state information for the next iteration 277e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner CurLoop = 0; 27899a57216a935a512c418032f590a4660bad9d846Chris Lattner Preheader = 0; 27954959d6cf68a9b575c98c074babe9867682a7271Devang Patel 2804282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // If this loop is nested inside of another one, save the alias information 2814282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // for when we process the outer loop. 2824282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner if (L->getParentLoop()) 2834282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner LoopToAliasSetMap[L] = CurAST; 2844282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner else 2854282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner delete CurAST; 28654959d6cf68a9b575c98c074babe9867682a7271Devang Patel return Changed; 287e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 288e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 289e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// SinkRegion - Walk the specified region of the CFG (defined by all blocks 290e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// dominated by the specified block, and that are in the current loop) in 2913a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson/// reverse depth first order w.r.t the DominatorTree. This allows us to visit 292e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// uses before definitions, allowing us to sink a loop body in one pass without 293e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// iteration. 294e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// 29526042420d642e810f5cdfb2da6156b74aaf80945Devang Patelvoid LICM::SinkRegion(DomTreeNode *N) { 2963a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson assert(N != 0 && "Null dominator tree node?"); 2973a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson BasicBlock *BB = N->getBlock(); 298e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 299e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // If this subregion is not in the top level loop at all, exit. 300e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner if (!CurLoop->contains(BB)) return; 301e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 3020de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner // We are processing blocks in reverse dfo, so process children first. 30326042420d642e810f5cdfb2da6156b74aaf80945Devang Patel const std::vector<DomTreeNode*> &Children = N->getChildren(); 304e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner for (unsigned i = 0, e = Children.size(); i != e; ++i) 305e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner SinkRegion(Children[i]); 306e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 307e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Only need to process the contents of this block if it is not part of a 308e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // subloop (which would already have been processed). 309e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner if (inSubLoop(BB)) return; 310e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 311a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner for (BasicBlock::iterator II = BB->end(); II != BB->begin(); ) { 312a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner Instruction &I = *--II; 3130de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner 3140de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner // If the instruction is dead, we would try to sink it because it isn't used 3150de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner // in the loop, instead, just delete it. 3160de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner if (isInstructionTriviallyDead(&I)) { 317cb7f65342291caa3636cb50c0ee04b383cd79f8dChris Lattner DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n'); 3180de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner ++II; 3190de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner CurAST->deleteValue(&I); 3200de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner I.eraseFromParent(); 3210de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner Changed = true; 3220de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner continue; 3230de5cad74d8d2987b92b8d76af3f1eab988b3c7bChris Lattner } 324fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 325e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Check to see if we can sink this instruction to the exit blocks 326e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // of the loop. We can do this if the all users of the instruction are 327e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // outside of the loop. In this case, it doesn't even matter if the 328e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // operands of the instruction are loop invariant. 329e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // 33070ac2dcb841dc62f08e16f0b0e2cefbf01baa4c5Chris Lattner if (isNotUsedInLoop(I) && canSinkOrHoistInst(I)) { 331a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner ++II; 332e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner sink(I); 333a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner } 334e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner } 335e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner} 336e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 337952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// HoistRegion - Walk the specified region of the CFG (defined by all blocks 338952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// dominated by the specified block, and that are in the current loop) in depth 3393a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson/// first order w.r.t the DominatorTree. This allows us to visit definitions 340952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// before uses, allowing us to hoist a loop body in one pass without iteration. 341952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// 34226042420d642e810f5cdfb2da6156b74aaf80945Devang Patelvoid LICM::HoistRegion(DomTreeNode *N) { 3433a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson assert(N != 0 && "Null dominator tree node?"); 3443a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson BasicBlock *BB = N->getBlock(); 345952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 346b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner // If this subregion is not in the top level loop at all, exit. 347ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (!CurLoop->contains(BB)) return; 348952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 349a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Only need to process the contents of this block if it is not part of a 350a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // subloop (which would already have been processed). 351ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (!inSubLoop(BB)) 352a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ) { 353a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Instruction &I = *II++; 354fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 3552ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner // Try constant folding this instruction. If all the operands are 3562ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner // constants, it is technically hoistable, but it would be better to just 3572ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner // fold it. 3582ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner if (Constant *C = ConstantFoldInstruction(&I)) { 3592ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner DEBUG(dbgs() << "LICM folding inst: " << I << " --> " << *C << '\n'); 3602ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner CurAST->copyValue(&I, C); 3612ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner CurAST->deleteValue(&I); 3622ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner I.replaceAllUsesWith(C); 3632ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner I.eraseFromParent(); 3642ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner continue; 3652ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner } 3662ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner 367e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Try hoisting the instruction out to the preheader. We can only do this 368e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // if all of the operands of the instruction are loop invariant and if it 369e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // is safe to hoist the instruction. 370e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // 371adc799112dc180b3cd099038c05101b85d217716Chris Lattner if (CurLoop->hasLoopInvariantOperands(&I) && canSinkOrHoistInst(I) && 372e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner isSafeToExecuteUnconditionally(I)) 3733c80a51cfd5e7187439ce4c051da77ee46e0ff9aChris Lattner hoist(I); 3742ac6e2354ac9961b00fa351635ed04baf7fdd234Chris Lattner } 375952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 37626042420d642e810f5cdfb2da6156b74aaf80945Devang Patel const std::vector<DomTreeNode*> &Children = N->getChildren(); 377952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner for (unsigned i = 0, e = Children.size(); i != e; ++i) 37856b7ee20dad7160a117ea0d102fc5432074ce2d0Chris Lattner HoistRegion(Children[i]); 379952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner} 380952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 381a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// canSinkOrHoistInst - Return true if the hoister and sinker can handle this 382a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// instruction. 383a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 384a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::canSinkOrHoistInst(Instruction &I) { 385ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // Loads have extra constraints we have to verify before we can hoist them. 386ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { 387ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (LI->isVolatile()) 388ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner return false; // Don't hoist volatile loads! 389ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 390967948b4e25cae3de68f38fddaa75d838e676decChris Lattner // Loads from constant memory are always safe to move, even if they end up 391967948b4e25cae3de68f38fddaa75d838e676decChris Lattner // in the same alias set as something that ends up being modified. 392dab249b3b762cff0ff16069b3233e4c885e75347Dan Gohman if (AA->pointsToConstantMemory(LI->getOperand(0))) 393967948b4e25cae3de68f38fddaa75d838e676decChris Lattner return true; 394967948b4e25cae3de68f38fddaa75d838e676decChris Lattner 395ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // Don't hoist loads which have may-aliased stores in loop. 396f3e1d6977ee5fb6b66df314d65e28e2c35d6e244Chris Lattner unsigned Size = 0; 397f3e1d6977ee5fb6b66df314d65e28e2c35d6e244Chris Lattner if (LI->getType()->isSized()) 398fc2a3ed0c9e32cf7edaf5030fa0972b916cc5f0bDan Gohman Size = AA->getTypeStoreSize(LI->getType()); 399f3e1d6977ee5fb6b66df314d65e28e2c35d6e244Chris Lattner return !pointerInvalidatedByLoop(LI->getOperand(0), Size); 400118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } else if (CallInst *CI = dyn_cast<CallInst>(&I)) { 401118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // Handle obvious cases efficiently. 402dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands AliasAnalysis::ModRefBehavior Behavior = AA->getModRefBehavior(CI); 403dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands if (Behavior == AliasAnalysis::DoesNotAccessMemory) 404dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands return true; 405dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands else if (Behavior == AliasAnalysis::OnlyReadsMemory) { 406dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands // If this call only reads from memory and there are no writes to memory 407dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands // in the loop, we can hoist or sink the call as appropriate. 408dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands bool FoundMod = false; 409dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end(); 410dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands I != E; ++I) { 411dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands AliasSet &AS = *I; 412dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands if (!AS.isForwardingAliasSet() && AS.isMod()) { 413dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands FoundMod = true; 414dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands break; 415118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 416118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 417dff6710717b159f089c76a07eda074eb6347eb92Duncan Sands if (!FoundMod) return true; 418118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 419118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner 420118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // FIXME: This should use mod/ref information to see if we can hoist or sink 421118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // the call. 422fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 423118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner return false; 424ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner } 425ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 4263da59db637a887474c1b1346c1f3ccf53b6c4663Reid Spencer // Otherwise these instructions are hoistable/sinkable 427832254e1c2387c0cbeb0a820b8315fbe85cb003aReid Spencer return isa<BinaryOperator>(I) || isa<CastInst>(I) || 428d8af90c1da64b81a7aa167b5adcc1e81b0741252Dan Gohman isa<SelectInst>(I) || isa<GetElementPtrInst>(I) || isa<CmpInst>(I) || 429d8af90c1da64b81a7aa167b5adcc1e81b0741252Dan Gohman isa<InsertElementInst>(I) || isa<ExtractElementInst>(I) || 430d8af90c1da64b81a7aa167b5adcc1e81b0741252Dan Gohman isa<ShuffleVectorInst>(I); 431a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 432a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 433a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isNotUsedInLoop - Return true if the only users of this instruction are 434a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// outside of the loop. If this is true, we can sink the instruction to the 435a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// exit blocks of the loop. 436a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 437a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isNotUsedInLoop(Instruction &I) { 438ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner for (Value::use_iterator UI = I.use_begin(), E = I.use_end(); UI != E; ++UI) { 439ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner Instruction *User = cast<Instruction>(*UI); 440ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (PHINode *PN = dyn_cast<PHINode>(User)) { 441ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner // PHI node uses occur in predecessor blocks! 442ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 443ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (PN->getIncomingValue(i) == &I) 444ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (CurLoop->contains(PN->getIncomingBlock(i))) 445ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner return false; 44692329c7fbe572892c17aa2d2542a10e3ea16132fDan Gohman } else if (CurLoop->contains(User)) { 447a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 448ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } 449ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } 450a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 451a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 452a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 453a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 454a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// sink - When an instruction is found to only be used outside of the loop, 455a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// this function moves it to the exit blocks and patches up SSA form as needed. 456a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// This method is guaranteed to remove the original instruction from its 457a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// position, and may either delete it or move it to outside of the loop. 458a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 459a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnervoid LICM::sink(Instruction &I) { 46039a383124b70dda1fea18288235114029ede76cfNick Lewycky DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n"); 461a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 462b7211a2ce13a0365e0e1dd2f27adda2ee3d1288bDevang Patel SmallVector<BasicBlock*, 8> ExitBlocks; 463d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner CurLoop->getUniqueExitBlocks(ExitBlocks); 464df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner 465df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner if (isa<LoadInst>(I)) ++NumMovedLoads; 466118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner else if (isa<CallInst>(I)) ++NumMovedCalls; 467df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner ++NumSunk; 468df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner Changed = true; 469df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner 470a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The case where there is only a single exit node of this loop is common 471a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // enough that we handle it as a special (more efficient) case. It is more 472a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // efficient to handle because there are no PHI nodes that need to be placed. 473a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (ExitBlocks.size() == 1) { 474a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[0], I.getParent())) { 475a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Instruction is not used, just delete it. 4762741c971044d2165be572749b94398043caccfebChris Lattner CurAST->deleteValue(&I); 4771bf5ebc7be0d5b05e4175c7adb767b38896adef1Devang Patel // If I has users in unreachable blocks, eliminate. 478228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // If I is not void type then replaceAllUsesWith undef. 479228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // This allows ValueHandlers and custom metadata to adjust itself. 480a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 481228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel I.replaceAllUsesWith(UndefValue::get(I.getType())); 4823c80a51cfd5e7187439ce4c051da77ee46e0ff9aChris Lattner I.eraseFromParent(); 483a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 484a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Move the instruction to the start of the exit block, after any PHI 485a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // nodes in it. 486d9a5daeb7719c83136c0dc43d6ef732402d1a1b5Chris Lattner I.moveBefore(ExitBlocks[0]->getFirstNonPHI()); 4874282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner 4884282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // This instruction is no longer in the AST for the current loop, because 4894282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // we just sunk it out of the loop. If we just sunk it into an outer 4904282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner // loop, we will rediscover the operation when we process it. 4914282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner CurAST->deleteValue(&I); 492a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 493d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner return; 494d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 495d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 496d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner if (ExitBlocks.empty()) { 497a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The instruction is actually dead if there ARE NO exit blocks. 4982741c971044d2165be572749b94398043caccfebChris Lattner CurAST->deleteValue(&I); 4991bf5ebc7be0d5b05e4175c7adb767b38896adef1Devang Patel // If I has users in unreachable blocks, eliminate. 500228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // If I is not void type then replaceAllUsesWith undef. 501228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel // This allows ValueHandlers and custom metadata to adjust itself. 502a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 503228ebd0f4cf9207d32d61ef4b11b81736895dc09Devang Patel I.replaceAllUsesWith(UndefValue::get(I.getType())); 5043c80a51cfd5e7187439ce4c051da77ee46e0ff9aChris Lattner I.eraseFromParent(); 505d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner return; 506d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 507d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 508a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Otherwise, if we have multiple exits, use the SSAUpdater to do all of the 509a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // hard work of inserting PHI nodes as necessary. 510a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SmallVector<PHINode*, 8> NewPHIs; 511a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SSAUpdater SSA(&NewPHIs); 512a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 513a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 514fc6e29d4ab52b7d3efd83846ed495a9ca7e51e49Duncan Sands SSA.Initialize(I.getType(), I.getName()); 515d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 516a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Insert a copy of the instruction in each exit block of the loop that is 517a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // dominated by the instruction. Each exit block is known to only be in the 518a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // ExitBlocks list once. 519a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner BasicBlock *InstOrigBB = I.getParent(); 520d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner unsigned NumInserted = 0; 521a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 522d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 523d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner BasicBlock *ExitBlock = ExitBlocks[i]; 524a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 525d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner if (!isExitBlockDominatedByBlockInLoop(ExitBlock, InstOrigBB)) 526d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner continue; 527d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 528a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Insert the code after the last PHI node. 529d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner BasicBlock::iterator InsertPt = ExitBlock->getFirstNonPHI(); 530a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 531d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // If this is the first exit block processed, just move the original 532d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // instruction, otherwise clone the original instruction and insert 533d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // the copy. 534d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner Instruction *New; 535a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (NumInserted++ == 0) { 536a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner I.moveBefore(InsertPt); 537d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner New = &I; 538d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } else { 539d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner New = I.clone(); 540d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner if (!I.getName().empty()) 541d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner New->setName(I.getName()+".le"); 542d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner ExitBlock->getInstList().insert(InsertPt, New); 543a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 544d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner 545a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Now that we have inserted the instruction, inform SSAUpdater. 546a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 547a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SSA.AddAvailableValue(ExitBlock, New); 548d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 549a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 550d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner // If the instruction doesn't dominate any exit blocks, it must be dead. 551d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner if (NumInserted == 0) { 552d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner CurAST->deleteValue(&I); 553a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (!I.use_empty()) 554a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner I.replaceAllUsesWith(UndefValue::get(I.getType())); 555d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner I.eraseFromParent(); 556a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner return; 557d7bc19dfee3f2ce8e9c8b9193bdfb93a67008a39Chris Lattner } 558a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 559a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Next, rewrite uses of the instruction, inserting PHI nodes as needed. 560a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; ) { 561a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Grab the use before incrementing the iterator. 562a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner Use &U = UI.getUse(); 563a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Increment the iterator before removing the use from the list. 564a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner ++UI; 565a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner SSA.RewriteUseAfterInsertions(U); 566a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 567a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner 568a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner // Update CurAST for NewPHIs if I had pointer type. 569a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner if (I.getType()->isPointerTy()) 570a6a36f59b42703c5da0f68e0db37605c2e1633bfChris Lattner for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i) 5719c282011e6b7a6e23a3a163ec9c865890449e8dcChris Lattner CurAST->copyValue(&I, NewPHIs[i]); 57298917503c702e16f35ccdec3f6b4c48e5c4759acChris Lattner 57398917503c702e16f35ccdec3f6b4c48e5c4759acChris Lattner // Finally, remove the instruction from CurAST. It is no longer in the loop. 57498917503c702e16f35ccdec3f6b4c48e5c4759acChris Lattner CurAST->deleteValue(&I); 575a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 576952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 57794170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// hoist - When an instruction is found to only use loop invariant operands 57894170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// that is safe to hoist, this instruction is called to do the dirty work. 57994170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 580a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnervoid LICM::hoist(Instruction &I) { 581f15826999bc560ee6f67cff5ecd71bf9cce7a7aaDavid Greene DEBUG(dbgs() << "LICM hoisting to " << Preheader->getName() << ": " 58267d1d1f8322bdc460158888cd233be8d1cb1d4abEvan Cheng << I << "\n"); 583ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 584d9a5daeb7719c83136c0dc43d6ef732402d1a1b5Chris Lattner // Move the new node to the Preheader, before its terminator. 585d9a5daeb7719c83136c0dc43d6ef732402d1a1b5Chris Lattner I.moveBefore(Preheader->getTerminator()); 586fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 587a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (isa<LoadInst>(I)) ++NumMovedLoads; 588118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner else if (isa<CallInst>(I)) ++NumMovedCalls; 5899646e6b6af1f924f9366a2bffc6dde102f84d231Chris Lattner ++NumHoisted; 590e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner Changed = true; 591e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 592e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 593a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it is 594a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// not a trapping instruction or if it is a trapping instruction and is 595a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// guaranteed to execute. 5969966c03aad031f738718bed3bc00371e358beb5dTanya Lattner/// 597a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) { 59892094b4d928119eceac1484331acffe950f4651cChris Lattner // If it is not a trapping instruction, it is always safe to hoist. 5990b79a7727d68a507837e827803859424cf3d997bEli Friedman if (Inst.isSafeToSpeculativelyExecute()) 6000b79a7727d68a507837e827803859424cf3d997bEli Friedman return true; 601fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 60292094b4d928119eceac1484331acffe950f4651cChris Lattner // Otherwise we have to check to make sure that the instruction dominates all 60392094b4d928119eceac1484331acffe950f4651cChris Lattner // of the exit blocks. If it doesn't, then there is a path out of the loop 60492094b4d928119eceac1484331acffe950f4651cChris Lattner // which does not execute this instruction, so we can't hoist it. 60592094b4d928119eceac1484331acffe950f4651cChris Lattner 60692094b4d928119eceac1484331acffe950f4651cChris Lattner // If the instruction is in the header block for the loop (which is very 60792094b4d928119eceac1484331acffe950f4651cChris Lattner // common), it is always guaranteed to dominate the exit blocks. Since this 60892094b4d928119eceac1484331acffe950f4651cChris Lattner // is a common case, and can save some work, check it now. 609a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (Inst.getParent() == CurLoop->getHeader()) 61092094b4d928119eceac1484331acffe950f4651cChris Lattner return true; 61192094b4d928119eceac1484331acffe950f4651cChris Lattner 61292094b4d928119eceac1484331acffe950f4651cChris Lattner // Get the exit blocks for the current loop. 613b7211a2ce13a0365e0e1dd2f27adda2ee3d1288bDevang Patel SmallVector<BasicBlock*, 8> ExitBlocks; 6145fa802fe279f10f402e039bc931aa57c0e424bf5Chris Lattner CurLoop->getExitBlocks(ExitBlocks); 6159966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 6163a2b58f3adc5e9f9bffac7ce193f0570aa5a721fOwen Anderson // For each exit block, get the DT node and walk up the DT until the 61792094b4d928119eceac1484331acffe950f4651cChris Lattner // instruction's basic block is found or we exit the loop. 618a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 619a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[i], Inst.getParent())) 620a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 621fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 6229966c03aad031f738718bed3bc00371e358beb5dTanya Lattner return true; 6239966c03aad031f738718bed3bc00371e358beb5dTanya Lattner} 6249966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 625e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner/// PromoteAliasSet - Try to promote memory values to scalars by sinking 6262e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// stores out of the loop and moving loads to before the loop. We do this by 6272e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// looping over the stores in the loop, looking for stores to Must pointers 628e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner/// which are loop invariant. 6292e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// 630e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattnervoid LICM::PromoteAliasSet(AliasSet &AS) { 631e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // We can promote this alias set if it has a store, if it is a "Must" alias 632e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // set, if the pointer is loop invariant, and if we are not eliminating any 633e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // volatile loads or stores. 634e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() || 635e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner AS.isVolatile() || !CurLoop->isLoopInvariant(AS.begin()->getValue())) 636e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; 637e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 638e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner assert(!AS.empty() && 639e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner "Must alias set should have at least one pointer element in it!"); 640e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *SomePtr = AS.begin()->getValue(); 641fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 642e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // It isn't safe to promote a load/store from the loop if the load/store is 643e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // conditional. For example, turning: 6442e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 645e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // for () { if (c) *P += 1; } 6462e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 647e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // into: 648e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // 649e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // tmp = *P; for () { if (c) tmp +=1; } *P = tmp; 650e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // 651e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // is not safe, because *P may only be valid to access if 'c' is true. 652e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // 653e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // It is safe to promote P if all uses are direct load/stores and if at 654e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // least one is guaranteed to be executed. 655e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner bool GuaranteedToExecute = false; 656e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 657e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallVector<Instruction*, 64> LoopUses; 658e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallPtrSet<Value*, 4> PointerMustAliases; 659e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 660e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Check that all of the pointers in the alias set have the same type. We 661e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // cannot (yet) promote a memory location that is loaded and stored in 662e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // different sizes. 663e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) { 664e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *ASIV = ASI->getValue(); 665e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner PointerMustAliases.insert(ASIV); 66629d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner 66729d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner // Check that all of the pointers in the alias set have the same type. We 66829d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner // cannot (yet) promote a memory location that is loaded and stored in 66929d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner // different sizes. 670e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (SomePtr->getType() != ASIV->getType()) 671e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; 672e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 673e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (Value::use_iterator UI = ASIV->use_begin(), UE = ASIV->use_end(); 67419d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner UI != UE; ++UI) { 675e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Ignore instructions that are outside the loop. 67629d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner Instruction *Use = dyn_cast<Instruction>(*UI); 67792329c7fbe572892c17aa2d2542a10e3ea16132fDan Gohman if (!Use || !CurLoop->contains(Use)) 67829d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner continue; 679e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 680e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If there is an non-load/store instruction in the loop, we can't promote 681e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // it. 682e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (isa<LoadInst>(Use)) 683e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner assert(!cast<LoadInst>(Use)->isVolatile() && "AST broken"); 684e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner else if (isa<StoreInst>(Use)) 685e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner assert(!cast<StoreInst>(Use)->isVolatile() && 686e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Use->getOperand(0) != ASIV && "AST broken"); 687e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner else 688e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; // Not a load or store. 68919d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner 69019d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner if (!GuaranteedToExecute) 69119d9d4364e514f316f8757b577bb8bb33c22dbfcChris Lattner GuaranteedToExecute = isSafeToExecuteUnconditionally(*Use); 692e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 693e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LoopUses.push_back(Use); 69429d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner } 695e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 696e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 697e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If there isn't a guaranteed-to-execute instruction, we can't promote. 698e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!GuaranteedToExecute) 699e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner return; 700e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 701e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Otherwise, this is safe to promote, lets do it! 702e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " <<*SomePtr<<'\n'); 703e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Changed = true; 704e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner ++NumPromoted; 705bc2265abe1d1b830995bb2f6322409bc7d7c5740Devang Patel 706e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // We use the SSAUpdater interface to insert phi nodes as required. 707e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallVector<PHINode*, 16> NewPHIs; 708e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SSAUpdater SSA(&NewPHIs); 709e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 710e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // It wants to know some value of the same type as what we'll be inserting. 711e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *SomeValue; 712e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (isa<LoadInst>(LoopUses[0])) 713e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SomeValue = LoopUses[0]; 714e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner else 715e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SomeValue = cast<StoreInst>(LoopUses[0])->getOperand(0); 716fc6e29d4ab52b7d3efd83846ed495a9ca7e51e49Duncan Sands SSA.Initialize(SomeValue->getType(), SomeValue->getName()); 717e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 718e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // First step: bucket up uses of the pointers by the block they occur in. 719e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // This is important because we have to handle multiple defs/uses in a block 720e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // ourselves: SSAUpdater is purely for cross-block references. 721e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // FIXME: Want a TinyVector<Instruction*> since there is usually 0/1 element. 722e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner DenseMap<BasicBlock*, std::vector<Instruction*> > UsesByBlock; 723e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = LoopUses.size(); i != e; ++i) { 724e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Instruction *User = LoopUses[i]; 725e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner UsesByBlock[User->getParent()].push_back(User); 726e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 727e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 728e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Okay, now we can iterate over all the blocks in the loop with uses, 729e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // processing them. Keep track of which loads are loading a live-in value. 730e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallVector<LoadInst*, 32> LiveInLoads; 731469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner DenseMap<Value*, Value*> ReplacedLoads; 732e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 733e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned LoopUse = 0, e = LoopUses.size(); LoopUse != e; ++LoopUse) { 734e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Instruction *User = LoopUses[LoopUse]; 735e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner std::vector<Instruction*> &BlockUses = UsesByBlock[User->getParent()]; 736e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 737e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If this block has already been processed, ignore this repeat use. 738e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (BlockUses.empty()) continue; 739e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 740e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Okay, this is the first use in the block. If this block just has a 741e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // single user in it, we can rewrite it trivially. 742e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (BlockUses.size() == 1) { 743e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If it is a store, it is a trivial def of the value in the block. 744e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (isa<StoreInst>(User)) { 745e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SSA.AddAvailableValue(User->getParent(), 746e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner cast<StoreInst>(User)->getOperand(0)); 747e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } else { 748e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Otherwise it is a load, queue it to rewrite as a live-in load. 749e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LiveInLoads.push_back(cast<LoadInst>(User)); 750e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 751e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner BlockUses.clear(); 75229d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner continue; 753e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 754e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 755e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Otherwise, check to see if this block is all loads. If so, we can queue 756e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // them all as live in loads. 757e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner bool HasStore = false; 758e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = BlockUses.size(); i != e; ++i) { 759e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (isa<StoreInst>(BlockUses[i])) { 760e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner HasStore = true; 761e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner break; 762e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 763e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 76429d929363d9b8a2c0d40c5d50fec022c736cb654Chris Lattner 765e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!HasStore) { 766e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = BlockUses.size(); i != e; ++i) 767e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LiveInLoads.push_back(cast<LoadInst>(BlockUses[i])); 768e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner BlockUses.clear(); 769e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner continue; 770e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 771e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 772e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Otherwise, we have mixed loads and stores (or just a bunch of stores). 773e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Since SSAUpdater is purely for cross-block values, we need to determine 774e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // the order of these instructions in the block. If the first use in the 775e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // block is a load, then it uses the live in value. The last store defines 776e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // the live out value. We handle this by doing a linear scan of the block. 777e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner BasicBlock *BB = User->getParent(); 778e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *StoredValue = 0; 779e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) { 780e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (LoadInst *L = dyn_cast<LoadInst>(II)) { 781469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // If this is a load from an unrelated pointer, ignore it. 782e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!PointerMustAliases.count(L->getOperand(0))) continue; 783e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 784e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If we haven't seen a store yet, this is a live in use, otherwise 785e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // use the stored value. 786469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner if (StoredValue) { 787e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner L->replaceAllUsesWith(StoredValue); 788469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner ReplacedLoads[L] = StoredValue; 789469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner } else { 790e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LiveInLoads.push_back(L); 791469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner } 792e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner continue; 793e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 794e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 795e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (StoreInst *S = dyn_cast<StoreInst>(II)) { 796445560881898fe212c185bd4c0485140d7b4fc88Chris Lattner // If this is a store to an unrelated pointer, ignore it. 797e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (!PointerMustAliases.count(S->getOperand(1))) continue; 798fb3ee1930bfd0902f5fa3e6526775e3791e38d3cChris Lattner 799e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Remember that this is the active value in the block. 800e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner StoredValue = S->getOperand(0); 801e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 802e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 803e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 804e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // The last stored value that happened is the live-out for the block. 805e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner assert(StoredValue && "Already checked that there is a store in block"); 806e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SSA.AddAvailableValue(BB, StoredValue); 807e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner BlockUses.clear(); 808e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 809e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 810e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Now that all the intra-loop values are classified, set up the preheader. 811e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // It gets a load of the pointer we're promoting, and it is the live-out value 812e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // from the preheader. 813e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LoadInst *PreheaderLoad = new LoadInst(SomePtr,SomePtr->getName()+".promoted", 814e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Preheader->getTerminator()); 815e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SSA.AddAvailableValue(Preheader, PreheaderLoad); 816e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 817e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Now that the preheader is good to go, set up the exit blocks. Each exit 818e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // block gets a store of the live-out values that feed them. Since we've 819e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // already told the SSA updater about the defs in the loop and the preheader 820e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // definition, it is all set and we can start using it. 821e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner SmallVector<BasicBlock*, 8> ExitBlocks; 822e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner CurLoop->getUniqueExitBlocks(ExitBlocks); 823e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 824e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner BasicBlock *ExitBlock = ExitBlocks[i]; 825e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock); 826e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Instruction *InsertPos = ExitBlock->getFirstNonPHI(); 827e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner new StoreInst(LiveInValue, SomePtr, InsertPos); 828e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 829fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 830e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Okay, now we rewrite all loads that use live-in values in the loop, 831e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // inserting PHI nodes as necessary. 832e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = LiveInLoads.size(); i != e; ++i) { 833e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner LoadInst *ALoad = LiveInLoads[i]; 8349c282011e6b7a6e23a3a163ec9c865890449e8dcChris Lattner Value *NewVal = SSA.GetValueInMiddleOfBlock(ALoad->getParent()); 8359c282011e6b7a6e23a3a163ec9c865890449e8dcChris Lattner ALoad->replaceAllUsesWith(NewVal); 8369c282011e6b7a6e23a3a163ec9c865890449e8dcChris Lattner CurAST->copyValue(ALoad, NewVal); 837469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner ReplacedLoads[ALoad] = NewVal; 838e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 839e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 840e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Now that everything is rewritten, delete the old instructions from the body 841e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // of the loop. They should all be dead now. 842e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = LoopUses.size(); i != e; ++i) { 843e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner Instruction *User = LoopUses[i]; 844469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner 845469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // If this is a load that still has uses, then the load must have been added 846469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // as a live value in the SSAUpdate data structure for a block (e.g. because 847469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // the loaded value was stored later). In this case, we need to recursively 848469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // propagate the updates until we get to the real value. 849469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner if (!User->use_empty()) { 850469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner Value *NewVal = ReplacedLoads[User]; 851469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner assert(NewVal && "not a replaced load?"); 852469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner 853469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // Propagate down to the ultimate replacee. The intermediately loads 854469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // could theoretically already have been deleted, so we don't want to 855469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner // dereference the Value*'s. 856469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner DenseMap<Value*, Value*>::iterator RLI = ReplacedLoads.find(NewVal); 857469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner while (RLI != ReplacedLoads.end()) { 858469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner NewVal = RLI->second; 859469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner RLI = ReplacedLoads.find(NewVal); 860469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner } 861469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner 862469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner User->replaceAllUsesWith(NewVal); 863469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner CurAST->copyValue(User, NewVal); 864469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner } 865469996400c4ab89d5ddb2eb80acc1c1553439f07Chris Lattner 866e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner CurAST->deleteValue(User); 867e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner User->eraseFromParent(); 868e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner } 869e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 870e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // If the preheader load is itself a pointer, we need to tell alias analysis 871e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // about the new pointer we created in the preheader block and about any PHI 872e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // nodes that just got inserted. 873e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner if (PreheaderLoad->getType()->isPointerTy()) { 874e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // Copy any value stored to or loaded from a must-alias of the pointer. 875e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner CurAST->copyValue(SomeValue, PreheaderLoad); 876fd93908ae8b9684fe71c239e3c6cfe13ff6a2663Misha Brukman 877e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i) 878e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner CurAST->copyValue(SomeValue, NewPHIs[i]); 8792e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 880e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 881e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner // fwew, we're done! 882f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner} 88391d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 884e488064922f12c4cf07f3aef9a4d2d3ffd15f9c0Chris Lattner 88591d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel/// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info. 88691d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patelvoid LICM::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, Loop *L) { 8874282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner AliasSetTracker *AST = LoopToAliasSetMap.lookup(L); 88891d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel if (!AST) 88991d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel return; 89091d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 89191d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel AST->copyValue(From, To); 89291d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel} 89391d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 89491d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel/// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias 89591d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel/// set. 89691d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patelvoid LICM::deleteAnalysisValue(Value *V, Loop *L) { 8974282e32712da220fd97177772e22ec1ee7e50af2Chris Lattner AliasSetTracker *AST = LoopToAliasSetMap.lookup(L); 89891d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel if (!AST) 89991d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel return; 90091d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel 90191d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel AST->deleteValue(V); 90291d22c8b1ec2ad8f2f29804b729473ccf720fb3eDevang Patel} 903