LICM.cpp revision ea9403f2aa078e840a49792d906390395f0cd2f6
1e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner//===-- LICM.cpp - Loop Invariant Code Motion Pass ------------------------===// 2b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 3b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// The LLVM Compiler Infrastructure 4b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 5b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// This file was developed by the LLVM research group and is distributed under 6b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// the University of Illinois Open Source License. See LICENSE.TXT for details. 7b576c94c15af9a440f69d9d03c2afead7971118cJohn Criswell// 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 1492094b4d928119eceac1484331acffe950f4651cChris Lattner// live in registers. 1592094b4d928119eceac1484331acffe950f4651cChris Lattner// 1692094b4d928119eceac1484331acffe950f4651cChris Lattner// This pass uses alias analysis for two purposes: 172e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// 182e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// 1. Moving loop invariant loads out of loops. If we can determine that a 192e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// load inside of a loop never aliases anything stored to, we can hoist it 2092094b4d928119eceac1484331acffe950f4651cChris Lattner// 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 292e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// the mem2reg functionality to construct the appropriate SSA form for the 302e6e741b737960ecd0b68610875050019aac0f07Chris Lattner// variable. 31e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner// 32e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner//===----------------------------------------------------------------------===// 33e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 34e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner#include "llvm/Transforms/Scalar.h" 352e6e741b737960ecd0b68610875050019aac0f07Chris Lattner#include "llvm/Transforms/Utils/PromoteMemToReg.h" 36e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner#include "llvm/Transforms/Utils/Local.h" 37e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner#include "llvm/Analysis/LoopInfo.h" 38f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner#include "llvm/Analysis/AliasAnalysis.h" 390252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner#include "llvm/Analysis/AliasSetTracker.h" 40952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner#include "llvm/Analysis/Dominators.h" 412e6e741b737960ecd0b68610875050019aac0f07Chris Lattner#include "llvm/Instructions.h" 422e6e741b737960ecd0b68610875050019aac0f07Chris Lattner#include "llvm/DerivedTypes.h" 43fb743a937f6856e3ab1f8ed599677038750a550eChris Lattner#include "llvm/Target/TargetData.h" 442e6e741b737960ecd0b68610875050019aac0f07Chris Lattner#include "llvm/Support/CFG.h" 452e6e741b737960ecd0b68610875050019aac0f07Chris Lattner#include "Support/CommandLine.h" 466806f5614d2ec260fda954c951d33f58e77ed610Chris Lattner#include "Support/Debug.h" 476806f5614d2ec260fda954c951d33f58e77ed610Chris Lattner#include "Support/Statistic.h" 48b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner#include "llvm/Assembly/Writer.h" 49e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner#include <algorithm> 5092094b4d928119eceac1484331acffe950f4651cChris Lattnerusing namespace llvm; 51d0fde30ce850b78371fd1386338350591f9ff494Brian Gaeke 52e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattnernamespace { 534a650af59912110a246c0a041bff38c92f0e56a2Chris Lattner cl::opt<bool> 544a650af59912110a246c0a041bff38c92f0e56a2Chris Lattner DisablePromotion("disable-licm-promotion", cl::Hidden, 554a650af59912110a246c0a041bff38c92f0e56a2Chris Lattner cl::desc("Disable memory promotion in LICM pass")); 562e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 57a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Statistic<> NumSunk("licm", "Number of instructions sunk out of loop"); 58a92f696b74a99325026ebbdbffd2a44317e0c10bChris Lattner Statistic<> NumHoisted("licm", "Number of instructions hoisted out of loop"); 59a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Statistic<> NumMovedLoads("licm", "Number of load insts hoisted or sunk"); 604a650af59912110a246c0a041bff38c92f0e56a2Chris Lattner Statistic<> NumPromoted("licm", 614a650af59912110a246c0a041bff38c92f0e56a2Chris Lattner "Number of memory locations promoted to registers"); 622e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 63ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner struct LICM : public FunctionPass { 647e70829632f82de15db187845666aaca6e04b792Chris Lattner virtual bool runOnFunction(Function &F); 65e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 6694170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// This transformation requires natural loop information & requires that 6794170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// loop preheaders be inserted into the CFG... 6894170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 69e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner virtual void getAnalysisUsage(AnalysisUsage &AU) const { 70cb2610ea037a17115ef3a01a6bdaab4e3cfdca27Chris Lattner AU.setPreservesCFG(); 7198bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner AU.addRequiredID(LoopSimplifyID); 725f0eb8da62308126d5b61e3eee5bee75b9dc5194Chris Lattner AU.addRequired<LoopInfo>(); 73952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner AU.addRequired<DominatorTree>(); 740252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AU.addRequired<DominanceFrontier>(); // For scalar promotion (mem2reg) 75f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner AU.addRequired<AliasAnalysis>(); 76e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner } 77e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 78e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner private: 7992094b4d928119eceac1484331acffe950f4651cChris Lattner // Various analyses that we use... 802e6e741b737960ecd0b68610875050019aac0f07Chris Lattner AliasAnalysis *AA; // Current AliasAnalysis information 8192094b4d928119eceac1484331acffe950f4651cChris Lattner LoopInfo *LI; // Current LoopInfo 8292094b4d928119eceac1484331acffe950f4651cChris Lattner DominatorTree *DT; // Dominator Tree for the current Loop... 8343f820d1f7638656be2158efac7dd8f5b08b8b77Chris Lattner DominanceFrontier *DF; // Current Dominance Frontier 8492094b4d928119eceac1484331acffe950f4651cChris Lattner 8592094b4d928119eceac1484331acffe950f4651cChris Lattner // State that is updated as we process loops 862e6e741b737960ecd0b68610875050019aac0f07Chris Lattner bool Changed; // Set to true when we change anything. 872e6e741b737960ecd0b68610875050019aac0f07Chris Lattner BasicBlock *Preheader; // The preheader block of the current loop... 882e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Loop *CurLoop; // The current loop we are working on... 890252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AliasSetTracker *CurAST; // AliasSet information for the current loop... 90e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 9194170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// visitLoop - Hoist expressions out of the specified loop... 9294170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 930252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner void visitLoop(Loop *L, AliasSetTracker &AST); 94e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 95952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// HoistRegion - Walk the specified region of the CFG (defined by all 96952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// blocks dominated by the specified block, and that are in the current 97952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// loop) in depth first order w.r.t the DominatorTree. This allows us to 98cf00c4ab3ba308d45d98c5ccab87362cf802facbMisha Brukman /// visit definitions before uses, allowing us to hoist a loop body in one 99952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// pass without iteration. 100952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// 101952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner void HoistRegion(DominatorTree::Node *N); 102952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 103b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner /// inSubLoop - Little predicate that returns true if the specified basic 104b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner /// block is in a subloop of the current one, not the current one itself. 10594170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 106b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner bool inSubLoop(BasicBlock *BB) { 107b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop"); 108e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner for (unsigned i = 0, e = CurLoop->getSubLoops().size(); i != e; ++i) 109e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner if (CurLoop->getSubLoops()[i]->contains(BB)) 110b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner return true; // A subloop actually contains this block! 111b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner return false; 112e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner } 113e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 114a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// isExitBlockDominatedByBlockInLoop - This method checks to see if the 115a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// specified exit block of the loop is dominated by the specified block 116a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// that is in the body of the loop. We use these constraints to 117a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// dramatically limit the amount of the dominator tree that needs to be 118a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// searched. 119a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isExitBlockDominatedByBlockInLoop(BasicBlock *ExitBlock, 120a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *BlockInLoop) const { 121a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If the block in the loop is the loop header, it must be dominated! 122a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *LoopHeader = CurLoop->getHeader(); 123a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (BlockInLoop == LoopHeader) 124a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 125a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 126a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner DominatorTree::Node *BlockInLoopNode = DT->getNode(BlockInLoop); 127a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner DominatorTree::Node *IDom = DT->getNode(ExitBlock); 128a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 129a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Because the exit block is not in the loop, we know we have to get _at 130a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // least_ it's immediate dominator. 131a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner do { 132a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Get next Immediate Dominator. 133a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner IDom = IDom->getIDom(); 134a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 135a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If we have got to the header of the loop, then the instructions block 136a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // did not dominate the exit node, so we can't hoist it. 137a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (IDom->getBlock() == LoopHeader) 138a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 139a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 140a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } while (IDom != BlockInLoopNode); 141a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 142a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 143a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 144a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 145a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// sink - When an instruction is found to only be used outside of the loop, 146a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// this function moves it to the exit blocks and patches up SSA form as 147a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// needed. 148a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// 149a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner void sink(Instruction &I); 150a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 15194170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// hoist - When an instruction is found to only use loop invariant operands 15294170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// that is safe to hoist, this instruction is called to do the dirty work. 15394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 1547e70829632f82de15db187845666aaca6e04b792Chris Lattner void hoist(Instruction &I); 155e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 156a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it 157a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// is not a trapping instruction or if it is a trapping instruction and is 158a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// guaranteed to execute. 1599966c03aad031f738718bed3bc00371e358beb5dTanya Lattner /// 160a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isSafeToExecuteUnconditionally(Instruction &I); 1619966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 16294170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// pointerInvalidatedByLoop - Return true if the body of this loop may 16394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// store into the memory location pointed to by V. 16494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 1652e6e741b737960ecd0b68610875050019aac0f07Chris Lattner bool pointerInvalidatedByLoop(Value *V) { 1660252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Check to see if any of the basic blocks in CurLoop invalidate *V. 1670252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner return CurAST->getAliasSetForPointer(V, 0).isMod(); 1682e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 169f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner 17094170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// isLoopInvariant - Return true if the specified value is loop invariant 17194170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 172e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner inline bool isLoopInvariant(Value *V) { 173e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner if (Instruction *I = dyn_cast<Instruction>(V)) 174e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner return !CurLoop->contains(I->getParent()); 175e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner return true; // All non-instructions are loop invariant 176e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner } 177a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 178a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool canSinkOrHoistInst(Instruction &I); 179a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isLoopInvariantInst(Instruction &I); 180a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isNotUsedInLoop(Instruction &I); 181e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 1822e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// PromoteValuesInLoop - Look at the stores in the loop and promote as many 1832e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// to scalars as we can. 1842e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// 1852e6e741b737960ecd0b68610875050019aac0f07Chris Lattner void PromoteValuesInLoop(); 1862e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 1872e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// findPromotableValuesInLoop - Check the current loop for stores to 188352361b409d16045e703d986aa7fd77295173ef3Misha Brukman /// definite pointers, which are not loaded and stored through may aliases. 1892e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// If these are found, create an alloca for the value, add it to the 1902e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// PromotedValues list, and keep track of the mapping from value to 1912e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// alloca... 1922e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// 1932e6e741b737960ecd0b68610875050019aac0f07Chris Lattner void findPromotableValuesInLoop( 1942e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::vector<std::pair<AllocaInst*, Value*> > &PromotedValues, 1952e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::map<Value*, AllocaInst*> &Val2AlMap); 196e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner }; 197f629309f74cf1a64aa7fd1cd5784fd7db9a8f59eChris Lattner 198a6275ccdf5e1aa208afde56c498e2b13e16442f0Chris Lattner RegisterOpt<LICM> X("licm", "Loop Invariant Code Motion"); 199e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 200e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 20192094b4d928119eceac1484331acffe950f4651cChris LattnerFunctionPass *llvm::createLICMPass() { return new LICM(); } 202e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 20394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// runOnFunction - For LICM, this simply traverses the loop structure of the 20494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// function, hoisting expressions out of loops if possible. 20594170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 2067e70829632f82de15db187845666aaca6e04b792Chris Lattnerbool LICM::runOnFunction(Function &) { 2072e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Changed = false; 208e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2092e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Get our Loop and Alias Analysis information... 2102e6e741b737960ecd0b68610875050019aac0f07Chris Lattner LI = &getAnalysis<LoopInfo>(); 211f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner AA = &getAnalysis<AliasAnalysis>(); 21243f820d1f7638656be2158efac7dd8f5b08b8b77Chris Lattner DF = &getAnalysis<DominanceFrontier>(); 21311a49a722f657294f38865019af51f82dc31c1c3Tanya Lattner DT = &getAnalysis<DominatorTree>(); 214f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner 2152e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Hoist expressions out of all of the top-level loops. 2162e6e741b737960ecd0b68610875050019aac0f07Chris Lattner const std::vector<Loop*> &TopLevelLoops = LI->getTopLevelLoops(); 2172e6e741b737960ecd0b68610875050019aac0f07Chris Lattner for (std::vector<Loop*>::const_iterator I = TopLevelLoops.begin(), 2182e6e741b737960ecd0b68610875050019aac0f07Chris Lattner E = TopLevelLoops.end(); I != E; ++I) { 2190252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AliasSetTracker AST(*AA); 220ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner visitLoop(*I, AST); 2212e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 222e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner return Changed; 223e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 224e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 22594170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner 22694170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// visitLoop - Hoist expressions out of the specified loop... 22794170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 2280252e49f6d6973b6f347c8feafc49e28af27163aChris Lattnervoid LICM::visitLoop(Loop *L, AliasSetTracker &AST) { 229e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // Recurse through all subloops before we process this loop... 2302e6e741b737960ecd0b68610875050019aac0f07Chris Lattner for (std::vector<Loop*>::const_iterator I = L->getSubLoops().begin(), 2312e6e741b737960ecd0b68610875050019aac0f07Chris Lattner E = L->getSubLoops().end(); I != E; ++I) { 2320252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AliasSetTracker SubAST(*AA); 233ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner visitLoop(*I, SubAST); 2342e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 2352e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Incorporate information about the subloops into this loop... 2360252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AST.add(SubAST); 2372e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 238e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner CurLoop = L; 2390252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner CurAST = &AST; 240e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 24199a57216a935a512c418032f590a4660bad9d846Chris Lattner // Get the preheader block to move instructions into... 24299a57216a935a512c418032f590a4660bad9d846Chris Lattner Preheader = L->getLoopPreheader(); 24399a57216a935a512c418032f590a4660bad9d846Chris Lattner assert(Preheader&&"Preheader insertion pass guarantees we have a preheader!"); 24499a57216a935a512c418032f590a4660bad9d846Chris Lattner 2452e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Loop over the body of this loop, looking for calls, invokes, and stores. 2460252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Because subloops have already been incorporated into AST, we skip blocks in 2472e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // subloops. 2482e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 249a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (std::vector<BasicBlock*>::const_iterator I = L->getBlocks().begin(), 250a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner E = L->getBlocks().end(); I != E; ++I) 2512e6e741b737960ecd0b68610875050019aac0f07Chris Lattner if (LI->getLoopFor(*I) == L) // Ignore blocks in subloops... 2520252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AST.add(**I); // Incorporate the specified basic block 2532e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 254e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // We want to visit all of the instructions in this loop... that are not parts 255e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // of our subloops (they have already had their invariants hoisted out of 256e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // their loop, into this loop, so there is no need to process the BODIES of 257e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // the subloops). 258e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // 259952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // Traverse the body of the loop in depth first order on the dominator tree so 260952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // that we are guaranteed to see definitions before we see uses. This allows 261952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // us to perform the LICM transformation in one pass, without iteration. 262952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // 26311a49a722f657294f38865019af51f82dc31c1c3Tanya Lattner HoistRegion(DT->getNode(L->getHeader())); 264e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2652e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Now that all loop invariants have been removed from the loop, promote any 2662e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // memory references to scalars that we can... 2672e6e741b737960ecd0b68610875050019aac0f07Chris Lattner if (!DisablePromotion) 2682e6e741b737960ecd0b68610875050019aac0f07Chris Lattner PromoteValuesInLoop(); 2692e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 270e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // Clear out loops state information for the next iteration 271e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner CurLoop = 0; 27299a57216a935a512c418032f590a4660bad9d846Chris Lattner Preheader = 0; 273e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 274e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 275952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// HoistRegion - Walk the specified region of the CFG (defined by all blocks 276952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// dominated by the specified block, and that are in the current loop) in depth 277cf00c4ab3ba308d45d98c5ccab87362cf802facbMisha Brukman/// first order w.r.t the DominatorTree. This allows us to visit definitions 278952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// before uses, allowing us to hoist a loop body in one pass without iteration. 279952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// 280952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattnervoid LICM::HoistRegion(DominatorTree::Node *N) { 281952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner assert(N != 0 && "Null dominator tree node?"); 282ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner BasicBlock *BB = N->getBlock(); 283952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 284b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner // If this subregion is not in the top level loop at all, exit. 285ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (!CurLoop->contains(BB)) return; 286952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 287a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Only need to process the contents of this block if it is not part of a 288a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // subloop (which would already have been processed). 289ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (!inSubLoop(BB)) 290a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ) { 291a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Instruction &I = *II++; 292a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 293a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // We can only handle simple expressions and loads with this code. 294a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (canSinkOrHoistInst(I)) { 295a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // First check to see if we can sink this instruction to the exit blocks 296a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // of the loop. We can do this if the only users of the instruction are 297a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // outside of the loop. In this case, it doesn't even matter if the 298a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // operands of the instruction are loop invariant. 299a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // 300a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (isNotUsedInLoop(I)) 301a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner sink(I); 302a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 303a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If we can't sink the instruction, try hoisting it out to the 304a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // preheader. We can only do this if all of the operands of the 305a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // instruction are loop invariant and if it is safe to hoist the 306a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // instruction. 307a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // 308a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner else if (isLoopInvariantInst(I) && isSafeToExecuteUnconditionally(I)) 309a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner hoist(I); 310a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 311ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner } 312952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 313952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner const std::vector<DominatorTree::Node*> &Children = N->getChildren(); 314952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner for (unsigned i = 0, e = Children.size(); i != e; ++i) 315952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner HoistRegion(Children[i]); 316952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner} 317952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 318a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// canSinkOrHoistInst - Return true if the hoister and sinker can handle this 319a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// instruction. 320a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 321a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::canSinkOrHoistInst(Instruction &I) { 322ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // Loads have extra constraints we have to verify before we can hoist them. 323ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { 324ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (LI->isVolatile()) 325ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner return false; // Don't hoist volatile loads! 326ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 327ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // Don't hoist loads which have may-aliased stores in loop. 328a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return !pointerInvalidatedByLoop(LI->getOperand(0)); 329ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner } 330ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 331a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return isa<BinaryOperator>(I) || isa<ShiftInst>(I) || isa<CastInst>(I) || 332a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner isa<GetElementPtrInst>(I) || isa<VANextInst>(I) || isa<VAArgInst>(I); 333a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 334a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 335a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isNotUsedInLoop - Return true if the only users of this instruction are 336a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// outside of the loop. If this is true, we can sink the instruction to the 337a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// exit blocks of the loop. 338a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 339a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isNotUsedInLoop(Instruction &I) { 340ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner for (Value::use_iterator UI = I.use_begin(), E = I.use_end(); UI != E; ++UI) { 341ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner Instruction *User = cast<Instruction>(*UI); 342ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (PHINode *PN = dyn_cast<PHINode>(User)) { 343ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner // PHI node uses occur in predecessor blocks! 344ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 345ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (PN->getIncomingValue(i) == &I) 346ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (CurLoop->contains(PN->getIncomingBlock(i))) 347ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner return false; 348ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } else if (CurLoop->contains(User->getParent())) { 349a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 350ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } 351ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } 352a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 353a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 354a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 355a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 356a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isLoopInvariantInst - Return true if all operands of this instruction are 357a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// loop invariant. We also filter out non-hoistable instructions here just for 358a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// efficiency. 359a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 360a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isLoopInvariantInst(Instruction &I) { 361a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The instruction is loop invariant if all of its operands are loop-invariant 362a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) 363a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!isLoopInvariant(I.getOperand(i))) 364a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 365a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 366ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // If we got this far, the instruction is loop invariant! 367ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner return true; 368ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner} 369ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 370a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// sink - When an instruction is found to only be used outside of the loop, 371a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// this function moves it to the exit blocks and patches up SSA form as 372a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// needed. 373a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 374a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnervoid LICM::sink(Instruction &I) { 375a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner DEBUG(std::cerr << "LICM sinking instruction: " << I); 376a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 377a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner const std::vector<BasicBlock*> &ExitBlocks = CurLoop->getExitBlocks(); 378df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner std::vector<Value*> Operands(I.op_begin(), I.op_end()); 379df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner 380df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner if (isa<LoadInst>(I)) ++NumMovedLoads; 381df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner ++NumSunk; 382df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner Changed = true; 383df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner 384a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The case where there is only a single exit node of this loop is common 385a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // enough that we handle it as a special (more efficient) case. It is more 386a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // efficient to handle because there are no PHI nodes that need to be placed. 387a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (ExitBlocks.size() == 1) { 388a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[0], I.getParent())) { 389a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Instruction is not used, just delete it. 390a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getInstList().erase(&I); 391a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 392a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Move the instruction to the start of the exit block, after any PHI 393a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // nodes in it. 394a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getInstList().remove(&I); 395a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 396a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock::iterator InsertPt = ExitBlocks[0]->begin(); 397a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner while (isa<PHINode>(InsertPt)) ++InsertPt; 398a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner ExitBlocks[0]->getInstList().insert(InsertPt, &I); 399a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 400a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else if (ExitBlocks.size() == 0) { 401a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The instruction is actually dead if there ARE NO exit blocks. 402a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getInstList().erase(&I); 403a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 404a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Otherwise, if we have multiple exits, use the PromoteMem2Reg function to 405a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // do all of the hard work of inserting PHI nodes as necessary. We convert 406a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // the value into a stack object to get it to do this. 407a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 408a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Firstly, we create a stack object to hold the value... 409a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner AllocaInst *AI = new AllocaInst(I.getType(), 0, I.getName(), 410a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getParent()->front().begin()); 411a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 412a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Secondly, insert load instructions for each use of the instruction 413a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // outside of the loop. 414a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner while (!I.use_empty()) { 415a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Instruction *U = cast<Instruction>(I.use_back()); 416a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 417a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If the user is a PHI Node, we actually have to insert load instructions 418a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // in all predecessor blocks, not in the PHI block itself! 419a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (PHINode *UPN = dyn_cast<PHINode>(U)) { 420a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Only insert into each predecessor once, so that we don't have 421a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // different incoming values from the same block! 422a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner std::map<BasicBlock*, Value*> InsertedBlocks; 423a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = UPN->getNumIncomingValues(); i != e; ++i) 424a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (UPN->getIncomingValue(i) == &I) { 425a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *Pred = UPN->getIncomingBlock(i); 426a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Value *&PredVal = InsertedBlocks[Pred]; 427a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!PredVal) { 428a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Insert a new load instruction right before the terminator in 429a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // the predecessor block. 430a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner PredVal = new LoadInst(AI, "", Pred->getTerminator()); 431a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 432a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 433a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner UPN->setIncomingValue(i, PredVal); 434a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 435a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 436a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 437a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner LoadInst *L = new LoadInst(AI, "", U); 438a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner U->replaceUsesOfWith(&I, L); 439a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 440a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 441a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 442a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Thirdly, insert a copy of the instruction in each exit block of the loop 443a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // that is dominated by the instruction, storing the result into the memory 444a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // location. Be careful not to insert the instruction into any particular 445a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // basic block more than once. 446a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner std::set<BasicBlock*> InsertedBlocks; 447a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *InstOrigBB = I.getParent(); 448a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 449a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 450a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *ExitBlock = ExitBlocks[i]; 451a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 452a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (isExitBlockDominatedByBlockInLoop(ExitBlock, InstOrigBB)) { 453a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If we haven't already processed this exit block, do so now. 454e3cfe8d563fa06b274587aa38b1359ff707f33deChris Lattner if (InsertedBlocks.insert(ExitBlock).second) { 455a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Insert the code after the last PHI node... 456a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock::iterator InsertPt = ExitBlock->begin(); 457a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner while (isa<PHINode>(InsertPt)) ++InsertPt; 458a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 459a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If this is the first exit block processed, just move the original 460a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // instruction, otherwise clone the original instruction and insert 461a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // the copy. 462a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Instruction *New; 4637d3ced934f1bb2c6845676c7333ef879d5219e88Chris Lattner if (InsertedBlocks.size() == 1) { 464a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getInstList().remove(&I); 465a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner ExitBlock->getInstList().insert(InsertPt, &I); 466a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner New = &I; 467a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 468a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner New = I.clone(); 469a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner New->setName(I.getName()+".le"); 470a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner ExitBlock->getInstList().insert(InsertPt, New); 471a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 472a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 473a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Now that we have inserted the instruction, store it into the alloca 474a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner new StoreInst(New, AI, InsertPt); 475a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 476a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 477a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 478a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 479a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Finally, promote the fine value to SSA form. 480a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner std::vector<AllocaInst*> Allocas; 481a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Allocas.push_back(AI); 482a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner PromoteMemToReg(Allocas, *DT, *DF, AA->getTargetData()); 483a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 484a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 485a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Since we just sunk an instruction, check to see if any other instructions 486a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // used by this instruction are now sinkable. If so, sink them too. 487df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner for (unsigned i = 0, e = Operands.size(); i != e; ++i) 488df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner if (Instruction *OpI = dyn_cast<Instruction>(Operands[i])) 489a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (CurLoop->contains(OpI->getParent()) && canSinkOrHoistInst(*OpI) && 490df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner isNotUsedInLoop(*OpI) && isSafeToExecuteUnconditionally(*OpI)) 491a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner sink(*OpI); 492a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 493952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 49494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// hoist - When an instruction is found to only use loop invariant operands 49594170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// that is safe to hoist, this instruction is called to do the dirty work. 49694170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 497a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnervoid LICM::hoist(Instruction &I) { 498b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner DEBUG(std::cerr << "LICM hoisting to"; 499b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner WriteAsOperand(std::cerr, Preheader, false); 500a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner std::cerr << ": " << I); 501ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 50299a57216a935a512c418032f590a4660bad9d846Chris Lattner // Remove the instruction from its current basic block... but don't delete the 50399a57216a935a512c418032f590a4660bad9d846Chris Lattner // instruction. 504a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getInstList().remove(&I); 505e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 5069646e6b6af1f924f9366a2bffc6dde102f84d231Chris Lattner // Insert the new node in Preheader, before the terminator. 507a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Preheader->getInstList().insert(Preheader->getTerminator(), &I); 5089646e6b6af1f924f9366a2bffc6dde102f84d231Chris Lattner 509a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (isa<LoadInst>(I)) ++NumMovedLoads; 5109646e6b6af1f924f9366a2bffc6dde102f84d231Chris Lattner ++NumHoisted; 511e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner Changed = true; 512e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 513e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 514a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it is 515a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// not a trapping instruction or if it is a trapping instruction and is 516a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// guaranteed to execute. 5179966c03aad031f738718bed3bc00371e358beb5dTanya Lattner/// 518a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) { 51992094b4d928119eceac1484331acffe950f4651cChris Lattner // If it is not a trapping instruction, it is always safe to hoist. 52092094b4d928119eceac1484331acffe950f4651cChris Lattner if (!Inst.isTrapping()) return true; 52192094b4d928119eceac1484331acffe950f4651cChris Lattner 52292094b4d928119eceac1484331acffe950f4651cChris Lattner // Otherwise we have to check to make sure that the instruction dominates all 52392094b4d928119eceac1484331acffe950f4651cChris Lattner // of the exit blocks. If it doesn't, then there is a path out of the loop 52492094b4d928119eceac1484331acffe950f4651cChris Lattner // which does not execute this instruction, so we can't hoist it. 52592094b4d928119eceac1484331acffe950f4651cChris Lattner 52692094b4d928119eceac1484331acffe950f4651cChris Lattner // If the instruction is in the header block for the loop (which is very 52792094b4d928119eceac1484331acffe950f4651cChris Lattner // common), it is always guaranteed to dominate the exit blocks. Since this 52892094b4d928119eceac1484331acffe950f4651cChris Lattner // is a common case, and can save some work, check it now. 529a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (Inst.getParent() == CurLoop->getHeader()) 53092094b4d928119eceac1484331acffe950f4651cChris Lattner return true; 53192094b4d928119eceac1484331acffe950f4651cChris Lattner 53292094b4d928119eceac1484331acffe950f4651cChris Lattner // Get the exit blocks for the current loop. 533a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner const std::vector<BasicBlock*> &ExitBlocks = CurLoop->getExitBlocks(); 5349966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 53592094b4d928119eceac1484331acffe950f4651cChris Lattner // For each exit block, get the DT node and walk up the DT until the 53692094b4d928119eceac1484331acffe950f4651cChris Lattner // instruction's basic block is found or we exit the loop. 537a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 538a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[i], Inst.getParent())) 539a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 54011a49a722f657294f38865019af51f82dc31c1c3Tanya Lattner 5419966c03aad031f738718bed3bc00371e358beb5dTanya Lattner return true; 5429966c03aad031f738718bed3bc00371e358beb5dTanya Lattner} 5439966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 544eb53ae4f2dc39e75e725b21b52d77d29cf1c11c9Chris Lattner 5452e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// PromoteValuesInLoop - Try to promote memory values to scalars by sinking 5462e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// stores out of the loop and moving loads to before the loop. We do this by 5472e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// looping over the stores in the loop, looking for stores to Must pointers 5482e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// which are loop invariant. We promote these memory locations to use allocas 5492e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// instead. These allocas can easily be raised to register values by the 5502e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// PromoteMem2Reg functionality. 5512e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// 5522e6e741b737960ecd0b68610875050019aac0f07Chris Lattnervoid LICM::PromoteValuesInLoop() { 5532e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // PromotedValues - List of values that are promoted out of the loop. Each 554065a616adad624152618b1b0084ff074e5b03bbbChris Lattner // value has an alloca instruction for it, and a canonical version of the 5552e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // pointer. 5562e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::vector<std::pair<AllocaInst*, Value*> > PromotedValues; 5572e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::map<Value*, AllocaInst*> ValueToAllocaMap; // Map of ptr to alloca 5582e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 5592e6e741b737960ecd0b68610875050019aac0f07Chris Lattner findPromotableValuesInLoop(PromotedValues, ValueToAllocaMap); 5602e6e741b737960ecd0b68610875050019aac0f07Chris Lattner if (ValueToAllocaMap.empty()) return; // If there are values to promote... 5612e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 5622e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Changed = true; 5632e6e741b737960ecd0b68610875050019aac0f07Chris Lattner NumPromoted += PromotedValues.size(); 5642e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 5652e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Emit a copy from the value into the alloca'd value in the loop preheader 5662e6e741b737960ecd0b68610875050019aac0f07Chris Lattner TerminatorInst *LoopPredInst = Preheader->getTerminator(); 5672e6e741b737960ecd0b68610875050019aac0f07Chris Lattner for (unsigned i = 0, e = PromotedValues.size(); i != e; ++i) { 5682e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Load from the memory we are promoting... 5692e6e741b737960ecd0b68610875050019aac0f07Chris Lattner LoadInst *LI = new LoadInst(PromotedValues[i].second, 5702e6e741b737960ecd0b68610875050019aac0f07Chris Lattner PromotedValues[i].second->getName()+".promoted", 5712e6e741b737960ecd0b68610875050019aac0f07Chris Lattner LoopPredInst); 5722e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Store into the temporary alloca... 5732e6e741b737960ecd0b68610875050019aac0f07Chris Lattner new StoreInst(LI, PromotedValues[i].first, LoopPredInst); 5742e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 5752e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 5762e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Scan the basic blocks in the loop, replacing uses of our pointers with 5770ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // uses of the allocas in question. 5782e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 5792e6e741b737960ecd0b68610875050019aac0f07Chris Lattner const std::vector<BasicBlock*> &LoopBBs = CurLoop->getBlocks(); 5802e6e741b737960ecd0b68610875050019aac0f07Chris Lattner for (std::vector<BasicBlock*>::const_iterator I = LoopBBs.begin(), 5812e6e741b737960ecd0b68610875050019aac0f07Chris Lattner E = LoopBBs.end(); I != E; ++I) { 5822e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Rewrite all loads and stores in the block of the pointer... 5832e6e741b737960ecd0b68610875050019aac0f07Chris Lattner for (BasicBlock::iterator II = (*I)->begin(), E = (*I)->end(); 5842e6e741b737960ecd0b68610875050019aac0f07Chris Lattner II != E; ++II) { 585e408e25132b8de8c757db1e3ddcd70432dfeb24dChris Lattner if (LoadInst *L = dyn_cast<LoadInst>(II)) { 5862e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::map<Value*, AllocaInst*>::iterator 5872e6e741b737960ecd0b68610875050019aac0f07Chris Lattner I = ValueToAllocaMap.find(L->getOperand(0)); 5882e6e741b737960ecd0b68610875050019aac0f07Chris Lattner if (I != ValueToAllocaMap.end()) 5892e6e741b737960ecd0b68610875050019aac0f07Chris Lattner L->setOperand(0, I->second); // Rewrite load instruction... 590e408e25132b8de8c757db1e3ddcd70432dfeb24dChris Lattner } else if (StoreInst *S = dyn_cast<StoreInst>(II)) { 5912e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::map<Value*, AllocaInst*>::iterator 5922e6e741b737960ecd0b68610875050019aac0f07Chris Lattner I = ValueToAllocaMap.find(S->getOperand(1)); 5932e6e741b737960ecd0b68610875050019aac0f07Chris Lattner if (I != ValueToAllocaMap.end()) 5942e6e741b737960ecd0b68610875050019aac0f07Chris Lattner S->setOperand(1, I->second); // Rewrite store instruction... 5952e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 5962e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 5970ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner } 5982e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 5990ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // Now that the body of the loop uses the allocas instead of the original 6000ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // memory locations, insert code to copy the alloca value back into the 6010ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // original memory location on all exits from the loop. Note that we only 6020ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // want to insert one copy of the code in each exit block, though the loop may 6030ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // exit to the same block more than once. 6040ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // 6050ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner std::set<BasicBlock*> ProcessedBlocks; 6060ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner 6070ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner const std::vector<BasicBlock*> &ExitBlocks = CurLoop->getExitBlocks(); 6080ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 609f594a03197ddd6437ca5eb3c2c61d339528e0da4Chris Lattner if (ProcessedBlocks.insert(ExitBlocks[i]).second) { 6100ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // Copy all of the allocas into their memory locations... 6110ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner BasicBlock::iterator BI = ExitBlocks[i]->begin(); 6120ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner while (isa<PHINode>(*BI)) 6130ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner ++BI; // Skip over all of the phi nodes in the block... 6140ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner Instruction *InsertPos = BI; 6150ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner for (unsigned i = 0, e = PromotedValues.size(); i != e; ++i) { 6160ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // Load from the alloca... 6170ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner LoadInst *LI = new LoadInst(PromotedValues[i].first, "", InsertPos); 6180ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // Store into the memory we promoted... 6190ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner new StoreInst(LI, PromotedValues[i].second, InsertPos); 6202e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 6210ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner } 6222e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 6232e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Now that we have done the deed, use the mem2reg functionality to promote 6242e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // all of the new allocas we just created into real SSA registers... 6252e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 6262e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::vector<AllocaInst*> PromotedAllocas; 6272e6e741b737960ecd0b68610875050019aac0f07Chris Lattner PromotedAllocas.reserve(PromotedValues.size()); 6282e6e741b737960ecd0b68610875050019aac0f07Chris Lattner for (unsigned i = 0, e = PromotedValues.size(); i != e; ++i) 6292e6e741b737960ecd0b68610875050019aac0f07Chris Lattner PromotedAllocas.push_back(PromotedValues[i].first); 63043f820d1f7638656be2158efac7dd8f5b08b8b77Chris Lattner PromoteMemToReg(PromotedAllocas, *DT, *DF, AA->getTargetData()); 6312e6e741b737960ecd0b68610875050019aac0f07Chris Lattner} 6322e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 633352361b409d16045e703d986aa7fd77295173ef3Misha Brukman/// findPromotableValuesInLoop - Check the current loop for stores to definite 6342e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// pointers, which are not loaded and stored through may aliases. If these are 6352e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// found, create an alloca for the value, add it to the PromotedValues list, 6362e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// and keep track of the mapping from value to alloca... 6372e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// 6382e6e741b737960ecd0b68610875050019aac0f07Chris Lattnervoid LICM::findPromotableValuesInLoop( 6392e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::vector<std::pair<AllocaInst*, Value*> > &PromotedValues, 6402e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::map<Value*, AllocaInst*> &ValueToAllocaMap) { 6412e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Instruction *FnStart = CurLoop->getHeader()->getParent()->begin()->begin(); 6422e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 6430252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Loop over all of the alias sets in the tracker object... 6440252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end(); 6450252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner I != E; ++I) { 6460252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AliasSet &AS = *I; 6470252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // We can promote this alias set if it has a store, if it is a "Must" alias 6480252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // set, and if the pointer is loop invariant. 6490252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner if (!AS.isForwardingAliasSet() && AS.isMod() && AS.isMustAlias() && 6500252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner isLoopInvariant(AS.begin()->first)) { 6510252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner assert(AS.begin() != AS.end() && 6520252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner "Must alias set should have at least one pointer element in it!"); 6530252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner Value *V = AS.begin()->first; 6540252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner 6550252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Check that all of the pointers in the alias set have the same type. We 6560252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // cannot (yet) promote a memory location that is loaded and stored in 6570252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // different sizes. 6580252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner bool PointerOk = true; 6590252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner for (AliasSet::iterator I = AS.begin(), E = AS.end(); I != E; ++I) 6600252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner if (V->getType() != I->first->getType()) { 6610252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner PointerOk = false; 6620252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner break; 6632e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 6640252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner 6650252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner if (PointerOk) { 6660252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner const Type *Ty = cast<PointerType>(V->getType())->getElementType(); 6670252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AllocaInst *AI = new AllocaInst(Ty, 0, V->getName()+".tmp", FnStart); 6680252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner PromotedValues.push_back(std::make_pair(AI, V)); 6690252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner 6700252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner for (AliasSet::iterator I = AS.begin(), E = AS.end(); I != E; ++I) 6710252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner ValueToAllocaMap.insert(std::make_pair(I->first, AI)); 6720252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner 6730252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner DEBUG(std::cerr << "LICM: Promoting value: " << *V << "\n"); 6742e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 6752e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 6762e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 677f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner} 678