LICM.cpp revision 118dd0ce3d8e4b0a945afc95c9538d5005abacde
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 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// 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"); 60118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner Statistic<> NumMovedCalls("licm", "Number of call insts hoisted or sunk"); 614a650af59912110a246c0a041bff38c92f0e56a2Chris Lattner Statistic<> NumPromoted("licm", 624a650af59912110a246c0a041bff38c92f0e56a2Chris Lattner "Number of memory locations promoted to registers"); 632e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 64ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner struct LICM : public FunctionPass { 657e70829632f82de15db187845666aaca6e04b792Chris Lattner virtual bool runOnFunction(Function &F); 66e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 6794170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// This transformation requires natural loop information & requires that 6894170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// loop preheaders be inserted into the CFG... 6994170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 70e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner virtual void getAnalysisUsage(AnalysisUsage &AU) const { 71cb2610ea037a17115ef3a01a6bdaab4e3cfdca27Chris Lattner AU.setPreservesCFG(); 7298bf436e2e2ab463d79c54a42a46b12028905330Chris Lattner AU.addRequiredID(LoopSimplifyID); 735f0eb8da62308126d5b61e3eee5bee75b9dc5194Chris Lattner AU.addRequired<LoopInfo>(); 74952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner AU.addRequired<DominatorTree>(); 750252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AU.addRequired<DominanceFrontier>(); // For scalar promotion (mem2reg) 76f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner AU.addRequired<AliasAnalysis>(); 77e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner } 78e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 79e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner private: 8092094b4d928119eceac1484331acffe950f4651cChris Lattner // Various analyses that we use... 812e6e741b737960ecd0b68610875050019aac0f07Chris Lattner AliasAnalysis *AA; // Current AliasAnalysis information 8292094b4d928119eceac1484331acffe950f4651cChris Lattner LoopInfo *LI; // Current LoopInfo 8392094b4d928119eceac1484331acffe950f4651cChris Lattner DominatorTree *DT; // Dominator Tree for the current Loop... 8443f820d1f7638656be2158efac7dd8f5b08b8b77Chris Lattner DominanceFrontier *DF; // Current Dominance Frontier 8592094b4d928119eceac1484331acffe950f4651cChris Lattner 8692094b4d928119eceac1484331acffe950f4651cChris Lattner // State that is updated as we process loops 872e6e741b737960ecd0b68610875050019aac0f07Chris Lattner bool Changed; // Set to true when we change anything. 882e6e741b737960ecd0b68610875050019aac0f07Chris Lattner BasicBlock *Preheader; // The preheader block of the current loop... 892e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Loop *CurLoop; // The current loop we are working on... 900252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AliasSetTracker *CurAST; // AliasSet information for the current loop... 91e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 9294170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// visitLoop - Hoist expressions out of the specified loop... 9394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 940252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner void visitLoop(Loop *L, AliasSetTracker &AST); 95e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 96e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// SinkRegion - Walk the specified region of the CFG (defined by all blocks 97e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// dominated by the specified block, and that are in the current loop) in 98e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// reverse depth first order w.r.t the DominatorTree. This allows us to 99e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// visit uses before definitions, allowing us to sink a loop body in one 100e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// pass without iteration. 101e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner /// 102e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner void SinkRegion(DominatorTree::Node *N); 103e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 104952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// HoistRegion - Walk the specified region of the CFG (defined by all 105952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// blocks dominated by the specified block, and that are in the current 106952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// loop) in depth first order w.r.t the DominatorTree. This allows us to 107cf00c4ab3ba308d45d98c5ccab87362cf802facbMisha Brukman /// visit definitions before uses, allowing us to hoist a loop body in one 108952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// pass without iteration. 109952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner /// 110952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner void HoistRegion(DominatorTree::Node *N); 111952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 112b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner /// inSubLoop - Little predicate that returns true if the specified basic 113b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner /// block is in a subloop of the current one, not the current one itself. 11494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 115b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner bool inSubLoop(BasicBlock *BB) { 116b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop"); 117329c1c6c949d07e3fe9722ec633b4258217fd99dChris Lattner for (Loop::iterator I = CurLoop->begin(), E = CurLoop->end(); I != E; ++I) 118329c1c6c949d07e3fe9722ec633b4258217fd99dChris Lattner if ((*I)->contains(BB)) 119b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner return true; // A subloop actually contains this block! 120b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner return false; 121e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner } 122e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 123a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// isExitBlockDominatedByBlockInLoop - This method checks to see if the 124a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// specified exit block of the loop is dominated by the specified block 125a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// that is in the body of the loop. We use these constraints to 126a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// dramatically limit the amount of the dominator tree that needs to be 127a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// searched. 128a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isExitBlockDominatedByBlockInLoop(BasicBlock *ExitBlock, 129a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *BlockInLoop) const { 130a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If the block in the loop is the loop header, it must be dominated! 131a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *LoopHeader = CurLoop->getHeader(); 132a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (BlockInLoop == LoopHeader) 133a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 134a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 135a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner DominatorTree::Node *BlockInLoopNode = DT->getNode(BlockInLoop); 136a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner DominatorTree::Node *IDom = DT->getNode(ExitBlock); 137a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 138a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Because the exit block is not in the loop, we know we have to get _at 139a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // least_ it's immediate dominator. 140a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner do { 141a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Get next Immediate Dominator. 142a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner IDom = IDom->getIDom(); 143a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 144a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If we have got to the header of the loop, then the instructions block 145a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // did not dominate the exit node, so we can't hoist it. 146a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (IDom->getBlock() == LoopHeader) 147a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 148a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 149a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } while (IDom != BlockInLoopNode); 150a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 151a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 152a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 153a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 154a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// sink - When an instruction is found to only be used outside of the loop, 155a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// this function moves it to the exit blocks and patches up SSA form as 156a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// needed. 157a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// 158a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner void sink(Instruction &I); 159a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 16094170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// hoist - When an instruction is found to only use loop invariant operands 16194170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// that is safe to hoist, this instruction is called to do the dirty work. 16294170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 1637e70829632f82de15db187845666aaca6e04b792Chris Lattner void hoist(Instruction &I); 164e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 165a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it 166a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// is not a trapping instruction or if it is a trapping instruction and is 167a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner /// guaranteed to execute. 1689966c03aad031f738718bed3bc00371e358beb5dTanya Lattner /// 169a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isSafeToExecuteUnconditionally(Instruction &I); 1709966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 17194170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// pointerInvalidatedByLoop - Return true if the body of this loop may 17294170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// store into the memory location pointed to by V. 17394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 1742e6e741b737960ecd0b68610875050019aac0f07Chris Lattner bool pointerInvalidatedByLoop(Value *V) { 1750252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Check to see if any of the basic blocks in CurLoop invalidate *V. 1760252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner return CurAST->getAliasSetForPointer(V, 0).isMod(); 1772e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 178f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner 17994170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// isLoopInvariant - Return true if the specified value is loop invariant 18094170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner /// 181e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner inline bool isLoopInvariant(Value *V) { 182e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner if (Instruction *I = dyn_cast<Instruction>(V)) 183e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner return !CurLoop->contains(I->getParent()); 184e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner return true; // All non-instructions are loop invariant 185e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner } 186a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 187a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool canSinkOrHoistInst(Instruction &I); 188a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isLoopInvariantInst(Instruction &I); 189a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner bool isNotUsedInLoop(Instruction &I); 190e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 1912e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// PromoteValuesInLoop - Look at the stores in the loop and promote as many 1922e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// to scalars as we can. 1932e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// 1942e6e741b737960ecd0b68610875050019aac0f07Chris Lattner void PromoteValuesInLoop(); 1952e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 1962e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// findPromotableValuesInLoop - Check the current loop for stores to 197352361b409d16045e703d986aa7fd77295173ef3Misha Brukman /// definite pointers, which are not loaded and stored through may aliases. 1982e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// If these are found, create an alloca for the value, add it to the 1992e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// PromotedValues list, and keep track of the mapping from value to 2002e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// alloca... 2012e6e741b737960ecd0b68610875050019aac0f07Chris Lattner /// 2022e6e741b737960ecd0b68610875050019aac0f07Chris Lattner void findPromotableValuesInLoop( 2032e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::vector<std::pair<AllocaInst*, Value*> > &PromotedValues, 2042e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::map<Value*, AllocaInst*> &Val2AlMap); 205e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner }; 206f629309f74cf1a64aa7fd1cd5784fd7db9a8f59eChris Lattner 207a6275ccdf5e1aa208afde56c498e2b13e16442f0Chris Lattner RegisterOpt<LICM> X("licm", "Loop Invariant Code Motion"); 208e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 209e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 21092094b4d928119eceac1484331acffe950f4651cChris LattnerFunctionPass *llvm::createLICMPass() { return new LICM(); } 211e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 21294170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// runOnFunction - For LICM, this simply traverses the loop structure of the 21394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// function, hoisting expressions out of loops if possible. 21494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 2157e70829632f82de15db187845666aaca6e04b792Chris Lattnerbool LICM::runOnFunction(Function &) { 2162e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Changed = false; 217e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2182e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Get our Loop and Alias Analysis information... 2192e6e741b737960ecd0b68610875050019aac0f07Chris Lattner LI = &getAnalysis<LoopInfo>(); 220f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner AA = &getAnalysis<AliasAnalysis>(); 22143f820d1f7638656be2158efac7dd8f5b08b8b77Chris Lattner DF = &getAnalysis<DominanceFrontier>(); 22211a49a722f657294f38865019af51f82dc31c1c3Tanya Lattner DT = &getAnalysis<DominatorTree>(); 223f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner 2242e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Hoist expressions out of all of the top-level loops. 225329c1c6c949d07e3fe9722ec633b4258217fd99dChris Lattner for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) { 2260252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AliasSetTracker AST(*AA); 227ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner visitLoop(*I, AST); 2282e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 229e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner return Changed; 230e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 231e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 23294170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner 23394170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// visitLoop - Hoist expressions out of the specified loop... 23494170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 2350252e49f6d6973b6f347c8feafc49e28af27163aChris Lattnervoid LICM::visitLoop(Loop *L, AliasSetTracker &AST) { 236e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // Recurse through all subloops before we process this loop... 237329c1c6c949d07e3fe9722ec633b4258217fd99dChris Lattner for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) { 2380252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AliasSetTracker SubAST(*AA); 239ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner visitLoop(*I, SubAST); 2402e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 2412e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Incorporate information about the subloops into this loop... 2420252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AST.add(SubAST); 2432e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 244e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner CurLoop = L; 2450252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner CurAST = &AST; 246e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 24799a57216a935a512c418032f590a4660bad9d846Chris Lattner // Get the preheader block to move instructions into... 24899a57216a935a512c418032f590a4660bad9d846Chris Lattner Preheader = L->getLoopPreheader(); 24999a57216a935a512c418032f590a4660bad9d846Chris Lattner assert(Preheader&&"Preheader insertion pass guarantees we have a preheader!"); 25099a57216a935a512c418032f590a4660bad9d846Chris Lattner 2512e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Loop over the body of this loop, looking for calls, invokes, and stores. 2520252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Because subloops have already been incorporated into AST, we skip blocks in 2532e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // subloops. 2542e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 255a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (std::vector<BasicBlock*>::const_iterator I = L->getBlocks().begin(), 256a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner E = L->getBlocks().end(); I != E; ++I) 2572e6e741b737960ecd0b68610875050019aac0f07Chris Lattner if (LI->getLoopFor(*I) == L) // Ignore blocks in subloops... 2580252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AST.add(**I); // Incorporate the specified basic block 2592e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 260e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // We want to visit all of the instructions in this loop... that are not parts 261e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // of our subloops (they have already had their invariants hoisted out of 262e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // their loop, into this loop, so there is no need to process the BODIES of 263e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // the subloops). 264e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // 265952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // Traverse the body of the loop in depth first order on the dominator tree so 266952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // that we are guaranteed to see definitions before we see uses. This allows 267e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // us to sink instructions in one pass, without iteration. AFter sinking 268e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // instructions, we perform another pass to hoist them out of the loop. 269952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner // 270e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner SinkRegion(DT->getNode(L->getHeader())); 27111a49a722f657294f38865019af51f82dc31c1c3Tanya Lattner HoistRegion(DT->getNode(L->getHeader())); 272e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 2732e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Now that all loop invariants have been removed from the loop, promote any 2742e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // memory references to scalars that we can... 2752e6e741b737960ecd0b68610875050019aac0f07Chris Lattner if (!DisablePromotion) 2762e6e741b737960ecd0b68610875050019aac0f07Chris Lattner PromoteValuesInLoop(); 2772e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 278e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner // Clear out loops state information for the next iteration 279e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner CurLoop = 0; 28099a57216a935a512c418032f590a4660bad9d846Chris Lattner Preheader = 0; 281e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 282e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 283e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// SinkRegion - Walk the specified region of the CFG (defined by all blocks 284e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// dominated by the specified block, and that are in the current loop) in 285e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// reverse depth first order w.r.t the DominatorTree. This allows us to visit 286e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// uses before definitions, allowing us to sink a loop body in one pass without 287e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// iteration. 288e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner/// 289e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattnervoid LICM::SinkRegion(DominatorTree::Node *N) { 290e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner assert(N != 0 && "Null dominator tree node?"); 291e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner BasicBlock *BB = N->getBlock(); 292e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 293e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // If this subregion is not in the top level loop at all, exit. 294e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner if (!CurLoop->contains(BB)) return; 295e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 296e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // We are processing blocks in reverse dfo, so process children first... 297e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner const std::vector<DominatorTree::Node*> &Children = N->getChildren(); 298e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner for (unsigned i = 0, e = Children.size(); i != e; ++i) 299e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner SinkRegion(Children[i]); 300e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 301e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Only need to process the contents of this block if it is not part of a 302e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // subloop (which would already have been processed). 303e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner if (inSubLoop(BB)) return; 304e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 305a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner for (BasicBlock::iterator II = BB->end(); II != BB->begin(); ) { 306a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner Instruction &I = *--II; 307e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 308e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Check to see if we can sink this instruction to the exit blocks 309e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // of the loop. We can do this if the all users of the instruction are 310e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // outside of the loop. In this case, it doesn't even matter if the 311e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // operands of the instruction are loop invariant. 312e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // 313a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner if (canSinkOrHoistInst(I) && isNotUsedInLoop(I)) { 314a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner ++II; 315e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner sink(I); 316a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner } 317e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner } 318e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner} 319e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 320e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 321952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// HoistRegion - Walk the specified region of the CFG (defined by all blocks 322952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// dominated by the specified block, and that are in the current loop) in depth 323cf00c4ab3ba308d45d98c5ccab87362cf802facbMisha Brukman/// first order w.r.t the DominatorTree. This allows us to visit definitions 324952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// before uses, allowing us to hoist a loop body in one pass without iteration. 325952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner/// 326952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattnervoid LICM::HoistRegion(DominatorTree::Node *N) { 327952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner assert(N != 0 && "Null dominator tree node?"); 328ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner BasicBlock *BB = N->getBlock(); 329952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 330b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner // If this subregion is not in the top level loop at all, exit. 331ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (!CurLoop->contains(BB)) return; 332952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 333a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Only need to process the contents of this block if it is not part of a 334a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // subloop (which would already have been processed). 335ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (!inSubLoop(BB)) 336a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ) { 337a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Instruction &I = *II++; 338e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner 339e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // Try hoisting the instruction out to the preheader. We can only do this 340e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // if all of the operands of the instruction are loop invariant and if it 341e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // is safe to hoist the instruction. 342e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner // 343e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner if (isLoopInvariantInst(I) && canSinkOrHoistInst(I) && 344e4365b2e8c79f9b2d564f31fdcc0568da8e5d60fChris Lattner isSafeToExecuteUnconditionally(I)) 345a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner hoist(I); 346a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 347952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 348952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner const std::vector<DominatorTree::Node*> &Children = N->getChildren(); 349952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner for (unsigned i = 0, e = Children.size(); i != e; ++i) 350952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner HoistRegion(Children[i]); 351952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner} 352952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 353a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// canSinkOrHoistInst - Return true if the hoister and sinker can handle this 354a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// instruction. 355a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 356a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::canSinkOrHoistInst(Instruction &I) { 357ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // Loads have extra constraints we have to verify before we can hoist them. 358ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { 359ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner if (LI->isVolatile()) 360ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner return false; // Don't hoist volatile loads! 361ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 362ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // Don't hoist loads which have may-aliased stores in loop. 363a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return !pointerInvalidatedByLoop(LI->getOperand(0)); 364118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } else if (CallInst *CI = dyn_cast<CallInst>(&I)) { 365118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // Handle obvious cases efficiently. 366118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner if (Function *Callee = CI->getCalledFunction()) { 367118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner if (AA->doesNotAccessMemory(Callee)) 368118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner return true; 369118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner else if (AA->onlyReadsMemory(Callee)) { 370118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // If this call only reads from memory and there are no writes to memory 371118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // in the loop, we can hoist or sink the call as appropriate. 372118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner bool FoundMod = false; 373118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end(); 374118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner I != E; ++I) { 375118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner AliasSet &AS = *I; 376118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner if (!AS.isForwardingAliasSet() && AS.isMod()) { 377118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner FoundMod = true; 378118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner break; 379118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 380118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 381118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner if (!FoundMod) return true; 382118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 383118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner } 384118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner 385118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // FIXME: This should use mod/ref information to see if we can hoist or sink 386118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // the call. 387118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner 388118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner return false; 389ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner } 390ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 391a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return isa<BinaryOperator>(I) || isa<ShiftInst>(I) || isa<CastInst>(I) || 392118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner isa<SelectInst>(I) || 393a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner isa<GetElementPtrInst>(I) || isa<VANextInst>(I) || isa<VAArgInst>(I); 394a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 395a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 396a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isNotUsedInLoop - Return true if the only users of this instruction are 397a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// outside of the loop. If this is true, we can sink the instruction to the 398a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// exit blocks of the loop. 399a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 400a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isNotUsedInLoop(Instruction &I) { 401ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner for (Value::use_iterator UI = I.use_begin(), E = I.use_end(); UI != E; ++UI) { 402ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner Instruction *User = cast<Instruction>(*UI); 403ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (PHINode *PN = dyn_cast<PHINode>(User)) { 404ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner // PHI node uses occur in predecessor blocks! 405ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 406ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (PN->getIncomingValue(i) == &I) 407ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner if (CurLoop->contains(PN->getIncomingBlock(i))) 408ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner return false; 409ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } else if (CurLoop->contains(User->getParent())) { 410a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 411ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } 412ea9403f2aa078e840a49792d906390395f0cd2f6Chris Lattner } 413a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return true; 414a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 415a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 416a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 417a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isLoopInvariantInst - Return true if all operands of this instruction are 418a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// loop invariant. We also filter out non-hoistable instructions here just for 419a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// efficiency. 420a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 421a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isLoopInvariantInst(Instruction &I) { 422a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The instruction is loop invariant if all of its operands are loop-invariant 423a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) 424a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!isLoopInvariant(I.getOperand(i))) 425a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 426a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 427ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner // If we got this far, the instruction is loop invariant! 428ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner return true; 429ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner} 430ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 431a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// sink - When an instruction is found to only be used outside of the loop, 432a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// this function moves it to the exit blocks and patches up SSA form as needed. 433a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// This method is guaranteed to remove the original instruction from its 434a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner/// position, and may either delete it or move it to outside of the loop. 435a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// 436a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnervoid LICM::sink(Instruction &I) { 437a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner DEBUG(std::cerr << "LICM sinking instruction: " << I); 438a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 439a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner const std::vector<BasicBlock*> &ExitBlocks = CurLoop->getExitBlocks(); 440df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner 441df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner if (isa<LoadInst>(I)) ++NumMovedLoads; 442118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner else if (isa<CallInst>(I)) ++NumMovedCalls; 443df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner ++NumSunk; 444df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner Changed = true; 445df45bd3803ae0965a83cd1f30ee051b9f43e73ddChris Lattner 446a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The case where there is only a single exit node of this loop is common 447a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // enough that we handle it as a special (more efficient) case. It is more 448a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // efficient to handle because there are no PHI nodes that need to be placed. 449a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (ExitBlocks.size() == 1) { 450a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[0], I.getParent())) { 451a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Instruction is not used, just delete it. 452ba7df4c48235964f1b8d133c98886781b5f853e2Chris Lattner CurAST->remove(&I); 453a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getInstList().erase(&I); 454a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 455a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Move the instruction to the start of the exit block, after any PHI 456a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // nodes in it. 457a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getInstList().remove(&I); 458a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 459a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock::iterator InsertPt = ExitBlocks[0]->begin(); 460a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner while (isa<PHINode>(InsertPt)) ++InsertPt; 461a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner ExitBlocks[0]->getInstList().insert(InsertPt, &I); 462a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 463a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else if (ExitBlocks.size() == 0) { 464a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // The instruction is actually dead if there ARE NO exit blocks. 465ba7df4c48235964f1b8d133c98886781b5f853e2Chris Lattner CurAST->remove(&I); 466a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getInstList().erase(&I); 467a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 468a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Otherwise, if we have multiple exits, use the PromoteMem2Reg function to 469a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // do all of the hard work of inserting PHI nodes as necessary. We convert 470a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // the value into a stack object to get it to do this. 471a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 472a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Firstly, we create a stack object to hold the value... 473a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner AllocaInst *AI = new AllocaInst(I.getType(), 0, I.getName(), 474a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getParent()->front().begin()); 475a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 476a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Secondly, insert load instructions for each use of the instruction 477a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // outside of the loop. 478a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner while (!I.use_empty()) { 479a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Instruction *U = cast<Instruction>(I.use_back()); 480a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 481a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If the user is a PHI Node, we actually have to insert load instructions 482a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // in all predecessor blocks, not in the PHI block itself! 483a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (PHINode *UPN = dyn_cast<PHINode>(U)) { 484a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Only insert into each predecessor once, so that we don't have 485a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // different incoming values from the same block! 486a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner std::map<BasicBlock*, Value*> InsertedBlocks; 487a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = UPN->getNumIncomingValues(); i != e; ++i) 488a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (UPN->getIncomingValue(i) == &I) { 489a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *Pred = UPN->getIncomingBlock(i); 490a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Value *&PredVal = InsertedBlocks[Pred]; 491a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!PredVal) { 492a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Insert a new load instruction right before the terminator in 493a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // the predecessor block. 494a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner PredVal = new LoadInst(AI, "", Pred->getTerminator()); 495a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 496a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 497a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner UPN->setIncomingValue(i, PredVal); 498a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 499a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 500a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 501a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner LoadInst *L = new LoadInst(AI, "", U); 502a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner U->replaceUsesOfWith(&I, L); 503a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 504a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 505a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 506a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Thirdly, insert a copy of the instruction in each exit block of the loop 507a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // that is dominated by the instruction, storing the result into the memory 508a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // location. Be careful not to insert the instruction into any particular 509a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // basic block more than once. 510a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner std::set<BasicBlock*> InsertedBlocks; 511a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *InstOrigBB = I.getParent(); 512a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 513a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 514a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock *ExitBlock = ExitBlocks[i]; 515a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 516a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (isExitBlockDominatedByBlockInLoop(ExitBlock, InstOrigBB)) { 517a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If we haven't already processed this exit block, do so now. 518e3cfe8d563fa06b274587aa38b1359ff707f33deChris Lattner if (InsertedBlocks.insert(ExitBlock).second) { 519a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Insert the code after the last PHI node... 520a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner BasicBlock::iterator InsertPt = ExitBlock->begin(); 521a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner while (isa<PHINode>(InsertPt)) ++InsertPt; 522a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 523a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // If this is the first exit block processed, just move the original 524a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // instruction, otherwise clone the original instruction and insert 525a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // the copy. 526a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Instruction *New; 5277d3ced934f1bb2c6845676c7333ef879d5219e88Chris Lattner if (InsertedBlocks.size() == 1) { 528a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getInstList().remove(&I); 529a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner ExitBlock->getInstList().insert(InsertPt, &I); 530a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner New = &I; 531a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } else { 532a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner New = I.clone(); 533a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner New->setName(I.getName()+".le"); 534a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner ExitBlock->getInstList().insert(InsertPt, New); 535a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 536a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 537a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Now that we have inserted the instruction, store it into the alloca 538a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner new StoreInst(New, AI, InsertPt); 539a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 540a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 541a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 542a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner 543a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner // If the instruction doesn't dominate any exit blocks, it must be dead. 544a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner if (InsertedBlocks.empty()) { 545a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner CurAST->remove(&I); 546a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner I.getParent()->getInstList().erase(&I); 547a3df8a964aa9d0d171fd4f6e491c7d1cf9dee500Chris Lattner } 548a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner 549a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner // Finally, promote the fine value to SSA form. 550a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner std::vector<AllocaInst*> Allocas; 551a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Allocas.push_back(AI); 552a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner PromoteMemToReg(Allocas, *DT, *DF, AA->getTargetData()); 553a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner } 554a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner} 555952eaee239d6c38f5121ed68277555344c2d6bf0Chris Lattner 55694170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// hoist - When an instruction is found to only use loop invariant operands 55794170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// that is safe to hoist, this instruction is called to do the dirty work. 55894170596b715928794a55bc5a1671e3992fd2dc9Chris Lattner/// 559a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnervoid LICM::hoist(Instruction &I) { 560b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner DEBUG(std::cerr << "LICM hoisting to"; 561b461373fbcdc5909cc7331fa64791cd039de4bc8Chris Lattner WriteAsOperand(std::cerr, Preheader, false); 562a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner std::cerr << ": " << I); 563ed6dfc2856cd44a8aa608a9074eabbf42dd6cadcChris Lattner 56499a57216a935a512c418032f590a4660bad9d846Chris Lattner // Remove the instruction from its current basic block... but don't delete the 56599a57216a935a512c418032f590a4660bad9d846Chris Lattner // instruction. 566a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner I.getParent()->getInstList().remove(&I); 567e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 5689646e6b6af1f924f9366a2bffc6dde102f84d231Chris Lattner // Insert the new node in Preheader, before the terminator. 569a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner Preheader->getInstList().insert(Preheader->getTerminator(), &I); 5709646e6b6af1f924f9366a2bffc6dde102f84d231Chris Lattner 571a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (isa<LoadInst>(I)) ++NumMovedLoads; 572118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner else if (isa<CallInst>(I)) ++NumMovedCalls; 5739646e6b6af1f924f9366a2bffc6dde102f84d231Chris Lattner ++NumHoisted; 574e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner Changed = true; 575e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner} 576e0e734eea052a4e8372e6f430ef41149128ba0a6Chris Lattner 577a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it is 578a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// not a trapping instruction or if it is a trapping instruction and is 579a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner/// guaranteed to execute. 5809966c03aad031f738718bed3bc00371e358beb5dTanya Lattner/// 581a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattnerbool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) { 58292094b4d928119eceac1484331acffe950f4651cChris Lattner // If it is not a trapping instruction, it is always safe to hoist. 58392094b4d928119eceac1484331acffe950f4651cChris Lattner if (!Inst.isTrapping()) return true; 58492094b4d928119eceac1484331acffe950f4651cChris Lattner 58592094b4d928119eceac1484331acffe950f4651cChris Lattner // Otherwise we have to check to make sure that the instruction dominates all 58692094b4d928119eceac1484331acffe950f4651cChris Lattner // of the exit blocks. If it doesn't, then there is a path out of the loop 58792094b4d928119eceac1484331acffe950f4651cChris Lattner // which does not execute this instruction, so we can't hoist it. 58892094b4d928119eceac1484331acffe950f4651cChris Lattner 58992094b4d928119eceac1484331acffe950f4651cChris Lattner // If the instruction is in the header block for the loop (which is very 59092094b4d928119eceac1484331acffe950f4651cChris Lattner // common), it is always guaranteed to dominate the exit blocks. Since this 59192094b4d928119eceac1484331acffe950f4651cChris Lattner // is a common case, and can save some work, check it now. 592a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (Inst.getParent() == CurLoop->getHeader()) 59392094b4d928119eceac1484331acffe950f4651cChris Lattner return true; 59492094b4d928119eceac1484331acffe950f4651cChris Lattner 59592094b4d928119eceac1484331acffe950f4651cChris Lattner // Get the exit blocks for the current loop. 596a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner const std::vector<BasicBlock*> &ExitBlocks = CurLoop->getExitBlocks(); 5979966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 59892094b4d928119eceac1484331acffe950f4651cChris Lattner // For each exit block, get the DT node and walk up the DT until the 59992094b4d928119eceac1484331acffe950f4651cChris Lattner // instruction's basic block is found or we exit the loop. 600a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 601a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner if (!isExitBlockDominatedByBlockInLoop(ExitBlocks[i], Inst.getParent())) 602a2706518f9cc34358cba1072f78235aa091d6d93Chris Lattner return false; 60311a49a722f657294f38865019af51f82dc31c1c3Tanya Lattner 6049966c03aad031f738718bed3bc00371e358beb5dTanya Lattner return true; 6059966c03aad031f738718bed3bc00371e358beb5dTanya Lattner} 6069966c03aad031f738718bed3bc00371e358beb5dTanya Lattner 607eb53ae4f2dc39e75e725b21b52d77d29cf1c11c9Chris Lattner 6082e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// PromoteValuesInLoop - Try to promote memory values to scalars by sinking 6092e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// stores out of the loop and moving loads to before the loop. We do this by 6102e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// looping over the stores in the loop, looking for stores to Must pointers 6112e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// which are loop invariant. We promote these memory locations to use allocas 6122e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// instead. These allocas can easily be raised to register values by the 6132e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// PromoteMem2Reg functionality. 6142e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// 6152e6e741b737960ecd0b68610875050019aac0f07Chris Lattnervoid LICM::PromoteValuesInLoop() { 6162e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // PromotedValues - List of values that are promoted out of the loop. Each 617065a616adad624152618b1b0084ff074e5b03bbbChris Lattner // value has an alloca instruction for it, and a canonical version of the 6182e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // pointer. 6192e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::vector<std::pair<AllocaInst*, Value*> > PromotedValues; 6202e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::map<Value*, AllocaInst*> ValueToAllocaMap; // Map of ptr to alloca 6212e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 6222e6e741b737960ecd0b68610875050019aac0f07Chris Lattner findPromotableValuesInLoop(PromotedValues, ValueToAllocaMap); 6232e6e741b737960ecd0b68610875050019aac0f07Chris Lattner if (ValueToAllocaMap.empty()) return; // If there are values to promote... 6242e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 6252e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Changed = true; 6262e6e741b737960ecd0b68610875050019aac0f07Chris Lattner NumPromoted += PromotedValues.size(); 6272e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 6282e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Emit a copy from the value into the alloca'd value in the loop preheader 6292e6e741b737960ecd0b68610875050019aac0f07Chris Lattner TerminatorInst *LoopPredInst = Preheader->getTerminator(); 6302e6e741b737960ecd0b68610875050019aac0f07Chris Lattner for (unsigned i = 0, e = PromotedValues.size(); i != e; ++i) { 6312e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Load from the memory we are promoting... 6322e6e741b737960ecd0b68610875050019aac0f07Chris Lattner LoadInst *LI = new LoadInst(PromotedValues[i].second, 6332e6e741b737960ecd0b68610875050019aac0f07Chris Lattner PromotedValues[i].second->getName()+".promoted", 6342e6e741b737960ecd0b68610875050019aac0f07Chris Lattner LoopPredInst); 6352e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Store into the temporary alloca... 6362e6e741b737960ecd0b68610875050019aac0f07Chris Lattner new StoreInst(LI, PromotedValues[i].first, LoopPredInst); 6372e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 6382e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 6392e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Scan the basic blocks in the loop, replacing uses of our pointers with 6400ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // uses of the allocas in question. 6412e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 6422e6e741b737960ecd0b68610875050019aac0f07Chris Lattner const std::vector<BasicBlock*> &LoopBBs = CurLoop->getBlocks(); 6432e6e741b737960ecd0b68610875050019aac0f07Chris Lattner for (std::vector<BasicBlock*>::const_iterator I = LoopBBs.begin(), 6442e6e741b737960ecd0b68610875050019aac0f07Chris Lattner E = LoopBBs.end(); I != E; ++I) { 6452e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Rewrite all loads and stores in the block of the pointer... 6462e6e741b737960ecd0b68610875050019aac0f07Chris Lattner for (BasicBlock::iterator II = (*I)->begin(), E = (*I)->end(); 6472e6e741b737960ecd0b68610875050019aac0f07Chris Lattner II != E; ++II) { 648e408e25132b8de8c757db1e3ddcd70432dfeb24dChris Lattner if (LoadInst *L = dyn_cast<LoadInst>(II)) { 6492e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::map<Value*, AllocaInst*>::iterator 6502e6e741b737960ecd0b68610875050019aac0f07Chris Lattner I = ValueToAllocaMap.find(L->getOperand(0)); 6512e6e741b737960ecd0b68610875050019aac0f07Chris Lattner if (I != ValueToAllocaMap.end()) 6522e6e741b737960ecd0b68610875050019aac0f07Chris Lattner L->setOperand(0, I->second); // Rewrite load instruction... 653e408e25132b8de8c757db1e3ddcd70432dfeb24dChris Lattner } else if (StoreInst *S = dyn_cast<StoreInst>(II)) { 6542e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::map<Value*, AllocaInst*>::iterator 6552e6e741b737960ecd0b68610875050019aac0f07Chris Lattner I = ValueToAllocaMap.find(S->getOperand(1)); 6562e6e741b737960ecd0b68610875050019aac0f07Chris Lattner if (I != ValueToAllocaMap.end()) 6572e6e741b737960ecd0b68610875050019aac0f07Chris Lattner S->setOperand(1, I->second); // Rewrite store instruction... 6582e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 6592e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 6600ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner } 6612e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 6620ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // Now that the body of the loop uses the allocas instead of the original 6630ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // memory locations, insert code to copy the alloca value back into the 6640ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // original memory location on all exits from the loop. Note that we only 6650ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // want to insert one copy of the code in each exit block, though the loop may 6660ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // exit to the same block more than once. 6670ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // 6680ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner std::set<BasicBlock*> ProcessedBlocks; 6690ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner 6700ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner const std::vector<BasicBlock*> &ExitBlocks = CurLoop->getExitBlocks(); 6710ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 672f594a03197ddd6437ca5eb3c2c61d339528e0da4Chris Lattner if (ProcessedBlocks.insert(ExitBlocks[i]).second) { 6730ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // Copy all of the allocas into their memory locations... 6740ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner BasicBlock::iterator BI = ExitBlocks[i]->begin(); 6750ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner while (isa<PHINode>(*BI)) 6760ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner ++BI; // Skip over all of the phi nodes in the block... 6770ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner Instruction *InsertPos = BI; 6780ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner for (unsigned i = 0, e = PromotedValues.size(); i != e; ++i) { 6790ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // Load from the alloca... 6800ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner LoadInst *LI = new LoadInst(PromotedValues[i].first, "", InsertPos); 6810ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner // Store into the memory we promoted... 6820ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner new StoreInst(LI, PromotedValues[i].second, InsertPos); 6832e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 6840ed2da9ac733c51ba004c067d3b552c1fa54613dChris Lattner } 6852e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 6862e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // Now that we have done the deed, use the mem2reg functionality to promote 6872e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // all of the new allocas we just created into real SSA registers... 6882e6e741b737960ecd0b68610875050019aac0f07Chris Lattner // 6892e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::vector<AllocaInst*> PromotedAllocas; 6902e6e741b737960ecd0b68610875050019aac0f07Chris Lattner PromotedAllocas.reserve(PromotedValues.size()); 6912e6e741b737960ecd0b68610875050019aac0f07Chris Lattner for (unsigned i = 0, e = PromotedValues.size(); i != e; ++i) 6922e6e741b737960ecd0b68610875050019aac0f07Chris Lattner PromotedAllocas.push_back(PromotedValues[i].first); 69343f820d1f7638656be2158efac7dd8f5b08b8b77Chris Lattner PromoteMemToReg(PromotedAllocas, *DT, *DF, AA->getTargetData()); 6942e6e741b737960ecd0b68610875050019aac0f07Chris Lattner} 6952e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 696352361b409d16045e703d986aa7fd77295173ef3Misha Brukman/// findPromotableValuesInLoop - Check the current loop for stores to definite 6972e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// pointers, which are not loaded and stored through may aliases. If these are 6982e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// found, create an alloca for the value, add it to the PromotedValues list, 6992e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// and keep track of the mapping from value to alloca... 7002e6e741b737960ecd0b68610875050019aac0f07Chris Lattner/// 7012e6e741b737960ecd0b68610875050019aac0f07Chris Lattnervoid LICM::findPromotableValuesInLoop( 7022e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::vector<std::pair<AllocaInst*, Value*> > &PromotedValues, 7032e6e741b737960ecd0b68610875050019aac0f07Chris Lattner std::map<Value*, AllocaInst*> &ValueToAllocaMap) { 7042e6e741b737960ecd0b68610875050019aac0f07Chris Lattner Instruction *FnStart = CurLoop->getHeader()->getParent()->begin()->begin(); 7052e6e741b737960ecd0b68610875050019aac0f07Chris Lattner 7060252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Loop over all of the alias sets in the tracker object... 7070252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end(); 7080252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner I != E; ++I) { 7090252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AliasSet &AS = *I; 7100252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // We can promote this alias set if it has a store, if it is a "Must" alias 711118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // set, if the pointer is loop invariant, if if we are not eliminating any 712118dd0ce3d8e4b0a945afc95c9538d5005abacdeChris Lattner // volatile loads or stores. 7130252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner if (!AS.isForwardingAliasSet() && AS.isMod() && AS.isMustAlias() && 71400ad4a2d170bc129c17ad7d8efe94daad8038796Chris Lattner !AS.isVolatile() && isLoopInvariant(AS.begin()->first)) { 7150252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner assert(AS.begin() != AS.end() && 7160252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner "Must alias set should have at least one pointer element in it!"); 7170252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner Value *V = AS.begin()->first; 7180252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner 7190252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // Check that all of the pointers in the alias set have the same type. We 7200252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // cannot (yet) promote a memory location that is loaded and stored in 7210252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner // different sizes. 7220252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner bool PointerOk = true; 7230252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner for (AliasSet::iterator I = AS.begin(), E = AS.end(); I != E; ++I) 7240252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner if (V->getType() != I->first->getType()) { 7250252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner PointerOk = false; 7260252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner break; 7272e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 7280252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner 7290252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner if (PointerOk) { 7300252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner const Type *Ty = cast<PointerType>(V->getType())->getElementType(); 7310252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner AllocaInst *AI = new AllocaInst(Ty, 0, V->getName()+".tmp", FnStart); 7320252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner PromotedValues.push_back(std::make_pair(AI, V)); 7330252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner 7340252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner for (AliasSet::iterator I = AS.begin(), E = AS.end(); I != E; ++I) 7350252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner ValueToAllocaMap.insert(std::make_pair(I->first, AI)); 7360252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner 7370252e49f6d6973b6f347c8feafc49e28af27163aChris Lattner DEBUG(std::cerr << "LICM: Promoting value: " << *V << "\n"); 7382e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 7392e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 7402e6e741b737960ecd0b68610875050019aac0f07Chris Lattner } 741f5e84aa0887d3fcd752d4a4fa1bb0e526be49f20Chris Lattner} 742