LoopUnswitch.cpp revision cd35e09a4a3c640b9da0b1dfe3548a605c929ae5
15821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//===-- LoopUnswitch.cpp - Hoist loop-invariant conditionals in loop ------===// 25821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 35821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// The LLVM Compiler Infrastructure 45821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 55821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// This file is distributed under the University of Illinois Open Source 65821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// License. See LICENSE.TXT for details. 75821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 85821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//===----------------------------------------------------------------------===// 95821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// This pass transforms loops that contain branches on loop-invariant conditions 115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// to have multiple loops. For example, it turns the left into the right code: 125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// for (...) if (lic) 149ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch// A for (...) 15c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles)// if (lic) A; B; C 165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// B else 175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// C for (...) 181e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles)// A; C 195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 201e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles)// This can increase the size of the code exponentially (doubling it every time 215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// a loop is unswitched) so we only unswitch if the resultant code will be 225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// smaller than a threshold. 235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 242a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)// This pass expects LICM to be run before it to hoist invariant conditions out 255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// of the loop, to make the unswitching opportunity obvious. 265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//===----------------------------------------------------------------------===// 285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 292a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)#define DEBUG_TYPE "loop-unswitch" 305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Transforms/Scalar.h" 315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Constants.h" 322a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)#include "llvm/DerivedTypes.h" 335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Function.h" 345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Instructions.h" 355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Analysis/InlineCost.h" 365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Analysis/InstructionSimplify.h" 375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Analysis/LoopInfo.h" 385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Analysis/LoopPass.h" 395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Analysis/Dominators.h" 405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Analysis/ScalarEvolution.h" 415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Transforms/Utils/Cloning.h" 425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Transforms/Utils/Local.h" 435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Transforms/Utils/BasicBlockUtils.h" 445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/ADT/Statistic.h" 455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/ADT/SmallPtrSet.h" 465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/ADT/STLExtras.h" 475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Support/CommandLine.h" 485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Support/Debug.h" 495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Support/raw_ostream.h" 505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include <algorithm> 515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include <set> 525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)using namespace llvm; 535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)STATISTIC(NumBranches, "Number of branches unswitched"); 555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)STATISTIC(NumSwitches, "Number of switches unswitched"); 565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)STATISTIC(NumSelects , "Number of selects unswitched"); 575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)STATISTIC(NumTrivial , "Number of unswitches that are trivial"); 585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)STATISTIC(NumSimplify, "Number of simplifications of unswitched code"); 595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// The specific value of 50 here was chosen based only on intuition and a 615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// few specific examples. 625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static cl::opt<unsigned> 635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)Threshold("loop-unswitch-threshold", cl::desc("Max loop size to unswitch"), 645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) cl::init(50), cl::Hidden); 655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)namespace { 675821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) class LoopUnswitch : public LoopPass { 685821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LoopInfo *LI; // Loop information 695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPPassManager *LPM; 705821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 715821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // LoopProcessWorklist - Used to check if second loop needs processing 725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // after RewriteLoopBodyWithConditionConstant rewrites first loop. 735821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) std::vector<Loop*> LoopProcessWorklist; 745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) SmallPtrSet<Value *,8> UnswitchedVals; 755821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 765821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bool OptimizeForSize; 775821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bool redoLoop; 785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 795821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Loop *currentLoop; 80c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) DominatorTree *DT; 81c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) BasicBlock *loopHeader; 82c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) BasicBlock *loopPreheader; 83c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 84c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) // LoopBlocks contains all of the basic blocks of the loop, including the 85c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) // preheader of the loop, the body of the loop, and the exit blocks of the 86c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) // loop, in that order. 87c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) std::vector<BasicBlock*> LoopBlocks; 88c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) // NewBlocks contained cloned copy of basic blocks from LoopBlocks. 89c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) std::vector<BasicBlock*> NewBlocks; 90c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 91c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) public: 92c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) static char ID; // Pass ID, replacement for typeid 93c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) explicit LoopUnswitch(bool Os = false) : 94c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) LoopPass(ID), OptimizeForSize(Os), redoLoop(false), 95c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) currentLoop(NULL), DT(NULL), loopHeader(NULL), 96c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) loopPreheader(NULL) { 97c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) initializeLoopUnswitchPass(*PassRegistry::getPassRegistry()); 98c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) } 99c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 100c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) bool runOnLoop(Loop *L, LPPassManager &LPM); 101c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) bool processCurrentLoop(); 102c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 103c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) /// This transformation requires natural loop information & requires that 104c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) /// loop preheaders be inserted into the CFG. 105c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) /// 106c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) virtual void getAnalysisUsage(AnalysisUsage &AU) const { 107c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) AU.addRequiredID(LoopSimplifyID); 108c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) AU.addPreservedID(LoopSimplifyID); 109c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) AU.addRequired<LoopInfo>(); 110c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) AU.addPreserved<LoopInfo>(); 111c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) AU.addRequiredID(LCSSAID); 112c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) AU.addPreservedID(LCSSAID); 113c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) AU.addPreserved<DominatorTree>(); 114c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) AU.addPreserved<ScalarEvolution>(); 115c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) } 116c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 117c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) private: 118c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 119c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) virtual void releaseMemory() { 120c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) UnswitchedVals.clear(); 121c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) } 122c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 123c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) /// RemoveLoopFromWorklist - If the specified loop is on the loop worklist, 124c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) /// remove it. 125c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) void RemoveLoopFromWorklist(Loop *L) { 126c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) std::vector<Loop*>::iterator I = std::find(LoopProcessWorklist.begin(), 127c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) LoopProcessWorklist.end(), L); 128c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) if (I != LoopProcessWorklist.end()) 129c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) LoopProcessWorklist.erase(I); 130c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) } 131c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 132c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) void initLoopData() { 133c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) loopHeader = currentLoop->getHeader(); 134c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) loopPreheader = currentLoop->getLoopPreheader(); 135c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) } 136c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 137c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) /// Split all of the edges from inside the loop to their exit blocks. 138c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) /// Update the appropriate Phi nodes as we do so. 139c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) void SplitExitEdges(Loop *L, const SmallVector<BasicBlock *, 8> &ExitBlocks); 140c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 141c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) bool UnswitchIfProfitable(Value *LoopCond, Constant *Val); 1425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val, 1435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *ExitBlock); 1445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void UnswitchNontrivialCondition(Value *LIC, Constant *OnVal, Loop *L); 1455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC, 1475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Constant *Val, bool isEqual); 1485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val, 1505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *TrueDest, 1515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *FalseDest, 1525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Instruction *InsertPt); 1535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L); 1555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void RemoveBlockIfDead(BasicBlock *BB, 1565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) std::vector<Instruction*> &Worklist, Loop *l); 1575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) void RemoveLoopFromHierarchy(Loop *L); 1585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bool IsTrivialUnswitchCondition(Value *Cond, Constant **Val = 0, 1595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock **LoopExit = 0); 1605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) }; 1625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 1635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)char LoopUnswitch::ID = 0; 1645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)INITIALIZE_PASS_BEGIN(LoopUnswitch, "loop-unswitch", "Unswitch loops", 1655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) false, false) 1665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)INITIALIZE_PASS_DEPENDENCY(LoopSimplify) 1675821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)INITIALIZE_PASS_DEPENDENCY(LoopInfo) 1685821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)INITIALIZE_PASS_DEPENDENCY(LCSSA) 1695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)INITIALIZE_PASS_END(LoopUnswitch, "loop-unswitch", "Unswitch loops", 1705821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) false, false) 1715821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)Pass *llvm::createLoopUnswitchPass(bool Os) { 1735821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return new LoopUnswitch(Os); 1745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 1755821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1765821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// FindLIVLoopCondition - Cond is a condition that occurs in L. If it is 1775821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// invariant in the loop, or has an invariant piece, return the invariant. 1785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// Otherwise, return null. 1795821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) { 1805821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // We can never unswitch on vector conditions. 1815821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (Cond->getType()->isVectorTy()) 1825821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return 0; 1835821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1845821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Constants should be folded, not unswitched on! 1855821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (isa<Constant>(Cond)) return 0; 1865821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1875821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // TODO: Handle: br (VARIANT|INVARIANT). 1885821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1895821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Hoist simple values out. 1905821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (L->makeLoopInvariant(Cond, Changed)) 1915821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return Cond; 1925821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1935821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Cond)) 1945821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (BO->getOpcode() == Instruction::And || 1955821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BO->getOpcode() == Instruction::Or) { 1965821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If either the left or right side is invariant, we can unswitch on this, 1975821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // which will cause the branch to go away in one loop and the condition to 1985821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // simplify in the other one. 1995821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (Value *LHS = FindLIVLoopCondition(BO->getOperand(0), L, Changed)) 2005821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return LHS; 2015821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (Value *RHS = FindLIVLoopCondition(BO->getOperand(1), L, Changed)) 2025821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return RHS; 2035821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 2040f1bc08d4cfcc34181b0b5cbf065c40f687bf740Torne (Richard Coles) 2055821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return 0; 2065821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 2075821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 2085821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)bool LoopUnswitch::runOnLoop(Loop *L, LPPassManager &LPM_Ref) { 2095821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LI = &getAnalysis<LoopInfo>(); 2105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPM = &LPM_Ref; 2115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DT = getAnalysisIfAvailable<DominatorTree>(); 2125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) currentLoop = L; 2135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Function *F = currentLoop->getHeader()->getParent(); 2145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bool Changed = false; 2155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) do { 2165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) assert(currentLoop->isLCSSAForm(*DT)); 2175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) redoLoop = false; 2185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Changed |= processCurrentLoop(); 2190f1bc08d4cfcc34181b0b5cbf065c40f687bf740Torne (Richard Coles) } while(redoLoop); 2205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 2211e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (Changed) { 222a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) // FIXME: Reconstruct dom info, because it is not preserved properly. 223c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) if (DT) 224c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) DT->runOnFunction(*F); 2255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 2265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return Changed; 2275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 2285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 2295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// processCurrentLoop - Do actual work and unswitch loop if possible 2305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// and profitable. 23190dce4d38c5ff5333bea97d859d4e484e27edf0cTorne (Richard Coles)bool LoopUnswitch::processCurrentLoop() { 23290dce4d38c5ff5333bea97d859d4e484e27edf0cTorne (Richard Coles) bool Changed = false; 2335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LLVMContext &Context = currentLoop->getHeader()->getContext(); 2345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 2355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Loop over all of the basic blocks in the loop. If we find an interior 2365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // block that is branching on a loop-invariant condition, we can unswitch this 2375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // loop. 2385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (Loop::block_iterator I = currentLoop->block_begin(), 2395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) E = currentLoop->block_end(); I != E; ++I) { 2405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) TerminatorInst *TI = (*I)->getTerminator(); 2415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { 2425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If this isn't branching on an invariant condition, we can't unswitch 2435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // it. 2445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (BI->isConditional()) { 245868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) // See if this, or some part of it, is loop invariant. If so, we can 2465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // unswitch on it if we desire. 2475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Value *LoopCond = FindLIVLoopCondition(BI->getCondition(), 2485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) currentLoop, Changed); 249868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) if (LoopCond && UnswitchIfProfitable(LoopCond, 2505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ConstantInt::getTrue(Context))) { 2515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ++NumBranches; 2525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return true; 2535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 2545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 2555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { 2565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), 2575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) currentLoop, Changed); 2585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (LoopCond && SI->getNumCases() > 1) { 2595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Find a value to unswitch on: 2605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // FIXME: this should chose the most expensive case! 2615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // FIXME: scan for a case with a non-critical edge? 2625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Constant *UnswitchVal = SI->getCaseValue(1); 2635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Do not process same value again and again. 2645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!UnswitchedVals.insert(UnswitchVal)) 2655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) continue; 2665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 2675821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (UnswitchIfProfitable(LoopCond, UnswitchVal)) { 2685821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ++NumSwitches; 2695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return true; 2705821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 2715821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 2725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 2735821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 2745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Scan the instructions to check for unswitchable values. 2755821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (BasicBlock::iterator BBI = (*I)->begin(), E = (*I)->end(); 2765821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BBI != E; ++BBI) 2775821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (SelectInst *SI = dyn_cast<SelectInst>(BBI)) { 2785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), 2795821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) currentLoop, Changed); 2805821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (LoopCond && UnswitchIfProfitable(LoopCond, 2815821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ConstantInt::getTrue(Context))) { 2822a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) ++NumSelects; 2832a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) return true; 2842a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 2852a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 2865821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 2875821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return Changed; 2885821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 2895821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 2905821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// isTrivialLoopExitBlock - Check to see if all paths from BB exit the 2915821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// loop with no side effects (including infinite loops). 2922a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)/// 2932a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)/// If true, we return true and set ExitBB to the block we 2945821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// exit through. 2952a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)/// 2965821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static bool isTrivialLoopExitBlockHelper(Loop *L, BasicBlock *BB, 2975821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *&ExitBB, 2982a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) std::set<BasicBlock*> &Visited) { 2992a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) if (!Visited.insert(BB).second) { 3002a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // Already visited. Without more analysis, this could indicate an infinte loop. 3015821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return false; 3025821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } else if (!L->contains(BB)) { 3032a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // Otherwise, this is a loop exit, this is fine so long as this is the 3042a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // first exit. 3055821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (ExitBB != 0) return false; 3065821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ExitBB = BB; 3075821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return true; 3082a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 3095821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 3105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Otherwise, this is an unvisited intra-loop node. Check all successors. 3115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) { 3125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Check to see if the successor is a trivial loop exit. 3135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!isTrivialLoopExitBlockHelper(L, *SI, ExitBB, Visited)) 3145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return false; 3155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 3165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 3175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Okay, everything after this looks good, check to make sure that this block 3185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // doesn't include any side effects. 3195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 3205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (I->mayHaveSideEffects()) 3215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return false; 3225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 3235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return true; 3245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 3255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 3265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// isTrivialLoopExitBlock - Return true if the specified block unconditionally 3275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// leads to an exit from the specified loop, and has no side-effects in the 3282a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)/// process. If so, return the block that is exited to, otherwise return null. 3292a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)static BasicBlock *isTrivialLoopExitBlock(Loop *L, BasicBlock *BB) { 3302a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) std::set<BasicBlock*> Visited; 3312a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) Visited.insert(L->getHeader()); // Branches to header make infinite loops. 3322a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) BasicBlock *ExitBB = 0; 3335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (isTrivialLoopExitBlockHelper(L, BB, ExitBB, Visited)) 3345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return ExitBB; 3355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return 0; 3365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 3375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 3385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// IsTrivialUnswitchCondition - Check to see if this unswitch condition is 3395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// trivial: that is, that the condition controls whether or not the loop does 3405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// anything at all. If this is a trivial condition, unswitching produces no 3415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// code duplications (equivalently, it produces a simpler loop and a new empty 342eb525c5499e34cc9c4b825d6d9e75bb07cc06aceBen Murdoch/// loop, which gets deleted). 343eb525c5499e34cc9c4b825d6d9e75bb07cc06aceBen Murdoch/// 344eb525c5499e34cc9c4b825d6d9e75bb07cc06aceBen Murdoch/// If this is a trivial condition, return true, otherwise return false. When 345eb525c5499e34cc9c4b825d6d9e75bb07cc06aceBen Murdoch/// returning true, this sets Cond and Val to the condition that controls the 346eb525c5499e34cc9c4b825d6d9e75bb07cc06aceBen Murdoch/// trivial condition: when Cond dynamically equals Val, the loop is known to 347eb525c5499e34cc9c4b825d6d9e75bb07cc06aceBen Murdoch/// exit. Finally, this sets LoopExit to the BB that the loop exits to when 348eb525c5499e34cc9c4b825d6d9e75bb07cc06aceBen Murdoch/// Cond == Val. 3495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// 350a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)bool LoopUnswitch::IsTrivialUnswitchCondition(Value *Cond, Constant **Val, 351a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) BasicBlock **LoopExit) { 352a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) BasicBlock *Header = currentLoop->getHeader(); 3531e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) TerminatorInst *HeaderTerm = Header->getTerminator(); 3541e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) LLVMContext &Context = Header->getContext(); 355a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 356a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) BasicBlock *LoopExitBB = 0; 3575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (BranchInst *BI = dyn_cast<BranchInst>(HeaderTerm)) { 358868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) // If the header block doesn't end with a conditional branch on Cond, we 359c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) // can't handle it. 3605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!BI->isConditional() || BI->getCondition() != Cond) 3615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return false; 3621e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) 3631e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // Check to see if a successor of the branch is guaranteed to 3641e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // exit through a unique exit block without having any 3651e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // side-effects. If so, determine the value of Cond that causes it to do 3661e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // this. 3671e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if ((LoopExitBB = isTrivialLoopExitBlock(currentLoop, 3681e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) BI->getSuccessor(0)))) { 3691e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (Val) *Val = ConstantInt::getTrue(Context); 3701e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) } else if ((LoopExitBB = isTrivialLoopExitBlock(currentLoop, 3711e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) BI->getSuccessor(1)))) { 3721e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (Val) *Val = ConstantInt::getFalse(Context); 3731e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) } 3741e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) } else if (SwitchInst *SI = dyn_cast<SwitchInst>(HeaderTerm)) { 3751e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // If this isn't a switch on Cond, we can't handle it. 3761e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (SI->getCondition() != Cond) return false; 3771e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) 3781e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // Check to see if a successor of the switch is guaranteed to go to the 3791e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // latch block or exit through a one exit block without having any 3801e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // side-effects. If so, determine the value of Cond that causes it to do 381a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) // this. Note that we can't trivially unswitch on the default case. 382a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) 3831e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if ((LoopExitBB = isTrivialLoopExitBlock(currentLoop, 3841e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) SI->getSuccessor(i)))) { 3851e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // Okay, we found a trivial case, remember the value that is trivial. 3861e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (Val) *Val = SI->getCaseValue(i); 3871e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) break; 3881e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) } 3891e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) } 3901e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) 3911e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // If we didn't find a single unique LoopExit block, or if the loop exit block 3921e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // contains phi nodes, this isn't trivial. 3931e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (!LoopExitBB || isa<PHINode>(LoopExitBB->begin())) 3941e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) return false; // Can't handle this. 3951e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) 3961e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (LoopExit) *LoopExit = LoopExitBB; 3971e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) 3981e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // We already know that nothing uses any scalar values defined inside of this 3991e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // loop. As such, we just have to check to see if this loop will execute any 4001e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // side-effecting instructions (e.g. stores, calls, volatile loads) in the 4011e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // part of the loop that the code *would* execute. We already checked the 4021e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // tail, check the header now. 4031e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) for (BasicBlock::iterator I = Header->begin(), E = Header->end(); I != E; ++I) 4041e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (I->mayHaveSideEffects()) 4051e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) return false; 4061e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) return true; 4071e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles)} 4081e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) 4091e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles)/// UnswitchIfProfitable - We have found that we can unswitch currentLoop when 410a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)/// LoopCond == Val to simplify the loop. If we decide that this is profitable, 411a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)/// unswitch the loop, reprocess the pieces, then return true. 412a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val) { 413a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 414a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) initLoopData(); 415a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 4161e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // If LoopSimplify was unable to form a preheader, don't do any unswitching. 4171e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (!loopPreheader) 4181e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) return false; 419a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 420a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) Function *F = loopHeader->getParent(); 421a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 422a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) Constant *CondVal = 0; 423a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) BasicBlock *ExitBlock = 0; 424a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) if (IsTrivialUnswitchCondition(LoopCond, &CondVal, &ExitBlock)) { 425a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) // If the condition is trivial, always unswitch. There is no code growth 426a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) // for this case. 427a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) UnswitchTrivialCondition(currentLoop, LoopCond, CondVal, ExitBlock); 428a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) return true; 429a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) } 430a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 431a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) // Check to see if it would be profitable to unswitch current loop. 432a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 433a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) // Do not do non-trivial unswitch while optimizing for size. 434a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) if (OptimizeForSize || F->hasFnAttr(Attribute::OptimizeForSize)) 435a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) return false; 436a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 437a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) // FIXME: This is overly conservative because it does not take into 438a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) // consideration code simplification opportunities and code that can 4391e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // be shared by the resultant unswitched loops. 4401e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) CodeMetrics Metrics; 4415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (Loop::block_iterator I = currentLoop->block_begin(), 442868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) E = currentLoop->block_end(); 4435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) I != E; ++I) 4445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Metrics.analyzeBasicBlock(*I); 4455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 4465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Limit the number of instructions to avoid causing significant code 4475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // expansion, and the number of basic blocks, to avoid loops with 4485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // large numbers of branches which cause loop unswitching to go crazy. 4495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // This is a very ad-hoc heuristic. 4505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (Metrics.NumInsts > Threshold || 4515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Metrics.NumBlocks * 5 > Threshold || 4525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Metrics.containsIndirectBr || Metrics.isRecursive) { 4535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DEBUG(dbgs() << "NOT unswitching loop %" 4545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) << currentLoop->getHeader()->getName() << ", cost too high: " 4555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) << currentLoop->getBlocks().size() << "\n"); 456868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) return false; 4575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 4585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 4595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) UnswitchNontrivialCondition(LoopCond, Val, currentLoop); 4605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return true; 4615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 462868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) 4635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// CloneLoop - Recursively clone the specified loop and all of its children, 4645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// mapping the blocks with the specified map. 4655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static Loop *CloneLoop(Loop *L, Loop *PL, ValueToValueMapTy &VM, 4665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LoopInfo *LI, LPPassManager *LPM) { 4675821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Loop *New = new Loop(); 4685821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPM->insertLoop(New, PL); 4695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 4705821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Add all of the blocks in L to the new loop. 471868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 4725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) I != E; ++I) 4735821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (LI->getLoopFor(*I) == L) 4745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) New->addBasicBlockToLoop(cast<BasicBlock>(VM[*I]), LI->getBase()); 4755821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 4765821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Add all of the subloops to the new loop. 4775821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) 4785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) CloneLoop(*I, New, VM, LI, LPM); 479868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) 4805821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return New; 4815821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 4825821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 4835821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// EmitPreheaderBranchOnCondition - Emit a conditional branch on two values 4845821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// if LIC == Val, branch to TrueDst, otherwise branch to FalseDest. Insert the 4855821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// code immediately before InsertPt. 4865821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val, 4872a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) BasicBlock *TrueDest, 4882a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) BasicBlock *FalseDest, 4892a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) Instruction *InsertPt) { 4902a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // Insert a conditional branch on LIC to the two preheaders. The original 4915821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // code is the true version and the new code is the false version. 492868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) Value *BranchVal = LIC; 4935821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!isa<ConstantInt>(Val) || 4945821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Val->getType() != Type::getInt1Ty(LIC->getContext())) 4955821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BranchVal = new ICmpInst(InsertPt, ICmpInst::ICMP_EQ, LIC, Val, "tmp"); 4965821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) else if (Val != ConstantInt::getTrue(Val->getContext())) 497868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) // We want to enter the new loop when the condition is true. 4985821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) std::swap(TrueDest, FalseDest); 4995821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5005821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Insert the new branch. 5015821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BranchInst *BI = BranchInst::Create(TrueDest, FalseDest, BranchVal, InsertPt); 502868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) 5035821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If either edge is critical, split it. This helps preserve LoopSimplify 5045821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // form for enclosing loops. 5055821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) SplitCriticalEdge(BI, 0, this); 50658537e28ecd584eab876aee8be7156509866d23aTorne (Richard Coles) SplitCriticalEdge(BI, 1, this); 507868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)} 5085821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5095821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// UnswitchTrivialCondition - Given a loop that has a trivial unswitchable 5105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// condition in it (a cond branch from its header block to its latch block, 511f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles)/// where the path through the loop that doesn't execute its body has no 512f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles)/// side-effects), unswitch it. This doesn't involve any code duplication, just 513f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles)/// moving the conditional branch outside of the loop and updating loop info. 514f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles)void LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond, 515f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) Constant *Val, 516f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) BasicBlock *ExitBlock) { 517f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) DEBUG(dbgs() << "loop-unswitch: Trivial-Unswitch loop %" 518f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) << loopHeader->getName() << " [" << L->getBlocks().size() 519f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) << " blocks] in Function " << L->getHeader()->getParent()->getName() 520f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) << " on cond: " << *Val << " == " << *Cond << "\n"); 521f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) 522f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) // First step, split the preheader, so that we know that there is a safe place 523f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) // to insert the conditional branch. We will change loopPreheader to have a 524f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) // conditional branch on Cond. 5255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *NewPH = SplitEdge(loopPreheader, loopHeader, this); 5265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Now that we have a place to insert the conditional branch, create a place 5285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // to branch to: this is the exit block out of the loop that we should 5295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // short-circuit to. 5305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Split this block now, so that the loop maintains its exit block, and so 5325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // that the jump from the preheader can execute the contents of the exit block 5335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // without actually branching to it (the exit block should be dominated by the 5345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // loop header, not the preheader). 5355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) assert(!L->contains(ExitBlock) && "Exit block is in the loop?"); 5365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *NewExit = SplitBlock(ExitBlock, ExitBlock->begin(), this); 5375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Okay, now we have a position to branch from and a position to branch to, 5395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // insert the new conditional branch. 5405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) EmitPreheaderBranchOnCondition(Cond, Val, NewExit, NewPH, 5415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) loopPreheader->getTerminator()); 5425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPM->deleteSimpleAnalysisValue(loopPreheader->getTerminator(), L); 5435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) loopPreheader->getTerminator()->eraseFromParent(); 5445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // We need to reprocess this loop, it could be unswitched again. 5465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) redoLoop = true; 5475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Now that we know that the loop is never entered when this condition is a 5495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // particular value, rewrite the loop with this info. We know that this will 5505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // at least eliminate the old branch. 5515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RewriteLoopBodyWithConditionConstant(L, Cond, Val, false); 5525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ++NumTrivial; 5535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 5545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// SplitExitEdges - Split all of the edges from inside the loop to their exit 5569ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch/// blocks. Update the appropriate Phi nodes as we do so. 5579ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdochvoid LoopUnswitch::SplitExitEdges(Loop *L, 5589ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch const SmallVector<BasicBlock *, 8> &ExitBlocks){ 5599ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch 5609ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 5619ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch BasicBlock *ExitBlock = ExitBlocks[i]; 5629ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch SmallVector<BasicBlock *, 4> Preds(pred_begin(ExitBlock), 5639ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch pred_end(ExitBlock)); 5649ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch // Although SplitBlockPredecessors doesn't preserve loop-simplify in 5659ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch // general, if we call it on all predecessors of all exits then it does. 5669ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch SplitBlockPredecessors(ExitBlock, Preds.data(), Preds.size(), 5679ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch ".us-lcssa", this); 5689ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch } 5699ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch} 5709ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch 5719ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch/// UnswitchNontrivialCondition - We determined that the loop is profitable 5729ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch/// to unswitch when LIC equal Val. Split it into loop versions and test the 5739ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch/// condition outside of either loop. Return the loops created as Out1/Out2. 5749ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdochvoid LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val, 5759ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch Loop *L) { 576c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) Function *F = loopHeader->getParent(); 5775821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DEBUG(dbgs() << "loop-unswitch: Unswitching loop %" 5785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) << loopHeader->getName() << " [" << L->getBlocks().size() 579c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) << " blocks] in Function " << F->getName() 580c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) << " when '" << *Val << "' == " << *LIC << "\n"); 581c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 582c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) if (ScalarEvolution *SE = getAnalysisIfAvailable<ScalarEvolution>()) 583c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) SE->forgetLoop(L); 584c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 585c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) LoopBlocks.clear(); 5865821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) NewBlocks.clear(); 587c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) 5885821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // First step, split the preheader and exit blocks, and add these blocks to 5895821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // the LoopBlocks list. 590c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) BasicBlock *NewPreheader = SplitEdge(loopPreheader, loopHeader, this); 591c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles) LoopBlocks.push_back(NewPreheader); 5925821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5935821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // We want the loop to come after the preheader, but before the exit blocks. 5945821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end()); 5955821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5965821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) SmallVector<BasicBlock*, 8> ExitBlocks; 5975821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) L->getUniqueExitBlocks(ExitBlocks); 5985821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 5995821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Split all of the edges from inside the loop to their exit blocks. Update 6005821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // the appropriate Phi nodes as we do so. 6015821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) SplitExitEdges(L, ExitBlocks); 6025821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6035821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // The exit blocks may have been changed due to edge splitting, recompute. 6045821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ExitBlocks.clear(); 6055821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) L->getUniqueExitBlocks(ExitBlocks); 606a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 607a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) // Add exit blocks to the loop blocks. 608a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) LoopBlocks.insert(LoopBlocks.end(), ExitBlocks.begin(), ExitBlocks.end()); 6095821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Next step, clone all of the basic blocks that make up the loop (including 6112a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // the loop preheader and exit blocks), keeping track of the mapping between 6122a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // the instructions and blocks. 6132a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) NewBlocks.reserve(LoopBlocks.size()); 6142a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) ValueToValueMapTy VMap; 6152a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) { 6165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *NewBB = CloneBasicBlock(LoopBlocks[i], VMap, ".us", F); 6175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) NewBlocks.push_back(NewBB); 6185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) VMap[LoopBlocks[i]] = NewBB; // Keep the BB mapping. 6191e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], NewBB, L); 6205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 6215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6221e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // Splice the newly inserted blocks into the function right before the 6231e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // original preheader. 6241e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) F->getBasicBlockList().splice(NewPreheader, F->getBasicBlockList(), 6255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) NewBlocks[0], F->end()); 6265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Now we create the new Loop object for the versioned loop. 6285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Loop *NewLoop = CloneLoop(L, L->getParentLoop(), VMap, LI, LPM); 6295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Loop *ParentLoop = L->getParentLoop(); 6305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (ParentLoop) { 6315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Make sure to add the cloned preheader and exit blocks to the parent loop 6325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // as well. 6335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ParentLoop->addBasicBlockToLoop(NewBlocks[0], LI->getBase()); 6345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 6355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 636868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 6375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *NewExit = cast<BasicBlock>(VMap[ExitBlocks[i]]); 6385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // The new exit block should be in the same loop as the old one. 6395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (Loop *ExitBBLoop = LI->getLoopFor(ExitBlocks[i])) 6405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ExitBBLoop->addBasicBlockToLoop(NewExit, LI->getBase()); 6415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) assert(NewExit->getTerminator()->getNumSuccessors() == 1 && 6431e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) "Exit block should have been split to have one successor!"); 6445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *ExitSucc = NewExit->getTerminator()->getSuccessor(0); 6455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If the successor of the exit block had PHI nodes, add an entry for 6475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // NewExit. 6485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) PHINode *PN; 6495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (BasicBlock::iterator I = ExitSucc->begin(); isa<PHINode>(I); ++I) { 6505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) PN = cast<PHINode>(I); 6515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Value *V = PN->getIncomingValueForBlock(ExitBlocks[i]); 6525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ValueToValueMapTy::iterator It = VMap.find(V); 6535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (It != VMap.end()) V = It->second; 6545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) PN->addIncoming(V, NewExit); 6552a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 6562a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 6575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Rewrite the code to refer to itself. 6595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (unsigned i = 0, e = NewBlocks.size(); i != e; ++i) 6605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (BasicBlock::iterator I = NewBlocks[i]->begin(), 6615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) E = NewBlocks[i]->end(); I != E; ++I) 6625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemapInstruction(I, VMap,RF_NoModuleLevelChanges|RF_IgnoreMissingEntries); 6635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Rewrite the original preheader to select between versions of the loop. 6655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BranchInst *OldBR = cast<BranchInst>(loopPreheader->getTerminator()); 6665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) assert(OldBR->isUnconditional() && OldBR->getSuccessor(0) == LoopBlocks[0] && 667868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) "Preheader splitting did not work correctly!"); 6685821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Emit the new branch that selects between the two versions of this loop. 6705821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) EmitPreheaderBranchOnCondition(LIC, Val, NewBlocks[0], LoopBlocks[0], OldBR); 6715821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPM->deleteSimpleAnalysisValue(OldBR, L); 6725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) OldBR->eraseFromParent(); 6732a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 6745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LoopProcessWorklist.push_back(NewLoop); 6755821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) redoLoop = true; 6765821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6772a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // Keep a WeakVH holding onto LIC. If the first call to RewriteLoopBody 6785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // deletes the instruction (for example by simplifying a PHI that feeds into 6792a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // the condition that we're unswitching on), we don't rewrite the second 6802a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // iteration. 6815821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) WeakVH LICHandle(LIC); 6825821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6835821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Now we rewrite the original code to know that the condition is true and the 6845821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // new code to know that the condition is false. 6855821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RewriteLoopBodyWithConditionConstant(L, LIC, Val, false); 6865821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6875821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // It's possible that simplifying one loop could cause the other to be 6885821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // changed to another value or a constant. If its a constant, don't simplify 6895821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // it. 6905821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!LoopProcessWorklist.empty() && LoopProcessWorklist.back() == NewLoop && 6915821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LICHandle && !isa<Constant>(LICHandle)) 6925821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RewriteLoopBodyWithConditionConstant(NewLoop, LICHandle, Val, true); 6935821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 6945821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 6955821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// RemoveFromWorklist - Remove all instances of I from the worklist vector 696868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)/// specified. 697868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)static void RemoveFromWorklist(Instruction *I, 698868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) std::vector<Instruction*> &Worklist) { 6995821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) std::vector<Instruction*>::iterator WI = std::find(Worklist.begin(), 7005821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Worklist.end(), I); 7015821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) while (WI != Worklist.end()) { 7025821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) unsigned Offset = WI-Worklist.begin(); 7035821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Worklist.erase(WI); 7045821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) WI = std::find(Worklist.begin()+Offset, Worklist.end(), I); 7055821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 7065821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 7075821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 7085821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// ReplaceUsesOfWith - When we find that I really equals V, remove I from the 7095821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// program, replacing all uses with V and update the worklist. 7105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static void ReplaceUsesOfWith(Instruction *I, Value *V, 7115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) std::vector<Instruction*> &Worklist, 7125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Loop *L, LPPassManager *LPM) { 7135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DEBUG(dbgs() << "Replace with '" << *V << "': " << *I); 7145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 7155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Add uses to the worklist, which may be dead now. 7165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 717868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) if (Instruction *Use = dyn_cast<Instruction>(I->getOperand(i))) 7185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Worklist.push_back(Use); 7195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 7205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Add users to the worklist which may be simplified now. 7215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); 7225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) UI != E; ++UI) 7235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Worklist.push_back(cast<Instruction>(*UI)); 7245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPM->deleteSimpleAnalysisValue(I, L); 7255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemoveFromWorklist(I, Worklist); 7261e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) I->replaceAllUsesWith(V); 7271e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) I->eraseFromParent(); 728a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) ++NumSimplify; 7291e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles)} 7301e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) 7315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// RemoveBlockIfDead - If the specified block is dead, remove it, update loop 7325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// information, and remove any dead successors it has. 7335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// 7345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)void LoopUnswitch::RemoveBlockIfDead(BasicBlock *BB, 7355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) std::vector<Instruction*> &Worklist, 7365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Loop *L) { 7375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (pred_begin(BB) != pred_end(BB)) { 7385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // This block isn't dead, since an edge to BB was just removed, see if there 7395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // are any easy simplifications we can do now. 7405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (BasicBlock *Pred = BB->getSinglePredecessor()) { 7415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If it has one pred, fold phi nodes in BB. 7425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) while (isa<PHINode>(BB->begin())) 7435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ReplaceUsesOfWith(BB->begin(), 7445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) cast<PHINode>(BB->begin())->getIncomingValue(0), 7455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Worklist, L, LPM); 7465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 747868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) // If this is the header of a loop and the only pred is the latch, we now 7485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // have an unreachable loop. 7495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (Loop *L = LI->getLoopFor(BB)) 7505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (loopHeader == BB && L->contains(Pred)) { 7515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Remove the branch from the latch to the header block, this makes 7525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // the header dead, which will make the latch dead (because the header 7535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // dominates the latch). 7545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPM->deleteSimpleAnalysisValue(Pred->getTerminator(), L); 7555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Pred->getTerminator()->eraseFromParent(); 7565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) new UnreachableInst(BB->getContext(), Pred); 7575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 7585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // The loop is now broken, remove it from LI. 7595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemoveLoopFromHierarchy(L); 7605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 761868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) // Reprocess the header, which now IS dead. 7625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemoveBlockIfDead(BB, Worklist, L); 7635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return; 7645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 7651e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) 7661e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // If pred ends in a uncond branch, add uncond branch to worklist so that 7671e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) // the two blocks will get merged. 7681e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (BranchInst *BI = dyn_cast<BranchInst>(Pred->getTerminator())) 7695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (BI->isUnconditional()) 7705821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Worklist.push_back(BI); 7715821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 7725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return; 7735821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 7745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 7755821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DEBUG(dbgs() << "Nuking dead block: " << *BB); 7765821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 7775821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Remove the instructions in the basic block from the worklist. 7785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { 7795821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemoveFromWorklist(I, Worklist); 7805821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 7815821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Anything that uses the instructions in this basic block should have their 7825821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // uses replaced with undefs. 7835821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If I is not void type then replaceAllUsesWith undef. 7845821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // This allows ValueHandlers and custom metadata to adjust itself. 7855821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!I->getType()->isVoidTy()) 7865821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) I->replaceAllUsesWith(UndefValue::get(I->getType())); 7875821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 7885821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 7895821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If this is the edge to the header block for a loop, remove the loop and 7905821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // promote all subloops. 7915821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (Loop *BBLoop = LI->getLoopFor(BB)) { 7925821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (BBLoop->getLoopLatch() == BB) { 7935821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemoveLoopFromHierarchy(BBLoop); 7945821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (currentLoop == BBLoop) { 795868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) currentLoop = 0; 7965821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) redoLoop = false; 7975821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 7985821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 7995821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 8005821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8015821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Remove the block from the loop info, which removes it from any loops it 8025821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // was in. 8035821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LI->removeBlock(BB); 8045821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8055821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8065821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Remove phi node entries in successors for this block. 8075821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) TerminatorInst *TI = BB->getTerminator(); 8085821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) SmallVector<BasicBlock*, 4> Succs; 8091e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) { 8105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Succs.push_back(TI->getSuccessor(i)); 8112a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) TI->getSuccessor(i)->removePredecessor(BB); 8125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 8135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Unique the successors, remove anything with multiple uses. 8155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) array_pod_sort(Succs.begin(), Succs.end()); 8165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Succs.erase(std::unique(Succs.begin(), Succs.end()), Succs.end()); 8175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Remove the basic block, including all of the instructions contained in it. 8195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPM->deleteSimpleAnalysisValue(BB, L); 8205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BB->eraseFromParent(); 8215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Remove successor blocks here that are not dead, so that we know we only 8225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // have dead blocks in this list. Nondead blocks have a way of becoming dead, 8235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // then getting removed before we revisit them, which is badness. 8245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // 8255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (unsigned i = 0; i != Succs.size(); ++i) 8265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (pred_begin(Succs[i]) != pred_end(Succs[i])) { 8275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // One exception is loop headers. If this block was the preheader for a 8285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // loop, then we DO want to visit the loop so the loop gets deleted. 8295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // We know that if the successor is a loop header, that this loop had to 8305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // be the preheader: the case where this was the latch block was handled 8315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // above and headers can only have two predecessors. 8325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!LI->isLoopHeader(Succs[i])) { 8335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Succs.erase(Succs.begin()+i); 8345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) --i; 8355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 8365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 8375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (unsigned i = 0, e = Succs.size(); i != e; ++i) 8395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemoveBlockIfDead(Succs[i], Worklist, L); 8401e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles)} 8415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// RemoveLoopFromHierarchy - We have discovered that the specified loop has 8435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// become unwrapped, either because the backedge was deleted, or because the 8445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// edge into the header was removed. If the edge into the header from the 8455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// latch block was removed, the loop is unwrapped but subloops are still alive, 8465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// so they just reparent loops. If the loops are actually dead, they will be 8475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// removed later. 8485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)void LoopUnswitch::RemoveLoopFromHierarchy(Loop *L) { 849868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) LPM->deleteLoopFromQueue(L); 8505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemoveLoopFromWorklist(L); 8515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 8525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// RewriteLoopBodyWithConditionConstant - We know either that the value LIC has 8545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// the value specified by Val in the specified loop, or we know it does NOT have 8555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// that value. Rewrite any uses of LIC or of properties correlated to it. 856868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC, 8575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Constant *Val, 8585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) bool IsEqual) { 8595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) assert(!isa<Constant>(LIC) && "Why are we unswitching on a constant?"); 8605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // FIXME: Support correlated properties, like: 8625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // for (...) 863868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) // if (li1 < li2) 8645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // ... 8655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // if (li1 > li2) 8665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // ... 8675821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8685821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // FOLD boolean conditions (X|LIC), (X&LIC). Fold conditional branches, 8695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // selects, switches. 870868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) std::vector<Instruction*> Worklist; 8715821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LLVMContext &Context = Val->getContext(); 8725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8735821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If we know that LIC == Val, or that LIC == NotVal, just replace uses of LIC 8755821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // in the loop with the appropriate one directly. 876868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) if (IsEqual || (isa<ConstantInt>(Val) && 8775821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Val->getType()->isIntegerTy(1))) { 8785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Value *Replacement; 8795821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (IsEqual) 8805821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Replacement = Val; 8815821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) else 882868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) Replacement = ConstantInt::get(Type::getInt1Ty(Val->getContext()), 8835821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) !cast<ConstantInt>(Val)->getZExtValue()); 8845821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 8855821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (Value::use_iterator UI = LIC->use_begin(), E = LIC->use_end(); 8865821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) UI != E; ++UI) { 8875821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Instruction *U = dyn_cast<Instruction>(*UI); 8885821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!U || !L->contains(U)) 8895821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) continue; 8905821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) U->replaceUsesOfWith(LIC, Replacement); 8912a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) Worklist.push_back(U); 8922a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 8932a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) SimplifyCode(Worklist, L); 8942a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) return; 8952a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 8962a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 8975821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Otherwise, we don't know the precise value of LIC, but we do know that it 8985821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // is certainly NOT "Val". As such, simplify any uses in the loop that we 8995821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // can. This case occurs when we unswitch switch statements. 9005821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (Value::use_iterator UI = LIC->use_begin(), E = LIC->use_end(); 9015821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) UI != E; ++UI) { 9025821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Instruction *U = dyn_cast<Instruction>(*UI); 9035821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!U || !L->contains(U)) 9045821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) continue; 9055821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 9065821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Worklist.push_back(U); 9075821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 9085821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // TODO: We could do other simplifications, for example, turning 9095821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // 'icmp eq LIC, Val' -> false. 9105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 9115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If we know that LIC is not Val, use this info to simplify code. 9125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) SwitchInst *SI = dyn_cast<SwitchInst>(U); 9135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (SI == 0 || !isa<ConstantInt>(Val)) continue; 9145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 9155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) unsigned DeadCase = SI->findCaseValue(cast<ConstantInt>(Val)); 9161e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (DeadCase == 0) continue; // Default case is live for multiple values. 9171e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) 9185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Found a dead case value. Don't remove PHI nodes in the 9195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // successor if they become single-entry, those PHI nodes may 9205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // be in the Users list. 9215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 9225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *Switch = SI->getParent(); 9235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *SISucc = SI->getSuccessor(DeadCase); 9245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *Latch = L->getLoopLatch(); 9255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!SI->findCaseDest(SISucc)) continue; // Edge is critical. 9265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If the DeadCase successor dominates the loop latch, then the 9275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // transformation isn't safe since it will delete the sole predecessor edge 9285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // to the latch. 9295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (Latch && DT->dominates(SISucc, Latch)) 9305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) continue; 9315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 9325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // FIXME: This is a hack. We need to keep the successor around 9335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // and hooked up so as to preserve the loop structure, because 9345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // trying to update it is complicated. So instead we preserve the 9355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // loop structure and put the block on a dead code path. 9365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) SplitEdge(Switch, SISucc, this); 9375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Compute the successors instead of relying on the return value 9385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // of SplitEdge, since it may have split the switch successor 9395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // after PHI nodes. 9402a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) BasicBlock *NewSISucc = SI->getSuccessor(DeadCase); 9412a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) BasicBlock *OldSISucc = *succ_begin(NewSISucc); 9422a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // Create an "unreachable" destination. 9432a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) BasicBlock *Abort = BasicBlock::Create(Context, "us-unreachable", 9449ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch Switch->getParent(), 9459ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch OldSISucc); 9469ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch new UnreachableInst(Context, Abort); 9479ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch // Force the new case destination to branch to the "unreachable" 9489ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch // block while maintaining a (dead) CFG edge to the old block. 9499ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch NewSISucc->getTerminator()->eraseFromParent(); 9509ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch BranchInst::Create(Abort, OldSISucc, 9515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ConstantInt::getTrue(Context), NewSISucc); 9525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Release the PHI operands for this edge. 9535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) for (BasicBlock::iterator II = NewSISucc->begin(); 9549ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch PHINode *PN = dyn_cast<PHINode>(II); ++II) 9559ab5563a3196760eb381d102cbb2bc0f7abc6a50Ben Murdoch PN->setIncomingValue(PN->getBasicBlockIndex(Switch), 9565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) UndefValue::get(PN->getType())); 9575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Tell the domtree about the new block. We don't fully update the 9585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // domtree here -- instead we force it to do a full recomputation 9595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // after the pass is complete -- but we do need to inform it of 9605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // new blocks. 9615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (DT) 9625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DT->addNewBlock(Abort, NewSISucc); 9635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 9645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 9655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) SimplifyCode(Worklist, L); 9665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 9675821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 9685821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// SimplifyCode - Okay, now that we have simplified some instructions in the 9695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// loop, walk over it and constant prop, dce, and fold control flow where 9705821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// possible. Note that this is effectively a very simple loop-structure-aware 9715821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// optimizer. During processing of this loop, L could very well be deleted, so 9725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// it must not be used. 9735821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// 9745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// FIXME: When the loop optimizer is more mature, separate this out to a new 9755821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// pass. 9765821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// 9775821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)void LoopUnswitch::SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L) { 978868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) while (!Worklist.empty()) { 9795821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Instruction *I = Worklist.back(); 9805821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Worklist.pop_back(); 9815821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 9825821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Simple DCE. 9835821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (isInstructionTriviallyDead(I)) { 9842a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) DEBUG(dbgs() << "Remove dead instruction '" << *I); 9852a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 9868bcbed890bc3ce4d7a057a8f32cab53fa534672eTorne (Richard Coles) // Add uses to the worklist, which may be dead now. 987f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 988f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) if (Instruction *Use = dyn_cast<Instruction>(I->getOperand(i))) 989f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) Worklist.push_back(Use); 990f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) LPM->deleteSimpleAnalysisValue(I, L); 991f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) RemoveFromWorklist(I, Worklist); 992f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) I->eraseFromParent(); 993f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) ++NumSimplify; 994f2477e01787aa58f445919b809d89e252beef54fTorne (Richard Coles) continue; 9952a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 9962a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 9972a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // See if instruction simplification can hack this up. This is common for 9982a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // things like "select false, X, Y" after unswitching made the condition be 999868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) // 'false'. 10002a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) if (Value *V = SimplifyInstruction(I, 0, DT)) 10012a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) if (LI->replacementPreservesLCSSAForm(I, V)) { 10022a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) ReplaceUsesOfWith(I, V, Worklist, L, LPM); 10032a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) continue; 10042a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) } 10052a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 10065821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Special case hacks that appear commonly in unswitched code. 10075821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (BranchInst *BI = dyn_cast<BranchInst>(I)) { 10085821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (BI->isUnconditional()) { 10095821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If BI's parent is the only pred of the successor, fold the two blocks 10105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // together. 10115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *Pred = BI->getParent(); 10125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *Succ = BI->getSuccessor(0); 10135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *SinglePred = Succ->getSinglePredecessor(); 10145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!SinglePred) continue; // Nothing to do. 10155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) assert(SinglePred == Pred && "CFG broken"); 10162a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) 10175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DEBUG(dbgs() << "Merging blocks: " << Pred->getName() << " <- " 10185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) << Succ->getName() << "\n"); 10195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 10205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Resolve any single entry PHI nodes in Succ. 10215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) while (PHINode *PN = dyn_cast<PHINode>(Succ->begin())) 10225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ReplaceUsesOfWith(PN, PN->getIncomingValue(0), Worklist, L, LPM); 10235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 10245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // If Succ has any successors with PHI nodes, update them to have 10255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // entries coming from Pred instead of Succ. 10265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Succ->replaceAllUsesWith(Pred); 10275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 10285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Move all of the successor contents from Succ to Pred. 10295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Pred->getInstList().splice(BI, Succ->getInstList(), Succ->begin(), 10305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Succ->end()); 10315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPM->deleteSimpleAnalysisValue(BI, L); 10321e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) BI->eraseFromParent(); 10335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemoveFromWorklist(BI, Worklist); 10345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 10355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Remove Succ from the loop tree. 10365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LI->removeBlock(Succ); 10375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPM->deleteSimpleAnalysisValue(Succ, L); 10385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Succ->eraseFromParent(); 10391e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) ++NumSimplify; 10401e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) continue; 10415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 10425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 10431e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) if (ConstantInt *CB = dyn_cast<ConstantInt>(BI->getCondition())){ 10445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Conditional branch. Turn it into an unconditional branch, then 10455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // remove dead blocks. 10465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) continue; // FIXME: Enable. 10475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 10481e9bf3e0803691d0a228da41fc608347b6db4340Torne (Richard Coles) DEBUG(dbgs() << "Folded branch: " << *BI); 10495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *DeadSucc = BI->getSuccessor(CB->getZExtValue()); 10505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BasicBlock *LiveSucc = BI->getSuccessor(!CB->getZExtValue()); 10515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) DeadSucc->removePredecessor(BI->getParent(), true); 10525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Worklist.push_back(BranchInst::Create(LiveSucc, BI)); 10535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) LPM->deleteSimpleAnalysisValue(BI, L); 10545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) BI->eraseFromParent(); 10555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemoveFromWorklist(BI, Worklist); 10565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) ++NumSimplify; 10575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 10585821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) RemoveBlockIfDead(DeadSucc, Worklist, L); 10595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 10605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) continue; 10615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 10625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 10635821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 10645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)