LoopUnswitch.cpp revision 2b67f07d2b27fca793fb825731af1750cd1e5ddd
18e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels//===-- LoopUnswitch.cpp - Hoist loop-invariant conditionals in loop ------===// 28e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// 38e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// The LLVM Compiler Infrastructure 48e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// 58e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// This file was developed by the LLVM research group and is distributed under 68e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// the University of Illinois Open Source License. See LICENSE.TXT for details. 78e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// 88e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels//===----------------------------------------------------------------------===// 98e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// 108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// This pass transforms loops that contain branches on loop-invariant conditions 118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// to have multiple loops. For example, it turns the left into the right code: 128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// 138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// for (...) if (lic) 148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// A for (...) 158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// if (lic) A; B; C 168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// B else 178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// C for (...) 188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// A; C 198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// 208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// This can increase the size of the code exponentially (doubling it every time 218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// a loop is unswitched) so we only unswitch if the resultant code will be 228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// smaller than a threshold. 238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// 248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// This pass expects LICM to be run before it to hoist invariant conditions out 258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// of the loop, to make the unswitching opportunity obvious. 268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// 278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels//===----------------------------------------------------------------------===// 288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#define DEBUG_TYPE "loop-unswitch" 308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/Transforms/Scalar.h" 318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/Constants.h" 328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/Function.h" 338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/Instructions.h" 348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/Analysis/LoopInfo.h" 358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/Transforms/Utils/Cloning.h" 368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/Transforms/Utils/Local.h" 378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/Transforms/Utils/BasicBlockUtils.h" 388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/ADT/Statistic.h" 398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/ADT/PostOrderIterator.h" 408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/Support/Debug.h" 418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include "llvm/Support/CommandLine.h" 428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include <algorithm> 438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include <iostream> 448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels#include <set> 458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsusing namespace llvm; 468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsnamespace { 488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Statistic<> NumBranches("loop-unswitch", "Number of branches unswitched"); 498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Statistic<> NumSwitches("loop-unswitch", "Number of switches unswitched"); 508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Statistic<> NumSelects ("loop-unswitch", "Number of selects unswitched"); 518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Statistic<> NumTrivial ("loop-unswitch", 528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels "Number of unswitches that are trivial"); 538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Statistic<> NumSimplify("loop-unswitch", 548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels "Number of simplifications of unswitched code"); 558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels cl::opt<unsigned> 568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Threshold("loop-unswitch-threshold", cl::desc("Max loop size to unswitch"), 578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels cl::init(10), cl::Hidden); 588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels class LoopUnswitch : public FunctionPass { 608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopInfo *LI; // Loop information 618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // LoopProcessWorklist - List of loops we need to process. 638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<Loop*> LoopProcessWorklist; 648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels public: 658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels virtual bool runOnFunction(Function &F); 668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels bool visitLoop(Loop *L); 678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels /// This transformation requires natural loop information & requires that 698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels /// loop preheaders be inserted into the CFG... 708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels /// 718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels virtual void getAnalysisUsage(AnalysisUsage &AU) const { 728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels AU.addRequiredID(LoopSimplifyID); 738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels AU.addPreservedID(LoopSimplifyID); 748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels AU.addRequired<LoopInfo>(); 758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels AU.addPreserved<LoopInfo>(); 768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels AU.addRequiredID(LCSSAID); 778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels AU.addPreservedID(LCSSAID); 788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels private: 818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels /// RemoveLoopFromWorklist - If the specified loop is on the loop worklist, 828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels /// remove it. 838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels void RemoveLoopFromWorklist(Loop *L) { 848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<Loop*>::iterator I = std::find(LoopProcessWorklist.begin(), 858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopProcessWorklist.end(), L); 868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (I != LoopProcessWorklist.end()) 878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopProcessWorklist.erase(I); 888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels bool UnswitchIfProfitable(Value *LoopCond, Constant *Val,Loop *L); 918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels unsigned getLoopUnswitchCost(Loop *L, Value *LIC); 928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels void UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val, 938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *ExitBlock); 948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels void UnswitchNontrivialCondition(Value *LIC, Constant *OnVal, Loop *L); 958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To); 968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt); 978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels void RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC, 998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Constant *Val, bool isEqual); 1008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels void SimplifyCode(std::vector<Instruction*> &Worklist); 1028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels void RemoveBlockIfDead(BasicBlock *BB, 1038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<Instruction*> &Worklist); 1048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels void RemoveLoopFromHierarchy(Loop *L); 1058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels }; 1068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RegisterOpt<LoopUnswitch> X("loop-unswitch", "Unswitch loops"); 1078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 1088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas EckelsFunctionPass *llvm::createLoopUnswitchPass() { return new LoopUnswitch(); } 1108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsbool LoopUnswitch::runOnFunction(Function &F) { 1128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels bool Changed = false; 1138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LI = &getAnalysis<LoopInfo>(); 1148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Populate the worklist of loops to process in post-order. 1168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) 1178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (po_iterator<Loop*> LI = po_begin(*I), E = po_end(*I); LI != E; ++LI) 1188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopProcessWorklist.push_back(*LI); 1198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Process the loops in worklist order, this is a post-order visitation of 1218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // the loops. We use a worklist of loops so that loops can be removed at any 1228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // time if they are deleted (e.g. the backedge of a loop is removed). 1238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels while (!LoopProcessWorklist.empty()) { 1248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Loop *L = LoopProcessWorklist.back(); 1258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopProcessWorklist.pop_back(); 1268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Changed |= visitLoop(L); 1278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 1288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return Changed; 1308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 1318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// FindLIVLoopCondition - Cond is a condition that occurs in L. If it is 1338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// invariant in the loop, or has an invariant piece, return the invariant. 1348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// Otherwise, return null. 1358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsstatic Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) { 1368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Constants should be folded, not unswitched on! 1378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (isa<Constant>(Cond)) return false; 1388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // TODO: Handle: br (VARIANT|INVARIANT). 1408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // TODO: Hoist simple expressions out of loops. 1418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (L->isLoopInvariant(Cond)) return Cond; 1428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Cond)) 1448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BO->getOpcode() == Instruction::And || 1458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BO->getOpcode() == Instruction::Or) { 1468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If either the left or right side is invariant, we can unswitch on this, 1478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // which will cause the branch to go away in one loop and the condition to 1488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // simplify in the other one. 1498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Value *LHS = FindLIVLoopCondition(BO->getOperand(0), L, Changed)) 1508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return LHS; 1518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Value *RHS = FindLIVLoopCondition(BO->getOperand(1), L, Changed)) 1528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return RHS; 1538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 1548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return 0; 1568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 1578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsbool LoopUnswitch::visitLoop(Loop *L) { 1598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(L->isLCSSAForm()); 1608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels bool Changed = false; 1628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Loop over all of the basic blocks in the loop. If we find an interior 1648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // block that is branching on a loop-invariant condition, we can unswitch this 1658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // loop. 1668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 1678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels I != E; ++I) { 1688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels TerminatorInst *TI = (*I)->getTerminator(); 1698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { 1708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If this isn't branching on an invariant condition, we can't unswitch 1718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // it. 1728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BI->isConditional()) { 1738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // See if this, or some part of it, is loop invariant. If so, we can 1748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // unswitch on it if we desire. 1758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Value *LoopCond = FindLIVLoopCondition(BI->getCondition(), L, Changed); 1768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (LoopCond && UnswitchIfProfitable(LoopCond, ConstantBool::True, L)) { 1778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++NumBranches; 1788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return true; 1798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 1808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 1818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { 1828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), L, Changed); 1838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (LoopCond && SI->getNumCases() > 1) { 1848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Find a value to unswitch on: 1858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // FIXME: this should chose the most expensive case! 1868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Constant *UnswitchVal = SI->getCaseValue(1); 1878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (UnswitchIfProfitable(LoopCond, UnswitchVal, L)) { 1888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++NumSwitches; 1898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return true; 1908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 1918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 1928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 1938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 1948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Scan the instructions to check for unswitchable values. 1958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (BasicBlock::iterator BBI = (*I)->begin(), E = (*I)->end(); 1968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BBI != E; ++BBI) 1978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (SelectInst *SI = dyn_cast<SelectInst>(BBI)) { 1988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), L, Changed); 1998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (LoopCond && UnswitchIfProfitable(LoopCond, ConstantBool::True, L)) { 2008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++NumSelects; 2018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return true; 2028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 2038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 2048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 2058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(L->isLCSSAForm()); 2078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return Changed; 2098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 2108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// isTrivialLoopExitBlock - Check to see if all paths from BB either: 2128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 1. Exit the loop with no side effects. 2138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 2. Branch to the latch block with no side-effects. 2148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 2158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// If these conditions are true, we return true and set ExitBB to the block we 2168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// exit through. 2178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 2188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsstatic bool isTrivialLoopExitBlockHelper(Loop *L, BasicBlock *BB, 2198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *&ExitBB, 2208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::set<BasicBlock*> &Visited) { 2218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!Visited.insert(BB).second) { 2228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Already visited and Ok, end of recursion. 2238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return true; 2248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else if (!L->contains(BB)) { 2258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Otherwise, this is a loop exit, this is fine so long as this is the 2268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // first exit. 2278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (ExitBB != 0) return false; 2288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ExitBB = BB; 2298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return true; 2308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 2318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Otherwise, this is an unvisited intra-loop node. Check all successors. 2338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) { 2348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Check to see if the successor is a trivial loop exit. 2358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!isTrivialLoopExitBlockHelper(L, *SI, ExitBB, Visited)) 2368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return false; 2378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 2388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Okay, everything after this looks good, check to make sure that this block 2408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // doesn't include any side effects. 2418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 2428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (I->mayWriteToMemory()) 2438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return false; 2448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return true; 2468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 2478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// isTrivialLoopExitBlock - Return true if the specified block unconditionally 2498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// leads to an exit from the specified loop, and has no side-effects in the 2508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// process. If so, return the block that is exited to, otherwise return null. 2518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsstatic BasicBlock *isTrivialLoopExitBlock(Loop *L, BasicBlock *BB) { 2528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::set<BasicBlock*> Visited; 2538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Visited.insert(L->getHeader()); // Branches to header are ok. 2548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *ExitBB = 0; 2558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (isTrivialLoopExitBlockHelper(L, BB, ExitBB, Visited)) 2568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return ExitBB; 2578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return 0; 2588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 2598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// IsTrivialUnswitchCondition - Check to see if this unswitch condition is 2618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// trivial: that is, that the condition controls whether or not the loop does 2628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// anything at all. If this is a trivial condition, unswitching produces no 2638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// code duplications (equivalently, it produces a simpler loop and a new empty 2648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// loop, which gets deleted). 2658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 2668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// If this is a trivial condition, return true, otherwise return false. When 2678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// returning true, this sets Cond and Val to the condition that controls the 2688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// trivial condition: when Cond dynamically equals Val, the loop is known to 2698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// exit. Finally, this sets LoopExit to the BB that the loop exits to when 2708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// Cond == Val. 2718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 2728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsstatic bool IsTrivialUnswitchCondition(Loop *L, Value *Cond, Constant **Val = 0, 2738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock **LoopExit = 0) { 2748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *Header = L->getHeader(); 2758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels TerminatorInst *HeaderTerm = Header->getTerminator(); 2768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *LoopExitBB = 0; 2788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BranchInst *BI = dyn_cast<BranchInst>(HeaderTerm)) { 2798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If the header block doesn't end with a conditional branch on Cond, we 2808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // can't handle it. 2818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!BI->isConditional() || BI->getCondition() != Cond) 2828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return false; 2838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Check to see if a successor of the branch is guaranteed to go to the 2858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // latch block or exit through a one exit block without having any 2868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // side-effects. If so, determine the value of Cond that causes it to do 2878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // this. 2888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if ((LoopExitBB = isTrivialLoopExitBlock(L, BI->getSuccessor(0)))) { 2898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Val) *Val = ConstantBool::True; 2908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else if ((LoopExitBB = isTrivialLoopExitBlock(L, BI->getSuccessor(1)))) { 2918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Val) *Val = ConstantBool::False; 2928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 2938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else if (SwitchInst *SI = dyn_cast<SwitchInst>(HeaderTerm)) { 2948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If this isn't a switch on Cond, we can't handle it. 2958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (SI->getCondition() != Cond) return false; 2968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 2978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Check to see if a successor of the switch is guaranteed to go to the 2988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // latch block or exit through a one exit block without having any 2998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // side-effects. If so, determine the value of Cond that causes it to do 3008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // this. Note that we can't trivially unswitch on the default case. 3018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) 3028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if ((LoopExitBB = isTrivialLoopExitBlock(L, SI->getSuccessor(i)))) { 3038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Okay, we found a trivial case, remember the value that is trivial. 3048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Val) *Val = SI->getCaseValue(i); 3058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels break; 3068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 3078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 3088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If we didn't find a single unique LoopExit block, or if the loop exit block 3108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // contains phi nodes, this isn't trivial. 3118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!LoopExitBB || isa<PHINode>(LoopExitBB->begin())) 3128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return false; // Can't handle this. 3138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (LoopExit) *LoopExit = LoopExitBB; 3158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // We already know that nothing uses any scalar values defined inside of this 3178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // loop. As such, we just have to check to see if this loop will execute any 3188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // side-effecting instructions (e.g. stores, calls, volatile loads) in the 3198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // part of the loop that the code *would* execute. We already checked the 3208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // tail, check the header now. 3218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (BasicBlock::iterator I = Header->begin(), E = Header->end(); I != E; ++I) 3228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (I->mayWriteToMemory()) 3238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return false; 3248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return true; 3258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 3268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// getLoopUnswitchCost - Return the cost (code size growth) that will happen if 3288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// we choose to unswitch the specified loop on the specified value. 3298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 3308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsunsigned LoopUnswitch::getLoopUnswitchCost(Loop *L, Value *LIC) { 3318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If the condition is trivial, always unswitch. There is no code growth for 3328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // this case. 3338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (IsTrivialUnswitchCondition(L, LIC)) 3348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return 0; 3358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels unsigned Cost = 0; 3378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // FIXME: this is brain dead. It should take into consideration code 3388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // shrinkage. 3398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 3408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels I != E; ++I) { 3418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *BB = *I; 3428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Do not include empty blocks in the cost calculation. This happen due to 3438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // loop canonicalization and will be removed. 3448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BB->begin() == BasicBlock::iterator(BB->getTerminator())) 3458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels continue; 3468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Count basic blocks. 3488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++Cost; 3498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 3508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return Cost; 3528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 3538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// UnswitchIfProfitable - We have found that we can unswitch L when 3558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// LoopCond == Val to simplify the loop. If we decide that this is profitable, 3568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// unswitch the loop, reprocess the pieces, then return true. 3578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsbool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val,Loop *L){ 3588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Check to see if it would be profitable to unswitch this loop. 3598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels unsigned Cost = getLoopUnswitchCost(L, LoopCond); 3608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Cost > Threshold) { 3618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // FIXME: this should estimate growth by the amount of code shared by the 3628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // resultant unswitched loops. 3638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // 3648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels DEBUG(std::cerr << "NOT unswitching loop %" 3658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels << L->getHeader()->getName() << ", cost too high: " 3668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels << L->getBlocks().size() << "\n"); 3678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return false; 3688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 3698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If this is a trivial condition to unswitch (which results in no code 3718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // duplication), do it now. 3728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Constant *CondVal; 3738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *ExitBlock; 3748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (IsTrivialUnswitchCondition(L, LoopCond, &CondVal, &ExitBlock)) { 3758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels UnswitchTrivialCondition(L, LoopCond, CondVal, ExitBlock); 3768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else { 3778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels UnswitchNontrivialCondition(LoopCond, Val, L); 3788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 3798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return true; 3818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 3828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// SplitBlock - Split the specified block at the specified instruction - every 3848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// thing before SplitPt stays in Old and everything starting with SplitPt moves 3858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// to a new block. The two blocks are joined by an unconditional branch and 3868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// the loop info is updated. 3878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 3888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas EckelsBasicBlock *LoopUnswitch::SplitBlock(BasicBlock *Old, Instruction *SplitPt) { 3898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock::iterator SplitIt = SplitPt; 3908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels while (isa<PHINode>(SplitIt)) 3918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++SplitIt; 3928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split"); 3938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // The new block lives in whichever loop the old one did. 3958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Loop *L = LI->getLoopFor(Old)) 3968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels L->addBasicBlockToLoop(New, *LI); 3978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 3988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return New; 3998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 4008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas EckelsBasicBlock *LoopUnswitch::SplitEdge(BasicBlock *BB, BasicBlock *Succ) { 4038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels TerminatorInst *LatchTerm = BB->getTerminator(); 4048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels unsigned SuccNum = 0; 4058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = LatchTerm->getNumSuccessors(); ; ++i) { 4068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(i != e && "Didn't find edge?"); 4078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (LatchTerm->getSuccessor(i) == Succ) { 4088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels SuccNum = i; 4098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels break; 4108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 4118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 4128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If this is a critical edge, let SplitCriticalEdge do it. 4148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (SplitCriticalEdge(BB->getTerminator(), SuccNum, this)) 4158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return LatchTerm->getSuccessor(SuccNum); 4168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If the edge isn't critical, then BB has a single successor or Succ has a 4188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // single pred. Split the block. 4198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock::iterator SplitPoint; 4208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BasicBlock *SP = Succ->getSinglePredecessor()) { 4218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If the successor only has a single pred, split the top of the successor 4228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // block. 4238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(SP == BB && "CFG broken"); 4248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return SplitBlock(Succ, Succ->begin()); 4258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else { 4268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Otherwise, if BB has a single successor, split it at the bottom of the 4278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // block. 4288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(BB->getTerminator()->getNumSuccessors() == 1 && 4298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels "Should have a single succ!"); 4308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return SplitBlock(BB, BB->getTerminator()); 4318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 4328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 4338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// RemapInstruction - Convert the instruction operands from referencing the 4378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// current values into those specified by ValueMap. 4388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// 4398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsstatic inline void RemapInstruction(Instruction *I, 4408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::map<const Value *, Value*> &ValueMap) { 4418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) { 4428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Value *Op = I->getOperand(op); 4438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::map<const Value *, Value*>::iterator It = ValueMap.find(Op); 4448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (It != ValueMap.end()) Op = It->second; 4458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels I->setOperand(op, Op); 4468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 4478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 4488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// CloneLoop - Recursively clone the specified loop and all of its children, 4508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// mapping the blocks with the specified map. 4518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsstatic Loop *CloneLoop(Loop *L, Loop *PL, std::map<const Value*, Value*> &VM, 4528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopInfo *LI) { 4538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Loop *New = new Loop(); 4548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (PL) 4568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels PL->addChildLoop(New); 4578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels else 4588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LI->addTopLevelLoop(New); 4598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Add all of the blocks in L to the new loop. 4618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 4628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels I != E; ++I) 4638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (LI->getLoopFor(*I) == L) 4648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels New->addBasicBlockToLoop(cast<BasicBlock>(VM[*I]), *LI); 4658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Add all of the subloops to the new loop. 4678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) 4688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels CloneLoop(*I, New, VM, LI); 4698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return New; 4718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 4728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// EmitPreheaderBranchOnCondition - Emit a conditional branch on two values 4748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// if LIC == Val, branch to TrueDst, otherwise branch to FalseDest. Insert the 4758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// code immediately before InsertPt. 4768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsstatic void EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val, 4778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *TrueDest, 4788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *FalseDest, 4798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Instruction *InsertPt) { 4808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Insert a conditional branch on LIC to the two preheaders. The original 4818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // code is the true version and the new code is the false version. 4828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Value *BranchVal = LIC; 4838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!isa<ConstantBool>(Val)) { 4848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BranchVal = BinaryOperator::createSetEQ(LIC, Val, "tmp", InsertPt); 4858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else if (Val != ConstantBool::True) { 4868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // We want to enter the new loop when the condition is true. 4878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::swap(TrueDest, FalseDest); 4888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 4898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Insert the new branch. 4918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels new BranchInst(TrueDest, FalseDest, BranchVal, InsertPt); 4928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 4938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 4958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// UnswitchTrivialCondition - Given a loop that has a trivial unswitchable 4968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// condition in it (a cond branch from its header block to its latch block, 4978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// where the path through the loop that doesn't execute its body has no 4988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// side-effects), unswitch it. This doesn't involve any code duplication, just 4998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// moving the conditional branch outside of the loop and updating loop info. 5008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsvoid LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond, 5018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Constant *Val, 5028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *ExitBlock) { 5038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels DEBUG(std::cerr << "loop-unswitch: Trivial-Unswitch loop %" 5048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels << L->getHeader()->getName() << " [" << L->getBlocks().size() 5058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels << " blocks] in Function " << L->getHeader()->getParent()->getName() 5068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels << " on cond: " << *Val << " == " << *Cond << "\n"); 5078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // First step, split the preheader, so that we know that there is a safe place 5098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // to insert the conditional branch. We will change 'OrigPH' to have a 5108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // conditional branch on Cond. 5118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *OrigPH = L->getLoopPreheader(); 5128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *NewPH = SplitEdge(OrigPH, L->getHeader()); 5138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Now that we have a place to insert the conditional branch, create a place 5158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // to branch to: this is the exit block out of the loop that we should 5168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // short-circuit to. 5178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Split this block now, so that the loop maintains its exit block, and so 5198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // that the jump from the preheader can execute the contents of the exit block 5208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // without actually branching to it (the exit block should be dominated by the 5218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // loop header, not the preheader). 5228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(!L->contains(ExitBlock) && "Exit block is in the loop?"); 5238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *NewExit = SplitBlock(ExitBlock, ExitBlock->begin()); 5248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Okay, now we have a position to branch from and a position to branch to, 5268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // insert the new conditional branch. 5278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels EmitPreheaderBranchOnCondition(Cond, Val, NewExit, NewPH, 5288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels OrigPH->getTerminator()); 5298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels OrigPH->getTerminator()->eraseFromParent(); 5308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // We need to reprocess this loop, it could be unswitched again. 5328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopProcessWorklist.push_back(L); 5338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Now that we know that the loop is never entered when this condition is a 5358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // particular value, rewrite the loop with this info. We know that this will 5368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // at least eliminate the old branch. 5378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RewriteLoopBodyWithConditionConstant(L, Cond, Val, false); 5388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++NumTrivial; 5398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 5408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// VersionLoop - We determined that the loop is profitable to unswitch when LIC 5438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// equal Val. Split it into loop versions and test the condition outside of 5448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// either loop. Return the loops created as Out1/Out2. 5458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsvoid LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val, 5468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Loop *L) { 5478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Function *F = L->getHeader()->getParent(); 5488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels DEBUG(std::cerr << "loop-unswitch: Unswitching loop %" 5498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels << L->getHeader()->getName() << " [" << L->getBlocks().size() 5508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels << " blocks] in Function " << F->getName() 5518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels << " when '" << *Val << "' == " << *LIC << "\n"); 5528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // LoopBlocks contains all of the basic blocks of the loop, including the 5548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // preheader of the loop, the body of the loop, and the exit blocks of the 5558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // loop, in that order. 5568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<BasicBlock*> LoopBlocks; 5578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // First step, split the preheader and exit blocks, and add these blocks to 5598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // the LoopBlocks list. 5608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *OrigPreheader = L->getLoopPreheader(); 5618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopBlocks.push_back(SplitEdge(OrigPreheader, L->getHeader())); 5628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // We want the loop to come after the preheader, but before the exit blocks. 5648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end()); 5658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<BasicBlock*> ExitBlocks; 5678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels L->getExitBlocks(ExitBlocks); 5688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::sort(ExitBlocks.begin(), ExitBlocks.end()); 5698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ExitBlocks.erase(std::unique(ExitBlocks.begin(), ExitBlocks.end()), 5708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ExitBlocks.end()); 5718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Split all of the edges from inside the loop to their exit blocks. Update 5738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // the appropriate Phi nodes as we do so. 5748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels unsigned NumBlocks = L->getBlocks().size(); 5758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 5778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *ExitBlock = ExitBlocks[i]; 5788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<BasicBlock*> Preds(pred_begin(ExitBlock), pred_end(ExitBlock)); 5798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned j = 0, e = Preds.size(); j != e; ++j) { 5818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(L->contains(Preds[j]) && 5828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels "All preds of loop exit blocks must be the same loop!"); 5838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock* MiddleBlock = SplitEdge(Preds[j], ExitBlock); 5848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock* StartBlock = Preds[j]; 5858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock* EndBlock; 5868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (MiddleBlock->getSinglePredecessor() == ExitBlock) { 5878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels EndBlock = MiddleBlock; 5888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels MiddleBlock = EndBlock->getSinglePredecessor();; 5898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else { 5908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels EndBlock = ExitBlock; 5918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 5928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 5938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::set<PHINode*> InsertedPHIs; 5948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels PHINode* OldLCSSA = 0; 5958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (BasicBlock::iterator I = EndBlock->begin(); 5968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels (OldLCSSA = dyn_cast<PHINode>(I)); ++I) { 5978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Value* OldValue = OldLCSSA->getIncomingValueForBlock(MiddleBlock); 5988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels PHINode* NewLCSSA = new PHINode(OldLCSSA->getType(), 5998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels OldLCSSA->getName() + ".us-lcssa", 6008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels MiddleBlock->getTerminator()); 6018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels NewLCSSA->addIncoming(OldValue, StartBlock); 6028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels OldLCSSA->setIncomingValue(OldLCSSA->getBasicBlockIndex(MiddleBlock), 6038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels NewLCSSA); 6048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels InsertedPHIs.insert(NewLCSSA); 6058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 6068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Instruction* InsertPt = EndBlock->begin(); 6088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels while (dyn_cast<PHINode>(InsertPt)) ++InsertPt; 6098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (BasicBlock::iterator I = MiddleBlock->begin(); 6108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels (OldLCSSA = dyn_cast<PHINode>(I)) && InsertedPHIs.count(OldLCSSA) == 0; 6118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++I) { 6128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels PHINode *NewLCSSA = new PHINode(OldLCSSA->getType(), 6138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels OldLCSSA->getName() + ".us-lcssa", 6148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels InsertPt); 6158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels OldLCSSA->replaceAllUsesWith(NewLCSSA); 6168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels NewLCSSA->addIncoming(OldLCSSA, MiddleBlock); 6178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 6188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 6198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 6208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // The exit blocks may have been changed due to edge splitting, recompute. 6228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ExitBlocks.clear(); 6238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels L->getExitBlocks(ExitBlocks); 6248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::sort(ExitBlocks.begin(), ExitBlocks.end()); 6258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ExitBlocks.erase(std::unique(ExitBlocks.begin(), ExitBlocks.end()), 6268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ExitBlocks.end()); 6278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Add exit blocks to the loop blocks. 6298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopBlocks.insert(LoopBlocks.end(), ExitBlocks.begin(), ExitBlocks.end()); 6308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Next step, clone all of the basic blocks that make up the loop (including 6328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // the loop preheader and exit blocks), keeping track of the mapping between 6338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // the instructions and blocks. 6348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<BasicBlock*> NewBlocks; 6358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels NewBlocks.reserve(LoopBlocks.size()); 6368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::map<const Value*, Value*> ValueMap; 6378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) { 6388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *New = CloneBasicBlock(LoopBlocks[i], ValueMap, ".us", F); 6398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels NewBlocks.push_back(New); 6408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ValueMap[LoopBlocks[i]] = New; // Keep the BB mapping. 6418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 6428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Splice the newly inserted blocks into the function right before the 6448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // original preheader. 6458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels F->getBasicBlockList().splice(LoopBlocks[0], F->getBasicBlockList(), 6468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels NewBlocks[0], F->end()); 6478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Now we create the new Loop object for the versioned loop. 6498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Loop *NewLoop = CloneLoop(L, L->getParentLoop(), ValueMap, LI); 6508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Loop *ParentLoop = L->getParentLoop(); 6518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (ParentLoop) { 6528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Make sure to add the cloned preheader and exit blocks to the parent loop 6538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // as well. 6548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ParentLoop->addBasicBlockToLoop(NewBlocks[0], *LI); 6558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 6568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 6588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *NewExit = cast<BasicBlock>(ValueMap[ExitBlocks[i]]); 6598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // The new exit block should be in the same loop as the old one. 6608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Loop *ExitBBLoop = LI->getLoopFor(ExitBlocks[i])) 6618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ExitBBLoop->addBasicBlockToLoop(NewExit, *LI); 6628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(NewExit->getTerminator()->getNumSuccessors() == 1 && 6648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels "Exit block should have been split to have one successor!"); 6658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *ExitSucc = NewExit->getTerminator()->getSuccessor(0); 6668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If the successor of the exit block had PHI nodes, add an entry for 6688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // NewExit. 6698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels PHINode *PN; 6708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (BasicBlock::iterator I = ExitSucc->begin(); 6718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels (PN = dyn_cast<PHINode>(I)); ++I) { 6728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Value *V = PN->getIncomingValueForBlock(ExitBlocks[i]); 6738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::map<const Value *, Value*>::iterator It = ValueMap.find(V); 6748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (It != ValueMap.end()) V = It->second; 6758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels PN->addIncoming(V, NewExit); 6768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 6778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 6788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Rewrite the code to refer to itself. 6808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = NewBlocks.size(); i != e; ++i) 6818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (BasicBlock::iterator I = NewBlocks[i]->begin(), 6828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels E = NewBlocks[i]->end(); I != E; ++I) 6838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemapInstruction(I, ValueMap); 6848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Rewrite the original preheader to select between versions of the loop. 6868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BranchInst *OldBR = cast<BranchInst>(OrigPreheader->getTerminator()); 6878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(OldBR->isUnconditional() && OldBR->getSuccessor(0) == LoopBlocks[0] && 6888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels "Preheader splitting did not work correctly!"); 6898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Emit the new branch that selects between the two versions of this loop. 6918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels EmitPreheaderBranchOnCondition(LIC, Val, NewBlocks[0], LoopBlocks[0], OldBR); 6928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels OldBR->eraseFromParent(); 6938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopProcessWorklist.push_back(L); 6958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LoopProcessWorklist.push_back(NewLoop); 6968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 6978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Now we rewrite the original code to know that the condition is true and the 6988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // new code to know that the condition is false. 6998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RewriteLoopBodyWithConditionConstant(L , LIC, Val, false); 7008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // It's possible that simplifying one loop could cause the other to be 7028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // deleted. If so, don't simplify it. 7038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!LoopProcessWorklist.empty() && LoopProcessWorklist.back() == NewLoop) 7048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RewriteLoopBodyWithConditionConstant(NewLoop, LIC, Val, true); 7058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 7068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// RemoveFromWorklist - Remove all instances of I from the worklist vector 7088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// specified. 7098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsstatic void RemoveFromWorklist(Instruction *I, 7108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<Instruction*> &Worklist) { 7118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<Instruction*>::iterator WI = std::find(Worklist.begin(), 7128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist.end(), I); 7138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels while (WI != Worklist.end()) { 7148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels unsigned Offset = WI-Worklist.begin(); 7158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist.erase(WI); 7168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels WI = std::find(Worklist.begin()+Offset, Worklist.end(), I); 7178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 7188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 7198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// ReplaceUsesOfWith - When we find that I really equals V, remove I from the 7218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// program, replacing all uses with V and update the worklist. 7228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsstatic void ReplaceUsesOfWith(Instruction *I, Value *V, 7238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<Instruction*> &Worklist) { 7248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels DEBUG(std::cerr << "Replace with '" << *V << "': " << *I); 7258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Add uses to the worklist, which may be dead now. 7278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 7288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Instruction *Use = dyn_cast<Instruction>(I->getOperand(i))) 7298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist.push_back(Use); 7308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Add users to the worklist which may be simplified now. 7328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); 7338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels UI != E; ++UI) 7348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist.push_back(cast<Instruction>(*UI)); 7358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels I->replaceAllUsesWith(V); 7368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels I->eraseFromParent(); 7378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveFromWorklist(I, Worklist); 7388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++NumSimplify; 7398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 7408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// RemoveBlockIfDead - If the specified block is dead, remove it, update loop 7428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// information, and remove any dead successors it has. 7438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 7448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsvoid LoopUnswitch::RemoveBlockIfDead(BasicBlock *BB, 7458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<Instruction*> &Worklist) { 7468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (pred_begin(BB) != pred_end(BB)) { 7478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // This block isn't dead, since an edge to BB was just removed, see if there 7488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // are any easy simplifications we can do now. 7498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BasicBlock *Pred = BB->getSinglePredecessor()) { 7508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If it has one pred, fold phi nodes in BB. 7518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels while (isa<PHINode>(BB->begin())) 7528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ReplaceUsesOfWith(BB->begin(), 7538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels cast<PHINode>(BB->begin())->getIncomingValue(0), 7548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist); 7558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If this is the header of a loop and the only pred is the latch, we now 7578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // have an unreachable loop. 7588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Loop *L = LI->getLoopFor(BB)) 7598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (L->getHeader() == BB && L->contains(Pred)) { 7608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Remove the branch from the latch to the header block, this makes 7618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // the header dead, which will make the latch dead (because the header 7628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // dominates the latch). 7638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Pred->getTerminator()->eraseFromParent(); 7648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels new UnreachableInst(Pred); 7658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // The loop is now broken, remove it from LI. 7678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveLoopFromHierarchy(L); 7688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Reprocess the header, which now IS dead. 7708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveBlockIfDead(BB, Worklist); 7718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return; 7728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 7738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If pred ends in a uncond branch, add uncond branch to worklist so that 7758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // the two blocks will get merged. 7768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BranchInst *BI = dyn_cast<BranchInst>(Pred->getTerminator())) 7778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BI->isUnconditional()) 7788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist.push_back(BI); 7798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 7808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels return; 7818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 7828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels DEBUG(std::cerr << "Nuking dead block: " << *BB); 7848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Remove the instructions in the basic block from the worklist. 7868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { 7878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveFromWorklist(I, Worklist); 7888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Anything that uses the instructions in this basic block should have their 7908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // uses replaced with undefs. 7918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!I->use_empty()) 7928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels I->replaceAllUsesWith(UndefValue::get(I->getType())); 7938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 7948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 7958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If this is the edge to the header block for a loop, remove the loop and 7968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // promote all subloops. 7978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Loop *BBLoop = LI->getLoopFor(BB)) { 7988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BBLoop->getLoopLatch() == BB) 7998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveLoopFromHierarchy(BBLoop); 8008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Remove the block from the loop info, which removes it from any loops it 8038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // was in. 8048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LI->removeBlock(BB); 8058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Remove phi node entries in successors for this block. 8088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels TerminatorInst *TI = BB->getTerminator(); 8098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<BasicBlock*> Succs; 8108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) { 8118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Succs.push_back(TI->getSuccessor(i)); 8128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels TI->getSuccessor(i)->removePredecessor(BB); 8138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Unique the successors, remove anything with multiple uses. 8168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::sort(Succs.begin(), Succs.end()); 8178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Succs.erase(std::unique(Succs.begin(), Succs.end()), Succs.end()); 8188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Remove the basic block, including all of the instructions contained in it. 8208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BB->eraseFromParent(); 8218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Remove successor blocks here that are not dead, so that we know we only 8238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // have dead blocks in this list. Nondead blocks have a way of becoming dead, 8248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // then getting removed before we revisit them, which is badness. 8258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // 8268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0; i != Succs.size(); ++i) 8278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (pred_begin(Succs[i]) != pred_end(Succs[i])) { 8288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // One exception is loop headers. If this block was the preheader for a 8298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // loop, then we DO want to visit the loop so the loop gets deleted. 8308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // We know that if the successor is a loop header, that this loop had to 8318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // be the preheader: the case where this was the latch block was handled 8328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // above and headers can only have two predecessors. 8338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!LI->isLoopHeader(Succs[i])) { 8348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Succs.erase(Succs.begin()+i); 8358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels --i; 8368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = Succs.size(); i != e; ++i) 8408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveBlockIfDead(Succs[i], Worklist); 8418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 8428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// RemoveLoopFromHierarchy - We have discovered that the specified loop has 8448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// become unwrapped, either because the backedge was deleted, or because the 8458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// edge into the header was removed. If the edge into the header from the 8468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// latch block was removed, the loop is unwrapped but subloops are still alive, 8478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// so they just reparent loops. If the loops are actually dead, they will be 8488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// removed later. 8498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsvoid LoopUnswitch::RemoveLoopFromHierarchy(Loop *L) { 8508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Loop *ParentLoop = L->getParentLoop()) { // Not a top-level loop. 8518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Reparent all of the blocks in this loop. Since BBLoop had a parent, 8528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // they are now all in it. 8538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 8548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels I != E; ++I) 8558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (LI->getLoopFor(*I) == L) // Don't change blocks in subloops. 8568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LI->changeLoopFor(*I, ParentLoop); 8578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Remove the loop from its parent loop. 8598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (Loop::iterator I = ParentLoop->begin(), E = ParentLoop->end();; 8608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++I) { 8618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(I != E && "Couldn't find loop"); 8628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (*I == L) { 8638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ParentLoop->removeChildLoop(I); 8648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels break; 8658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Move all subloops into the parent loop. 8698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels while (L->begin() != L->end()) 8708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ParentLoop->addChildLoop(L->removeChildLoop(L->end()-1)); 8718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else { 8728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Reparent all of the blocks in this loop. Since BBLoop had no parent, 8738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // they no longer in a loop at all. 8748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0; i != L->getBlocks().size(); ++i) { 8768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Don't change blocks in subloops. 8778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (LI->getLoopFor(L->getBlocks()[i]) == L) { 8788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LI->removeBlock(L->getBlocks()[i]); 8798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels --i; 8808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Remove the loop from the top-level LoopInfo object. 8848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (LoopInfo::iterator I = LI->begin(), E = LI->end();; ++I) { 8858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(I != E && "Couldn't find loop"); 8868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (*I == L) { 8878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LI->removeLoop(I); 8888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels break; 8898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Move all of the subloops to the top-level. 8938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels while (L->begin() != L->end()) 8948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LI->addTopLevelLoop(L->removeChildLoop(L->end()-1)); 8958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 8968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 8978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels delete L; 8988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveLoopFromWorklist(L); 8998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 9008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// RewriteLoopBodyWithConditionConstant - We know either that the value LIC has 9048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// the value specified by Val in the specified loop, or we know it does NOT have 9058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels// that value. Rewrite any uses of LIC or of properties correlated to it. 9068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsvoid LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC, 9078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Constant *Val, 9088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels bool IsEqual) { 9098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(!isa<Constant>(LIC) && "Why are we unswitching on a constant?"); 9108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // FIXME: Support correlated properties, like: 9128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // for (...) 9138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // if (li1 < li2) 9148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // ... 9158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // if (li1 > li2) 9168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // ... 9178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // FOLD boolean conditions (X|LIC), (X&LIC). Fold conditional branches, 9198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // selects, switches. 9208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<User*> Users(LIC->use_begin(), LIC->use_end()); 9218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels std::vector<Instruction*> Worklist; 9228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If we know that LIC == Val, or that LIC == NotVal, just replace uses of LIC 9248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // in the loop with the appropriate one directly. 9258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (IsEqual || isa<ConstantBool>(Val)) { 9268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Value *Replacement; 9278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (IsEqual) 9288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Replacement = Val; 9298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels else 9308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Replacement = ConstantBool::get(!cast<ConstantBool>(Val)->getValue()); 9318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = Users.size(); i != e; ++i) 9338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Instruction *U = cast<Instruction>(Users[i])) { 9348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!L->contains(U->getParent())) 9358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels continue; 9368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels U->replaceUsesOfWith(LIC, Replacement); 9378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist.push_back(U); 9388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 9398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else { 9408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Otherwise, we don't know the precise value of LIC, but we do know that it 9418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // is certainly NOT "Val". As such, simplify any uses in the loop that we 9428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // can. This case occurs when we unswitch switch statements. 9438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = Users.size(); i != e; ++i) 9448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Instruction *U = cast<Instruction>(Users[i])) { 9458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!L->contains(U->getParent())) 9468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels continue; 9478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist.push_back(U); 9498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If we know that LIC is not Val, use this info to simplify code. 9518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (SwitchInst *SI = dyn_cast<SwitchInst>(U)) { 9528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i) { 9538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (SI->getCaseValue(i) == Val) { 9548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Found a dead case value. Don't remove PHI nodes in the 9558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // successor if they become single-entry, those PHI nodes may 9568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // be in the Users list. 9578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // FIXME: This is a hack. We need to keep the successor around 9598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // and hooked up so as to preserve the loop structure, because 9608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // trying to update it is complicated. So instead we preserve the 9618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // loop structure and put the block on an dead code path. 9628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock* Old = SI->getParent(); 9648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock* Split = SplitBlock(Old, SI); 9658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Instruction* OldTerm = Old->getTerminator(); 9678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BranchInst* Branch = new BranchInst(Split, 9688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels SI->getSuccessor(i), 9698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ConstantBool::True, 9708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels OldTerm); 9718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Old->getTerminator()->eraseFromParent(); 9738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (BasicBlock::iterator II = SI->getSuccessor(i)->begin(), 9758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels IE = SI->getSuccessor(i)->end(); II != IE; ++II) { 9768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (isa<PHINode>(*II)) { 9778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels (*II).replaceUsesOfWith(Split, Old); 9788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 9798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 9808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels SI->removeCase(i); 9828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels break; 9838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 9848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 9858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 9868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // TODO: We could do other simplifications, for example, turning 9888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // LIC == Val -> false. 9898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 9908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 9918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels SimplifyCode(Worklist); 9938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 9948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 9958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// SimplifyCode - Okay, now that we have simplified some instructions in the 9968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// loop, walk over it and constant prop, dce, and fold control flow where 9978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// possible. Note that this is effectively a very simple loop-structure-aware 9988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// optimizer. During processing of this loop, L could very well be deleted, so 9998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// it must not be used. 10008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 10018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// FIXME: When the loop optimizer is more mature, separate this out to a new 10028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// pass. 10038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels/// 10048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckelsvoid LoopUnswitch::SimplifyCode(std::vector<Instruction*> &Worklist) { 10058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels while (!Worklist.empty()) { 10068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Instruction *I = Worklist.back(); 10078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist.pop_back(); 10088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 10098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Simple constant folding. 10108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Constant *C = ConstantFoldInstruction(I)) { 10118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ReplaceUsesOfWith(I, C, Worklist); 10128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels continue; 10138e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 10148e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 10158e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Simple DCE. 10168e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (isInstructionTriviallyDead(I)) { 10178e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels DEBUG(std::cerr << "Remove dead instruction '" << *I); 10188e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 10198e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Add uses to the worklist, which may be dead now. 10208e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 10218e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (Instruction *Use = dyn_cast<Instruction>(I->getOperand(i))) 10228e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist.push_back(Use); 10238e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels I->eraseFromParent(); 10248e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveFromWorklist(I, Worklist); 10258e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++NumSimplify; 10268e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels continue; 10278e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 10288e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 10298e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Special case hacks that appear commonly in unswitched code. 10308e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels switch (I->getOpcode()) { 10318e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels case Instruction::Select: 10328e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (ConstantBool *CB = dyn_cast<ConstantBool>(I->getOperand(0))) { 10338e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ReplaceUsesOfWith(I, I->getOperand(!CB->getValue()+1), Worklist); 10348e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels continue; 10358e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 10368e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels break; 10378e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels case Instruction::And: 10388e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (isa<ConstantBool>(I->getOperand(0))) // constant -> RHS 10398e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels cast<BinaryOperator>(I)->swapOperands(); 10408e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (ConstantBool *CB = dyn_cast<ConstantBool>(I->getOperand(1))) { 10418e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (CB->getValue()) // X & 1 -> X 10428e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ReplaceUsesOfWith(I, I->getOperand(0), Worklist); 10438e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels else // X & 0 -> 0 10448e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ReplaceUsesOfWith(I, I->getOperand(1), Worklist); 10458e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels continue; 10468e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 10478e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels break; 10488e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels case Instruction::Or: 10498e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (isa<ConstantBool>(I->getOperand(0))) // constant -> RHS 10508e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels cast<BinaryOperator>(I)->swapOperands(); 10518e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (ConstantBool *CB = dyn_cast<ConstantBool>(I->getOperand(1))) { 10528e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (CB->getValue()) // X | 1 -> 1 10538e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ReplaceUsesOfWith(I, I->getOperand(1), Worklist); 10548e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels else // X | 0 -> X 10558e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ReplaceUsesOfWith(I, I->getOperand(0), Worklist); 10568e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels continue; 10578e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 10588e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels break; 10598e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels case Instruction::Br: { 10608e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BranchInst *BI = cast<BranchInst>(I); 10618e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (BI->isUnconditional()) { 10628e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If BI's parent is the only pred of the successor, fold the two blocks 10638e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // together. 10648e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *Pred = BI->getParent(); 10658e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *Succ = BI->getSuccessor(0); 10668e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *SinglePred = Succ->getSinglePredecessor(); 10678e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels if (!SinglePred) continue; // Nothing to do. 10688e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels assert(SinglePred == Pred && "CFG broken"); 10698e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 10708e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels DEBUG(std::cerr << "Merging blocks: " << Pred->getName() << " <- " 10718e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels << Succ->getName() << "\n"); 10728e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 10738e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Resolve any single entry PHI nodes in Succ. 10748e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels while (PHINode *PN = dyn_cast<PHINode>(Succ->begin())) 10758e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ReplaceUsesOfWith(PN, PN->getIncomingValue(0), Worklist); 10768e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 10778e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Move all of the successor contents from Succ to Pred. 10788e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Pred->getInstList().splice(BI, Succ->getInstList(), Succ->begin(), 10798e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Succ->end()); 10808e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BI->eraseFromParent(); 10818e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveFromWorklist(BI, Worklist); 10828e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 10838e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // If Succ has any successors with PHI nodes, update them to have 10848e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // entries coming from Pred instead of Succ. 10858e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Succ->replaceAllUsesWith(Pred); 10868e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 10878e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Remove Succ from the loop tree. 10888e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels LI->removeBlock(Succ); 10898e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Succ->eraseFromParent(); 10908e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++NumSimplify; 10918e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } else if (ConstantBool *CB = dyn_cast<ConstantBool>(BI->getCondition())){ 10928e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // Conditional branch. Turn it into an unconditional branch, then 10938e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels // remove dead blocks. 10948e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels break; // FIXME: Enable. 10958e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 10968e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels DEBUG(std::cerr << "Folded branch: " << *BI); 10978e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *DeadSucc = BI->getSuccessor(CB->getValue()); 10988e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BasicBlock *LiveSucc = BI->getSuccessor(!CB->getValue()); 10998e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels DeadSucc->removePredecessor(BI->getParent(), true); 11008e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels Worklist.push_back(new BranchInst(LiveSucc, BI)); 11018e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels BI->eraseFromParent(); 11028e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveFromWorklist(BI, Worklist); 11038e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels ++NumSimplify; 11048e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels 11058e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels RemoveBlockIfDead(DeadSucc, Worklist); 11068e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 11078e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels break; 11088e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 11098e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 11108e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels } 11118e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels} 11128e01cdce135d5d816f92d7bb83f9a930aa1b45aeLucas Eckels