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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56056 91177308-0d34-0410-b5e6-96231b3b80d8
721 lines
28 KiB
C++
721 lines
28 KiB
C++
//===- IndVarSimplify.cpp - Induction Variable Elimination ----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This transformation analyzes and transforms the induction variables (and
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// computations derived from them) into simpler forms suitable for subsequent
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// analysis and transformation.
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//
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// This transformation makes the following changes to each loop with an
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// identifiable induction variable:
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// 1. All loops are transformed to have a SINGLE canonical induction variable
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// which starts at zero and steps by one.
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// 2. The canonical induction variable is guaranteed to be the first PHI node
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// in the loop header block.
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// 3. Any pointer arithmetic recurrences are raised to use array subscripts.
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//
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// If the trip count of a loop is computable, this pass also makes the following
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// changes:
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// 1. The exit condition for the loop is canonicalized to compare the
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// induction value against the exit value. This turns loops like:
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// 'for (i = 7; i*i < 1000; ++i)' into 'for (i = 0; i != 25; ++i)'
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// 2. Any use outside of the loop of an expression derived from the indvar
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// is changed to compute the derived value outside of the loop, eliminating
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// the dependence on the exit value of the induction variable. If the only
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// purpose of the loop is to compute the exit value of some derived
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// expression, this transformation will make the loop dead.
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//
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// This transformation should be followed by strength reduction after all of the
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// desired loop transformations have been performed. Additionally, on targets
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// where it is profitable, the loop could be transformed to count down to zero
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// (the "do loop" optimization).
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "indvars"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/Constants.h"
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#include "llvm/Instructions.h"
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#include "llvm/Type.h"
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#include "llvm/Analysis/ScalarEvolutionExpander.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/LoopPass.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/GetElementPtrTypeIterator.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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using namespace llvm;
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STATISTIC(NumRemoved , "Number of aux indvars removed");
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STATISTIC(NumPointer , "Number of pointer indvars promoted");
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STATISTIC(NumInserted, "Number of canonical indvars added");
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STATISTIC(NumReplaced, "Number of exit values replaced");
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STATISTIC(NumLFTR , "Number of loop exit tests replaced");
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namespace {
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class VISIBILITY_HIDDEN IndVarSimplify : public LoopPass {
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LoopInfo *LI;
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ScalarEvolution *SE;
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bool Changed;
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public:
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static char ID; // Pass identification, replacement for typeid
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IndVarSimplify() : LoopPass(&ID) {}
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bool runOnLoop(Loop *L, LPPassManager &LPM);
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bool doInitialization(Loop *L, LPPassManager &LPM);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<ScalarEvolution>();
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AU.addRequiredID(LCSSAID);
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AU.addRequiredID(LoopSimplifyID);
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AU.addRequired<LoopInfo>();
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AU.addPreservedID(LoopSimplifyID);
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AU.addPreservedID(LCSSAID);
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AU.setPreservesCFG();
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}
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private:
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void EliminatePointerRecurrence(PHINode *PN, BasicBlock *Preheader,
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std::set<Instruction*> &DeadInsts);
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Instruction *LinearFunctionTestReplace(Loop *L, SCEV *IterationCount,
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SCEVExpander &RW);
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void RewriteLoopExitValues(Loop *L, SCEV *IterationCount);
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void DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts);
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void OptimizeCanonicalIVType(Loop *L);
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};
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}
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char IndVarSimplify::ID = 0;
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static RegisterPass<IndVarSimplify>
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X("indvars", "Canonicalize Induction Variables");
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LoopPass *llvm::createIndVarSimplifyPass() {
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return new IndVarSimplify();
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}
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/// DeleteTriviallyDeadInstructions - If any of the instructions is the
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/// specified set are trivially dead, delete them and see if this makes any of
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/// their operands subsequently dead.
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void IndVarSimplify::
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DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts) {
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while (!Insts.empty()) {
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Instruction *I = *Insts.begin();
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Insts.erase(Insts.begin());
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if (isInstructionTriviallyDead(I)) {
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for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
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if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i)))
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Insts.insert(U);
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SE->deleteValueFromRecords(I);
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DOUT << "INDVARS: Deleting: " << *I;
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I->eraseFromParent();
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Changed = true;
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}
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}
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}
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/// EliminatePointerRecurrence - Check to see if this is a trivial GEP pointer
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/// recurrence. If so, change it into an integer recurrence, permitting
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/// analysis by the SCEV routines.
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void IndVarSimplify::EliminatePointerRecurrence(PHINode *PN,
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BasicBlock *Preheader,
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std::set<Instruction*> &DeadInsts) {
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assert(PN->getNumIncomingValues() == 2 && "Noncanonicalized loop!");
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unsigned PreheaderIdx = PN->getBasicBlockIndex(Preheader);
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unsigned BackedgeIdx = PreheaderIdx^1;
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if (GetElementPtrInst *GEPI =
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dyn_cast<GetElementPtrInst>(PN->getIncomingValue(BackedgeIdx)))
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if (GEPI->getOperand(0) == PN) {
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assert(GEPI->getNumOperands() == 2 && "GEP types must match!");
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DOUT << "INDVARS: Eliminating pointer recurrence: " << *GEPI;
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// Okay, we found a pointer recurrence. Transform this pointer
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// recurrence into an integer recurrence. Compute the value that gets
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// added to the pointer at every iteration.
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Value *AddedVal = GEPI->getOperand(1);
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// Insert a new integer PHI node into the top of the block.
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PHINode *NewPhi = PHINode::Create(AddedVal->getType(),
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PN->getName()+".rec", PN);
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NewPhi->addIncoming(Constant::getNullValue(NewPhi->getType()), Preheader);
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// Create the new add instruction.
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Value *NewAdd = BinaryOperator::CreateAdd(NewPhi, AddedVal,
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GEPI->getName()+".rec", GEPI);
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NewPhi->addIncoming(NewAdd, PN->getIncomingBlock(BackedgeIdx));
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// Update the existing GEP to use the recurrence.
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GEPI->setOperand(0, PN->getIncomingValue(PreheaderIdx));
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// Update the GEP to use the new recurrence we just inserted.
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GEPI->setOperand(1, NewAdd);
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// If the incoming value is a constant expr GEP, try peeling out the array
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// 0 index if possible to make things simpler.
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if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEPI->getOperand(0)))
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if (CE->getOpcode() == Instruction::GetElementPtr) {
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unsigned NumOps = CE->getNumOperands();
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assert(NumOps > 1 && "CE folding didn't work!");
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if (CE->getOperand(NumOps-1)->isNullValue()) {
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// Check to make sure the last index really is an array index.
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gep_type_iterator GTI = gep_type_begin(CE);
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for (unsigned i = 1, e = CE->getNumOperands()-1;
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i != e; ++i, ++GTI)
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/*empty*/;
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if (isa<SequentialType>(*GTI)) {
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// Pull the last index out of the constant expr GEP.
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SmallVector<Value*, 8> CEIdxs(CE->op_begin()+1, CE->op_end()-1);
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Constant *NCE = ConstantExpr::getGetElementPtr(CE->getOperand(0),
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&CEIdxs[0],
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CEIdxs.size());
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Value *Idx[2];
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Idx[0] = Constant::getNullValue(Type::Int32Ty);
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Idx[1] = NewAdd;
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GetElementPtrInst *NGEPI = GetElementPtrInst::Create(
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NCE, Idx, Idx + 2,
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GEPI->getName(), GEPI);
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SE->deleteValueFromRecords(GEPI);
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GEPI->replaceAllUsesWith(NGEPI);
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GEPI->eraseFromParent();
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GEPI = NGEPI;
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}
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}
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}
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// Finally, if there are any other users of the PHI node, we must
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// insert a new GEP instruction that uses the pre-incremented version
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// of the induction amount.
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if (!PN->use_empty()) {
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BasicBlock::iterator InsertPos = PN; ++InsertPos;
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while (isa<PHINode>(InsertPos)) ++InsertPos;
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Value *PreInc =
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GetElementPtrInst::Create(PN->getIncomingValue(PreheaderIdx),
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NewPhi, "", InsertPos);
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PreInc->takeName(PN);
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PN->replaceAllUsesWith(PreInc);
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}
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// Delete the old PHI for sure, and the GEP if its otherwise unused.
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DeadInsts.insert(PN);
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++NumPointer;
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Changed = true;
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}
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}
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/// LinearFunctionTestReplace - This method rewrites the exit condition of the
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/// loop to be a canonical != comparison against the incremented loop induction
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/// variable. This pass is able to rewrite the exit tests of any loop where the
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/// SCEV analysis can determine a loop-invariant trip count of the loop, which
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/// is actually a much broader range than just linear tests.
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///
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/// This method returns a "potentially dead" instruction whose computation chain
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/// should be deleted when convenient.
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Instruction *IndVarSimplify::LinearFunctionTestReplace(Loop *L,
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SCEV *IterationCount,
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SCEVExpander &RW) {
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// Find the exit block for the loop. We can currently only handle loops with
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// a single exit.
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SmallVector<BasicBlock*, 8> ExitBlocks;
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L->getExitBlocks(ExitBlocks);
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if (ExitBlocks.size() != 1) return 0;
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BasicBlock *ExitBlock = ExitBlocks[0];
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// Make sure there is only one predecessor block in the loop.
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BasicBlock *ExitingBlock = 0;
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for (pred_iterator PI = pred_begin(ExitBlock), PE = pred_end(ExitBlock);
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PI != PE; ++PI)
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if (L->contains(*PI)) {
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if (ExitingBlock == 0)
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ExitingBlock = *PI;
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else
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return 0; // Multiple exits from loop to this block.
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}
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assert(ExitingBlock && "Loop info is broken");
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if (!isa<BranchInst>(ExitingBlock->getTerminator()))
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return 0; // Can't rewrite non-branch yet
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BranchInst *BI = cast<BranchInst>(ExitingBlock->getTerminator());
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assert(BI->isConditional() && "Must be conditional to be part of loop!");
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Instruction *PotentiallyDeadInst = dyn_cast<Instruction>(BI->getCondition());
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// If the exiting block is not the same as the backedge block, we must compare
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// against the preincremented value, otherwise we prefer to compare against
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// the post-incremented value.
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BasicBlock *Header = L->getHeader();
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pred_iterator HPI = pred_begin(Header);
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assert(HPI != pred_end(Header) && "Loop with zero preds???");
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if (!L->contains(*HPI)) ++HPI;
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assert(HPI != pred_end(Header) && L->contains(*HPI) &&
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"No backedge in loop?");
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SCEVHandle TripCount = IterationCount;
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Value *IndVar;
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if (*HPI == ExitingBlock) {
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// The IterationCount expression contains the number of times that the
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// backedge actually branches to the loop header. This is one less than the
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// number of times the loop executes, so add one to it.
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ConstantInt *OneC = ConstantInt::get(IterationCount->getType(), 1);
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TripCount = SE->getAddExpr(IterationCount, SE->getConstant(OneC));
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IndVar = L->getCanonicalInductionVariableIncrement();
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} else {
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// We have to use the preincremented value...
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IndVar = L->getCanonicalInductionVariable();
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}
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DOUT << "INDVARS: LFTR: TripCount = " << *TripCount
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<< " IndVar = " << *IndVar << "\n";
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// Expand the code for the iteration count into the preheader of the loop.
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BasicBlock *Preheader = L->getLoopPreheader();
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Value *ExitCnt = RW.expandCodeFor(TripCount, Preheader->getTerminator());
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// Insert a new icmp_ne or icmp_eq instruction before the branch.
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ICmpInst::Predicate Opcode;
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if (L->contains(BI->getSuccessor(0)))
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Opcode = ICmpInst::ICMP_NE;
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else
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Opcode = ICmpInst::ICMP_EQ;
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Value *Cond = new ICmpInst(Opcode, IndVar, ExitCnt, "exitcond", BI);
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BI->setCondition(Cond);
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++NumLFTR;
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Changed = true;
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return PotentiallyDeadInst;
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}
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/// RewriteLoopExitValues - Check to see if this loop has a computable
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/// loop-invariant execution count. If so, this means that we can compute the
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/// final value of any expressions that are recurrent in the loop, and
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/// substitute the exit values from the loop into any instructions outside of
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/// the loop that use the final values of the current expressions.
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void IndVarSimplify::RewriteLoopExitValues(Loop *L, SCEV *IterationCount) {
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BasicBlock *Preheader = L->getLoopPreheader();
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// Scan all of the instructions in the loop, looking at those that have
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// extra-loop users and which are recurrences.
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SCEVExpander Rewriter(*SE, *LI);
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// We insert the code into the preheader of the loop if the loop contains
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// multiple exit blocks, or in the exit block if there is exactly one.
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BasicBlock *BlockToInsertInto;
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SmallVector<BasicBlock*, 8> ExitBlocks;
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L->getUniqueExitBlocks(ExitBlocks);
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if (ExitBlocks.size() == 1)
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BlockToInsertInto = ExitBlocks[0];
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else
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BlockToInsertInto = Preheader;
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BasicBlock::iterator InsertPt = BlockToInsertInto->getFirstNonPHI();
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bool HasConstantItCount = isa<SCEVConstant>(IterationCount);
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std::set<Instruction*> InstructionsToDelete;
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std::map<Instruction*, Value*> ExitValues;
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// Find all values that are computed inside the loop, but used outside of it.
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// Because of LCSSA, these values will only occur in LCSSA PHI Nodes. Scan
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// the exit blocks of the loop to find them.
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for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
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BasicBlock *ExitBB = ExitBlocks[i];
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// If there are no PHI nodes in this exit block, then no values defined
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// inside the loop are used on this path, skip it.
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PHINode *PN = dyn_cast<PHINode>(ExitBB->begin());
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if (!PN) continue;
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unsigned NumPreds = PN->getNumIncomingValues();
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// Iterate over all of the PHI nodes.
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BasicBlock::iterator BBI = ExitBB->begin();
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while ((PN = dyn_cast<PHINode>(BBI++))) {
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// Iterate over all of the values in all the PHI nodes.
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for (unsigned i = 0; i != NumPreds; ++i) {
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// If the value being merged in is not integer or is not defined
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// in the loop, skip it.
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Value *InVal = PN->getIncomingValue(i);
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if (!isa<Instruction>(InVal) ||
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// SCEV only supports integer expressions for now.
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!isa<IntegerType>(InVal->getType()))
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continue;
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// If this pred is for a subloop, not L itself, skip it.
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if (LI->getLoopFor(PN->getIncomingBlock(i)) != L)
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continue; // The Block is in a subloop, skip it.
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// Check that InVal is defined in the loop.
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Instruction *Inst = cast<Instruction>(InVal);
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if (!L->contains(Inst->getParent()))
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continue;
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// We require that this value either have a computable evolution or that
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// the loop have a constant iteration count. In the case where the loop
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// has a constant iteration count, we can sometimes force evaluation of
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// the exit value through brute force.
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SCEVHandle SH = SE->getSCEV(Inst);
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if (!SH->hasComputableLoopEvolution(L) && !HasConstantItCount)
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continue; // Cannot get exit evolution for the loop value.
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// Okay, this instruction has a user outside of the current loop
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// and varies predictably *inside* the loop. Evaluate the value it
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// contains when the loop exits, if possible.
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SCEVHandle ExitValue = SE->getSCEVAtScope(Inst, L->getParentLoop());
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if (isa<SCEVCouldNotCompute>(ExitValue) ||
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!ExitValue->isLoopInvariant(L))
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continue;
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Changed = true;
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++NumReplaced;
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// See if we already computed the exit value for the instruction, if so,
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// just reuse it.
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Value *&ExitVal = ExitValues[Inst];
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if (!ExitVal)
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ExitVal = Rewriter.expandCodeFor(ExitValue, InsertPt);
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DOUT << "INDVARS: RLEV: AfterLoopVal = " << *ExitVal
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<< " LoopVal = " << *Inst << "\n";
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PN->setIncomingValue(i, ExitVal);
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// If this instruction is dead now, schedule it to be removed.
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if (Inst->use_empty())
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InstructionsToDelete.insert(Inst);
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// See if this is a single-entry LCSSA PHI node. If so, we can (and
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// have to) remove
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// the PHI entirely. This is safe, because the NewVal won't be variant
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// in the loop, so we don't need an LCSSA phi node anymore.
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if (NumPreds == 1) {
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SE->deleteValueFromRecords(PN);
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PN->replaceAllUsesWith(ExitVal);
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PN->eraseFromParent();
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break;
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}
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}
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}
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}
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DeleteTriviallyDeadInstructions(InstructionsToDelete);
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}
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bool IndVarSimplify::doInitialization(Loop *L, LPPassManager &LPM) {
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Changed = false;
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// First step. Check to see if there are any trivial GEP pointer recurrences.
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// If there are, change them into integer recurrences, permitting analysis by
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// the SCEV routines.
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//
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BasicBlock *Header = L->getHeader();
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BasicBlock *Preheader = L->getLoopPreheader();
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SE = &LPM.getAnalysis<ScalarEvolution>();
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std::set<Instruction*> DeadInsts;
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for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
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PHINode *PN = cast<PHINode>(I);
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if (isa<PointerType>(PN->getType()))
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EliminatePointerRecurrence(PN, Preheader, DeadInsts);
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}
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if (!DeadInsts.empty())
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DeleteTriviallyDeadInstructions(DeadInsts);
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return Changed;
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}
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bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
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LI = &getAnalysis<LoopInfo>();
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SE = &getAnalysis<ScalarEvolution>();
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Changed = false;
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BasicBlock *Header = L->getHeader();
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std::set<Instruction*> DeadInsts;
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// Verify the input to the pass in already in LCSSA form.
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assert(L->isLCSSAForm());
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// Check to see if this loop has a computable loop-invariant execution count.
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// If so, this means that we can compute the final value of any expressions
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// that are recurrent in the loop, and substitute the exit values from the
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// loop into any instructions outside of the loop that use the final values of
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// the current expressions.
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//
|
|
SCEVHandle IterationCount = SE->getIterationCount(L);
|
|
if (!isa<SCEVCouldNotCompute>(IterationCount))
|
|
RewriteLoopExitValues(L, IterationCount);
|
|
|
|
// Next, analyze all of the induction variables in the loop, canonicalizing
|
|
// auxillary induction variables.
|
|
std::vector<std::pair<PHINode*, SCEVHandle> > IndVars;
|
|
|
|
for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
|
|
PHINode *PN = cast<PHINode>(I);
|
|
if (PN->getType()->isInteger()) { // FIXME: when we have fast-math, enable!
|
|
SCEVHandle SCEV = SE->getSCEV(PN);
|
|
if (SCEV->hasComputableLoopEvolution(L))
|
|
// FIXME: It is an extremely bad idea to indvar substitute anything more
|
|
// complex than affine induction variables. Doing so will put expensive
|
|
// polynomial evaluations inside of the loop, and the str reduction pass
|
|
// currently can only reduce affine polynomials. For now just disable
|
|
// indvar subst on anything more complex than an affine addrec.
|
|
if (SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SCEV))
|
|
if (AR->isAffine())
|
|
IndVars.push_back(std::make_pair(PN, SCEV));
|
|
}
|
|
}
|
|
|
|
// If there are no induction variables in the loop, there is nothing more to
|
|
// do.
|
|
if (IndVars.empty()) {
|
|
// Actually, if we know how many times the loop iterates, lets insert a
|
|
// canonical induction variable to help subsequent passes.
|
|
if (!isa<SCEVCouldNotCompute>(IterationCount)) {
|
|
SCEVExpander Rewriter(*SE, *LI);
|
|
Rewriter.getOrInsertCanonicalInductionVariable(L,
|
|
IterationCount->getType());
|
|
if (Instruction *I = LinearFunctionTestReplace(L, IterationCount,
|
|
Rewriter)) {
|
|
std::set<Instruction*> InstructionsToDelete;
|
|
InstructionsToDelete.insert(I);
|
|
DeleteTriviallyDeadInstructions(InstructionsToDelete);
|
|
}
|
|
}
|
|
return Changed;
|
|
}
|
|
|
|
// Compute the type of the largest recurrence expression.
|
|
//
|
|
const Type *LargestType = IndVars[0].first->getType();
|
|
bool DifferingSizes = false;
|
|
for (unsigned i = 1, e = IndVars.size(); i != e; ++i) {
|
|
const Type *Ty = IndVars[i].first->getType();
|
|
DifferingSizes |=
|
|
Ty->getPrimitiveSizeInBits() != LargestType->getPrimitiveSizeInBits();
|
|
if (Ty->getPrimitiveSizeInBits() > LargestType->getPrimitiveSizeInBits())
|
|
LargestType = Ty;
|
|
}
|
|
|
|
// Create a rewriter object which we'll use to transform the code with.
|
|
SCEVExpander Rewriter(*SE, *LI);
|
|
|
|
// Now that we know the largest of of the induction variables in this loop,
|
|
// insert a canonical induction variable of the largest size.
|
|
Value *IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L,LargestType);
|
|
++NumInserted;
|
|
Changed = true;
|
|
DOUT << "INDVARS: New CanIV: " << *IndVar;
|
|
|
|
if (!isa<SCEVCouldNotCompute>(IterationCount)) {
|
|
IterationCount = SE->getTruncateOrZeroExtend(IterationCount, LargestType);
|
|
if (Instruction *DI = LinearFunctionTestReplace(L, IterationCount,Rewriter))
|
|
DeadInsts.insert(DI);
|
|
}
|
|
|
|
// Now that we have a canonical induction variable, we can rewrite any
|
|
// recurrences in terms of the induction variable. Start with the auxillary
|
|
// induction variables, and recursively rewrite any of their uses.
|
|
BasicBlock::iterator InsertPt = Header->getFirstNonPHI();
|
|
|
|
// If there were induction variables of other sizes, cast the primary
|
|
// induction variable to the right size for them, avoiding the need for the
|
|
// code evaluation methods to insert induction variables of different sizes.
|
|
if (DifferingSizes) {
|
|
SmallVector<unsigned,4> InsertedSizes;
|
|
InsertedSizes.push_back(LargestType->getPrimitiveSizeInBits());
|
|
for (unsigned i = 0, e = IndVars.size(); i != e; ++i) {
|
|
unsigned ithSize = IndVars[i].first->getType()->getPrimitiveSizeInBits();
|
|
if (std::find(InsertedSizes.begin(), InsertedSizes.end(), ithSize)
|
|
== InsertedSizes.end()) {
|
|
PHINode *PN = IndVars[i].first;
|
|
InsertedSizes.push_back(ithSize);
|
|
Instruction *New = new TruncInst(IndVar, PN->getType(), "indvar",
|
|
InsertPt);
|
|
Rewriter.addInsertedValue(New, SE->getSCEV(New));
|
|
DOUT << "INDVARS: Made trunc IV for " << *PN
|
|
<< " NewVal = " << *New << "\n";
|
|
}
|
|
}
|
|
}
|
|
|
|
// Rewrite all induction variables in terms of the canonical induction
|
|
// variable.
|
|
while (!IndVars.empty()) {
|
|
PHINode *PN = IndVars.back().first;
|
|
Value *NewVal = Rewriter.expandCodeFor(IndVars.back().second, InsertPt);
|
|
DOUT << "INDVARS: Rewrote IV '" << *IndVars.back().second << "' " << *PN
|
|
<< " into = " << *NewVal << "\n";
|
|
NewVal->takeName(PN);
|
|
|
|
// Replace the old PHI Node with the inserted computation.
|
|
PN->replaceAllUsesWith(NewVal);
|
|
DeadInsts.insert(PN);
|
|
IndVars.pop_back();
|
|
++NumRemoved;
|
|
Changed = true;
|
|
}
|
|
|
|
#if 0
|
|
// Now replace all derived expressions in the loop body with simpler
|
|
// expressions.
|
|
for (LoopInfo::block_iterator I = L->block_begin(), E = L->block_end();
|
|
I != E; ++I) {
|
|
BasicBlock *BB = *I;
|
|
if (LI->getLoopFor(BB) == L) { // Not in a subloop...
|
|
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
|
|
if (I->getType()->isInteger() && // Is an integer instruction
|
|
!I->use_empty() &&
|
|
!Rewriter.isInsertedInstruction(I)) {
|
|
SCEVHandle SH = SE->getSCEV(I);
|
|
Value *V = Rewriter.expandCodeFor(SH, I, I->getType());
|
|
if (V != I) {
|
|
if (isa<Instruction>(V))
|
|
V->takeName(I);
|
|
I->replaceAllUsesWith(V);
|
|
DeadInsts.insert(I);
|
|
++NumRemoved;
|
|
Changed = true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
#endif
|
|
|
|
DeleteTriviallyDeadInstructions(DeadInsts);
|
|
OptimizeCanonicalIVType(L);
|
|
assert(L->isLCSSAForm());
|
|
return Changed;
|
|
}
|
|
|
|
/// OptimizeCanonicalIVType - If loop induction variable is always
|
|
/// sign or zero extended then extend the type of the induction
|
|
/// variable.
|
|
void IndVarSimplify::OptimizeCanonicalIVType(Loop *L) {
|
|
PHINode *PH = L->getCanonicalInductionVariable();
|
|
if (!PH) return;
|
|
|
|
// Check loop iteration count.
|
|
SCEVHandle IC = SE->getIterationCount(L);
|
|
if (isa<SCEVCouldNotCompute>(IC)) return;
|
|
SCEVConstant *IterationCount = dyn_cast<SCEVConstant>(IC);
|
|
if (!IterationCount) return;
|
|
|
|
unsigned IncomingEdge = L->contains(PH->getIncomingBlock(0));
|
|
unsigned BackEdge = IncomingEdge^1;
|
|
|
|
// Check IV uses. If all IV uses are either SEXT or ZEXT (except
|
|
// IV increment instruction) then this IV is suitable for this
|
|
// transformation.
|
|
bool isSEXT = false;
|
|
BinaryOperator *Incr = NULL;
|
|
const Type *NewType = NULL;
|
|
for(Value::use_iterator UI = PH->use_begin(), UE = PH->use_end();
|
|
UI != UE; ++UI) {
|
|
const Type *CandidateType = NULL;
|
|
if (ZExtInst *ZI = dyn_cast<ZExtInst>(UI))
|
|
CandidateType = ZI->getDestTy();
|
|
else if (SExtInst *SI = dyn_cast<SExtInst>(UI)) {
|
|
CandidateType = SI->getDestTy();
|
|
isSEXT = true;
|
|
}
|
|
else if ((Incr = dyn_cast<BinaryOperator>(UI))) {
|
|
// Validate IV increment instruction.
|
|
if (PH->getIncomingValue(BackEdge) == Incr)
|
|
continue;
|
|
}
|
|
if (!CandidateType) {
|
|
NewType = NULL;
|
|
break;
|
|
}
|
|
if (!NewType)
|
|
NewType = CandidateType;
|
|
else if (NewType != CandidateType) {
|
|
NewType = NULL;
|
|
break;
|
|
}
|
|
}
|
|
|
|
// IV uses are not suitable then avoid this transformation.
|
|
if (!NewType || !Incr)
|
|
return;
|
|
|
|
// IV increment instruction has two uses, one is loop exit condition
|
|
// and second is the IV (phi node) itself.
|
|
ICmpInst *Exit = NULL;
|
|
for(Value::use_iterator II = Incr->use_begin(), IE = Incr->use_end();
|
|
II != IE; ++II) {
|
|
if (PH == *II) continue;
|
|
Exit = dyn_cast<ICmpInst>(*II);
|
|
break;
|
|
}
|
|
if (!Exit) return;
|
|
ConstantInt *EV = dyn_cast<ConstantInt>(Exit->getOperand(0));
|
|
if (!EV)
|
|
EV = dyn_cast<ConstantInt>(Exit->getOperand(1));
|
|
if (!EV) return;
|
|
|
|
// Check iteration count max value to avoid loops that wrap around IV.
|
|
APInt ICount = IterationCount->getValue()->getValue();
|
|
if (ICount.isNegative()) return;
|
|
uint32_t BW = PH->getType()->getPrimitiveSizeInBits();
|
|
APInt Max = (isSEXT ? APInt::getSignedMaxValue(BW) : APInt::getMaxValue(BW));
|
|
if (ICount.getZExtValue() > Max.getZExtValue()) return;
|
|
|
|
// Extend IV type.
|
|
|
|
SCEVExpander Rewriter(*SE, *LI);
|
|
Value *NewIV = Rewriter.getOrInsertCanonicalInductionVariable(L,NewType);
|
|
PHINode *NewPH = cast<PHINode>(NewIV);
|
|
Instruction *NewIncr = cast<Instruction>(NewPH->getIncomingValue(BackEdge));
|
|
|
|
// Replace all SEXT or ZEXT uses.
|
|
SmallVector<Instruction *, 4> PHUses;
|
|
for(Value::use_iterator UI = PH->use_begin(), UE = PH->use_end();
|
|
UI != UE; ++UI) {
|
|
Instruction *I = cast<Instruction>(UI);
|
|
PHUses.push_back(I);
|
|
}
|
|
while (!PHUses.empty()){
|
|
Instruction *Use = PHUses.back(); PHUses.pop_back();
|
|
if (Incr == Use) continue;
|
|
|
|
SE->deleteValueFromRecords(Use);
|
|
Use->replaceAllUsesWith(NewIV);
|
|
Use->eraseFromParent();
|
|
}
|
|
|
|
// Replace exit condition.
|
|
ConstantInt *NEV = ConstantInt::get(NewType, EV->getZExtValue());
|
|
Instruction *NE = new ICmpInst(Exit->getPredicate(),
|
|
NewIncr, NEV, "new.exit",
|
|
Exit->getParent()->getTerminator());
|
|
SE->deleteValueFromRecords(Exit);
|
|
Exit->replaceAllUsesWith(NE);
|
|
Exit->eraseFromParent();
|
|
|
|
// Remove old IV and increment instructions.
|
|
SE->deleteValueFromRecords(PH);
|
|
PH->removeIncomingValue((unsigned)0);
|
|
PH->removeIncomingValue((unsigned)0);
|
|
SE->deleteValueFromRecords(Incr);
|
|
Incr->eraseFromParent();
|
|
}
|
|
|