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8a08769bad
take into account the instrucion pointed by InsertPt. Thanks to it, returning the new value of InsertPt to the InsertBinop() caller can be avoided. The bug was, actually, in visitAddRecExpr() method which wasn't correctly handling changes of InsertPt. There shouldn't be any performance regression, as -gvn pass (run after -indvars) removes any redundant binops. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52291 91177308-0d34-0410-b5e6-96231b3b80d8
250 lines
9.3 KiB
C++
250 lines
9.3 KiB
C++
//===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis --*- C++ -*-===//
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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 file contains the implementation of the scalar evolution expander,
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// which is used to generate the code corresponding to a given scalar evolution
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// expression.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/ScalarEvolutionExpander.h"
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#include "llvm/Analysis/LoopInfo.h"
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using namespace llvm;
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/// InsertCastOfTo - Insert a cast of V to the specified type, doing what
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/// we can to share the casts.
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Value *SCEVExpander::InsertCastOfTo(Instruction::CastOps opcode, Value *V,
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const Type *Ty) {
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// FIXME: keep track of the cast instruction.
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if (Constant *C = dyn_cast<Constant>(V))
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return ConstantExpr::getCast(opcode, C, Ty);
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if (Argument *A = dyn_cast<Argument>(V)) {
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// Check to see if there is already a cast!
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for (Value::use_iterator UI = A->use_begin(), E = A->use_end();
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UI != E; ++UI) {
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if ((*UI)->getType() == Ty)
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if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI)))
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if (CI->getOpcode() == opcode) {
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// If the cast isn't the first instruction of the function, move it.
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if (BasicBlock::iterator(CI) !=
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A->getParent()->getEntryBlock().begin()) {
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CI->moveBefore(A->getParent()->getEntryBlock().begin());
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}
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return CI;
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}
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}
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return CastInst::Create(opcode, V, Ty, V->getName(),
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A->getParent()->getEntryBlock().begin());
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}
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Instruction *I = cast<Instruction>(V);
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// Check to see if there is already a cast. If there is, use it.
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for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
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UI != E; ++UI) {
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if ((*UI)->getType() == Ty)
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if (CastInst *CI = dyn_cast<CastInst>(cast<Instruction>(*UI)))
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if (CI->getOpcode() == opcode) {
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BasicBlock::iterator It = I; ++It;
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if (isa<InvokeInst>(I))
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It = cast<InvokeInst>(I)->getNormalDest()->begin();
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while (isa<PHINode>(It)) ++It;
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if (It != BasicBlock::iterator(CI)) {
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// Splice the cast immediately after the operand in question.
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CI->moveBefore(It);
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}
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return CI;
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}
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}
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BasicBlock::iterator IP = I; ++IP;
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if (InvokeInst *II = dyn_cast<InvokeInst>(I))
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IP = II->getNormalDest()->begin();
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while (isa<PHINode>(IP)) ++IP;
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return CastInst::Create(opcode, V, Ty, V->getName(), IP);
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}
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/// InsertBinop - Insert the specified binary operator, doing a small amount
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/// of work to avoid inserting an obviously redundant operation.
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Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode, Value *LHS,
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Value *RHS, Instruction *InsertPt) {
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// Fold a binop with constant operands.
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if (Constant *CLHS = dyn_cast<Constant>(LHS))
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if (Constant *CRHS = dyn_cast<Constant>(RHS))
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return ConstantExpr::get(Opcode, CLHS, CRHS);
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// Do a quick scan to see if we have this binop nearby. If so, reuse it.
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unsigned ScanLimit = 6;
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BasicBlock::iterator BlockBegin = InsertPt->getParent()->begin();
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if (InsertPt != BlockBegin) {
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// Scanning starts from the last instruction before InsertPt.
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BasicBlock::iterator IP = InsertPt;
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--IP;
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for (; ScanLimit; --IP, --ScanLimit) {
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if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(IP))
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if (BinOp->getOpcode() == Opcode && BinOp->getOperand(0) == LHS &&
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BinOp->getOperand(1) == RHS)
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return BinOp;
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if (IP == BlockBegin) break;
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}
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}
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// If we haven't found this binop, insert it.
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return BinaryOperator::Create(Opcode, LHS, RHS, "tmp", InsertPt);
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}
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Value *SCEVExpander::visitMulExpr(SCEVMulExpr *S) {
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int FirstOp = 0; // Set if we should emit a subtract.
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if (SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getOperand(0)))
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if (SC->getValue()->isAllOnesValue())
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FirstOp = 1;
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int i = S->getNumOperands()-2;
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Value *V = expand(S->getOperand(i+1));
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// Emit a bunch of multiply instructions
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for (; i >= FirstOp; --i)
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V = InsertBinop(Instruction::Mul, V, expand(S->getOperand(i)),
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InsertPt);
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// -1 * ... ---> 0 - ...
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if (FirstOp == 1)
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V = InsertBinop(Instruction::Sub, Constant::getNullValue(V->getType()), V,
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InsertPt);
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return V;
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}
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Value *SCEVExpander::visitAddRecExpr(SCEVAddRecExpr *S) {
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const Type *Ty = S->getType();
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const Loop *L = S->getLoop();
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// We cannot yet do fp recurrences, e.g. the xform of {X,+,F} --> X+{0,+,F}
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assert(Ty->isInteger() && "Cannot expand fp recurrences yet!");
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// {X,+,F} --> X + {0,+,F}
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if (!isa<SCEVConstant>(S->getStart()) ||
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!cast<SCEVConstant>(S->getStart())->getValue()->isZero()) {
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Value *Start = expand(S->getStart());
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std::vector<SCEVHandle> NewOps(S->op_begin(), S->op_end());
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NewOps[0] = SE.getIntegerSCEV(0, Ty);
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Value *Rest = expand(SE.getAddRecExpr(NewOps, L));
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// FIXME: look for an existing add to use.
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return InsertBinop(Instruction::Add, Rest, Start, InsertPt);
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}
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// {0,+,1} --> Insert a canonical induction variable into the loop!
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if (S->getNumOperands() == 2 &&
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S->getOperand(1) == SE.getIntegerSCEV(1, Ty)) {
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// Create and insert the PHI node for the induction variable in the
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// specified loop.
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BasicBlock *Header = L->getHeader();
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PHINode *PN = PHINode::Create(Ty, "indvar", Header->begin());
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PN->addIncoming(Constant::getNullValue(Ty), L->getLoopPreheader());
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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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// Insert a unit add instruction right before the terminator corresponding
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// to the back-edge.
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Constant *One = ConstantInt::get(Ty, 1);
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Instruction *Add = BinaryOperator::CreateAdd(PN, One, "indvar.next",
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(*HPI)->getTerminator());
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pred_iterator PI = pred_begin(Header);
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if (*PI == L->getLoopPreheader())
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++PI;
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PN->addIncoming(Add, *PI);
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return PN;
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}
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// Get the canonical induction variable I for this loop.
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Value *I = getOrInsertCanonicalInductionVariable(L, Ty);
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// If this is a simple linear addrec, emit it now as a special case.
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if (S->getNumOperands() == 2) { // {0,+,F} --> i*F
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Value *F = expand(S->getOperand(1));
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// IF the step is by one, just return the inserted IV.
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if (ConstantInt *CI = dyn_cast<ConstantInt>(F))
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if (CI->getValue() == 1)
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return I;
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// If the insert point is directly inside of the loop, emit the multiply at
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// the insert point. Otherwise, L is a loop that is a parent of the insert
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// point loop. If we can, move the multiply to the outer most loop that it
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// is safe to be in.
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Instruction *MulInsertPt = InsertPt;
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Loop *InsertPtLoop = LI.getLoopFor(MulInsertPt->getParent());
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if (InsertPtLoop != L && InsertPtLoop &&
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L->contains(InsertPtLoop->getHeader())) {
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do {
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// If we cannot hoist the multiply out of this loop, don't.
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if (!InsertPtLoop->isLoopInvariant(F)) break;
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BasicBlock *InsertPtLoopPH = InsertPtLoop->getLoopPreheader();
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// If this loop hasn't got a preheader, we aren't able to hoist the
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// multiply.
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if (!InsertPtLoopPH)
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break;
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// Otherwise, move the insert point to the preheader.
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MulInsertPt = InsertPtLoopPH->getTerminator();
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InsertPtLoop = InsertPtLoop->getParentLoop();
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} while (InsertPtLoop != L);
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}
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return InsertBinop(Instruction::Mul, I, F, MulInsertPt);
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}
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// If this is a chain of recurrences, turn it into a closed form, using the
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// folders, then expandCodeFor the closed form. This allows the folders to
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// simplify the expression without having to build a bunch of special code
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// into this folder.
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SCEVHandle IH = SE.getUnknown(I); // Get I as a "symbolic" SCEV.
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SCEVHandle V = S->evaluateAtIteration(IH, SE);
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//cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
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return expand(V);
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}
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Value *SCEVExpander::visitSMaxExpr(SCEVSMaxExpr *S) {
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Value *LHS = expand(S->getOperand(0));
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for (unsigned i = 1; i < S->getNumOperands(); ++i) {
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Value *RHS = expand(S->getOperand(i));
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Value *ICmp = new ICmpInst(ICmpInst::ICMP_SGT, LHS, RHS, "tmp", InsertPt);
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LHS = SelectInst::Create(ICmp, LHS, RHS, "smax", InsertPt);
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}
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return LHS;
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}
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Value *SCEVExpander::visitUMaxExpr(SCEVUMaxExpr *S) {
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Value *LHS = expand(S->getOperand(0));
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for (unsigned i = 1; i < S->getNumOperands(); ++i) {
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Value *RHS = expand(S->getOperand(i));
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Value *ICmp = new ICmpInst(ICmpInst::ICMP_UGT, LHS, RHS, "tmp", InsertPt);
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LHS = SelectInst::Create(ICmp, LHS, RHS, "umax", InsertPt);
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}
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return LHS;
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}
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Value *SCEVExpander::expand(SCEV *S) {
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// Check to see if we already expanded this.
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std::map<SCEVHandle, Value*>::iterator I = InsertedExpressions.find(S);
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if (I != InsertedExpressions.end())
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return I->second;
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Value *V = visit(S);
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InsertedExpressions[S] = V;
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return V;
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}
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