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Move the scev expansion code into this pass, where it belongs. There is
still room for cleanup, but at least the code modification is out of the analysis now. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13135 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -50,6 +50,247 @@
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#include "Support/Statistic.h"
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using namespace llvm;
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namespace {
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/// SCEVExpander - This class uses information about analyze scalars to
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/// rewrite expressions in canonical form.
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///
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/// Clients should create an instance of this class when rewriting is needed,
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/// and destroying it when finished to allow the release of the associated
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/// memory.
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struct SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
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ScalarEvolution &SE;
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LoopInfo &LI;
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std::map<SCEVHandle, Value*> InsertedExpressions;
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std::set<Instruction*> InsertedInstructions;
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Instruction *InsertPt;
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friend class SCEVVisitor<SCEVExpander, Value*>;
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public:
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SCEVExpander(ScalarEvolution &se, LoopInfo &li) : SE(se), LI(li) {}
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/// isInsertedInstruction - Return true if the specified instruction was
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/// inserted by the code rewriter. If so, the client should not modify the
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/// instruction.
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bool isInsertedInstruction(Instruction *I) const {
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return InsertedInstructions.count(I);
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}
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/// getOrInsertCanonicalInductionVariable - This method returns the
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/// canonical induction variable of the specified type for the specified
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/// loop (inserting one if there is none). A canonical induction variable
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/// starts at zero and steps by one on each iteration.
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Value *getOrInsertCanonicalInductionVariable(const Loop *L, const Type *Ty){
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assert((Ty->isInteger() || Ty->isFloatingPoint()) &&
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"Can only insert integer or floating point induction variables!");
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SCEVHandle H = SCEVAddRecExpr::get(SCEVUnknown::getIntegerSCEV(0, Ty),
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SCEVUnknown::getIntegerSCEV(1, Ty), L);
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return expand(H);
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}
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/// addInsertedValue - Remember the specified instruction as being the
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/// canonical form for the specified SCEV.
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void addInsertedValue(Instruction *I, SCEV *S) {
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InsertedExpressions[S] = (Value*)I;
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InsertedInstructions.insert(I);
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}
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/// expandCodeFor - Insert code to directly compute the specified SCEV
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/// expression into the program. The inserted code is inserted into the
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/// specified block.
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///
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/// If a particular value sign is required, a type may be specified for the
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/// result.
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Value *expandCodeFor(SCEVHandle SH, Instruction *IP, const Type *Ty = 0) {
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// Expand the code for this SCEV.
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this->InsertPt = IP;
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return expandInTy(SH, Ty);
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}
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protected:
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Value *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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Value *expandInTy(SCEV *S, const Type *Ty) {
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Value *V = expand(S);
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if (Ty && V->getType() != 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(C, Ty);
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else if (Instruction *I = dyn_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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BasicBlock::iterator It = I; ++It;
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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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I->getParent()->getInstList().splice(It,
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CI->getParent()->getInstList(),
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CI);
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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 new CastInst(V, Ty, V->getName(), IP);
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} else {
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// FIXME: check to see if there is already a cast!
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return new CastInst(V, Ty, V->getName(), InsertPt);
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}
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}
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return V;
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}
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Value *visitConstant(SCEVConstant *S) {
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return S->getValue();
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}
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Value *visitTruncateExpr(SCEVTruncateExpr *S) {
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Value *V = expand(S->getOperand());
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return new CastInst(V, S->getType(), "tmp.", InsertPt);
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}
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Value *visitZeroExtendExpr(SCEVZeroExtendExpr *S) {
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Value *V = expandInTy(S->getOperand(),V->getType()->getUnsignedVersion());
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return new CastInst(V, S->getType(), "tmp.", InsertPt);
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}
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Value *visitAddExpr(SCEVAddExpr *S) {
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const Type *Ty = S->getType();
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Value *V = expandInTy(S->getOperand(S->getNumOperands()-1), Ty);
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// Emit a bunch of add instructions
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for (int i = S->getNumOperands()-2; i >= 0; --i)
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V = BinaryOperator::create(Instruction::Add, V,
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expandInTy(S->getOperand(i), Ty),
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"tmp.", InsertPt);
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return V;
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}
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Value *visitMulExpr(SCEVMulExpr *S);
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Value *visitUDivExpr(SCEVUDivExpr *S) {
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const Type *Ty = S->getType();
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Value *LHS = expandInTy(S->getLHS(), Ty);
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Value *RHS = expandInTy(S->getRHS(), Ty);
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return BinaryOperator::create(Instruction::Div, LHS, RHS, "tmp.",
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InsertPt);
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}
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Value *visitAddRecExpr(SCEVAddRecExpr *S);
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Value *visitUnknown(SCEVUnknown *S) {
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return S->getValue();
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}
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};
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}
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Value *SCEVExpander::visitMulExpr(SCEVMulExpr *S) {
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const Type *Ty = S->getType();
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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 = expandInTy(S->getOperand(i+1), Ty);
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// Emit a bunch of multiply instructions
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for (; i >= FirstOp; --i)
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V = BinaryOperator::create(Instruction::Mul, V,
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expandInTy(S->getOperand(i), Ty),
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"tmp.", InsertPt);
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// -1 * ... ---> 0 - ...
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if (FirstOp == 1)
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V = BinaryOperator::create(Instruction::Sub, Constant::getNullValue(Ty),
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V, "tmp.", 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->isIntegral() && "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()->isNullValue()) {
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Value *Start = expandInTy(S->getStart(), Ty);
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std::vector<SCEVHandle> NewOps(S->op_begin(), S->op_end());
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NewOps[0] = SCEVUnknown::getIntegerSCEV(0, Ty);
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Value *Rest = expandInTy(SCEVAddRecExpr::get(NewOps, L), Ty);
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// FIXME: look for an existing add to use.
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return BinaryOperator::create(Instruction::Add, Rest, Start, "tmp.",
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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) == SCEVUnknown::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 = new PHINode(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 = Ty->isFloatingPoint() ? (Constant*)ConstantFP::get(Ty, 1.0)
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: ConstantInt::get(Ty, 1);
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Instruction *Add = BinaryOperator::create(Instruction::Add, PN, One,
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"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 (S->getNumOperands() == 2) { // {0,+,F} --> i*F
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Value *F = expandInTy(S->getOperand(1), Ty);
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return BinaryOperator::create(Instruction::Mul, I, F, "tmp.", InsertPt);
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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 = SCEVUnknown::get(I); // Get I as a "symbolic" SCEV.
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SCEVHandle V = S->evaluateAtIteration(IH);
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//std::cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
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return expandInTy(V, Ty);
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}
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namespace {
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Statistic<> NumRemoved ("indvars", "Number of aux indvars removed");
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Statistic<> NumPointer ("indvars", "Number of pointer indvars promoted");
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@ -85,7 +326,7 @@ namespace {
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void EliminatePointerRecurrence(PHINode *PN, BasicBlock *Preheader,
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std::set<Instruction*> &DeadInsts);
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void LinearFunctionTestReplace(Loop *L, SCEV *IterationCount,
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ScalarEvolutionRewriter &RW);
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SCEVExpander &RW);
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void RewriteLoopExitValues(Loop *L);
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void DeleteTriviallyDeadInstructions(std::set<Instruction*> &Insts);
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@ -97,7 +338,6 @@ Pass *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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@ -182,7 +422,7 @@ void IndVarSimplify::EliminatePointerRecurrence(PHINode *PN,
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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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void IndVarSimplify::LinearFunctionTestReplace(Loop *L, SCEV *IterationCount,
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ScalarEvolutionRewriter &RW) {
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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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std::vector<BasicBlock*> ExitBlocks;
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@ -237,7 +477,7 @@ void IndVarSimplify::LinearFunctionTestReplace(Loop *L, SCEV *IterationCount,
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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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Value *ExitCnt = RW.expandCodeFor(TripCount, Preheader->getTerminator(),
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IndVar->getType());
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// Insert a new setne or seteq instruction before the branch.
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@ -266,7 +506,7 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L) {
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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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ScalarEvolutionRewriter Rewriter(*SE, *LI);
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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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@ -307,7 +547,7 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L) {
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if (!isa<SCEVCouldNotCompute>(ExitValue)) {
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Changed = true;
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++NumReplaced;
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Value *NewVal = Rewriter.ExpandCodeFor(ExitValue, InsertPt,
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Value *NewVal = Rewriter.expandCodeFor(ExitValue, InsertPt,
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I->getType());
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// Rewrite any users of the computed value outside of the loop
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@ -379,8 +619,8 @@ void IndVarSimplify::runOnLoop(Loop *L) {
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// Actually, if we know how many times the loop iterates, lets insert a
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// canonical induction variable to help subsequent passes.
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if (!isa<SCEVCouldNotCompute>(IterationCount)) {
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ScalarEvolutionRewriter Rewriter(*SE, *LI);
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Rewriter.GetOrInsertCanonicalInductionVariable(L,
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SCEVExpander Rewriter(*SE, *LI);
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Rewriter.getOrInsertCanonicalInductionVariable(L,
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IterationCount->getType());
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LinearFunctionTestReplace(L, IterationCount, Rewriter);
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}
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@ -399,12 +639,12 @@ void IndVarSimplify::runOnLoop(Loop *L) {
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}
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// Create a rewriter object which we'll use to transform the code with.
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ScalarEvolutionRewriter Rewriter(*SE, *LI);
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SCEVExpander Rewriter(*SE, *LI);
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// Now that we know the largest of of the induction variables in this loop,
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// insert a canonical induction variable of the largest size.
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LargestType = LargestType->getUnsignedVersion();
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Value *IndVar = Rewriter.GetOrInsertCanonicalInductionVariable(L,LargestType);
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Value *IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L,LargestType);
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++NumInserted;
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Changed = true;
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@ -440,7 +680,7 @@ void IndVarSimplify::runOnLoop(Loop *L) {
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std::map<unsigned, Value*> InsertedSizes;
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while (!IndVars.empty()) {
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PHINode *PN = IndVars.back().first;
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Value *NewVal = Rewriter.ExpandCodeFor(IndVars.back().second, InsertPt,
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Value *NewVal = Rewriter.expandCodeFor(IndVars.back().second, InsertPt,
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PN->getType());
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std::string Name = PN->getName();
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PN->setName("");
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@ -465,7 +705,7 @@ void IndVarSimplify::runOnLoop(Loop *L) {
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!I->use_empty() &&
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!Rewriter.isInsertedInstruction(I)) {
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SCEVHandle SH = SE->getSCEV(I);
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Value *V = Rewriter.ExpandCodeFor(SH, I, I->getType());
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Value *V = Rewriter.expandCodeFor(SH, I, I->getType());
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if (V != I) {
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if (isa<Instruction>(V)) {
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std::string Name = I->getName();
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