+++ /dev/null
-//===- llvm/Analysis/InductionVariable.h - Induction variables --*- C++ -*-===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This interface is used to identify and classify induction variables that
-// exist in the program. Induction variables must contain a PHI node that
-// exists in a loop header. Because of this, they are identified and managed by
-// this PHI node.
-//
-// Induction variables are classified into a type. Knowing that an induction
-// variable is of a specific type can constrain the values of the start and
-// step. For example, a SimpleLinear induction variable must have a start and
-// step values that are constants.
-//
-// Induction variables can be created with or without loop information. If no
-// loop information is available, induction variables cannot be recognized to be
-// more than SimpleLinear variables.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_ANALYSIS_INDUCTIONVARIABLE_H
-#define LLVM_ANALYSIS_INDUCTIONVARIABLE_H
-
-#include <iosfwd>
-
-namespace llvm {
-
-class Value;
-class PHINode;
-class Instruction;
-class LoopInfo; class Loop;
-
-class InductionVariable {
-public:
- enum iType { // Identify the type of this induction variable
- Canonical, // Starts at 0, counts by 1
- SimpleLinear, // Simple linear: Constant start, constant step
- Linear, // General linear: loop invariant start, and step
- Unknown, // Unknown type. Start & Step are null
- } InductionType;
-
- Value *Start, *Step, *End; // Start, step, and end expressions for this indvar
- PHINode *Phi; // The PHI node that corresponds to this indvar
-public:
-
- // Create an induction variable for the specified value. If it is a PHI, and
- // if it's recognizable, classify it and fill in instance variables.
- //
- InductionVariable(PHINode *PN, LoopInfo *LoopInfo = 0);
-
- // Classify Induction
- static enum iType Classify(const Value *Start, const Value *Step,
- const Loop *L = 0);
-
- // Get number of times this loop will execute. Returns NULL if unpredictable.
- Value* getExecutionCount(LoopInfo *LoopInfo);
-
- void print(std::ostream &OS) const;
-};
-
-} // End llvm namespace
-
-#endif
+++ /dev/null
-//===- InductionVariable.cpp - Induction variable classification ----------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements identification and classification of induction
-// variables. Induction variables must contain a PHI node that exists in a
-// loop header. Because of this, they are identified an managed by this PHI
-// node.
-//
-// Induction variables are classified into a type. Knowing that an induction
-// variable is of a specific type can constrain the values of the start and
-// step. For example, a SimpleLinear induction variable must have a start and
-// step values that are constants.
-//
-// Induction variables can be created with or without loop information. If no
-// loop information is available, induction variables cannot be recognized to be
-// more than SimpleLinear variables.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Analysis/InductionVariable.h"
-#include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Analysis/Expressions.h"
-#include "llvm/BasicBlock.h"
-#include "llvm/Instructions.h"
-#include "llvm/Type.h"
-#include "llvm/Constants.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Assembly/Writer.h"
-#include "Support/Debug.h"
-using namespace llvm;
-
-static bool isLoopInvariant(const Value *V, const Loop *L) {
- if (const Instruction *I = dyn_cast<Instruction>(V))
- return !L->contains(I->getParent());
- // non-instructions all dominate instructions/blocks
- return true;
-}
-
-enum InductionVariable::iType
-InductionVariable::Classify(const Value *Start, const Value *Step,
- const Loop *L) {
- // Check for canonical and simple linear expressions now...
- if (const ConstantInt *CStart = dyn_cast<ConstantInt>(Start))
- if (const ConstantInt *CStep = dyn_cast<ConstantInt>(Step)) {
- if (CStart->isNullValue() && CStep->equalsInt(1))
- return Canonical;
- else
- return SimpleLinear;
- }
-
- // Without loop information, we cannot do any better, so bail now...
- if (L == 0) return Unknown;
-
- if (isLoopInvariant(Start, L) && isLoopInvariant(Step, L))
- return Linear;
- return Unknown;
-}
-
-// Create an induction variable for the specified value. If it is a PHI, and
-// if it's recognizable, classify it and fill in instance variables.
-//
-InductionVariable::InductionVariable(PHINode *P, LoopInfo *LoopInfo): End(0) {
- InductionType = Unknown; // Assume the worst
- Phi = P;
-
- // If the PHI node has more than two predecessors, we don't know how to
- // handle it.
- //
- if (Phi->getNumIncomingValues() != 2) return;
-
- // FIXME: Handle FP induction variables.
- if (Phi->getType() == Type::FloatTy || Phi->getType() == Type::DoubleTy)
- return;
-
- // If we have loop information, make sure that this PHI node is in the header
- // of a loop...
- //
- const Loop *L = LoopInfo ? LoopInfo->getLoopFor(Phi->getParent()) : 0;
- if (L && L->getHeader() != Phi->getParent())
- return;
-
- Value *V1 = Phi->getIncomingValue(0);
- Value *V2 = Phi->getIncomingValue(1);
-
- if (L == 0) { // No loop information? Base everything on expression analysis
- ExprType E1 = ClassifyExpr(V1);
- ExprType E2 = ClassifyExpr(V2);
-
- if (E1.ExprTy > E2.ExprTy) // Make E1 be the simpler expression
- std::swap(E1, E2);
-
- // E1 must be a constant incoming value, and E2 must be a linear expression
- // with respect to the PHI node.
- //
- if (E1.ExprTy > ExprType::Constant || E2.ExprTy != ExprType::Linear ||
- E2.Var != Phi)
- return;
-
- // Okay, we have found an induction variable. Save the start and step values
- const Type *ETy = Phi->getType();
- if (isa<PointerType>(ETy)) ETy = Type::ULongTy;
-
- Start = (Value*)(E1.Offset ? E1.Offset : ConstantInt::get(ETy, 0));
- Step = (Value*)(E2.Offset ? E2.Offset : ConstantInt::get(ETy, 0));
- } else {
- // Okay, at this point, we know that we have loop information...
-
- // Make sure that V1 is the incoming value, and V2 is from the backedge of
- // the loop.
- if (L->contains(Phi->getIncomingBlock(0))) // Wrong order. Swap now.
- std::swap(V1, V2);
-
- Start = V1; // We know that Start has to be loop invariant...
- Step = 0;
-
- if (V2 == Phi) { // referencing the PHI directly? Must have zero step
- Step = Constant::getNullValue(Phi->getType());
- } else if (BinaryOperator *I = dyn_cast<BinaryOperator>(V2)) {
- if (I->getOpcode() == Instruction::Add) {
- if (I->getOperand(0) == Phi)
- Step = I->getOperand(1);
- else if (I->getOperand(1) == Phi)
- Step = I->getOperand(0);
- } else if (I->getOpcode() == Instruction::Sub &&
- I->getOperand(0) == Phi) {
- // If the incoming value is a constant, just form a constant negative
- // step. Otherwise, negate the step outside of the loop and use it.
- Value *V = I->getOperand(1);
- Constant *Zero = Constant::getNullValue(V->getType());
- if (Constant *CV = dyn_cast<Constant>(V))
- Step = ConstantExpr::get(Instruction::Sub, Zero, CV);
- else if (Instruction *I = dyn_cast<Instruction>(V)) {
- BasicBlock::iterator InsertPt = I;
- for (++InsertPt; isa<PHINode>(InsertPt); ++InsertPt)
- /*empty*/;
- Step = BinaryOperator::create(Instruction::Sub, Zero, V,
- V->getName()+".neg", InsertPt);
-
- } else {
- // Must be loop invariant
- Step = BinaryOperator::create(Instruction::Sub, Zero, V,
- V->getName()+".neg",
- Phi->getParent()->getParent()->begin()->begin());
- }
- }
- } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V2)) {
- if (GEP->getNumOperands() == 2 &&
- GEP->getOperand(0) == Phi)
- Step = GEP->getOperand(1);
- }
-
- if (Step == 0) { // Unrecognized step value...
- ExprType StepE = ClassifyExpr(V2);
- if (StepE.ExprTy != ExprType::Linear ||
- StepE.Var != Phi) return;
-
- const Type *ETy = Phi->getType();
- if (isa<PointerType>(ETy)) ETy = Type::ULongTy;
- Step = (Value*)(StepE.Offset ? StepE.Offset : ConstantInt::get(ETy, 0));
- } else { // We were able to get a step value, simplify with expr analysis
- ExprType StepE = ClassifyExpr(Step);
- if (StepE.ExprTy == ExprType::Linear && StepE.Offset == 0) {
- // No offset from variable? Grab the variable
- Step = StepE.Var;
- } else if (StepE.ExprTy == ExprType::Constant) {
- if (StepE.Offset)
- Step = (Value*)StepE.Offset;
- else
- Step = Constant::getNullValue(Step->getType());
- const Type *ETy = Phi->getType();
- if (isa<PointerType>(ETy)) ETy = Type::ULongTy;
- Step = (Value*)(StepE.Offset ? StepE.Offset : ConstantInt::get(ETy,0));
- }
- }
- }
-
- // Classify the induction variable type now...
- InductionType = InductionVariable::Classify(Start, Step, L);
-}
-
-
-Value *InductionVariable::getExecutionCount(LoopInfo *LoopInfo) {
- if (InductionType != Canonical) return 0;
-
- DEBUG(std::cerr << "entering getExecutionCount\n");
-
- // Don't recompute if already available
- if (End) {
- DEBUG(std::cerr << "returning cached End value.\n");
- return End;
- }
-
- const Loop *L = LoopInfo ? LoopInfo->getLoopFor(Phi->getParent()) : 0;
- if (!L) {
- DEBUG(std::cerr << "null loop. oops\n");
- return 0;
- }
-
- // >1 backedge => cannot predict number of iterations
- if (Phi->getNumIncomingValues() != 2) {
- DEBUG(std::cerr << ">2 incoming values. oops\n");
- return 0;
- }
-
- // Find final node: predecessor of the loop header that's also an exit
- BasicBlock *terminator = 0;
- for (pred_iterator PI = pred_begin(L->getHeader()),
- PE = pred_end(L->getHeader()); PI != PE; ++PI)
- if (L->isLoopExit(*PI)) {
- terminator = *PI;
- break;
- }
-
- // Break in the loop => cannot predict number of iterations
- // break: any block which is an exit node whose successor is not in loop,
- // and this block is not marked as the terminator
- //
- const std::vector<BasicBlock*> &blocks = L->getBlocks();
- for (std::vector<BasicBlock*>::const_iterator I = blocks.begin(),
- e = blocks.end(); I != e; ++I)
- if (L->isLoopExit(*I) && *I != terminator)
- for (succ_iterator SI = succ_begin(*I), SE = succ_end(*I); SI != SE; ++SI)
- if (!L->contains(*SI)) {
- DEBUG(std::cerr << "break found in loop");
- return 0;
- }
-
- BranchInst *B = dyn_cast<BranchInst>(terminator->getTerminator());
- if (!B) {
- DEBUG(std::cerr << "Terminator is not a cond branch!");
- return 0;
- }
- SetCondInst *SCI = dyn_cast<SetCondInst>(B->getCondition());
- if (!SCI) {
- DEBUG(std::cerr << "Not a cond branch on setcc!\n");
- return 0;
- }
-
- DEBUG(std::cerr << "sci:" << *SCI);
- Value *condVal0 = SCI->getOperand(0);
- Value *condVal1 = SCI->getOperand(1);
-
- // The induction variable is the one coming from the backedge
- Value *indVar = Phi->getIncomingValue(L->contains(Phi->getIncomingBlock(1)));
-
-
- // Check to see if indVar is one of the parameters in SCI and if the other is
- // loop-invariant, it is the UB
- if (indVar == condVal0) {
- if (isLoopInvariant(condVal1, L))
- End = condVal1;
- else {
- DEBUG(std::cerr << "not loop invariant 1\n");
- return 0;
- }
- } else if (indVar == condVal1) {
- if (isLoopInvariant(condVal0, L))
- End = condVal0;
- else {
- DEBUG(std::cerr << "not loop invariant 0\n");
- return 0;
- }
- } else {
- DEBUG(std::cerr << "Loop condition doesn't directly uses indvar\n");
- return 0;
- }
-
- switch (SCI->getOpcode()) {
- case Instruction::SetLT:
- case Instruction::SetNE: return End; // already done
- case Instruction::SetLE:
- // if compared to a constant int N, then predict N+1 iterations
- if (ConstantSInt *ubSigned = dyn_cast<ConstantSInt>(End)) {
- DEBUG(std::cerr << "signed int constant\n");
- return ConstantSInt::get(ubSigned->getType(), ubSigned->getValue()+1);
- } else if (ConstantUInt *ubUnsigned = dyn_cast<ConstantUInt>(End)) {
- DEBUG(std::cerr << "unsigned int constant\n");
- return ConstantUInt::get(ubUnsigned->getType(),
- ubUnsigned->getValue()+1);
- } else {
- DEBUG(std::cerr << "symbolic bound\n");
- // new expression N+1, insert right before the SCI. FIXME: If End is loop
- // invariant, then so is this expression. We should insert it in the loop
- // preheader if it exists.
- return BinaryOperator::create(Instruction::Add, End,
- ConstantInt::get(End->getType(), 1),
- "tripcount", SCI);
- }
-
- default:
- return 0; // cannot predict
- }
-}
-
-
-void InductionVariable::print(std::ostream &o) const {
- switch (InductionType) {
- case InductionVariable::Canonical: o << "Canonical "; break;
- case InductionVariable::SimpleLinear: o << "SimpleLinear "; break;
- case InductionVariable::Linear: o << "Linear "; break;
- case InductionVariable::Unknown: o << "Unrecognized "; break;
- }
- o << "Induction Variable: ";
- if (Phi) {
- WriteAsOperand(o, Phi);
- o << ":\n" << Phi;
- } else {
- o << "\n";
- }
- if (InductionType == InductionVariable::Unknown) return;
-
- o << " Start = "; WriteAsOperand(o, Start);
- o << " Step = " ; WriteAsOperand(o, Step);
- if (End) {
- o << " End = " ; WriteAsOperand(o, End);
- }
- o << "\n";
-}