//===- IndVarSimplify.cpp - Induction Variable Elimination ----------------===//
+//
+// The LLVM Compiler Infrastructure
//
-// InductionVariableSimplify - Transform induction variables in a program
-// to all use a single cannonical induction variable per loop.
+// 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.
+//
+//===----------------------------------------------------------------------===//
+//
+// Guarantees that all loops with identifiable, linear, induction variables will
+// be transformed to have a single, canonical, induction variable. After this
+// pass runs, it guarantees the the first PHI node of the header block in the
+// loop is the canonical induction variable if there is one.
//
//===----------------------------------------------------------------------===//
-#include "llvm/Transforms/Scalar/IndVarSimplify.h"
+#include "llvm/Transforms/Scalar.h"
#include "llvm/Analysis/InductionVariable.h"
#include "llvm/Analysis/LoopInfo.h"
-#include "llvm/Analysis/Dominators.h"
#include "llvm/iPHINode.h"
#include "llvm/iOther.h"
#include "llvm/Type.h"
-#include "llvm/ConstantVals.h"
+#include "llvm/Constants.h"
+#include "llvm/Support/CFG.h"
+#include "Support/Debug.h"
+#include "Support/Statistic.h"
#include "Support/STLExtras.h"
-#if 0
-#define DEBUG
-#include "llvm/Analysis/Writer.h"
-#endif
+namespace {
+ Statistic<> NumRemoved ("indvars", "Number of aux indvars removed");
+ Statistic<> NumInserted("indvars", "Number of canonical indvars added");
+}
// InsertCast - Cast Val to Ty, setting a useful name on the cast if Val has a
// name...
//
-static Instruction *InsertCast(Instruction *Val, const Type *Ty,
- BasicBlock::iterator It) {
- Instruction *Cast = new CastInst(Val, Ty);
- if (Val->hasName()) Cast->setName(Val->getName()+"-casted");
- Val->getParent()->getInstList().insert(It, Cast);
- return Cast;
+static Instruction *InsertCast(Value *Val, const Type *Ty,
+ Instruction *InsertBefore) {
+ return new CastInst(Val, Ty, Val->getName()+"-casted", InsertBefore);
}
-static bool TransformLoop(cfg::LoopInfo *Loops, cfg::Loop *Loop) {
+static bool TransformLoop(LoopInfo *Loops, Loop *Loop) {
// Transform all subloops before this loop...
bool Changed = reduce_apply_bool(Loop->getSubLoops().begin(),
Loop->getSubLoops().end(),
std::bind1st(std::ptr_fun(TransformLoop), Loops));
// Get the header node for this loop. All of the phi nodes that could be
// induction variables must live in this basic block.
- BasicBlock *Header = (BasicBlock*)Loop->getBlocks().front();
+ //
+ BasicBlock *Header = Loop->getHeader();
// Loop over all of the PHI nodes in the basic block, calculating the
// induction variables that they represent... stuffing the induction variable
// info into a vector...
//
std::vector<InductionVariable> IndVars; // Induction variables for block
- for (BasicBlock::iterator I = Header->begin();
- PHINode *PN = dyn_cast<PHINode>(*I); ++I)
+ BasicBlock::iterator AfterPHIIt = Header->begin();
+ for (; PHINode *PN = dyn_cast<PHINode>(AfterPHIIt); ++AfterPHIIt)
IndVars.push_back(InductionVariable(PN, Loops));
+ // AfterPHIIt now points to first non-phi instruction...
// If there are no phi nodes in this basic block, there can't be indvars...
if (IndVars.empty()) return Changed;
- // Loop over the induction variables, looking for a cannonical induction
+ // Loop over the induction variables, looking for a canonical induction
// variable, and checking to make sure they are not all unknown induction
// variables.
//
bool FoundIndVars = false;
- InductionVariable *Cannonical = 0;
+ InductionVariable *Canonical = 0;
for (unsigned i = 0; i < IndVars.size(); ++i) {
- if (IndVars[i].InductionType == InductionVariable::Cannonical)
- Cannonical = &IndVars[i];
+ if (IndVars[i].InductionType == InductionVariable::Canonical &&
+ !isa<PointerType>(IndVars[i].Phi->getType()))
+ Canonical = &IndVars[i];
if (IndVars[i].InductionType != InductionVariable::Unknown)
FoundIndVars = true;
}
- // No induction variables, bail early... don't add a cannonnical indvar
+ // No induction variables, bail early... don't add a canonical indvar
if (!FoundIndVars) return Changed;
- // Okay, we want to convert other induction variables to use a cannonical
+ // Okay, we want to convert other induction variables to use a canonical
// indvar. If we don't have one, add one now...
- if (!Cannonical) {
- // Create the PHI node for the new induction variable
- PHINode *PN = new PHINode(Type::UIntTy, "cann-indvar");
-
- // Insert the phi node at the end of the other phi nodes...
- Header->getInstList().insert(Header->begin()+IndVars.size(), PN);
+ if (!Canonical) {
+ // Create the PHI node for the new induction variable, and insert the phi
+ // node at the start of the PHI nodes...
+ PHINode *PN = new PHINode(Type::UIntTy, "cann-indvar", Header->begin());
// Create the increment instruction to add one to the counter...
Instruction *Add = BinaryOperator::create(Instruction::Add, PN,
ConstantUInt::get(Type::UIntTy,1),
- "add1-indvar");
-
- // Insert the add instruction after all of the PHI nodes...
- Header->getInstList().insert(Header->begin()+(IndVars.size()+1), Add);
+ "add1-indvar", AfterPHIIt);
// Figure out which block is incoming and which is the backedge for the loop
BasicBlock *Incoming, *BackEdgeBlock;
- BasicBlock::pred_iterator PI = Header->pred_begin();
- assert(PI != Header->pred_end() && "Loop headers should have 2 preds!");
+ pred_iterator PI = pred_begin(Header);
+ assert(PI != pred_end(Header) && "Loop headers should have 2 preds!");
if (Loop->contains(*PI)) { // First pred is back edge...
BackEdgeBlock = *PI++;
Incoming = *PI++;
Incoming = *PI++;
BackEdgeBlock = *PI++;
}
- assert(PI == Header->pred_end() && "Loop headers should have 2 preds!");
+ assert(PI == pred_end(Header) && "Loop headers should have 2 preds!");
// Add incoming values for the PHI node...
- PN->addIncoming(Constant::getNullConstant(Type::UIntTy), Incoming);
+ PN->addIncoming(Constant::getNullValue(Type::UIntTy), Incoming);
PN->addIncoming(Add, BackEdgeBlock);
// Analyze the new induction variable...
IndVars.push_back(InductionVariable(PN, Loops));
- assert(IndVars.back().InductionType == InductionVariable::Cannonical &&
- "Just inserted cannonical indvar that is not cannonical!");
- Cannonical = &IndVars.back();
+ assert(IndVars.back().InductionType == InductionVariable::Canonical &&
+ "Just inserted canonical indvar that is not canonical!");
+ Canonical = &IndVars.back();
+ ++NumInserted;
Changed = true;
+ } else {
+ // If we have a canonical induction variable, make sure that it is the first
+ // one in the basic block.
+ if (&Header->front() != Canonical->Phi)
+ Header->getInstList().splice(Header->begin(), Header->getInstList(),
+ Canonical->Phi);
}
-#ifdef DEBUG
- cerr << "Induction variables:\n";
-#endif
+ DEBUG(std::cerr << "Induction variables:\n");
// Get the current loop iteration count, which is always the value of the
- // cannonical phi node...
+ // canonical phi node...
//
- PHINode *IterCount = Cannonical->Phi;
+ PHINode *IterCount = Canonical->Phi;
- // Loop through and replace all of the auxillary induction variables with
- // references to the primary induction variable...
+ // Loop through and replace all of the auxiliary induction variables with
+ // references to the canonical induction variable...
//
- unsigned InsertPos = IndVars.size();
for (unsigned i = 0; i < IndVars.size(); ++i) {
InductionVariable *IV = &IndVars[i];
-#ifdef DEBUG
- cerr << IndVars[i];
-#endif
- // Don't modify the cannonical indvar or unrecognized indvars...
- if (IV != Cannonical && IV->InductionType != InductionVariable::Unknown) {
+
+ DEBUG(IV->print(std::cerr));
+
+ // Don't do math with pointers...
+ const Type *IVTy = IV->Phi->getType();
+ if (isa<PointerType>(IVTy)) IVTy = Type::ULongTy;
+
+ // Don't modify the canonical indvar or unrecognized indvars...
+ if (IV != Canonical && IV->InductionType != InductionVariable::Unknown) {
Instruction *Val = IterCount;
if (!isa<ConstantInt>(IV->Step) || // If the step != 1
!cast<ConstantInt>(IV->Step)->equalsInt(1)) {
- std::string Name; // Create a scale by the step value...
- if (IV->Phi->hasName()) Name = IV->Phi->getName()+"-scale";
// If the types are not compatible, insert a cast now...
- if (Val->getType() != IV->Step->getType())
- Val = InsertCast(Val, IV->Step->getType(),
- Header->begin()+InsertPos++);
+ if (Val->getType() != IVTy)
+ Val = InsertCast(Val, IVTy, AfterPHIIt);
+ if (IV->Step->getType() != IVTy)
+ IV->Step = InsertCast(IV->Step, IVTy, AfterPHIIt);
- Val = BinaryOperator::create(Instruction::Mul, Val, IV->Step, Name);
- // Insert the phi node at the end of the other phi nodes...
- Header->getInstList().insert(Header->begin()+InsertPos++, Val);
+ Val = BinaryOperator::create(Instruction::Mul, Val, IV->Step,
+ IV->Phi->getName()+"-scale", AfterPHIIt);
}
- if (!isa<Constant>(IV->Start) || // If the start != 0
- !cast<Constant>(IV->Start)->isNullValue()) {
- std::string Name; // Create a offset by the start value...
- if (IV->Phi->hasName()) Name = IV->Phi->getName()+"-offset";
-
+ // If the start != 0
+ if (IV->Start != Constant::getNullValue(IV->Start->getType())) {
// If the types are not compatible, insert a cast now...
- if (Val->getType() != IV->Start->getType())
- Val = InsertCast(Val, IV->Start->getType(),
- Header->begin()+InsertPos++);
-
- Val = BinaryOperator::create(Instruction::Add, Val, IV->Start, Name);
- // Insert the phi node at the end of the other phi nodes...
- Header->getInstList().insert(Header->begin()+InsertPos++, Val);
+ if (Val->getType() != IVTy)
+ Val = InsertCast(Val, IVTy, AfterPHIIt);
+ if (IV->Start->getType() != IVTy)
+ IV->Start = InsertCast(IV->Start, IVTy, AfterPHIIt);
+
+ // Insert the instruction after the phi nodes...
+ Val = BinaryOperator::create(Instruction::Add, Val, IV->Start,
+ IV->Phi->getName()+"-offset", AfterPHIIt);
}
// If the PHI node has a different type than val is, insert a cast now...
if (Val->getType() != IV->Phi->getType())
- Val = InsertCast(Val, IV->Phi->getType(),
- Header->begin()+InsertPos++);
+ Val = InsertCast(Val, IV->Phi->getType(), AfterPHIIt);
// Replace all uses of the old PHI node with the new computed value...
IV->Phi->replaceAllUsesWith(Val);
Val->setName(OldName);
// Delete the old, now unused, phi node...
- Header->getInstList().remove(IV->Phi);
- delete IV->Phi;
- InsertPos--; // Deleted an instr, decrement insert position
+ Header->getInstList().erase(IV->Phi);
Changed = true;
+ ++NumRemoved;
}
}
return Changed;
}
-bool InductionVariableSimplify::doit(Method *M) {
- if (M->isExternal()) return false;
+namespace {
+ struct InductionVariableSimplify : public FunctionPass {
+ virtual bool runOnFunction(Function &) {
+ LoopInfo &LI = getAnalysis<LoopInfo>();
- // Figure out the loop structure of the method...
- cfg::LoopInfo Loops(M);
+ // Induction Variables live in the header nodes of loops
+ return reduce_apply_bool(LI.getTopLevelLoops().begin(),
+ LI.getTopLevelLoops().end(),
+ std::bind1st(std::ptr_fun(TransformLoop), &LI));
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<LoopInfo>();
+ AU.addRequiredID(LoopSimplifyID);
+ AU.setPreservesCFG();
+ }
+ };
+ RegisterOpt<InductionVariableSimplify> X("indvars",
+ "Canonicalize Induction Variables");
+}
- // Induction Variables live in the header nodes of the loops of the method...
- return reduce_apply_bool(Loops.getTopLevelLoops().begin(),
- Loops.getTopLevelLoops().end(),
- std::bind1st(std::ptr_fun(TransformLoop), &Loops));
+Pass *createIndVarSimplifyPass() {
+ return new InductionVariableSimplify();
}
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