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Implement induction variable simplification

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1411 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2001-12-04 04:32:29 +00:00
parent fe196cf98b
commit 394437ff7e
1 changed files with 125 additions and 1 deletions
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126
lib/Transforms/Scalar/IndVarSimplify.cpp
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@ -10,8 +10,27 @@
#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 "Support/STLExtras.h"
#if 0
#define DEBUG
#include "llvm/Analysis/Writer.h"
#endif
// 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 bool TransformLoop(cfg::LoopInfo *Loops, cfg::Loop *Loop) {
// Transform all subloops before this loop...
bool Changed = reduce_apply_bool(Loop->getSubLoops().begin(),
@ -30,7 +49,7 @@ static bool TransformLoop(cfg::LoopInfo *Loops, cfg::Loop *Loop) {
PHINode *PN = dyn_cast<PHINode>(*I); ++I)
IndVars.push_back(InductionVariable(PN, Loops));
// If there are phi nodes in this basic block, there can't be indvars...
// 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
@ -52,7 +71,112 @@ static bool TransformLoop(cfg::LoopInfo *Loops, cfg::Loop *Loop) {
// Okay, we want to convert other induction variables to use a cannonical
// 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);
// 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);
// 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!");
if (Loop->contains(*PI)) { // First pred is back edge...
BackEdgeBlock = *PI++;
Incoming = *PI++;
} else {
Incoming = *PI++;
BackEdgeBlock = *PI++;
}
assert(PI == Header->pred_end() && "Loop headers should have 2 preds!");
// Add incoming values for the PHI node...
PN->addIncoming(Constant::getNullConstant(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();
}
#ifdef DEBUG
cerr << "Induction variables:\n";
#endif
// Get the current loop iteration count, which is always the value of the
// cannonical phi node...
//
PHINode *IterCount = Cannonical->Phi;
// Loop through and replace all of the auxillary induction variables with
// references to the primary induction variable...
//
unsigned InsertPos = IndVars.size();
for (unsigned i = 0; i < IndVars.size(); ++i) {
InductionVariable *IV = &IndVars[i];
#ifdef DEBUG
cerr << IndVars[i];
#endif
if (IV != Cannonical) { // Don't modify the cannonical indvar
Instruction *Val = IterCount;
if (!isa<ConstantInt>(IV->Step) || // If the step != 1
!cast<ConstantInt>(IV->Step)->equalsInt(1)) {
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++);
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);
}
if (!isa<Constant>(IV->Start) || // If the start != 0
!cast<Constant>(IV->Start)->isNullValue()) {
string Name; // Create a offset by the start value...
if (IV->Phi->hasName()) Name = IV->Phi->getName()+"-offset";
// 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 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++);
// Replace all uses of the old PHI node with the new computed value...
IV->Phi->replaceAllUsesWith(Val);
// Move the PHI name to it's new equivalent value...
string OldName = IV->Phi->getName();
IV->Phi->setName("");
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
}
}
return Changed;