ScalarEvolutionNormalization.cpp [plain text]
#include "llvm/IR/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ScalarEvolutionNormalization.h"
using namespace llvm;
static bool IVUseShouldUsePostIncValue(Instruction *User, Value *Operand,
const Loop *L, DominatorTree *DT) {
if (L->contains(User)) return false;
BasicBlock *LatchBlock = L->getLoopLatch();
if (!LatchBlock)
return false;
if (DT->dominates(LatchBlock, User->getParent()))
return true;
PHINode *PN = dyn_cast<PHINode>(User);
if (!PN || !Operand) return false;
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) == Operand &&
!DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
return false;
return true;
}
namespace {
class PostIncTransform {
TransformKind Kind;
PostIncLoopSet &Loops;
ScalarEvolution &SE;
DominatorTree &DT;
DenseMap<const SCEV*, const SCEV*> Transformed;
public:
PostIncTransform(TransformKind kind, PostIncLoopSet &loops,
ScalarEvolution &se, DominatorTree &dt):
Kind(kind), Loops(loops), SE(se), DT(dt) {}
const SCEV *TransformSubExpr(const SCEV *S, Instruction *User,
Value *OperandValToReplace);
protected:
const SCEV *TransformImpl(const SCEV *S, Instruction *User,
Value *OperandValToReplace);
};
}
const SCEV *PostIncTransform::
TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
if (const SCEVCastExpr *X = dyn_cast<SCEVCastExpr>(S)) {
const SCEV *O = X->getOperand();
const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
if (O != N)
switch (S->getSCEVType()) {
case scZeroExtend: return SE.getZeroExtendExpr(N, S->getType());
case scSignExtend: return SE.getSignExtendExpr(N, S->getType());
case scTruncate: return SE.getTruncateExpr(N, S->getType());
default: llvm_unreachable("Unexpected SCEVCastExpr kind!");
}
return S;
}
if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
SmallVector<const SCEV *, 8> Operands;
const Loop *L = AR->getLoop();
Instruction *LUser = L->getHeader()->begin();
for (SCEVNAryExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
I != E; ++I) {
Operands.push_back(TransformSubExpr(*I, LUser, 0));
}
const SCEV *Result = SE.getAddRecExpr(Operands, L, SCEV::FlagAnyWrap);
switch (Kind) {
case NormalizeAutodetect:
if (AR->isAffine() &&
IVUseShouldUsePostIncValue(User, OperandValToReplace, L, &DT)) {
Result = SE.getMinusSCEV(Result, AR->getStepRecurrence(SE));
Loops.insert(L);
}
#if 0
assert(S == TransformSubExpr(Result, User, OperandValToReplace) &&
"SCEV normalization is not invertible!");
#endif
break;
case Normalize:
if (Loops.count(L)) {
const SCEV *TransformedStep =
TransformSubExpr(AR->getStepRecurrence(SE),
User, OperandValToReplace);
Result = SE.getMinusSCEV(Result, TransformedStep);
}
#if 0
assert(S == TransformSubExpr(Result, User, OperandValToReplace) &&
"SCEV normalization is not invertible!");
#endif
break;
case Denormalize:
if (Loops.count(L))
Result = cast<SCEVAddRecExpr>(Result)->getPostIncExpr(SE);
break;
}
return Result;
}
if (const SCEVNAryExpr *X = dyn_cast<SCEVNAryExpr>(S)) {
SmallVector<const SCEV *, 8> Operands;
bool Changed = false;
for (SCEVNAryExpr::op_iterator I = X->op_begin(), E = X->op_end();
I != E; ++I) {
const SCEV *O = *I;
const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
Changed |= N != O;
Operands.push_back(N);
}
if (Changed)
switch (S->getSCEVType()) {
case scAddExpr: return SE.getAddExpr(Operands);
case scMulExpr: return SE.getMulExpr(Operands);
case scSMaxExpr: return SE.getSMaxExpr(Operands);
case scUMaxExpr: return SE.getUMaxExpr(Operands);
default: llvm_unreachable("Unexpected SCEVNAryExpr kind!");
}
return S;
}
if (const SCEVUDivExpr *X = dyn_cast<SCEVUDivExpr>(S)) {
const SCEV *LO = X->getLHS();
const SCEV *RO = X->getRHS();
const SCEV *LN = TransformSubExpr(LO, User, OperandValToReplace);
const SCEV *RN = TransformSubExpr(RO, User, OperandValToReplace);
if (LO != LN || RO != RN)
return SE.getUDivExpr(LN, RN);
return S;
}
llvm_unreachable("Unexpected SCEV kind!");
}
const SCEV *PostIncTransform::
TransformSubExpr(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
if (isa<SCEVConstant>(S) || isa<SCEVUnknown>(S))
return S;
const SCEV *Result = Transformed.lookup(S);
if (Result)
return Result;
Result = TransformImpl(S, User, OperandValToReplace);
Transformed[S] = Result;
return Result;
}
const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
const SCEV *S,
Instruction *User,
Value *OperandValToReplace,
PostIncLoopSet &Loops,
ScalarEvolution &SE,
DominatorTree &DT) {
PostIncTransform Transform(Kind, Loops, SE, DT);
return Transform.TransformSubExpr(S, User, OperandValToReplace);
}