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SCEV: Rewrite TrandformForPostIncUse to handle expression DAGs, not

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just expression trees.

Partially fixes PR11090. Test case will be with the full fix.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141868 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick 2011-10-13 17:21:09 +00:00
parent ce1823cd1b
commit 94f01db27b
1 changed files with 70 additions and 30 deletions
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100
lib/Analysis/ScalarEvolutionNormalization.cpp
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@ -60,20 +60,40 @@ static bool IVUseShouldUsePostIncValue(Instruction *User, Value *Operand,
return true;
}
const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
const SCEV *S,
Instruction *User,
Value *OperandValToReplace,
PostIncLoopSet &Loops,
ScalarEvolution &SE,
DominatorTree &DT) {
if (isa<SCEVConstant>(S) || isa<SCEVUnknown>(S))
return S;
namespace {
/// Hold the state used during post-inc expression transformation, including a
/// map of transformed expressions.
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);
};
} // namespace
/// Implement post-inc transformation for all valid expression types.
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 = TransformForPostIncUse(Kind, O, User, OperandValToReplace,
Loops, SE, DT);
const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
if (O != N)
switch (S->getSCEVType()) {
case scZeroExtend: return SE.getZeroExtendExpr(N, S->getType());
@ -93,9 +113,7 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
// Transform each operand.
for (SCEVNAryExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
I != E; ++I) {
const SCEV *O = *I;
const SCEV *N = TransformForPostIncUse(Kind, O, LUser, 0, Loops, SE, DT);
Operands.push_back(N);
Operands.push_back(TransformSubExpr(*I, LUser, 0));
}
// Conservatively use AnyWrap until/unless we need FlagNW.
const SCEV *Result = SE.getAddRecExpr(Operands, L, SCEV::FlagAnyWrap);
@ -104,8 +122,8 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
case NormalizeAutodetect:
if (IVUseShouldUsePostIncValue(User, OperandValToReplace, L, &DT)) {
const SCEV *TransformedStep =
TransformForPostIncUse(Kind, AR->getStepRecurrence(SE),
User, OperandValToReplace, Loops, SE, DT);
TransformSubExpr(AR->getStepRecurrence(SE),
User, OperandValToReplace);
Result = SE.getMinusSCEV(Result, TransformedStep);
Loops.insert(L);
}
@ -114,24 +132,20 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
// sometimes fails to canonicalize two equal SCEVs to exactly the same
// form. It's possibly a pessimization when this happens, but it isn't a
// correctness problem, so disable this assert for now.
assert(S == TransformForPostIncUse(Denormalize, Result,
User, OperandValToReplace,
Loops, SE, DT) &&
assert(S == TransformSubExpr(Result, User, OperandValToReplace) &&
"SCEV normalization is not invertible!");
#endif
break;
case Normalize:
if (Loops.count(L)) {
const SCEV *TransformedStep =
TransformForPostIncUse(Kind, AR->getStepRecurrence(SE),
User, OperandValToReplace, Loops, SE, DT);
TransformSubExpr(AR->getStepRecurrence(SE),
User, OperandValToReplace);
Result = SE.getMinusSCEV(Result, TransformedStep);
}
#if 0
// See the comment on the assert above.
assert(S == TransformForPostIncUse(Denormalize, Result,
User, OperandValToReplace,
Loops, SE, DT) &&
assert(S == TransformSubExpr(Result, User, OperandValToReplace) &&
"SCEV normalization is not invertible!");
#endif
break;
@ -150,8 +164,7 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
for (SCEVNAryExpr::op_iterator I = X->op_begin(), E = X->op_end();
I != E; ++I) {
const SCEV *O = *I;
const SCEV *N = TransformForPostIncUse(Kind, O, User, OperandValToReplace,
Loops, SE, DT);
const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
Changed |= N != O;
Operands.push_back(N);
}
@ -170,10 +183,8 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
if (const SCEVUDivExpr *X = dyn_cast<SCEVUDivExpr>(S)) {
const SCEV *LO = X->getLHS();
const SCEV *RO = X->getRHS();
const SCEV *LN = TransformForPostIncUse(Kind, LO, User, OperandValToReplace,
Loops, SE, DT);
const SCEV *RN = TransformForPostIncUse(Kind, RO, User, OperandValToReplace,
Loops, SE, DT);
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;
@ -182,3 +193,32 @@ const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
llvm_unreachable("Unexpected SCEV kind!");
return 0;
}
/// Manage recursive transformation across an expression DAG. Revisiting
/// expressions would lead to exponential recursion.
const SCEV *PostIncTransform::
TransformSubExpr(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
if (isa<SCEVConstant>(S) || isa<SCEVUnknown>(S))
return S;
const SCEV *&ExprRef = Transformed[S];
if (ExprRef)
return ExprRef;
ExprRef = TransformImpl(S, User, OperandValToReplace);
return ExprRef;
}
/// Top level driver for transforming an expression DAG into its requested
/// post-inc form (either "Normalized" or "Denormalized".
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);
}