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Expose isNonConstantNegative to users of ScalarEvolution. 

llvm-svn: 147700
This commit is contained in:
Andrew Trick 2012-01-07 00:27:31 +00:00
parent f64e1adcbb
commit 881a776875
3 changed files with 24 additions and 20 deletions
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4
llvm/include/llvm/Analysis/ScalarEvolution.h
View File

@ -119,6 +119,10 @@ namespace llvm {
///
bool isAllOnesValue() const;
/// isNonConstantNegative - Return true if the specified scev is negated,
/// but not a constant.
bool isNonConstantNegative() const;
/// print - Print out the internal representation of this scalar to the
/// specified stream. This should really only be used for debugging
/// purposes.

14
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -284,6 +284,20 @@ bool SCEV::isAllOnesValue() const {
return false;
}
/// isNonConstantNegative - Return true if the specified scev is negated, but
/// not a constant.
bool SCEV::isNonConstantNegative() const {
const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(this);
if (!Mul) return false;
// If there is a constant factor, it will be first.
const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
if (!SC) return false;
// Return true if the value is negative, this matches things like (-42 * V).
return SC->getValue()->getValue().isNegative();
}
SCEVCouldNotCompute::SCEVCouldNotCompute() :
SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}

26
llvm/lib/Analysis/ScalarEvolutionExpander.cpp
View File

@ -593,20 +593,6 @@ Value *SCEVExpander::expandAddToGEP(const SCEV *const *op_begin,
return expand(SE.getAddExpr(Ops));
}
/// isNonConstantNegative - Return true if the specified scev is negated, but
/// not a constant.
static bool isNonConstantNegative(const SCEV *F) {
const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(F);
if (!Mul) return false;
// If there is a constant factor, it will be first.
const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
if (!SC) return false;
// Return true if the value is negative, this matches things like (-42 * V).
return SC->getValue()->getValue().isNegative();
}
/// PickMostRelevantLoop - Given two loops pick the one that's most relevant for
/// SCEV expansion. If they are nested, this is the most nested. If they are
/// neighboring, pick the later.
@ -685,10 +671,10 @@ public:
// If one operand is a non-constant negative and the other is not,
// put the non-constant negative on the right so that a sub can
// be used instead of a negate and add.
if (isNonConstantNegative(LHS.second)) {
if (!isNonConstantNegative(RHS.second))
if (LHS.second->isNonConstantNegative()) {
if (!RHS.second->isNonConstantNegative())
return false;
} else if (isNonConstantNegative(RHS.second))
} else if (RHS.second->isNonConstantNegative())
return true;
// Otherwise they are equivalent according to this comparison.
@ -749,7 +735,7 @@ Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
for (++I; I != E && I->first == CurLoop; ++I)
NewOps.push_back(I->second);
Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, expand(Op));
} else if (isNonConstantNegative(Op)) {
} else if (Op->isNonConstantNegative()) {
// Instead of doing a negate and add, just do a subtract.
Value *W = expandCodeFor(SE.getNegativeSCEV(Op), Ty);
Sum = InsertNoopCastOfTo(Sum, Ty);
@ -1044,7 +1030,7 @@ SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
// If the stride is negative, insert a sub instead of an add for the increment
// (unless it's a constant, because subtracts of constants are canonicalized
// to adds).
bool useSubtract = !ExpandTy->isPointerTy() && isNonConstantNegative(Step);
bool useSubtract = !ExpandTy->isPointerTy() && Step->isNonConstantNegative();
if (useSubtract)
Step = SE.getNegativeSCEV(Step);
// Expand the step somewhere that dominates the loop header.
@ -1167,7 +1153,7 @@ Value *SCEVExpander::expandAddRecExprLiterally(const SCEVAddRecExpr *S) {
// inserting an extra IV increment. StepV might fold into PostLoopOffset,
// but hopefully expandCodeFor handles that.
bool useSubtract =
!ExpandTy->isPointerTy() && isNonConstantNegative(Step);
!ExpandTy->isPointerTy() && Step->isNonConstantNegative();
if (useSubtract)
Step = SE.getNegativeSCEV(Step);
// Expand the step somewhere that dominates the loop header.