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[ConstantRange] Simplify makeGNWR implementation; NFC 

Compute results in more direct ways, avoid subset intersect
operations. Extract the core code for computing mul nowrap ranges
into separate static functions, so they can be reused.

llvm-svn: 360189
This commit is contained in:
Nikita Popov 2019-05-07 20:34:46 +00:00
parent 34e9c41164
commit f610110f1a
1 changed files with 68 additions and 104 deletions
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172
llvm/lib/IR/ConstantRange.cpp
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@ -180,132 +180,96 @@ bool ConstantRange::getEquivalentICmp(CmpInst::Predicate &Pred,
return Success;
}
/// Exact mul nuw region for single element RHS.
static ConstantRange makeExactMulNUWRegion(const APInt &V) {
unsigned BitWidth = V.getBitWidth();
if (V == 0)
return ConstantRange::getFull(V.getBitWidth());
return ConstantRange::getNonEmpty(
APIntOps::RoundingUDiv(APInt::getMinValue(BitWidth), V,
APInt::Rounding::UP),
APIntOps::RoundingUDiv(APInt::getMaxValue(BitWidth), V,
APInt::Rounding::DOWN) + 1);
}
/// Exact mul nsw region for single element RHS.
static ConstantRange makeExactMulNSWRegion(const APInt &V) {
// Handle special case for 0, -1 and 1. See the last for reason why we
// specialize -1 and 1.
unsigned BitWidth = V.getBitWidth();
if (V == 0 || V.isOneValue())
return ConstantRange::getFull(BitWidth);
APInt MinValue = APInt::getSignedMinValue(BitWidth);
APInt MaxValue = APInt::getSignedMaxValue(BitWidth);
// e.g. Returning [-127, 127], represented as [-127, -128).
if (V.isAllOnesValue())
return ConstantRange(-MaxValue, MinValue);
APInt Lower, Upper;
if (V.isNegative()) {
Lower = APIntOps::RoundingSDiv(MaxValue, V, APInt::Rounding::UP);
Upper = APIntOps::RoundingSDiv(MinValue, V, APInt::Rounding::DOWN);
} else {
Lower = APIntOps::RoundingSDiv(MinValue, V, APInt::Rounding::UP);
Upper = APIntOps::RoundingSDiv(MaxValue, V, APInt::Rounding::DOWN);
}
// ConstantRange ctor take a half inclusive interval [Lower, Upper + 1).
// Upper + 1 is guaranteed not to overflow, because |divisor| > 1. 0, -1,
// and 1 are already handled as special cases.
return ConstantRange(Lower, Upper + 1);
}
ConstantRange
ConstantRange::makeGuaranteedNoWrapRegion(Instruction::BinaryOps BinOp,
const ConstantRange &Other,
unsigned NoWrapKind) {
using OBO = OverflowingBinaryOperator;
// Computes the intersection of CR0 and CR1. It is different from
// intersectWith in that the ConstantRange returned will only contain elements
// in both CR0 and CR1 (i.e. SubsetIntersect(X, Y) is a *subset*, proper or
// not, of both X and Y).
auto SubsetIntersect =
[](const ConstantRange &CR0, const ConstantRange &CR1) {
return CR0.inverse().unionWith(CR1.inverse()).inverse();
};
assert(Instruction::isBinaryOp(BinOp) && "Binary operators only!");
assert((NoWrapKind == OBO::NoSignedWrap ||
NoWrapKind == OBO::NoUnsignedWrap) &&
"NoWrapKind invalid!");
bool Unsigned = NoWrapKind == OBO::NoUnsignedWrap;
unsigned BitWidth = Other.getBitWidth();
ConstantRange Result(BitWidth, /* full */ true);
switch (BinOp) {
default:
// Conservative answer: empty set
return getEmpty(BitWidth);
case Instruction::Add:
if (auto *C = Other.getSingleElement())
if (C->isNullValue())
// Full set: nothing signed / unsigned wraps when added to 0.
return getFull(BitWidth);
if (NoWrapKind == OBO::NoUnsignedWrap)
return ConstantRange(APInt::getNullValue(BitWidth),
-Other.getUnsignedMax());
if (NoWrapKind == OBO::NoSignedWrap) {
const APInt &SignedMin = Other.getSignedMin();
const APInt &SignedMax = Other.getSignedMax();
if (SignedMax.isStrictlyPositive())
Result = SubsetIntersect(
Result,
ConstantRange(APInt::getSignedMinValue(BitWidth),
APInt::getSignedMinValue(BitWidth) - SignedMax));
if (SignedMin.isNegative())
Result = SubsetIntersect(
Result,
ConstantRange(APInt::getSignedMinValue(BitWidth) - SignedMin,
APInt::getSignedMinValue(BitWidth)));
}
return Result;
case Instruction::Sub:
if (auto *C = Other.getSingleElement())
if (C->isNullValue())
// Full set: nothing signed / unsigned wraps when subtracting 0.
return getFull(BitWidth);
if (NoWrapKind == OBO::NoUnsignedWrap)
return ConstantRange(Other.getUnsignedMax(),
APInt::getMinValue(BitWidth));
if (NoWrapKind == OBO::NoSignedWrap) {
const APInt &SignedMin = Other.getSignedMin();
const APInt &SignedMax = Other.getSignedMax();
if (SignedMax.isStrictlyPositive())
Result = SubsetIntersect(
Result,
ConstantRange(APInt::getSignedMinValue(BitWidth) + SignedMax,
APInt::getSignedMinValue(BitWidth)));
if (SignedMin.isNegative())
Result = SubsetIntersect(
Result,
ConstantRange(APInt::getSignedMinValue(BitWidth),
APInt::getSignedMinValue(BitWidth) + SignedMin));
}
return Result;
case Instruction::Mul: {
// Equivalent to calling makeGuaranteedNoWrapRegion() on [V, V+1).
const bool Unsigned = NoWrapKind == OBO::NoUnsignedWrap;
const auto makeSingleValueRegion = [Unsigned,
BitWidth](APInt V) -> ConstantRange {
// Handle special case for 0, -1 and 1. See the last for reason why we
// specialize -1 and 1.
if (V == 0 || V.isOneValue())
return getFull(BitWidth);
APInt MinValue, MaxValue;
if (Unsigned) {
MinValue = APInt::getMinValue(BitWidth);
MaxValue = APInt::getMaxValue(BitWidth);
} else {
MinValue = APInt::getSignedMinValue(BitWidth);
MaxValue = APInt::getSignedMaxValue(BitWidth);
}
// e.g. Returning [-127, 127], represented as [-127, -128).
if (!Unsigned && V.isAllOnesValue())
return ConstantRange(-MaxValue, MinValue);
APInt Lower, Upper;
if (!Unsigned && V.isNegative()) {
Lower = APIntOps::RoundingSDiv(MaxValue, V, APInt::Rounding::UP);
Upper = APIntOps::RoundingSDiv(MinValue, V, APInt::Rounding::DOWN);
} else if (Unsigned) {
Lower = APIntOps::RoundingUDiv(MinValue, V, APInt::Rounding::UP);
Upper = APIntOps::RoundingUDiv(MaxValue, V, APInt::Rounding::DOWN);
} else {
Lower = APIntOps::RoundingSDiv(MinValue, V, APInt::Rounding::UP);
Upper = APIntOps::RoundingSDiv(MaxValue, V, APInt::Rounding::DOWN);
}
// ConstantRange ctor take a half inclusive interval [Lower, Upper + 1).
// Upper + 1 is guanranteed not to overflow, because |divisor| > 1. 0, -1,
// and 1 are already handled as special cases.
return ConstantRange(Lower, Upper + 1);
};
case Instruction::Add: {
if (Unsigned)
return makeSingleValueRegion(Other.getUnsignedMax());
return getNonEmpty(APInt::getNullValue(BitWidth),
-Other.getUnsignedMax());
return SubsetIntersect(makeSingleValueRegion(Other.getSignedMin()),
makeSingleValueRegion(Other.getSignedMax()));
APInt SignedMinVal = APInt::getSignedMinValue(BitWidth);
APInt SMin = Other.getSignedMin(), SMax = Other.getSignedMax();
return getNonEmpty(
SMin.isNegative() ? SignedMinVal - SMin : SignedMinVal,
SMax.isStrictlyPositive() ? SignedMinVal - SMax : SignedMinVal);
}
case Instruction::Sub: {
if (Unsigned)
return getNonEmpty(Other.getUnsignedMax(), APInt::getMinValue(BitWidth));
APInt SignedMinVal = APInt::getSignedMinValue(BitWidth);
APInt SMin = Other.getSignedMin(), SMax = Other.getSignedMax();
return getNonEmpty(
SMax.isStrictlyPositive() ? SignedMinVal + SMax : SignedMinVal,
SMin.isNegative() ? SignedMinVal + SMin : SignedMinVal);
}
case Instruction::Mul:
if (Unsigned)
return makeExactMulNUWRegion(Other.getUnsignedMax());
return makeExactMulNSWRegion(Other.getSignedMin())
.intersectWith(makeExactMulNSWRegion(Other.getSignedMax()));
}
}