ConstantRange::ConstantRange(const APInt &L, const APInt &U) :
Lower(L), Upper(U) {
assert(L.getBitWidth() == U.getBitWidth() &&
"ConstantRange with unequal bit widths");
assert((L != U || (L.isMaxValue() || L.isMinValue())) &&
"Lower == Upper, but they aren't min or max value!");
}
ConstantRange
ConstantRange::binaryOr(const ConstantRange &Other) const {
if (isEmptySet() || Other.isEmptySet())
return ConstantRange(getBitWidth(), /*isFullSet=*/false);
// TODO: replace this with something less conservative
APInt umax = APIntOps::umax(getUnsignedMin(), Other.getUnsignedMin());
if (umax.isMinValue())
return ConstantRange(getBitWidth(), /*isFullSet=*/true);
return ConstantRange(umax, APInt::getNullValue(getBitWidth()));
}
ConstantRange
ConstantRange::makeGuaranteedNoWrapRegion(Instruction::BinaryOps BinOp,
const APInt &C, unsigned NoWrapKind) {
typedef OverflowingBinaryOperator OBO;
// 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(BinOp >= Instruction::BinaryOpsBegin &&
BinOp < Instruction::BinaryOpsEnd && "Binary operators only!");
assert((NoWrapKind == OBO::NoSignedWrap ||
NoWrapKind == OBO::NoUnsignedWrap ||
NoWrapKind == (OBO::NoUnsignedWrap | OBO::NoSignedWrap)) &&
"NoWrapKind invalid!");
unsigned BitWidth = C.getBitWidth();
if (BinOp != Instruction::Add)
// Conservative answer: empty set
return ConstantRange(BitWidth, false);
if (C.isMinValue())
// Full set: nothing signed / unsigned wraps when added to 0.
return ConstantRange(BitWidth);
ConstantRange Result(BitWidth);
if (NoWrapKind & OBO::NoUnsignedWrap)
Result = SubsetIntersect(Result,
ConstantRange(APInt::getNullValue(BitWidth), -C));
if (NoWrapKind & OBO::NoSignedWrap) {
if (C.isStrictlyPositive())
Result = SubsetIntersect(
Result, ConstantRange(APInt::getSignedMinValue(BitWidth),
APInt::getSignedMinValue(BitWidth) - C));
else
Result = SubsetIntersect(
Result, ConstantRange(APInt::getSignedMinValue(BitWidth) - C,
APInt::getSignedMinValue(BitWidth)));
}
return Result;
}
bool GuardWideningImpl::combineRangeChecks(
SmallVectorImpl<GuardWideningImpl::RangeCheck> &Checks,
SmallVectorImpl<GuardWideningImpl::RangeCheck> &RangeChecksOut) {
unsigned OldCount = Checks.size();
while (!Checks.empty()) {
// Pick all of the range checks with a specific base and length, and try to
// merge them.
Value *CurrentBase = Checks.front().getBase();
Value *CurrentLength = Checks.front().getLength();
SmallVector<GuardWideningImpl::RangeCheck, 3> CurrentChecks;
auto IsCurrentCheck = [&](GuardWideningImpl::RangeCheck &RC) {
return RC.getBase() == CurrentBase && RC.getLength() == CurrentLength;
};
copy_if(Checks, std::back_inserter(CurrentChecks), IsCurrentCheck);
Checks.erase(remove_if(Checks, IsCurrentCheck), Checks.end());
assert(CurrentChecks.size() != 0 && "We know we have at least one!");
if (CurrentChecks.size() < 3) {
RangeChecksOut.insert(RangeChecksOut.end(), CurrentChecks.begin(),
CurrentChecks.end());
continue;
}
// CurrentChecks.size() will typically be 3 here, but so far there has been
// no need to hard-code that fact.
std::sort(CurrentChecks.begin(), CurrentChecks.end(),
[&](const GuardWideningImpl::RangeCheck &LHS,
const GuardWideningImpl::RangeCheck &RHS) {
return LHS.getOffsetValue().slt(RHS.getOffsetValue());
});
// Note: std::sort should not invalidate the ChecksStart iterator.
ConstantInt *MinOffset = CurrentChecks.front().getOffset(),
*MaxOffset = CurrentChecks.back().getOffset();
unsigned BitWidth = MaxOffset->getValue().getBitWidth();
if ((MaxOffset->getValue() - MinOffset->getValue())
.ugt(APInt::getSignedMinValue(BitWidth)))
return false;
APInt MaxDiff = MaxOffset->getValue() - MinOffset->getValue();
const APInt &HighOffset = MaxOffset->getValue();
auto OffsetOK = [&](const GuardWideningImpl::RangeCheck &RC) {
return (HighOffset - RC.getOffsetValue()).ult(MaxDiff);
};
if (MaxDiff.isMinValue() ||
!std::all_of(std::next(CurrentChecks.begin()), CurrentChecks.end(),
OffsetOK))
return false;
// We have a series of f+1 checks as:
//
// I+k_0 u< L ... Chk_0
// I_k_1 u< L ... Chk_1
// ...
// I_k_f u< L ... Chk_(f+1)
//
// with forall i in [0,f): k_f-k_i u< k_f-k_0 ... Precond_0
// k_f-k_0 u< INT_MIN+k_f ... Precond_1
// k_f != k_0 ... Precond_2
//
// Claim:
// Chk_0 AND Chk_(f+1) implies all the other checks
//
// Informal proof sketch:
//
// We will show that the integer range [I+k_0,I+k_f] does not unsigned-wrap
// (i.e. going from I+k_0 to I+k_f does not cross the -1,0 boundary) and
// thus I+k_f is the greatest unsigned value in that range.
//
// This combined with Ckh_(f+1) shows that everything in that range is u< L.
// Via Precond_0 we know that all of the indices in Chk_0 through Chk_(f+1)
// lie in [I+k_0,I+k_f], this proving our claim.
//
// To see that [I+k_0,I+k_f] is not a wrapping range, note that there are
// two possibilities: I+k_0 u< I+k_f or I+k_0 >u I+k_f (they can't be equal
// since k_0 != k_f). In the former case, [I+k_0,I+k_f] is not a wrapping
// range by definition, and the latter case is impossible:
//
// 0-----I+k_f---I+k_0----L---INT_MAX,INT_MIN------------------(-1)
// xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
//
// For Chk_0 to succeed, we'd have to have k_f-k_0 (the range highlighted
// with 'x' above) to be at least >u INT_MIN.
RangeChecksOut.emplace_back(CurrentChecks.front());
RangeChecksOut.emplace_back(CurrentChecks.back());
}
assert(RangeChecksOut.size() <= OldCount && "We pessimized!");
return RangeChecksOut.size() != OldCount;
}