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[ConstantFPRange] Implement ConstantFPRange::makeAllowedFCmpRegion
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@dtcxzyw
dtcxzyw committed Sep 26, 2024
1 parent 165a912 commit 203d316
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Showing 3 changed files with 169 additions and 12 deletions.
17 changes: 12 additions & 5 deletions llvm/include/llvm/IR/ConstantFPRange.h
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,6 @@ class [[nodiscard]] ConstantFPRange {

void makeEmpty();
void makeFull();
bool isNaNOnly() const;

/// Initialize a full or empty set for the specified semantics.
explicit ConstantFPRange(const fltSemantics &Sem, bool IsFullSet);
Expand Down Expand Up @@ -78,6 +77,9 @@ class [[nodiscard]] ConstantFPRange {
/// Helper for (-inf, inf) to represent all finite values.
static ConstantFPRange getFinite(const fltSemantics &Sem);

/// Helper for [-inf, inf] to represent all non-NaN values.
static ConstantFPRange getNonNaN(const fltSemantics &Sem);

/// Create a range which doesn't contain NaNs.
static ConstantFPRange getNonNaN(APFloat LowerVal, APFloat UpperVal) {
return ConstantFPRange(std::move(LowerVal), std::move(UpperVal),
Expand Down Expand Up @@ -123,8 +125,10 @@ class [[nodiscard]] ConstantFPRange {
/// { x : fcmp op x y is true}'.
///
/// Example: Pred = olt and Other = float 3 returns [-inf, 3)
static ConstantFPRange makeExactFCmpRegion(FCmpInst::Predicate Pred,
const APFloat &Other);
/// If the exact answer is not representable as a ConstantFPRange, return
/// std::nullopt.
static std::optional<ConstantFPRange>
makeExactFCmpRegion(FCmpInst::Predicate Pred, const APFloat &Other);

/// Does the predicate \p Pred hold between ranges this and \p Other?
/// NOTE: false does not mean that inverse predicate holds!
Expand All @@ -139,6 +143,7 @@ class [[nodiscard]] ConstantFPRange {
bool containsNaN() const { return MayBeQNaN || MayBeSNaN; }
bool containsQNaN() const { return MayBeQNaN; }
bool containsSNaN() const { return MayBeSNaN; }
bool isNaNOnly() const;

/// Get the semantics of this ConstantFPRange.
const fltSemantics &getSemantics() const { return Lower.getSemantics(); }
Expand All @@ -157,10 +162,12 @@ class [[nodiscard]] ConstantFPRange {
bool contains(const ConstantFPRange &CR) const;

/// If this set contains a single element, return it, otherwise return null.
const APFloat *getSingleElement() const;
const APFloat *getSingleElement(bool ExcludesNaN = false) const;

/// Return true if this set contains exactly one member.
bool isSingleElement() const { return getSingleElement() != nullptr; }
bool isSingleElement(bool ExcludesNaN = false) const {
return getSingleElement(ExcludesNaN) != nullptr;
}

/// Return true if the sign bit of all values in this range is 1.
/// Return false if the sign bit of all values in this range is 0.
Expand Down
119 changes: 112 additions & 7 deletions llvm/lib/IR/ConstantFPRange.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -103,11 +103,115 @@ ConstantFPRange ConstantFPRange::getNaNOnly(const fltSemantics &Sem,
MayBeSNaN);
}

ConstantFPRange ConstantFPRange::getNonNaN(const fltSemantics &Sem) {
return ConstantFPRange(APFloat::getInf(Sem, /*Negative=*/true),
APFloat::getInf(Sem, /*Negative=*/false),
/*MayBeQNaN=*/false, /*MayBeSNaN=*/false);
}

/// Return [-inf, V) or [-inf, V]
static ConstantFPRange makeLessThan(APFloat V, FCmpInst::Predicate Pred) {
const fltSemantics &Sem = V.getSemantics();
if (!(Pred & FCmpInst::FCMP_OEQ)) {
if (V.isNegInfinity())
return ConstantFPRange::getEmpty(Sem);
V.next(/*nextDown=*/true);
}
return ConstantFPRange::getNonNaN(APFloat::getInf(Sem, /*Negative=*/true),
std::move(V));
}

/// Return (V, +inf] or [V, +inf]
static ConstantFPRange makeGreaterThan(APFloat V, FCmpInst::Predicate Pred) {
const fltSemantics &Sem = V.getSemantics();
if (!(Pred & FCmpInst::FCMP_OEQ)) {
if (V.isPosInfinity())
return ConstantFPRange::getEmpty(Sem);
V.next(/*nextDown=*/false);
}
return ConstantFPRange::getNonNaN(std::move(V),
APFloat::getInf(Sem, /*Negative=*/false));
}

/// Make sure that +0/-0 are both included in the range.
static ConstantFPRange extendZeroIfEqual(const ConstantFPRange &CR,
FCmpInst::Predicate Pred) {
if (!(Pred & FCmpInst::FCMP_OEQ))
return CR;

APFloat Lower = CR.getLower();
APFloat Upper = CR.getUpper();
if (Lower.isPosZero())
Lower = APFloat::getZero(Lower.getSemantics(), /*Negative=*/true);
if (Upper.isNegZero())
Upper = APFloat::getZero(Upper.getSemantics(), /*Negative=*/false);
return ConstantFPRange(std::move(Lower), std::move(Upper), CR.containsQNaN(),
CR.containsSNaN());
}

static ConstantFPRange setNaNField(const ConstantFPRange &CR,
FCmpInst::Predicate Pred) {
bool ContainsNaN = FCmpInst::isUnordered(Pred);
return ConstantFPRange(CR.getLower(), CR.getUpper(),
/*MayBeQNaN=*/ContainsNaN, /*MayBeSNaN=*/ContainsNaN);
}

ConstantFPRange
ConstantFPRange::makeAllowedFCmpRegion(FCmpInst::Predicate Pred,
const ConstantFPRange &Other) {
// TODO
return getFull(Other.getSemantics());
if (Other.isEmptySet())
return Other;
if (Other.containsNaN() && FCmpInst::isUnordered(Pred))
return getFull(Other.getSemantics());
if (Other.isNaNOnly() && FCmpInst::isOrdered(Pred))
return getEmpty(Other.getSemantics());

switch (Pred) {
case FCmpInst::FCMP_TRUE:
return getFull(Other.getSemantics());
case FCmpInst::FCMP_FALSE:
return getEmpty(Other.getSemantics());
case FCmpInst::FCMP_ORD:
return getNonNaN(Other.getSemantics());
case FCmpInst::FCMP_UNO:
return getNaNOnly(Other.getSemantics(), /*MayBeQNaN=*/true,
/*MayBeSNaN=*/true);
case FCmpInst::FCMP_OEQ:
case FCmpInst::FCMP_UEQ:
return setNaNField(extendZeroIfEqual(Other, Pred), Pred);
case FCmpInst::FCMP_ONE:
case FCmpInst::FCMP_UNE:
if (const APFloat *SingleElement =
Other.getSingleElement(/*ExcludesNaN=*/true)) {
const fltSemantics &Sem = SingleElement->getSemantics();
if (SingleElement->isPosInfinity())
return setNaNField(
getNonNaN(APFloat::getInf(Sem, /*Negative=*/true),
APFloat::getLargest(Sem, /*Negative=*/false)),
Pred);
if (SingleElement->isNegInfinity())
return setNaNField(
getNonNaN(APFloat::getLargest(Sem, /*Negative=*/true),
APFloat::getInf(Sem, /*Negative=*/false)),
Pred);
}
return Pred == FCmpInst::FCMP_ONE ? getNonNaN(Other.getSemantics())
: getFull(Other.getSemantics());
case FCmpInst::FCMP_OLT:
case FCmpInst::FCMP_OLE:
case FCmpInst::FCMP_ULT:
case FCmpInst::FCMP_ULE:
return setNaNField(
extendZeroIfEqual(makeLessThan(Other.getUpper(), Pred), Pred), Pred);
case FCmpInst::FCMP_OGT:
case FCmpInst::FCMP_OGE:
case FCmpInst::FCMP_UGT:
case FCmpInst::FCMP_UGE:
return setNaNField(
extendZeroIfEqual(makeGreaterThan(Other.getLower(), Pred), Pred), Pred);
default:
llvm_unreachable("Unexpected predicate");
}
}

ConstantFPRange
Expand All @@ -117,9 +221,10 @@ ConstantFPRange::makeSatisfyingFCmpRegion(FCmpInst::Predicate Pred,
return getEmpty(Other.getSemantics());
}

ConstantFPRange ConstantFPRange::makeExactFCmpRegion(FCmpInst::Predicate Pred,
const APFloat &Other) {
return makeAllowedFCmpRegion(Pred, ConstantFPRange(Other));
std::optional<ConstantFPRange>
ConstantFPRange::makeExactFCmpRegion(FCmpInst::Predicate Pred,
const APFloat &Other) {
return std::nullopt;
}

bool ConstantFPRange::fcmp(FCmpInst::Predicate Pred,
Expand Down Expand Up @@ -161,8 +266,8 @@ bool ConstantFPRange::contains(const ConstantFPRange &CR) const {
strictCompare(CR.Upper, Upper) != APFloat::cmpGreaterThan;
}

const APFloat *ConstantFPRange::getSingleElement() const {
if (MayBeSNaN || MayBeQNaN)
const APFloat *ConstantFPRange::getSingleElement(bool ExcludesNaN) const {
if (!ExcludesNaN && (MayBeSNaN || MayBeQNaN))
return nullptr;
return Lower.bitwiseIsEqual(Upper) ? &Lower : nullptr;
}
Expand Down
45 changes: 45 additions & 0 deletions llvm/unittests/IR/ConstantFPRangeTest.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -161,6 +161,19 @@ static void EnumerateValuesInConstantFPRange(const ConstantFPRange &CR,
}
}

template <typename Fn>
static bool AnyOfValueInConstantFPRange(const ConstantFPRange &CR, Fn TestFn) {
const fltSemantics &Sem = CR.getSemantics();
unsigned Bits = APFloat::semanticsSizeInBits(Sem);
assert(Bits < 32 && "Too many bits");
for (unsigned I = 0, E = (1U << Bits) - 1; I != E; ++I) {
APFloat V(Sem, APInt(Bits, I));
if (CR.contains(V) && TestFn(V))
return true;
}
return false;
}

TEST_F(ConstantFPRangeTest, Basics) {
EXPECT_TRUE(Full.isFullSet());
EXPECT_FALSE(Full.isEmptySet());
Expand Down Expand Up @@ -263,12 +276,16 @@ TEST_F(ConstantFPRangeTest, SingleElement) {
EXPECT_EQ(*One.getSingleElement(), APFloat(1.0));
EXPECT_EQ(*PosZero.getSingleElement(), APFloat::getZero(Sem));
EXPECT_EQ(*PosInf.getSingleElement(), APFloat::getInf(Sem));
ConstantFPRange PosZeroOrNaN = PosZero.unionWith(NaN);
EXPECT_EQ(*PosZeroOrNaN.getSingleElement(/*ExcludesNaN=*/true),
APFloat::getZero(Sem));

EXPECT_FALSE(Full.isSingleElement());
EXPECT_FALSE(Empty.isSingleElement());
EXPECT_TRUE(One.isSingleElement());
EXPECT_FALSE(Some.isSingleElement());
EXPECT_FALSE(Zero.isSingleElement());
EXPECT_TRUE(PosZeroOrNaN.isSingleElement(/*ExcludesNaN=*/true));
}

TEST_F(ConstantFPRangeTest, ExhaustivelyEnumerate) {
Expand Down Expand Up @@ -425,4 +442,32 @@ TEST_F(ConstantFPRangeTest, MismatchedSemantics) {
#endif
#endif

TEST_F(ConstantFPRangeTest, makeAllowedFCmpRegion) {
for (auto Pred : FCmpInst::predicates()) {
EnumerateConstantFPRanges(
[Pred](const ConstantFPRange &CR) {
ConstantFPRange Res =
ConstantFPRange::makeAllowedFCmpRegion(Pred, CR);
ConstantFPRange Optimal =
ConstantFPRange::getEmpty(CR.getSemantics());
EnumerateValuesInConstantFPRange(
ConstantFPRange::getFull(CR.getSemantics()),
[&](const APFloat &V) {
if (AnyOfValueInConstantFPRange(CR, [&](const APFloat &U) {
return FCmpInst::compare(V, U, Pred);
}))
Optimal = Optimal.unionWith(ConstantFPRange(V));
});

ASSERT_TRUE(Res.contains(Optimal))
<< "Wrong result for makeAllowedFCmpRegion(" << Pred << ", " << CR
<< "). Expected " << Optimal << ", but got " << Res;
EXPECT_EQ(Res, Optimal)
<< "Suboptimal result for makeAllowedFCmpRegion(" << Pred << ", "
<< CR << ")";
},
/*Exhaustive=*/false);
}
}

} // anonymous namespace

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