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fix(libc): classify x87 unnormals as denormal in _LDtest and _LDclass #11283

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Merged
adriadam10 merged 1 commit into from
Oct 28, 2026
Merged

fix(libc): classify x87 unnormals as denormal in _LDtest and _LDclass #11283

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9 changes: 5 additions & 4 deletions core/libs/prx/libc/src/MathExact.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -42,8 +42,8 @@ short TestExtended(const ExtendedBits& bits) {
const int exponent = bits.signExponent & 0x7fff;
const std::uint64_t fraction = bits.mantissa & 0x7fffffffffffffffull;
if (exponent == 0x7fff) return fraction != 0 ? NotANumber : Infinite;
if (exponent != 0 || (bits.mantissa >> 63) != 0) return Finite;
return bits.mantissa != 0 ? Denormal : Zero;
if ((bits.mantissa >> 63) != 0) return Finite;
return exponent != 0 || bits.mantissa != 0 ? Denormal : Zero;
}

template<typename TFloat>
Expand Down Expand Up @@ -242,8 +242,9 @@ int APS5_VABI finitef_nid_postfix(float x) { return std::isfinite(x) ? 1 : 0; }

int APS5_VABI __fpclassifyl_nid_postfix(long double x) {
const ExtendedBits bits = Bits(x);
if ((bits.signExponent & 0x7fff) != 0 || bits.mantissa == 0) return TestExtended(bits);
return Denormal;
const int exponent = bits.signExponent & 0x7fff;
if (exponent == 0) return bits.mantissa != 0 ? Denormal : Zero;
return exponent != 0x7fff ? Finite : TestExtended(bits);
}
int APS5_VABI __isinfl_nid_postfix(long double x) { return TestExtended(Bits(x)) == Infinite ? 1 : 0; }
int APS5_VABI __isnanl_nid_postfix(long double x) { return TestExtended(Bits(x)) == NotANumber ? 1 : 0; }
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4 changes: 4 additions & 0 deletions core/libs/tests/GuestMathExact.cpp
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Expand Up @@ -130,6 +130,10 @@ static void CheckRoundingModes() {
static void CheckClassification() {
const long double pseudoDenormal = Extended(0x0000, 0x8000000000000000ull);
Require(_LDtest_nid_postfix(&pseudoDenormal) == -1 && __fpclassifyl_nid_postfix(pseudoDenormal) == -2);
for (const long double unnormal : {Extended(0x3fff, 0x4000000000000000ull), Extended(0x8001, 0), Extended(0x7ffe, 0x7fffffffffffffffull)}) {
Require(_LDtest_nid_postfix(&unnormal) == -2 && _LDclass_nid_postfix(unnormal) == -2);
Require(__fpclassifyl_nid_postfix(unnormal) == -1 && __isnormall_nid_postfix(unnormal) == 1);
}
const long double zero = 0.0L, infinity = INFINITY, nan = NAN, denormal = Extended(0, 1);
Require(_LDtest_nid_postfix(&zero) == 0 && _LDtest_nid_postfix(&infinity) == 1 && _LDtest_nid_postfix(&nan) == 2 && _LDtest_nid_postfix(&denormal) == -2);
Require(__fpclassifyl_nid_postfix(1.0L) == -1 && __fpclassifyl_nid_postfix(0.0L) == 0 && __fpclassifyl_nid_postfix(INFINITY) == 1);
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