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[libc] Fix bugs with negative and mixed normal/denormal inputs in hypot implementation. 

Fix a bug with negative and mixed normal/denormal inputs in hypot implementation.

Differential Revision: https://reviews.llvm.org/D114726
This commit is contained in:
Tue Ly 2021-11-29 13:33:11 -05:00
parent d6c0ef7887
commit dbed678f4b
2 changed files with 39 additions and 17 deletions
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5
libc/src/__support/FPUtil/Hypot.h
View File

@ -150,7 +150,7 @@ static inline T hypot(T x, T y) {
return abs(y);
}
if (x >= y) {
if (abs(x) >= abs(y)) {
a_exp = x_bits.getUnbiasedExponent();
a_mant = x_bits.getMantissa();
b_exp = y_bits.getUnbiasedExponent();
@ -178,10 +178,13 @@ static inline T hypot(T x, T y) {
y_mant_width = MantissaWidth<T>::value + 1;
} else {
leading_one = internal::findLeadingOne(a_mant, y_mant_width);
a_exp = 1;
}
if (b_exp != 0) {
b_mant |= one;
} else {
b_exp = 1;
}
a_mant_sq = static_cast<DUIntType>(a_mant) * a_mant;

51
libc/test/src/math/HypotTest.h
View File

@ -47,28 +47,47 @@ public:
void testSubnormalRange(Func func) {
constexpr UIntType count = 1000001;
constexpr UIntType step =
(FPBits::maxSubnormal - FPBits::minSubnormal) / count;
for (UIntType v = FPBits::minSubnormal, w = FPBits::maxSubnormal;
v <= FPBits::maxSubnormal && w >= FPBits::minSubnormal;
v += step, w -= step) {
T x = T(FPBits(v)), y = T(FPBits(w));
T result = func(x, y);
mpfr::BinaryInput<T> input{x, y};
ASSERT_MPFR_MATCH(mpfr::Operation::Hypot, input, result, 0.5);
for (unsigned scale = 0; scale < 4; ++scale) {
UIntType maxValue = FPBits::maxSubnormal << scale;
UIntType step = (maxValue - FPBits::minSubnormal) / count;
for (int signs = 0; signs < 4; ++signs) {
for (UIntType v = FPBits::minSubnormal, w = maxValue;
v <= maxValue && w >= FPBits::minSubnormal; v += step, w -= step) {
T x = T(FPBits(v)), y = T(FPBits(w));
if (signs % 2 == 1) {
x = -x;
}
if (signs >= 2) {
y = -y;
}
T result = func(x, y);
mpfr::BinaryInput<T> input{x, y};
ASSERT_MPFR_MATCH(mpfr::Operation::Hypot, input, result, 0.5);
}
}
}
}
void testNormalRange(Func func) {
constexpr UIntType count = 1000001;
constexpr UIntType step = (FPBits::maxNormal - FPBits::minNormal) / count;
for (UIntType v = FPBits::minNormal, w = FPBits::maxNormal;
v <= FPBits::maxNormal && w >= FPBits::minNormal;
v += step, w -= step) {
T x = T(FPBits(v)), y = T(FPBits(w));
T result = func(x, y);
mpfr::BinaryInput<T> input{x, y};
ASSERT_MPFR_MATCH(mpfr::Operation::Hypot, input, result, 0.5);
for (int signs = 0; signs < 4; ++signs) {
for (UIntType v = FPBits::minNormal, w = FPBits::maxNormal;
v <= FPBits::maxNormal && w >= FPBits::minNormal;
v += step, w -= step) {
T x = T(FPBits(v)), y = T(FPBits(w));
if (signs % 2 == 1) {
x = -x;
}
if (signs >= 2) {
y = -y;
}
T result = func(x, y);
mpfr::BinaryInput<T> input{x, y};
ASSERT_MPFR_MATCH(mpfr::Operation::Hypot, input, result, 0.5);
}
}
}
};