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[libc][NFC] Rename MAX_EXPONENT to MAX_BIASED_EXPONENT #75932

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Merged
merged 1 commit into from
Dec 20, 2023
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[libc][NFC] Rename MAX_EXPONENT to MAX_BIASED_EXPONENT #75932

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4 changes: 2 additions & 2 deletions libc/src/__support/FPUtil/FPBits.h
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Original file line number Diff line number Diff line change
Expand Up @@ -97,12 +97,12 @@ template <typename T> struct FPBits : private FloatProperties<T> {
static_assert(sizeof(T) == sizeof(StorageType),
"Data type and integral representation have different sizes.");

static constexpr int MAX_EXPONENT = (1 << EXP_LEN) - 1;
static constexpr int MAX_BIASED_EXPONENT = (1 << EXP_LEN) - 1;
static constexpr StorageType MIN_SUBNORMAL = StorageType(1);
static constexpr StorageType MAX_SUBNORMAL = FRACTION_MASK;
static constexpr StorageType MIN_NORMAL = (StorageType(1) << FRACTION_LEN);
static constexpr StorageType MAX_NORMAL =
((StorageType(MAX_EXPONENT) - 1) << FRACTION_LEN) | MAX_SUBNORMAL;
((StorageType(MAX_BIASED_EXPONENT) - 1) << FRACTION_LEN) | MAX_SUBNORMAL;

// We don't want accidental type promotions/conversions, so we require exact
// type match.
Expand Down
4 changes: 2 additions & 2 deletions libc/src/__support/FPUtil/Hypot.h
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Expand Up @@ -193,7 +193,7 @@ LIBC_INLINE T hypot(T x, T y) {
sticky_bits = sticky_bits || ((sum & 0x3U) != 0);
sum >>= 2;
++out_exp;
if (out_exp >= FPBits_t::MAX_EXPONENT) {
if (out_exp >= FPBits_t::MAX_BIASED_EXPONENT) {
if (int round_mode = quick_get_round();
round_mode == FE_TONEAREST || round_mode == FE_UPWARD)
return T(FPBits_t::inf());
Expand Down Expand Up @@ -251,7 +251,7 @@ LIBC_INLINE T hypot(T x, T y) {
if (y_new >= (ONE >> 1)) {
y_new -= ONE >> 1;
++out_exp;
if (out_exp >= FPBits_t::MAX_EXPONENT) {
if (out_exp >= FPBits_t::MAX_BIASED_EXPONENT) {
if (round_mode == FE_TONEAREST || round_mode == FE_UPWARD)
return T(FPBits_t::inf());
return T(FPBits_t(FPBits_t::MAX_NORMAL));
Expand Down
2 changes: 1 addition & 1 deletion libc/src/__support/FPUtil/ManipulationFunctions.h
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Expand Up @@ -130,7 +130,7 @@ LIBC_INLINE T ldexp(T x, int exp) {
// early. Because the result of the ldexp operation can be a subnormal number,
// we need to accommodate the (mantissaWidht + 1) worth of shift in
// calculating the limit.
int exp_limit = FPBits<T>::MAX_EXPONENT + FPBits<T>::FRACTION_LEN + 1;
int exp_limit = FPBits<T>::MAX_BIASED_EXPONENT + FPBits<T>::FRACTION_LEN + 1;
if (exp > exp_limit)
return bits.get_sign() ? T(FPBits<T>::neg_inf()) : T(FPBits<T>::inf());

Expand Down
8 changes: 4 additions & 4 deletions libc/src/__support/FPUtil/generic/FMA.h
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Expand Up @@ -128,9 +128,9 @@ template <> LIBC_INLINE double fma<double>(double x, double y, double z) {
y_exp += y_bits.get_biased_exponent();
z_exp += z_bits.get_biased_exponent();

if (LIBC_UNLIKELY(x_exp == FPBits::MAX_EXPONENT ||
y_exp == FPBits::MAX_EXPONENT ||
z_exp == FPBits::MAX_EXPONENT))
if (LIBC_UNLIKELY(x_exp == FPBits::MAX_BIASED_EXPONENT ||
y_exp == FPBits::MAX_BIASED_EXPONENT ||
z_exp == FPBits::MAX_BIASED_EXPONENT))
return x * y + z;

// Extract mantissa and append hidden leading bits.
Expand Down Expand Up @@ -255,7 +255,7 @@ template <> LIBC_INLINE double fma<double>(double x, double y, double z) {

// Finalize the result.
int round_mode = fputil::quick_get_round();
if (LIBC_UNLIKELY(r_exp >= FPBits::MAX_EXPONENT)) {
if (LIBC_UNLIKELY(r_exp >= FPBits::MAX_BIASED_EXPONENT)) {
if ((round_mode == FE_TOWARDZERO) ||
(round_mode == FE_UPWARD && prod_sign) ||
(round_mode == FE_DOWNWARD && !prod_sign)) {
Expand Down
16 changes: 8 additions & 8 deletions libc/src/__support/FPUtil/x86_64/LongDoubleBits.h
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Expand Up @@ -41,14 +41,14 @@ template <> struct FPBits<long double> : private FloatProperties<long double> {
public:
using FloatProperties<long double>::SIGN_MASK;

static constexpr int MAX_EXPONENT = 0x7FFF;
static constexpr int MAX_BIASED_EXPONENT = 0x7FFF;
static constexpr StorageType MIN_SUBNORMAL = StorageType(1);
// Subnormal numbers include the implicit bit in x86 long double formats.
static constexpr StorageType MAX_SUBNORMAL =
(StorageType(1) << FRACTION_LEN) - 1;
static constexpr StorageType MIN_NORMAL = (StorageType(3) << FRACTION_LEN);
static constexpr StorageType MAX_NORMAL =
(StorageType(MAX_EXPONENT - 1) << (FRACTION_LEN + 1)) |
(StorageType(MAX_BIASED_EXPONENT - 1) << (FRACTION_LEN + 1)) |
(StorageType(1) << FRACTION_LEN) | MAX_SUBNORMAL;

StorageType bits;
Expand Down Expand Up @@ -154,12 +154,12 @@ template <> struct FPBits<long double> : private FloatProperties<long double> {
}

LIBC_INLINE constexpr bool is_inf() const {
return get_biased_exponent() == MAX_EXPONENT && get_mantissa() == 0 &&
get_implicit_bit() == 1;
return get_biased_exponent() == MAX_BIASED_EXPONENT &&
get_mantissa() == 0 && get_implicit_bit() == 1;
}

LIBC_INLINE constexpr bool is_nan() const {
if (get_biased_exponent() == MAX_EXPONENT) {
if (get_biased_exponent() == MAX_BIASED_EXPONENT) {
return (get_implicit_bit() == 0) || get_mantissa() != 0;
} else if (get_biased_exponent() != 0) {
return get_implicit_bit() == 0;
Expand All @@ -168,7 +168,7 @@ template <> struct FPBits<long double> : private FloatProperties<long double> {
}

LIBC_INLINE constexpr bool is_inf_or_nan() const {
return (get_biased_exponent() == MAX_EXPONENT) ||
return (get_biased_exponent() == MAX_BIASED_EXPONENT) ||
(get_biased_exponent() != 0 && get_implicit_bit() == 0);
}

Expand All @@ -180,7 +180,7 @@ template <> struct FPBits<long double> : private FloatProperties<long double> {

LIBC_INLINE static constexpr long double inf(bool sign = false) {
FPBits<long double> bits(0.0l);
bits.set_biased_exponent(MAX_EXPONENT);
bits.set_biased_exponent(MAX_BIASED_EXPONENT);
bits.set_implicit_bit(1);
if (sign) {
bits.set_sign(true);
Expand All @@ -192,7 +192,7 @@ template <> struct FPBits<long double> : private FloatProperties<long double> {

LIBC_INLINE static constexpr long double build_nan(StorageType v) {
FPBits<long double> bits(0.0l);
bits.set_biased_exponent(MAX_EXPONENT);
bits.set_biased_exponent(MAX_BIASED_EXPONENT);
bits.set_implicit_bit(1);
bits.set_mantissa(v);
return bits;
Expand Down
4 changes: 2 additions & 2 deletions libc/src/__support/high_precision_decimal.h
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Expand Up @@ -344,8 +344,8 @@ class HighPrecisionDecimal {
int64_t temp_exponent = static_cast<int64_t>(this->decimal_point) +
static_cast<int64_t>(add_to_exponent);

// Theoretically these numbers should be MAX_EXPONENT for long double,
// but that should be ~16,000 which is much less than 1 << 30.
// Theoretically these numbers should be MAX_BIASED_EXPONENT for long
// double, but that should be ~16,000 which is much less than 1 << 30.
if (temp_exponent > (1 << 30)) {
temp_exponent = (1 << 30);
} else if (temp_exponent < -(1 << 30)) {
Expand Down
26 changes: 13 additions & 13 deletions libc/src/__support/str_to_float.h
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Expand Up @@ -338,7 +338,7 @@ simple_decimal_conversion(const char *__restrict numStart,
// float, return inf.
if (hpd.get_decimal_point() > 0 &&
exp10_to_exp2(hpd.get_decimal_point() - 1) > FloatProp::EXP_BIAS) {
output.num = {0, fputil::FPBits<T>::MAX_EXPONENT};
output.num = {0, fputil::FPBits<T>::MAX_BIASED_EXPONENT};
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Contributor Author

@gchatelet gchatelet Dec 19, 2023 •
edited
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@michaelrj-google What are the semantics for exponent in

llvm-project/libc/src/__support/str_to_float.h

Lines 31 to 34 in ab41ea4

template <class T> struct ExpandedFloat {
typename fputil::FPBits<T>::StorageType mantissa;
int32_t exponent;
};

Is it biased (aka unsigned) or regular exponent?

output.error = ERANGE;
return output;
}
Expand Down Expand Up @@ -388,8 +388,8 @@ simple_decimal_conversion(const char *__restrict numStart,
exp2 += FloatProp::EXP_BIAS;

// Handle the exponent being too large (and return inf).
if (exp2 >= FPBits::MAX_EXPONENT) {
output.num = {0, FPBits::MAX_EXPONENT};
if (exp2 >= FPBits::MAX_BIASED_EXPONENT) {
output.num = {0, FPBits::MAX_BIASED_EXPONENT};
output.error = ERANGE;
return output;
}
Expand Down Expand Up @@ -424,7 +424,7 @@ simple_decimal_conversion(const char *__restrict numStart,
// Check if this rounding causes exp2 to go out of range and make the result
// INF. If this is the case, then finalMantissa and exp2 are already the
// correct values for an INF result.
if (exp2 >= FPBits::MAX_EXPONENT) {
if (exp2 >= FPBits::MAX_BIASED_EXPONENT) {
output.error = ERANGE;
}
}
Expand Down Expand Up @@ -658,7 +658,7 @@ decimal_exp_to_float(ExpandedFloat<T> init_num, const char *__restrict numStart,
// float, return inf. These bounds are relatively loose, but are mostly
// serving as a first pass. Some close numbers getting through is okay.
if (exp10 > get_upper_bound<T>()) {
output.num = {0, FPBits::MAX_EXPONENT};
output.num = {0, FPBits::MAX_BIASED_EXPONENT};
output.error = ERANGE;
return output;
}
Expand Down Expand Up @@ -920,10 +920,10 @@ decimal_string_to_float(const char *__restrict src, const char DECIMAL_POINT,

// If the result is in the valid range, then we use it. The valid range is
// also within the int32 range, so this prevents overflow issues.
if (temp_exponent > FPBits::MAX_EXPONENT) {
exponent = FPBits::MAX_EXPONENT;
} else if (temp_exponent < -FPBits::MAX_EXPONENT) {
exponent = -FPBits::MAX_EXPONENT;
if (temp_exponent > FPBits::MAX_BIASED_EXPONENT) {
exponent = FPBits::MAX_BIASED_EXPONENT;
} else if (temp_exponent < -FPBits::MAX_BIASED_EXPONENT) {
exponent = -FPBits::MAX_BIASED_EXPONENT;
} else {
exponent = static_cast<int32_t>(temp_exponent);
}
Expand Down Expand Up @@ -1034,10 +1034,10 @@ hexadecimal_string_to_float(const char *__restrict src,

// If the result is in the valid range, then we use it. The valid range is
// also within the int32 range, so this prevents overflow issues.
if (temp_exponent > FPBits::MAX_EXPONENT) {
exponent = FPBits::MAX_EXPONENT;
} else if (temp_exponent < -FPBits::MAX_EXPONENT) {
exponent = -FPBits::MAX_EXPONENT;
if (temp_exponent > FPBits::MAX_BIASED_EXPONENT) {
exponent = FPBits::MAX_BIASED_EXPONENT;
} else if (temp_exponent < -FPBits::MAX_BIASED_EXPONENT) {
exponent = -FPBits::MAX_BIASED_EXPONENT;
} else {
exponent = static_cast<int32_t>(temp_exponent);
}
Expand Down
11 changes: 6 additions & 5 deletions libc/test/src/math/LdExpTest.h
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,8 @@ class LdExpTestTemplate : public LIBC_NAMESPACE::testing::Test {
}

void testOverflow(LdExpFunc func) {
NormalFloat x(FPBits::MAX_EXPONENT - 10, NormalFloat::ONE + 0xF00BA, 0);
NormalFloat x(FPBits::MAX_BIASED_EXPONENT - 10, NormalFloat::ONE + 0xF00BA,
0);
for (int32_t exp = 10; exp < 100; ++exp) {
ASSERT_FP_EQ(inf, func(T(x), exp));
ASSERT_FP_EQ(neg_inf, func(-T(x), exp));
Expand Down Expand Up @@ -125,25 +126,25 @@ class LdExpTestTemplate : public LIBC_NAMESPACE::testing::Test {
// Start with a normal number high exponent but pass a very low number for
// exp. The result should be a subnormal number.
x = NormalFloat(FPBits::EXP_BIAS, NormalFloat::ONE, 0);
int exp = -FPBits::MAX_EXPONENT - 5;
int exp = -FPBits::MAX_BIASED_EXPONENT - 5;
T result = func(x, exp);
FPBits result_bits(result);
ASSERT_FALSE(result_bits.is_zero());
// Verify that the result is indeed subnormal.
ASSERT_EQ(result_bits.get_biased_exponent(), uint16_t(0));
// But if the exp is so less that normalization leads to zero, then
// the result should be zero.
result = func(x, -FPBits::MAX_EXPONENT - FPBits::FRACTION_LEN - 5);
result = func(x, -FPBits::MAX_BIASED_EXPONENT - FPBits::FRACTION_LEN - 5);
ASSERT_TRUE(FPBits(result).is_zero());

// Start with a subnormal number but pass a very high number for exponent.
// The result should not be infinity.
x = NormalFloat(-FPBits::EXP_BIAS + 1, NormalFloat::ONE >> 10, 0);
exp = FPBits::MAX_EXPONENT + 5;
exp = FPBits::MAX_BIASED_EXPONENT + 5;
ASSERT_FALSE(FPBits(func(x, exp)).is_inf());
// But if the exp is large enough to oversome than the normalization shift,
// then it should result in infinity.
exp = FPBits::MAX_EXPONENT + 15;
exp = FPBits::MAX_BIASED_EXPONENT + 15;
ASSERT_FP_EQ(func(x, exp), inf);
}
};
Expand Down
11 changes: 6 additions & 5 deletions libc/test/src/math/smoke/LdExpTest.h
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Expand Up @@ -58,7 +58,8 @@ class LdExpTestTemplate : public LIBC_NAMESPACE::testing::Test {
}

void testOverflow(LdExpFunc func) {
NormalFloat x(FPBits::MAX_EXPONENT - 10, NormalFloat::ONE + 0xF00BA, 0);
NormalFloat x(FPBits::MAX_BIASED_EXPONENT - 10, NormalFloat::ONE + 0xF00BA,
0);
for (int32_t exp = 10; exp < 100; ++exp) {
ASSERT_FP_EQ(inf, func(T(x), exp));
ASSERT_FP_EQ(neg_inf, func(-T(x), exp));
Expand Down Expand Up @@ -125,25 +126,25 @@ class LdExpTestTemplate : public LIBC_NAMESPACE::testing::Test {
// Start with a normal number high exponent but pass a very low number for
// exp. The result should be a subnormal number.
x = NormalFloat(FPBits::EXP_BIAS, NormalFloat::ONE, 0);
int exp = -FPBits::MAX_EXPONENT - 5;
int exp = -FPBits::MAX_BIASED_EXPONENT - 5;
T result = func(x, exp);
FPBits result_bits(result);
ASSERT_FALSE(result_bits.is_zero());
// Verify that the result is indeed subnormal.
ASSERT_EQ(result_bits.get_biased_exponent(), uint16_t(0));
// But if the exp is so less that normalization leads to zero, then
// the result should be zero.
result = func(x, -FPBits::MAX_EXPONENT - FPBits::FRACTION_LEN - 5);
result = func(x, -FPBits::MAX_BIASED_EXPONENT - FPBits::FRACTION_LEN - 5);
ASSERT_TRUE(FPBits(result).is_zero());

// Start with a subnormal number but pass a very high number for exponent.
// The result should not be infinity.
x = NormalFloat(-FPBits::EXP_BIAS + 1, NormalFloat::ONE >> 10, 0);
exp = FPBits::MAX_EXPONENT + 5;
exp = FPBits::MAX_BIASED_EXPONENT + 5;
ASSERT_FALSE(FPBits(func(x, exp)).is_inf());
// But if the exp is large enough to oversome than the normalization shift,
// then it should result in infinity.
exp = FPBits::MAX_EXPONENT + 15;
exp = FPBits::MAX_BIASED_EXPONENT + 15;
ASSERT_FP_EQ(func(x, exp), inf);
}
};
Expand Down
2 changes: 1 addition & 1 deletion libc/test/utils/FPUtil/x86_long_double_test.cpp
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Expand Up @@ -22,7 +22,7 @@ TEST(LlvmLibcX86LongDoubleTest, is_nan) {
constexpr uint32_t COUNT = 100'000;

FPBits bits(0.0l);
bits.set_biased_exponent(FPBits::MAX_EXPONENT);
bits.set_biased_exponent(FPBits::MAX_BIASED_EXPONENT);
for (unsigned int i = 0; i < COUNT; ++i) {
// If exponent has the max value and the implicit bit is 0,
// then the number is a NaN for all values of mantissa.
Expand Down