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[libc][NFC] Make QNAN_MASK an implementation detail of FPBits #75945

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Merged
merged 3 commits into from
Dec 19, 2023
Merged

[libc][NFC] Make QNAN_MASK an implementation detail of FPBits #75945

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f8bcc8e
[libc][NFC] Make `QNAN_MASK` an implementation detail
gchatelet Dec 19, 2023
9a2aacb
Make the mask protected in FloatProperties
gchatelet Dec 19, 2023
b6c01a6
rename constants as suggested
gchatelet Dec 19, 2023
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5 changes: 4 additions & 1 deletion libc/src/__support/FPUtil/FPBits.h
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,11 @@ template <typename T> struct FPBits : private FloatProperties<T> {
using FloatProperties<T>::EXP_LEN;
using FloatProperties<T>::FRACTION_MASK;
using FloatProperties<T>::FRACTION_LEN;

private:
using FloatProperties<T>::QUIET_NAN_MASK;

public:
using FloatProperties<T>::SIGN_MASK;

// Reinterpreting bits as an integer value and interpreting the bits of an
Expand Down Expand Up @@ -90,7 +94,6 @@ template <typename T> struct FPBits : private FloatProperties<T> {
"Data type and integral representation have different sizes.");

static constexpr int MAX_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);
Expand Down
26 changes: 13 additions & 13 deletions libc/src/__support/FPUtil/FloatProperties.h
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Expand Up @@ -143,16 +143,6 @@ struct FPProperties : public internal::FPBaseProperties<fp_type> {
return StorageType(1) << position;
}

LIBC_INLINE_VAR static constexpr StorageType QNAN_MASK =
UP::ENCODING == internal::FPEncoding::X86_ExtendedPrecision
? bit_at(SIG_LEN - 1) | bit_at(SIG_LEN - 2) // 0b1100...
: bit_at(SIG_LEN - 1); // 0b1000...

LIBC_INLINE_VAR static constexpr StorageType SNAN_MASK =
UP::ENCODING == internal::FPEncoding::X86_ExtendedPrecision
? bit_at(SIG_LEN - 1) | bit_at(SIG_LEN - 3) // 0b1010...
: bit_at(SIG_LEN - 2); // 0b0100...

public:
// The number of bits after the decimal dot when the number is in normal form.
LIBC_INLINE_VAR static constexpr int FRACTION_LEN =
Expand All @@ -165,10 +155,20 @@ struct FPProperties : public internal::FPBaseProperties<fp_type> {
LIBC_INLINE_VAR static constexpr StorageType EXP_MANT_MASK =
EXP_MASK | SIG_MASK;

protected:
// If a number x is a NAN, then it is a quiet NAN if:
// QuietNaNMask & bits(x) != 0
// Else, it is a signalling NAN.
static constexpr StorageType QUIET_NAN_MASK = QNAN_MASK;
// QUIET_NAN_MASK & bits(x) != 0
LIBC_INLINE_VAR static constexpr StorageType QUIET_NAN_MASK =
UP::ENCODING == internal::FPEncoding::X86_ExtendedPrecision
? bit_at(SIG_LEN - 1) | bit_at(SIG_LEN - 2) // 0b1100...
: bit_at(SIG_LEN - 1); // 0b1000...

// If a number x is a NAN, then it is a signalling NAN if:
// SIGNALING_NAN_MASK & bits(x) != 0
LIBC_INLINE_VAR static constexpr StorageType SIGNALING_NAN_MASK =
UP::ENCODING == internal::FPEncoding::X86_ExtendedPrecision
? bit_at(SIG_LEN - 1) | bit_at(SIG_LEN - 3) // 0b1010...
: bit_at(SIG_LEN - 2); // 0b0100...
};

//-----------------------------------------------------------------------------
Expand Down
4 changes: 4 additions & 0 deletions libc/src/__support/FPUtil/x86_64/LongDoubleBits.h
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Expand Up @@ -35,7 +35,11 @@ template <> struct FPBits<long double> : private FloatProperties<long double> {
using FloatProperties<long double>::EXP_LEN;
using FloatProperties<long double>::FRACTION_MASK;
using FloatProperties<long double>::FRACTION_LEN;

private:
using FloatProperties<long double>::QUIET_NAN_MASK;

public:
using FloatProperties<long double>::SIGN_MASK;

static constexpr int MAX_EXPONENT = 0x7FFF;
Expand Down
1 change: 0 additions & 1 deletion libc/src/__support/str_to_float.h
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Expand Up @@ -1167,7 +1167,6 @@ LIBC_INLINE StrToNumResult<T> strtofloatingpoint(const char *__restrict src) {
index = left_paren;
}
}
nan_mantissa |= fputil::FloatProperties<T>::QUIET_NAN_MASK;
if (result.get_sign()) {
result = FPBits(result.build_quiet_nan(nan_mantissa));
result.set_sign(true);
Expand Down