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[libc][NFC] Remove remaining specializations in FloatProperties #75165

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Merged
merged 1 commit into from
Dec 12, 2023
Merged

[libc][NFC] Remove remaining specializations in FloatProperties #75165

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50 changes: 13 additions & 37 deletions libc/src/__support/FPUtil/FloatProperties.h
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Original file line number Diff line number Diff line change
Expand Up @@ -90,13 +90,12 @@ template <typename T, size_t count> static constexpr T mask_trailing_ones() {
return count == 0 ? 0 : ((~T(0)) >> (t_bits - count));
}

// Derives more properties from 'FPBaseProperties' above.
// This class serves as a halfway point between 'FPBaseProperties' and
// 'FPProperties' below.
} // namespace internal

template <FPType fp_type>
struct FPCommonProperties : private FPBaseProperties<fp_type> {
struct FPProperties : public internal::FPBaseProperties<fp_type> {
private:
using UP = FPBaseProperties<fp_type>;
using UP = internal::FPBaseProperties<fp_type>;
using UP::EXP_BITS;
using UP::SIG_BITS;
using UP::TOTAL_BITS;
Expand All @@ -123,15 +122,15 @@ struct FPCommonProperties : private FPBaseProperties<fp_type> {

// Masks
LIBC_INLINE_VAR static constexpr UIntType SIG_MASK =
mask_trailing_ones<UIntType, SIG_BITS>() << SIG_MASK_SHIFT;
internal::mask_trailing_ones<UIntType, SIG_BITS>() << SIG_MASK_SHIFT;
LIBC_INLINE_VAR static constexpr UIntType EXP_MASK =
mask_trailing_ones<UIntType, EXP_BITS>() << EXP_MASK_SHIFT;
internal::mask_trailing_ones<UIntType, EXP_BITS>() << EXP_MASK_SHIFT;
// Trailing underscore on SIGN_MASK_ is temporary - it will be removed
// once we can replace the public part below with the private one.
LIBC_INLINE_VAR static constexpr UIntType SIGN_MASK_ =
mask_trailing_ones<UIntType, SIGN_BITS>() << SIGN_MASK_SHIFT;
internal::mask_trailing_ones<UIntType, SIGN_BITS>() << SIGN_MASK_SHIFT;
LIBC_INLINE_VAR static constexpr UIntType FP_MASK =
mask_trailing_ones<UIntType, TOTAL_BITS>();
internal::mask_trailing_ones<UIntType, TOTAL_BITS>();
static_assert((SIG_MASK & EXP_MASK & SIGN_MASK_) == 0, "masks disjoint");
static_assert((SIG_MASK | EXP_MASK | SIGN_MASK_) == FP_MASK, "masks cover");

Expand All @@ -140,19 +139,19 @@ struct FPCommonProperties : private FPBaseProperties<fp_type> {
}

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

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

// The number of bits after the decimal dot when the number if in normal form.
LIBC_INLINE_VAR static constexpr int FRACTION_BITS =
UP::ENCODING == FPEncoding::X86_ExtendedPrecision ? SIG_BITS - 1
: SIG_BITS;
UP::ENCODING == internal::FPEncoding::X86_ExtendedPrecision ? SIG_BITS - 1
: SIG_BITS;

public:
// Public facing API to keep the change local to this file.
Expand All @@ -163,7 +162,7 @@ struct FPCommonProperties : private FPBaseProperties<fp_type> {
LIBC_INLINE_VAR static constexpr uint32_t MANTISSA_PRECISION =
MANTISSA_WIDTH + 1;
LIBC_INLINE_VAR static constexpr BitsType MANTISSA_MASK =
mask_trailing_ones<UIntType, MANTISSA_WIDTH>();
internal::mask_trailing_ones<UIntType, MANTISSA_WIDTH>();
LIBC_INLINE_VAR static constexpr uint32_t EXPONENT_WIDTH = EXP_BITS;
LIBC_INLINE_VAR static constexpr uint32_t EXPONENT_BIAS =
static_cast<uint32_t>(EXP_BIAS);
Expand All @@ -177,29 +176,6 @@ struct FPCommonProperties : private FPBaseProperties<fp_type> {
static constexpr BitsType QUIET_NAN_MASK = QNAN_MASK;
};

} // namespace internal

template <FPType fp_type>
struct FPProperties : public internal::FPCommonProperties<fp_type> {};

// ----------------
// Work In Progress
// ----------------
// The 'FPProperties' template specializations below are being slowly replaced
// with properties from 'FPCommonProperties' above. Once specializations are
// empty, 'FPProperties' declaration can be fully replace with
// 'FPCommonProperties' implementation.

// Properties for numbers represented in 80 bits long double on non-Windows x86
// platforms.
template <>
struct FPProperties<FPType::X86_Binary80>
: public internal::FPCommonProperties<FPType::X86_Binary80> {
// The x86 80 bit float represents the leading digit of the mantissa
// explicitly. This is the mask for that bit.
static constexpr BitsType EXPLICIT_BIT_MASK = (BitsType(1) << MANTISSA_WIDTH);
};

//-----------------------------------------------------------------------------
template <typename FP> LIBC_INLINE static constexpr FPType get_fp_type() {
if constexpr (cpp::is_same_v<FP, float> && __FLT_MANT_DIG__ == 24)
Expand Down
6 changes: 5 additions & 1 deletion libc/src/__support/FPUtil/x86_64/LongDoubleBits.h
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Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,11 @@ template <> struct FPBits<long double> {
}

LIBC_INLINE constexpr UIntType get_explicit_mantissa() const {
return bits & (FloatProp::MANTISSA_MASK | FloatProp::EXPLICIT_BIT_MASK);
// The x86 80 bit float represents the leading digit of the mantissa
// explicitly. This is the mask for that bit.
constexpr UIntType EXPLICIT_BIT_MASK =
(UIntType(1) << FloatProp::MANTISSA_WIDTH);
return bits & (FloatProp::MANTISSA_MASK | EXPLICIT_BIT_MASK);
}

LIBC_INLINE constexpr void set_biased_exponent(UIntType expVal) {
Expand Down