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[libc] clean up FPUtil long doubles

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Add quietNaNMask consts to FloatProperties and make LongDoubleBitsX86
clear the extra bits that aren't set when initializing with an 80 bit
long double.

Reviewed By: sivachandra, lntue

Differential Revision: https://reviews.llvm.org/D113625
This commit is contained in:
Michael Jones
2021-11-10 16:11:18 -08:00
parent 420ad7ce7d
commit 18da0c0a28
2 changed files with 21 additions and 1 deletions
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16
libc/src/__support/FPUtil/FloatProperties.h
View File

@@ -80,6 +80,12 @@ template <> struct FloatProperties<long double> {
FloatProperties<double>::exponentMask;
static constexpr uint32_t exponentBias =
FloatProperties<double>::exponentBias;
// 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 BitsType quietNaNMask =
FloatProperties<double>::quietNaNMask;
};
#elif defined(SPECIAL_X86_LONG_DOUBLE)
// Properties for numbers represented in 80 bits long double on non-Windows x86
@@ -99,6 +105,11 @@ template <> struct FloatProperties<long double> {
static constexpr BitsType exponentMask = ((BitsType(1) << exponentWidth) - 1)
<< (mantissaWidth + 1);
static constexpr uint32_t exponentBias = 16383;
// 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 BitsType quietNaNMask = BitsType(1) << (mantissaWidth - 1);
};
#else
// Properties for numbers represented in 128 bits long double on non x86
@@ -117,6 +128,11 @@ template <> struct FloatProperties<long double> {
<< (exponentWidth + mantissaWidth);
static constexpr BitsType exponentMask = ~(signMask | mantissaMask);
static constexpr uint32_t exponentBias = 16383;
// 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 BitsType quietNaNMask = BitsType(1) << (mantissaWidth - 1);
};
#endif

6
libc/src/__support/FPUtil/LongDoubleBitsX86.h
View File

@@ -89,7 +89,11 @@ template <> union FPBits<long double> {
template <typename XType,
cpp::EnableIfType<cpp::IsSame<long double, XType>::Value, int> = 0>
explicit FPBits(XType x) : val(x) {}
explicit FPBits(XType x) : val(x) {
// bits starts uninitialized, and setting it to a long double only
// overwrites the first 80 bits. This clears those upper bits.
bits = bits & ((UIntType(1) << 80) - 1);
}
template <typename XType,
cpp::EnableIfType<cpp::IsSame<XType, UIntType>::Value, int> = 0>