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[libc] add EXP_MAT_MASK to x87 long double

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A previous patch added the constant EXP_MANT_MASK to the FloatProperties
for other types of long double. This patch adds it to the special 80-bit
x87 long double.

Reviewed By: lntue

Differential Revision: https://reviews.llvm.org/D127550
This commit is contained in:
Michael Jones 2022-06-10 16:09:18 -07:00
parent 7e7021ca1a
commit 02f4affe2d
1 changed files with 11 additions and 0 deletions
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11
libc/src/__support/FPUtil/FloatProperties.h
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@ -109,16 +109,27 @@ template <> struct FloatProperties<long double> {
"Unexpected size of 'long double' type.");
static constexpr uint32_t BIT_WIDTH = (sizeof(BitsType) * 8) - 48;
static constexpr BitsType FULL_WIDTH_MASK = ((BitsType(1) << BIT_WIDTH) - 1);
static constexpr uint32_t MANTISSA_WIDTH = 63;
static constexpr uint32_t EXPONENT_WIDTH = 15;
static constexpr BitsType MANTISSA_MASK = (BitsType(1) << MANTISSA_WIDTH) - 1;
// 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);
static constexpr BitsType SIGN_MASK =
BitsType(1) << (EXPONENT_WIDTH + MANTISSA_WIDTH + 1);
static constexpr BitsType EXPONENT_MASK =
((BitsType(1) << EXPONENT_WIDTH) - 1) << (MANTISSA_WIDTH + 1);
static constexpr uint32_t EXPONENT_BIAS = 16383;
static constexpr BitsType EXP_MANT_MASK =
MANTISSA_MASK + EXPLICIT_BIT_MASK + EXPONENT_MASK;
static_assert(EXP_MANT_MASK == (~SIGN_MASK & FULL_WIDTH_MASK),
"Exponent and mantissa masks are not as expected.");
// If a number x is a NAN, then it is a quiet NAN if:
// QuietNaNMask & bits(x) != 0
// Else, it is a signalling NAN.