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Differential D127550

[libc] add EXP_MAT_MASK to x87 long double
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Authored by michaelrj on Jun 10 2022, 4:10 PM.

Details

Reviewers
sivachandra
lntue
Commits
rG02f4affe2d85: [libc] add EXP_MAT_MASK to x87 long double
Summary

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.

Diff Detail

Event Timeline

michaelrj created this revision.Jun 10 2022, 4:10 PM
Herald added projects: Restricted Project, Restricted Project. · View Herald TranscriptJun 10 2022, 4:10 PM
Herald added subscribers: libc-commits, ecnelises, tschuett. · View Herald Transcript
michaelrj requested review of this revision.Jun 10 2022, 4:10 PM
Harbormaster completed remote builds in B169187: Diff 436075.Jun 10 2022, 4:16 PM
lntue accepted this revision.Jun 10 2022, 4:20 PM
This revision is now accepted and ready to land.Jun 10 2022, 4:20 PM
Closed by commit rG02f4affe2d85: [libc] add EXP_MAT_MASK to x87 long double (authored by michaelrj). · Explain WhyJun 10 2022, 4:26 PM
This revision was automatically updated to reflect the committed changes.
michaelrj added a commit: rG02f4affe2d85: [libc] add EXP_MAT_MASK to x87 long double.

Revision Contents

PathSize
libc/
src/
__support/
FPUtil/
11 lines

Diff 436078

libc/src/__support/FPUtil/FloatProperties.h

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// Properties for numbers represented in 80 bits long double on non-Windows x86 // Properties for numbers represented in 80 bits long double on non-Windows x86
// platforms. // platforms.
template <> struct FloatProperties<long double> { template <> struct FloatProperties<long double> {
typedef __uint128_t BitsType; typedef __uint128_t BitsType;
static_assert(sizeof(BitsType) == sizeof(long double), static_assert(sizeof(BitsType) == sizeof(long double),
"Unexpected size of 'long double' type."); "Unexpected size of 'long double' type.");
static constexpr uint32_t BIT_WIDTH = (sizeof(BitsType) * 8) - 48; 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 MANTISSA_WIDTH = 63;
static constexpr uint32_t EXPONENT_WIDTH = 15; static constexpr uint32_t EXPONENT_WIDTH = 15;
static constexpr BitsType MANTISSA_MASK = (BitsType(1) << MANTISSA_WIDTH) - 1; 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 = static constexpr BitsType SIGN_MASK =
BitsType(1) << (EXPONENT_WIDTH + MANTISSA_WIDTH + 1); BitsType(1) << (EXPONENT_WIDTH + MANTISSA_WIDTH + 1);
static constexpr BitsType EXPONENT_MASK = static constexpr BitsType EXPONENT_MASK =
((BitsType(1) << EXPONENT_WIDTH) - 1) << (MANTISSA_WIDTH + 1); ((BitsType(1) << EXPONENT_WIDTH) - 1) << (MANTISSA_WIDTH + 1);
static constexpr uint32_t EXPONENT_BIAS = 16383; 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: // If a number x is a NAN, then it is a quiet NAN if:
// QuietNaNMask & bits(x) != 0 // QuietNaNMask & bits(x) != 0
// Else, it is a signalling NAN. // Else, it is a signalling NAN.
static constexpr BitsType QUIET_NAN_MASK = BitsType(1) static constexpr BitsType QUIET_NAN_MASK = BitsType(1)
<< (MANTISSA_WIDTH - 1); << (MANTISSA_WIDTH - 1);
}; };
#else #else
// Properties for numbers represented in 128 bits long double on non x86 // Properties for numbers represented in 128 bits long double on non x86
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