b6bc9d72f6
This is step 4 of https://discourse.llvm.org/t/rfc-customizable-namespace-to-allow-testing-the-libc-when-the-system-libc-is-also-llvms-libc/73079
200 lines
7.8 KiB
C++
200 lines
7.8 KiB
C++
//===-- Properties of floating point numbers --------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_SRC___SUPPORT_FPUTIL_FLOATPROPERTIES_H
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#define LLVM_LIBC_SRC___SUPPORT_FPUTIL_FLOATPROPERTIES_H
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#include "PlatformDefs.h"
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#include "src/__support/UInt128.h"
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#include <stdint.h>
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namespace LIBC_NAMESPACE {
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namespace fputil {
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template <typename T> struct FloatProperties {};
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template <> struct FloatProperties<float> {
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typedef uint32_t BitsType;
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static_assert(sizeof(BitsType) == sizeof(float),
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"Unexpected size of 'float' type.");
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static constexpr uint32_t BIT_WIDTH = sizeof(BitsType) * 8;
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static constexpr uint32_t MANTISSA_WIDTH = 23;
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// The mantissa precision includes the implicit bit.
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static constexpr uint32_t MANTISSA_PRECISION = MANTISSA_WIDTH + 1;
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static constexpr uint32_t EXPONENT_WIDTH = 8;
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static constexpr BitsType MANTISSA_MASK = (BitsType(1) << MANTISSA_WIDTH) - 1;
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static constexpr BitsType SIGN_MASK = BitsType(1)
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<< (EXPONENT_WIDTH + MANTISSA_WIDTH);
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static constexpr BitsType EXPONENT_MASK = ~(SIGN_MASK | MANTISSA_MASK);
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static constexpr uint32_t EXPONENT_BIAS = 127;
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static constexpr BitsType EXP_MANT_MASK = MANTISSA_MASK + EXPONENT_MASK;
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static_assert(EXP_MANT_MASK == ~SIGN_MASK,
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"Exponent and mantissa masks are not as expected.");
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// If a number x is a NAN, then it is a quiet NAN if:
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// QuietNaNMask & bits(x) != 0
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// Else, it is a signalling NAN.
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static constexpr BitsType QUIET_NAN_MASK = 0x00400000U;
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};
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template <> struct FloatProperties<double> {
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typedef uint64_t BitsType;
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static_assert(sizeof(BitsType) == sizeof(double),
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"Unexpected size of 'double' type.");
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static constexpr uint32_t BIT_WIDTH = sizeof(BitsType) * 8;
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static constexpr uint32_t MANTISSA_WIDTH = 52;
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static constexpr uint32_t MANTISSA_PRECISION = MANTISSA_WIDTH + 1;
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static constexpr uint32_t EXPONENT_WIDTH = 11;
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static constexpr BitsType MANTISSA_MASK = (BitsType(1) << MANTISSA_WIDTH) - 1;
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static constexpr BitsType SIGN_MASK = BitsType(1)
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<< (EXPONENT_WIDTH + MANTISSA_WIDTH);
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static constexpr BitsType EXPONENT_MASK = ~(SIGN_MASK | MANTISSA_MASK);
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static constexpr uint32_t EXPONENT_BIAS = 1023;
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static constexpr BitsType EXP_MANT_MASK = MANTISSA_MASK + EXPONENT_MASK;
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static_assert(EXP_MANT_MASK == ~SIGN_MASK,
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"Exponent and mantissa masks are not as expected.");
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// If a number x is a NAN, then it is a quiet NAN if:
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// QuietNaNMask & bits(x) != 0
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// Else, it is a signalling NAN.
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static constexpr BitsType QUIET_NAN_MASK = 0x0008000000000000ULL;
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};
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#if defined(LONG_DOUBLE_IS_DOUBLE)
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// Properties for numbers represented in 64 bits long double on Windows
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// platform.
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template <> struct FloatProperties<long double> {
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typedef uint64_t BitsType;
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static_assert(sizeof(BitsType) == sizeof(double),
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"Unexpected size of 'double' type.");
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static constexpr uint32_t BIT_WIDTH = FloatProperties<double>::BIT_WIDTH;
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static constexpr uint32_t MANTISSA_WIDTH =
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FloatProperties<double>::MANTISSA_WIDTH;
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static constexpr uint32_t MANTISSA_PRECISION = MANTISSA_WIDTH + 1;
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static constexpr uint32_t EXPONENT_WIDTH =
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FloatProperties<double>::EXPONENT_WIDTH;
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static constexpr BitsType MANTISSA_MASK =
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FloatProperties<double>::MANTISSA_MASK;
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static constexpr BitsType SIGN_MASK = FloatProperties<double>::SIGN_MASK;
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static constexpr BitsType EXPONENT_MASK =
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FloatProperties<double>::EXPONENT_MASK;
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static constexpr uint32_t EXPONENT_BIAS =
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FloatProperties<double>::EXPONENT_BIAS;
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static constexpr BitsType EXP_MANT_MASK =
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FloatProperties<double>::EXP_MANT_MASK;
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static_assert(EXP_MANT_MASK == ~SIGN_MASK,
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"Exponent and mantissa masks are not as expected.");
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// If a number x is a NAN, then it is a quiet NAN if:
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// QuietNaNMask & bits(x) != 0
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// Else, it is a signalling NAN.
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static constexpr BitsType QUIET_NAN_MASK =
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FloatProperties<double>::QUIET_NAN_MASK;
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};
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#elif defined(SPECIAL_X86_LONG_DOUBLE)
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// Properties for numbers represented in 80 bits long double on non-Windows x86
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// platforms.
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template <> struct FloatProperties<long double> {
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typedef UInt128 BitsType;
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static_assert(sizeof(BitsType) == sizeof(long double),
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"Unexpected size of 'long double' type.");
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static constexpr uint32_t BIT_WIDTH = (sizeof(BitsType) * 8) - 48;
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static constexpr BitsType FULL_WIDTH_MASK = ((BitsType(1) << BIT_WIDTH) - 1);
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static constexpr uint32_t MANTISSA_WIDTH = 63;
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static constexpr uint32_t MANTISSA_PRECISION = MANTISSA_WIDTH + 1;
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static constexpr uint32_t EXPONENT_WIDTH = 15;
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static constexpr BitsType MANTISSA_MASK = (BitsType(1) << MANTISSA_WIDTH) - 1;
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// The x86 80 bit float represents the leading digit of the mantissa
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// explicitly. This is the mask for that bit.
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static constexpr BitsType EXPLICIT_BIT_MASK = (BitsType(1) << MANTISSA_WIDTH);
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static constexpr BitsType SIGN_MASK =
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BitsType(1) << (EXPONENT_WIDTH + MANTISSA_WIDTH + 1);
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static constexpr BitsType EXPONENT_MASK =
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((BitsType(1) << EXPONENT_WIDTH) - 1) << (MANTISSA_WIDTH + 1);
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static constexpr uint32_t EXPONENT_BIAS = 16383;
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static constexpr BitsType EXP_MANT_MASK =
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MANTISSA_MASK | EXPLICIT_BIT_MASK | EXPONENT_MASK;
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static_assert(EXP_MANT_MASK == (~SIGN_MASK & FULL_WIDTH_MASK),
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"Exponent and mantissa masks are not as expected.");
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// If a number x is a NAN, then it is a quiet NAN if:
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// QuietNaNMask & bits(x) != 0
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// Else, it is a signalling NAN.
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static constexpr BitsType QUIET_NAN_MASK = BitsType(1)
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<< (MANTISSA_WIDTH - 1);
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};
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#else
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// Properties for numbers represented in 128 bits long double on non x86
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// platform.
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template <> struct FloatProperties<long double> {
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typedef UInt128 BitsType;
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static_assert(sizeof(BitsType) == sizeof(long double),
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"Unexpected size of 'long double' type.");
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static constexpr uint32_t BIT_WIDTH = sizeof(BitsType) << 3;
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static constexpr uint32_t MANTISSA_WIDTH = 112;
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static constexpr uint32_t MANTISSA_PRECISION = MANTISSA_WIDTH + 1;
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static constexpr uint32_t EXPONENT_WIDTH = 15;
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static constexpr BitsType MANTISSA_MASK = (BitsType(1) << MANTISSA_WIDTH) - 1;
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static constexpr BitsType SIGN_MASK = BitsType(1)
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<< (EXPONENT_WIDTH + MANTISSA_WIDTH);
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static constexpr BitsType EXPONENT_MASK = ~(SIGN_MASK | MANTISSA_MASK);
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static constexpr uint32_t EXPONENT_BIAS = 16383;
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static constexpr BitsType EXP_MANT_MASK = MANTISSA_MASK | EXPONENT_MASK;
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static_assert(EXP_MANT_MASK == ~SIGN_MASK,
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"Exponent and mantissa masks are not as expected.");
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// If a number x is a NAN, then it is a quiet NAN if:
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// QuietNaNMask & bits(x) != 0
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// Else, it is a signalling NAN.
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static constexpr BitsType QUIET_NAN_MASK = BitsType(1)
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<< (MANTISSA_WIDTH - 1);
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};
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#endif
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// Define the float type corresponding to the BitsType.
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template <typename BitsType> struct FloatType;
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template <> struct FloatType<uint32_t> {
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static_assert(sizeof(uint32_t) == sizeof(float),
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"Unexpected size of 'float' type.");
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typedef float Type;
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};
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template <> struct FloatType<uint64_t> {
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static_assert(sizeof(uint64_t) == sizeof(double),
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"Unexpected size of 'double' type.");
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typedef double Type;
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};
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template <typename BitsType>
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using FloatTypeT = typename FloatType<BitsType>::Type;
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} // namespace fputil
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} // namespace LIBC_NAMESPACE
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#endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_FLOATPROPERTIES_H
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