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[libc][math] Add initial support for C23 float128 math functions, starting with copysignf128. (#71731)
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19 files changed

+310
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19 files changed

+310
-15
lines changed

‎libc/CMakeLists.txt

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@@ -245,6 +245,7 @@ option(LIBC_INCLUDE_DOCS "Build the libc documentation." ${LLVM_INCLUDE_DOCS})
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include(CMakeParseArguments)
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include(LLVMLibCCheckCpuFeatures)
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include(CheckCompilerFeatures)
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include(LLVMLibCRules)
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if(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/entrypoints.txt")

‎libc/cmake/modules/CheckCompilerFeatures.cmake

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# ------------------------------------------------------------------------------
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# Compiler features definition and flags
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# ------------------------------------------------------------------------------
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# Initialize ALL_COMPILER_FEATURES as empty list.
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set(ALL_COMPILER_FEATURES "float128")
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# Making sure ALL_COMPILER_FEATURES is sorted.
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list(SORT ALL_COMPILER_FEATURES)
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# Function to check whether the compiler supports the provided set of features.
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# Usage:
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# compiler_supports(
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# <output variable>
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# <list of cpu features>
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# )
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function(compiler_supports output_var features)
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_intersection(var "${LIBC_CPU_FEATURES}" "${features}")
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if("${var}" STREQUAL "${features}")
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set(${output_var} TRUE PARENT_SCOPE)
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else()
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unset(${output_var} PARENT_SCOPE)
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endif()
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endfunction()
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# ------------------------------------------------------------------------------
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# Internal helpers and utilities.
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# ------------------------------------------------------------------------------
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# Computes the intersection between two lists.
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function(_intersection output_var list1 list2)
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foreach(element IN LISTS list1)
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if("${list2}" MATCHES "(^|;)${element}(;|$)")
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list(APPEND tmp "${element}")
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endif()
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endforeach()
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set(${output_var} ${tmp} PARENT_SCOPE)
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endfunction()
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set(AVAILABLE_COMPILER_FEATURES "")
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# Try compile a C file to check if flag is supported.
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set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
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foreach(feature IN LISTS ALL_COMPILER_FEATURES)
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try_compile(
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has_feature
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${CMAKE_CURRENT_BINARY_DIR}/compiler_features
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SOURCES ${LIBC_SOURCE_DIR}/cmake/modules/compiler_features/check_${feature}.cpp
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COMPILE_DEFINITIONS -I${LIBC_SOURCE_DIR} ${LIBC_COMPILE_OPTIONS_NATIVE}
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)
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if(has_feature)
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list(APPEND AVAILABLE_COMPILER_FEATURES ${feature})
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if(${feature} STREQUAL "float128")
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set(LIBC_COMPILER_HAS_FLOAT128 TRUE)
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endif()
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endif()
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endforeach()
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message(STATUS "Compiler features available: ${AVAILABLE_COMPILER_FEATURES}")

‎libc/cmake/modules/compiler_features/check_float128.cpp

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#include "src/__support/macros/properties/compiler.h"
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#ifndef LIBC_COMPILER_HAS_FLOAT128
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#error unsupported
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#endif

‎libc/config/linux/x86_64/entrypoints.txt

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@@ -360,6 +360,13 @@ set(TARGET_LIBM_ENTRYPOINTS
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libc.src.math.truncl
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)
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if(LIBC_COMPILER_HAS_FLOAT128)
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list(APPEND TARGET_LIBM_ENTRYPOINTS
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# math.h C23 _Float128 entrypoints
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libc.src.math.copysignf128
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)
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endif()
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if(LLVM_LIBC_FULL_BUILD)
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list(APPEND TARGET_LIBC_ENTRYPOINTS
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# assert.h entrypoints

‎libc/docs/math/index.rst

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@@ -96,9 +96,9 @@ Implementation Status
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* To check math functions enabled for embedded system:
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- `barebone-aarch32 <https://github.com/llvm/llvm-project/tree/main/libc/config/baremetal/arm/entrypoints.txt>`_
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- `baremetal-aarch32 <https://github.com/llvm/llvm-project/tree/main/libc/config/baremetal/arm/entrypoints.txt>`_
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- barebone-riscv32 - to be added
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- baremetal-riscv32 - to be added
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Basic Operations
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----------------
@@ -120,6 +120,8 @@ Basic Operations
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+--------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
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| copysignl | |check| | |check| | | |check| | |check| | | | |check| | | | | |
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+--------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
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| copysignf128 | |check| | |check| | | | | | | | | | | |
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+--------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
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| fabs | |check| | |check| | |check| | |check| | |check| | | | |check| | |check| | | | |
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+--------------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+---------+
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| fabsf | |check| | |check| | |check| | |check| | |check| | | | |check| | |check| | | | |

‎libc/spec/spec.td

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@@ -50,6 +50,9 @@ def DoubleType : NamedType<"double">;
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def LongDoubleType : NamedType<"long double">;
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def CharType : NamedType<"char">;
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// TODO: Add compatibility layer to use C23 type _Float128 if possible.
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def Float128Type : NamedType<"__float128">
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// Common types
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def VoidPtr : PtrType<VoidType>;
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def VoidPtrPtr : PtrType<VoidPtr>;

‎libc/spec/stdc.td

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@@ -358,6 +358,7 @@ def StdC : StandardSpec<"stdc"> {
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FunctionSpec<"copysign", RetValSpec<DoubleType>, [ArgSpec<DoubleType>, ArgSpec<DoubleType>]>,
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FunctionSpec<"copysignf", RetValSpec<FloatType>, [ArgSpec<FloatType>, ArgSpec<FloatType>]>,
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FunctionSpec<"copysignl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>, ArgSpec<LongDoubleType>]>,
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FunctionSpec<"copysignf128", RetValSpec<Float128Type>, [ArgSpec<Float128Type>, ArgSpec<Float128Type>]>,
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FunctionSpec<"ceil", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
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FunctionSpec<"ceilf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,

‎libc/src/__support/CPP/type_traits/is_floating_point.h

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@@ -11,6 +11,7 @@
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#include "src/__support/CPP/type_traits/is_same.h"
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#include "src/__support/CPP/type_traits/remove_cv.h"
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#include "src/__support/macros/attributes.h"
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#include "src/__support/macros/properties/compiler.h"
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namespace LIBC_NAMESPACE::cpp {
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@@ -23,8 +24,13 @@ template <typename T> struct is_floating_point {
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}
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public:
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#if defined(LIBC_COMPILER_HAS_FLOAT128)
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LIBC_INLINE_VAR static constexpr bool value =
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__is_unqualified_any_of<T, float, double, long double, float128>();
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#else
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LIBC_INLINE_VAR static constexpr bool value =
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__is_unqualified_any_of<T, float, double, long double>();
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#endif // LIBC_COMPILER_HAS_FLOAT128
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};
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template <typename T>
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LIBC_INLINE_VAR constexpr bool is_floating_point_v =

‎libc/src/__support/FPUtil/FloatProperties.h

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@@ -175,6 +175,38 @@ template <> struct FloatProperties<long double> {
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};
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#endif
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#if (defined(LIBC_COMPILER_HAS_FLOAT128) && \
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!defined(LIBC_FLOAT128_IS_LONG_DOUBLE))
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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<float128> {
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typedef UInt128 BitsType;
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static_assert(sizeof(BitsType) == sizeof(float128),
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"Unexpected size of 'float128' 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 // LIBC_COMPILER_HAS_FLOAT128
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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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‎libc/src/__support/macros/properties/compiler.h

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@@ -21,4 +21,25 @@
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#define LIBC_COMPILER_IS_MSC
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#endif
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// Check compiler features
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#if defined(FLT128_MANT_DIG)
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// C23 _Float128 type is available.
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#define LIBC_COMPILER_HAS_FLOAT128
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#define LIBC_FLOAT128_IS_C23
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using float128 = _Float128;
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#elif defined(__SIZEOF_FLOAT128__)
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// Builtin __float128 is available.
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#define LIBC_COMPILER_HAS_FLOAT128
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#define LIBC_FLOAT128_IS_BUILTIN
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using float128 = __float128;
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#elif (defined(__linux__) && defined(__aarch64__))
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// long double on Linux aarch64 is 128-bit floating point.
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#define LIBC_COMPILER_HAS_FLOAT128
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#define LIBC_FLOAT128_IS_LONG_DOUBLE
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using float128 = long double;
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#endif
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#endif // LLVM_LIBC_SRC___SUPPORT_MACROS_PROPERTIES_COMPILER_H

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