libm.h

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//
// libm.h
//
//      Partly imported from musl libc
//
// Support header for musl math code.
//
// SPDX-License-Identifier: MIT
//
 
#pragma once
 
#include <stdint.h>
#include <float.h>
#include <math.h>
 
// Define _STATIC_ASSERT for compatibility with legacy CRT headers
#ifndef _STATIC_ASSERT
#define _STATIC_ASSERT(expr) extern char (*__static_assert__(void)) [(expr) ? 1 : -1]
#endif
 
// Make sure the sizes are correct
_STATIC_ASSERT(sizeof(float) == 4);
_STATIC_ASSERT(sizeof(double) == 8);
_STATIC_ASSERT(sizeof(long double) == 8);
 
_Check_return_ int __cdecl _isnanf(_In_ float _X);
#define isnan _isnan
#define isnanf _isnanf
 
// musl has this in math.h
static __inline uint32_t __FLOAT_BITS(float __f)
{
    union {float __f; uint32_t __i;} __u;
    __u.__f = __f;
    return __u.__i;
}
 
static __inline uint64_t __DOUBLE_BITS(double __f)
{
    union {double __f; uint64_t __i;} __u;
    __u.__f = __f;
    return __u.__i;
}
 
#define signbit(x) \
    ((sizeof(x) == sizeof(float)) ? (int)(__FLOAT_BITS(x)>>31) : \
                                    (int)(__DOUBLE_BITS(x)>>63))
 
static inline void fp_force_evalf(float x)
{
    volatile float y;
    y = x;
    (void)y;
}
 
static inline void fp_force_eval(double x)
{
    volatile double y;
    y = x;
    (void)y;
}
 
#define FORCE_EVAL(x) do {                    \
    if (sizeof(x) == sizeof(float)) {         \
        fp_force_evalf(x);                    \
    } else {                                  \
        fp_force_eval(x);                     \
    }                                         \
} while(0)