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frexpl: Support smaller long double of LDBL_MANT_DIG == 53. 

- Currently, frexpl() supports only the following cases.
    1) LDBL_MANT_DIG == 64 or 113
    2) 'long double' is equivalent to 'double'
  This patch add support for LDBL_MANT_DIG == 53.
This commit is contained in:
Takashi Yano 2021-12-02 18:51:21 +09:00
parent dbc7d28ba9
commit 34876c05a5
1 changed files with 42 additions and 12 deletions
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54
newlib/libm/common/frexpl.c
View File

@ -33,16 +33,42 @@ POSSIBILITY OF SUCH DAMAGE.
#include "local.h"
/* On platforms where long double is as wide as double. */
#if defined(_LDBL_EQ_DBL) || (LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024)
#if defined(_LDBL_EQ_DBL)
long double
frexpl (long double x, int *eptr)
{
return frexp(x, eptr);
}
#endif
#else /* !_DBL_EQ_DBL */
# if (LDBL_MANT_DIG == 53) /* 64-bit long double */
static const double scale = 0x1p54;
union ldbl {
long double x;
struct {
# ifdef __IEEE_LITTLE_ENDIAN /* for Intel CPU */
__uint32_t fracl;
__uint32_t frach:20;
__uint32_t exp:11;
__uint32_t sign:1;
# endif
# ifdef __IEEE_BIG_ENDIAN
__uint32_t sign:1;
__uint32_t exp:11;
__uint32_t frach:20;
# ifndef ___IEEE_BYTES_LITTLE_ENDIAN
# else /* ARMEL without __VFP_FP__ */
__uint32_t frach:20;
__uint32_t exp:11;
__uint32_t sign:1;
# endif
__uint32_t fracl;
# endif
} u32;
};
# elif (LDBL_MANT_DIG == 64) /* 80-bit long double */
static const double scale = 0x1p65;
#if (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
# if (LDBL_MANT_DIG == 64) /* 80-bit long double */
union ldbl {
long double x;
struct {
@ -68,7 +94,9 @@ union ldbl {
# endif
} u32;
};
# else /* LDBL_MANT_DIG == 113, 128-bit long double */
# elif (LDBL_MANT_DIG == 113) /* 128-bit long double */
static const double scale = 0x1p114;
union ldbl {
long double x;
struct {
@ -96,9 +124,11 @@ union ldbl {
# endif
} u32;
};
# else
# error Unsupported long double format.
# endif
static const double two114 = 0x1p114;
static const int scale_exp = LDBL_MANT_DIG + 1;
long double
frexpl (long double x, int *eptr)
@ -107,16 +137,16 @@ frexpl (long double x, int *eptr)
u.x = x;
int e = u.u32.exp;
*eptr = 0;
if (e == 0x7fff || x == 0)
if (e == (LDBL_MAX_EXP*2 - 1) || x == 0)
return x; /* inf,nan,0 */
if (e == 0) /* subnormal */
{
u.x *= two114;
u.x *= scale;
e = u.u32.exp;
*eptr -= 114;
*eptr -= scale_exp;
}
*eptr += e - 16382;
u.u32.exp = 0x3ffe; /* 0 */
*eptr += e - (LDBL_MAX_EXP - 2);
u.u32.exp = LDBL_MAX_EXP - 2; /* -1 */
return u.x;
}
#endif /* End of 80-bit or 128-bit long double */
#endif /* !_LDBL_EQ_DBL */