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add support for m68k 80-bit long double variant 

since x86 and m68k are the only archs with 80-bit long double and each
has mandatory endianness, select the variant via endianness.
differences are minor: apparently just byte order and representation
of infinities. the m68k format is not well-documented anywhere I could
find, so if other differences are found they may require additional
changes later.
This commit is contained in:
Rich Felker 2018-06-14 11:00:58 -04:00
parent d5e55ba332
commit 18f02c42a2
2 changed files with 21 additions and 2 deletions
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11
src/internal/libm.h
View File

@ -28,6 +28,17 @@ union ldshape {
uint16_t se;
} i;
};
#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384 && __BYTE_ORDER == __BIG_ENDIAN
/* This is the m68k variant of 80-bit long double, and this definition only works
* on archs where the alignment requirement of uint64_t is <= 4. */
union ldshape {
long double f;
struct {
uint16_t se;
uint16_t pad;
uint64_t m;
} i;
};
#elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384 && __BYTE_ORDER == __LITTLE_ENDIAN
union ldshape {
long double f;

12
src/math/__fpclassifyl.c
View File

@ -13,10 +13,18 @@ int __fpclassifyl(long double x)
int msb = u.i.m>>63;
if (!e && !msb)
return u.i.m ? FP_SUBNORMAL : FP_ZERO;
if (e == 0x7fff) {
/* The x86 variant of 80-bit extended precision only admits
* one representation of each infinity, with the mantissa msb
* necessarily set. The version with it clear is invalid/nan.
* The m68k variant, however, allows either, and tooling uses
* the version with it clear. */
if (__BYTE_ORDER == __LITTLE_ENDIAN && !msb)
return FP_NAN;
return u.i.m << 1 ? FP_NAN : FP_INFINITE;
}
if (!msb)
return FP_NAN;
if (e == 0x7fff)
return u.i.m << 1 ? FP_NAN : FP_INFINITE;
return FP_NORMAL;
}
#elif LDBL_MANT_DIG == 113 && LDBL_MAX_EXP == 16384