diff options
Diffstat (limited to 'sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c | 73 |
1 files changed, 61 insertions, 12 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c b/sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c index 8a2d45e2d8..90f2ded03f 100644 --- a/sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c +++ b/sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c @@ -31,19 +31,20 @@ long double __mpn_construct_long_double (mp_srcptr frac_ptr, int expt, int sign) { union ibm_extended_long_double u; - unsigned long hidden2, lzcount; + unsigned long lzcount; unsigned long long hi, lo; + int exponent2; u.ieee.negative = sign; u.ieee.negative2 = sign; u.ieee.exponent = expt + IBM_EXTENDED_LONG_DOUBLE_BIAS; - u.ieee.exponent2 = expt - 53 + IBM_EXTENDED_LONG_DOUBLE_BIAS; + u.ieee.exponent2 = 0; + exponent2 = expt - 53 + IBM_EXTENDED_LONG_DOUBLE_BIAS; #if BITS_PER_MP_LIMB == 32 /* The low order 53 bits (52 + hidden) go into the lower double */ lo = frac_ptr[0]; lo |= (frac_ptr[1] & ((1LL << (53 - 32)) - 1)) << 32; - hidden2 = (frac_ptr[1] >> (52 - 32)) & ((mp_limb_t) 1); /* The high order 53 bits (52 + hidden) go into the upper double */ hi = (frac_ptr[1] >> (53 - 32)) & ((1 << 11) - 1); hi |= ((unsigned long long) frac_ptr[2]) << 11; @@ -51,7 +52,6 @@ __mpn_construct_long_double (mp_srcptr frac_ptr, int expt, int sign) #elif BITS_PER_MP_LIMB == 64 /* The low order 53 bits (52 + hidden) go into the lower double */ lo = frac_ptr[0] & (((mp_limb_t) 1 << 53) - 1); - hidden2 = (frac_ptr[0] >> 52) & ((mp_limb_t) 1); /* The high order 53 bits (52 + hidden) go into the upper double */ hi = (frac_ptr[0] >> 53) & (((mp_limb_t) 1 << 11) - 1); hi |= (frac_ptr[1] << 11); @@ -59,14 +59,62 @@ __mpn_construct_long_double (mp_srcptr frac_ptr, int expt, int sign) #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for" #endif + if ((hi & (1LL << 52)) == 0 && (hi | lo) != 0) + { + /* denormal number */ + unsigned long long val = hi ? hi : lo; + + if (sizeof (val) == sizeof (long)) + lzcount = __builtin_clzl (val); + else if ((val >> 32) != 0) + lzcount = __builtin_clzl ((long) (val >> 32)); + else + lzcount = __builtin_clzl ((long) val) + 32; + if (hi) + lzcount = lzcount - 11; + else + lzcount = lzcount + 42; + + if (lzcount > u.ieee.exponent) + { + lzcount = u.ieee.exponent; + u.ieee.exponent = 0; + exponent2 -= lzcount; + } + else + { + u.ieee.exponent -= (lzcount - 1); + exponent2 -= (lzcount - 1); + } + + if (lzcount <= 53) + { + hi = (hi << lzcount) | (lo >> (53 - lzcount)); + lo = (lo << lzcount) & ((1LL << 53) - 1); + } + else + { + hi = lo << (lzcount - 53); + lo = 0; + } + } + if (lo != 0L) { /* hidden2 bit of low double controls rounding of the high double. - If hidden2 is '1' then round up hi and adjust lo (2nd mantissa) + If hidden2 is '1' and either the explicit mantissa is non-zero + or hi is odd, then round up hi and adjust lo (2nd mantissa) plus change the sign of the low double to compensate. */ - if (hidden2) + if ((lo & (1LL << 52)) != 0 + && ((hi & 1) != 0 || (lo & ((1LL << 52) - 1)))) { hi++; + if ((hi & ((1LL << 52) - 1)) == 0) + { + if ((hi & (1LL << 53)) != 0) + hi -= 1LL << 52; + u.ieee.exponent++; + } u.ieee.negative2 = !sign; lo = (1LL << 53) - lo; } @@ -85,17 +133,18 @@ __mpn_construct_long_double (mp_srcptr frac_ptr, int expt, int sign) if (lzcount > 0) { lo = lo << lzcount; - u.ieee.exponent2 = u.ieee.exponent2 - lzcount; + exponent2 = exponent2 - lzcount; } + if (exponent2 > 0) + u.ieee.exponent2 = exponent2; + else + lo >>= 1 - exponent2; } else - { - u.ieee.negative2 = 0; - u.ieee.exponent2 = 0; - } + u.ieee.negative2 = 0; u.ieee.mantissa3 = lo & 0xffffffffLL; - u.ieee.mantissa2 = (lo >> 32) & 0xffffff; + u.ieee.mantissa2 = (lo >> 32) & 0xfffff; u.ieee.mantissa1 = hi & 0xffffffffLL; u.ieee.mantissa0 = (hi >> 32) & ((1LL << (LDBL_MANT_DIG - 86)) - 1); |