diff options
Diffstat (limited to 'gcc/real.c')
| -rw-r--r-- | gcc/real.c | 95 |
1 files changed, 95 insertions, 0 deletions
@@ -5010,6 +5010,101 @@ real_round (REAL_VALUE_TYPE *r, format_helper fmt, real_convert (r, fmt, r); } +/* Return true including 0 if integer part of R is even, else return + false. The function is not valid for rvc_inf and rvc_nan classes. */ + +bool +is_even (REAL_VALUE_TYPE *r) +{ + gcc_assert (r->cl != rvc_inf); + gcc_assert (r->cl != rvc_nan); + + if (r->cl == rvc_zero) + return true; + + /* For (-1,1), number is even. */ + if (REAL_EXP (r) <= 0) + return true; + + /* Check lowest bit, if not set, return true. */ + else if (REAL_EXP (r) <= SIGNIFICAND_BITS) + { + unsigned int n = SIGNIFICAND_BITS - REAL_EXP (r); + int w = n / HOST_BITS_PER_LONG; + + unsigned long num = ((unsigned long)1 << (n % HOST_BITS_PER_LONG)); + + if ((r->sig[w] & num) == 0) + return true; + } + else + return true; + + return false; +} + +/* Return true if R is halfway between two integers, else return + false. The function is not valid for rvc_inf and rvc_nan classes. */ + +bool +is_halfway_below (const REAL_VALUE_TYPE *r) +{ + gcc_assert (r->cl != rvc_inf); + gcc_assert (r->cl != rvc_nan); + int i; + + if (r->cl == rvc_zero) + return false; + + /* For numbers (-0.5,0) and (0,0.5). */ + if (REAL_EXP (r) < 0) + return false; + + else if (REAL_EXP (r) < SIGNIFICAND_BITS) + { + unsigned int n = SIGNIFICAND_BITS - REAL_EXP (r) - 1; + int w = n / HOST_BITS_PER_LONG; + + for (i = 0; i < w; ++i) + if (r->sig[i] != 0) + return false; + + unsigned long num = ((unsigned long)1 << (n % HOST_BITS_PER_LONG)); + + if (((r->sig[w] & num) != 0) && ((r->sig[w] & (num-1)) == 0)) + return true; + } + return false; +} + +/* Round X to nearest integer, rounding halfway cases towards even. */ + +void +real_roundeven (REAL_VALUE_TYPE *r, format_helper fmt, + const REAL_VALUE_TYPE *x) +{ + if (is_halfway_below (x)) + { + /* Special case as -0.5 rounds to -0.0 and + similarly +0.5 rounds to +0.0. */ + if (REAL_EXP (x) == 0) + { + *r = *x; + clear_significand_below (r, SIGNIFICAND_BITS); + } + else + { + do_add (r, x, &dconsthalf, x->sign); + if (!is_even (r)) + do_add (r, r, &dconstm1, x->sign); + } + if (fmt) + real_convert (r, fmt, r); + } + else + real_round (r, fmt, x); +} + /* Set the sign of R to the sign of X. */ void |