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| author | Szabolcs Nagy <nsz@port70.net> | 2014-10-29 00:34:37 +0100 |
|---|---|---|
| committer | Rich Felker <dalias@aerifal.cx> | 2014-10-31 11:35:40 -0400 |
| commit | 0ce946cf808274c2d6e5419b139e130c8ad4bd30 (patch) | |
| tree | e6614e756dde0afbcd48e38916d0208fed93ece1 /src/math/roundl.c | |
| parent | 79ca86094d70f43252b683c3a3ccb572d462cf28 (diff) | |
| download | musl-0ce946cf808274c2d6e5419b139e130c8ad4bd30.tar.gz musl-0ce946cf808274c2d6e5419b139e130c8ad4bd30.tar.xz musl-0ce946cf808274c2d6e5419b139e130c8ad4bd30.zip | |
math: use the rounding idiom consistently
the idiomatic rounding of x is n = x + toint - toint; where toint is either 1/EPSILON (x is non-negative) or 1.5/EPSILON (x may be negative and nearest rounding mode is assumed) and EPSILON is according to the evaluation precision (the type of toint is not very important, because single precision float can represent the 1/EPSILON of ieee binary128). in case of FLT_EVAL_METHOD!=0 this avoids a useless store to double or float precision, and the long double code became cleaner with 1/LDBL_EPSILON instead of ifdefs for toint. __rem_pio2f and __rem_pio2 functions slightly changed semantics: on i386 a double-rounding is avoided so close to half-way cases may get evaluated differently eg. as sin(pi/4-eps) instead of cos(pi/4+eps)
Diffstat (limited to 'src/math/roundl.c')
| -rw-r--r-- | src/math/roundl.c | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/src/math/roundl.c b/src/math/roundl.c index 8f3f28b3..f4ff6820 100644 --- a/src/math/roundl.c +++ b/src/math/roundl.c @@ -6,11 +6,9 @@ long double roundl(long double x) return round(x); } #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384 -#if LDBL_MANT_DIG == 64 -#define TOINT 0x1p63 -#elif LDBL_MANT_DIG == 113 -#define TOINT 0x1p112 -#endif + +static const long double toint = 1/LDBL_EPSILON; + long double roundl(long double x) { union ldshape u = {x}; @@ -22,10 +20,10 @@ long double roundl(long double x) if (u.i.se >> 15) x = -x; if (e < 0x3fff-1) { - FORCE_EVAL(x + TOINT); + FORCE_EVAL(x + toint); return 0*u.f; } - y = x + TOINT - TOINT - x; + y = x + toint - toint - x; if (y > 0.5) y = y + x - 1; else if (y <= -0.5) |