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lib/libm_dbl: Add round.c source code.

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This code is imported from musl, to match existing code in libm_dbl.

The file is also added to the build in stm32/Makefile.  It's not needed by
the core code but, similar to c5cc64175b,
allows round() to be used by user C modules or board extensions.
This commit is contained in:
Zoltán Vörös 2020-02-15 19:28:56 +01:00 committed by Damien George
parent a853fff838
commit 27767aafa2
2 changed files with 36 additions and 0 deletions
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35
lib/libm_dbl/round.c Normal file
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@ -0,0 +1,35 @@
#include "libm.h"
#if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
#define EPS DBL_EPSILON
#elif FLT_EVAL_METHOD==2
#define EPS LDBL_EPSILON
#endif
static const double_t toint = 1/EPS;
double round(double x)
{
union {double f; uint64_t i;} u = {x};
int e = u.i >> 52 & 0x7ff;
double_t y;
if (e >= 0x3ff+52)
return x;
if (u.i >> 63)
x = -x;
if (e < 0x3ff-1) {
/* raise inexact if x!=0 */
FORCE_EVAL(x + toint);
return 0*u.f;
}
y = x + toint - toint - x;
if (y > 0.5)
y = y + x - 1;
else if (y <= -0.5)
y = y + x + 1;
else
y = y + x;
if (u.i >> 63)
y = -y;
return y;
}

1
ports/stm32/Makefile
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@ -191,6 +191,7 @@ LIBM_SRC_C = $(addprefix lib/libm_dbl/,\
nearbyint.c \
pow.c \
rint.c \
round.c \
scalbn.c \
sin.c \
sinh.c \