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math: use float_t and double_t in scalbnf and scalbn 

remove STRICT_ASSIGN (c99 semantics is assumed) and use the conventional
union to prepare the scaling factor (so libm.h is no longer needed)
This commit is contained in:
Szabolcs Nagy 2013-09-04 15:52:54 +00:00
parent 34660d73bd
commit 2eaed464e2
2 changed files with 20 additions and 16 deletions
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18
src/math/scalbn.c
View File

@ -1,29 +1,31 @@
#include "libm.h"
#include <math.h>
#include <stdint.h>
double scalbn(double x, int n)
{
double scale;
union {double f; uint64_t i;} u;
double_t y = x;
if (n > 1023) {
x *= 0x1p1023;
y *= 0x1p1023;
n -= 1023;
if (n > 1023) {
x *= 0x1p1023;
y *= 0x1p1023;
n -= 1023;
if (n > 1023)
n = 1023;
}
} else if (n < -1022) {
x *= 0x1p-1022;
y *= 0x1p-1022;
n += 1022;
if (n < -1022) {
x *= 0x1p-1022;
y *= 0x1p-1022;
n += 1022;
if (n < -1022)
n = -1022;
}
}
INSERT_WORDS(scale, (uint32_t)(0x3ff+n)<<20, 0);
STRICT_ASSIGN(double, x, x * scale);
u.i = (uint64_t)(0x3ff+n)<<52;
x = y * u.f;
return x;
}

18
src/math/scalbnf.c
View File

@ -1,29 +1,31 @@
#include "libm.h"
#include <math.h>
#include <stdint.h>
float scalbnf(float x, int n)
{
float scale;
union {float f; uint32_t i;} u;
float_t y = x;
if (n > 127) {
x *= 0x1p127f;
y *= 0x1p127f;
n -= 127;
if (n > 127) {
x *= 0x1p127f;
y *= 0x1p127f;
n -= 127;
if (n > 127)
n = 127;
}
} else if (n < -126) {
x *= 0x1p-126f;
y *= 0x1p-126f;
n += 126;
if (n < -126) {
x *= 0x1p-126f;
y *= 0x1p-126f;
n += 126;
if (n < -126)
n = -126;
}
}
SET_FLOAT_WORD(scale, (uint32_t)(0x7f+n)<<23);
STRICT_ASSIGN(float, x, x * scale);
u.i = (uint32_t)(0x7f+n)<<23;
x = y * u.f;
return x;
}