old code was correct only if the result was stored (without the
excess precision) or musl was compiled with -ffloat-store.
(see note 160 in n1570.pdf section 6.8.6.4)
double scalbn(double x, int n)
{
+ /* make sure result is stored as double on overflow or underflow */
+ volatile double z;
double scale;
if (n > 1023) {
if (n > 1023) {
x *= 0x1p1023;
n -= 1023;
- if (n > 1023)
- return x * 0x1p1023;
+ if (n > 1023) {
+ z = x * 0x1p1023;
+ return z;
+ }
}
} else if (n < -1022) {
x *= 0x1p-1022;
if (n < -1022) {
x *= 0x1p-1022;
n += 1022;
- if (n < -1022)
- return x * 0x1p-1022;
+ if (n < -1022) {
+ z = x * 0x1p-1022;
+ return z;
+ }
}
}
INSERT_WORDS(scale, (uint32_t)(0x3ff+n)<<20, 0);
- return x * scale;
+ z = x * scale;
+ return z;
}
float scalbnf(float x, int n)
{
+ /* make sure result is stored as double on overflow or underflow */
+ volatile float z;
float scale;
if (n > 127) {
if (n > 127) {
x *= 0x1p127f;
n -= 127;
- if (n > 127)
- return x * 0x1p127f;
+ if (n > 127) {
+ z = x * 0x1p127f;
+ return z;
+ }
}
} else if (n < -126) {
x *= 0x1p-126f;
if (n < -126) {
x *= 0x1p-126f;
n += 126;
- if (n < -126)
- return x * 0x1p-126f;
+ if (n < -126) {
+ z = x * 0x1p-126f;
+ return z;
+ }
}
}
SET_FLOAT_WORD(scale, (uint32_t)(0x7f+n)<<23);
- return x * scale;
+ z = x * scale;
+ return z;
}