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libc: Add some missing bit-twiddly libm functions

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This commit is contained in:
K. Lange 2023-04-23 17:56:33 +09:00
parent 136cfe2b2e
commit ed40dc436e
2 changed files with 61 additions and 0 deletions
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5
base/usr/include/math.h
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@ -69,4 +69,9 @@ extern int fpclassify(double x);
#define isnan(x) (fpclassify(x) == FP_NAN)
#define isinf(x) (fpclassify(x) == FP_INFINITE)
extern float ceilf(float x);
extern double round(double x);
extern float roundf(float x);
extern long lroundf(float x);
_End_C_Header

56
libc/math/math.c
View File

@ -484,3 +484,59 @@ int fpclassify(double x) {
}
return FP_NORMAL;
}
double ceil(double x) {
union {
double asFloat;
uint64_t asInt;
} bits = {x};
int64_t exponent = ((bits.asInt >> 52) & 0x7FF) - 0x3ff;
uint64_t mantissa = (bits.asInt & 0xFffffFFFFffffULL);
if (exponent >= 52 || x == 0) return x;
if (exponent <= -1) return (bits.asInt >> 63) ? -0.0 : 1.0;
uint64_t mask = (0xfffffFFFFffffULL >> exponent);
if (!(mask & mantissa)) return x;
if (!(bits.asInt >> 63)) {
bits.asInt += mask;
}
bits.asInt &= ~mask;
return bits.asFloat;
}
double round(double x) {
union {
double asFloat;
uint64_t asInt;
} bits = {x};
int64_t exponent = ((bits.asInt >> 52) & 0x7FF) - 0x3ff;
uint64_t mantissa = (bits.asInt & 0xFffffFFFFffffULL);
if (exponent >= 52 || x == 0) return x;
if (exponent < -1) return (bits.asInt >> 63) ? -0.0 : 0.0;
if (exponent == -1) return x >= 0.5 ? 1.0 : (x <= -0.5 ? -1.0 : ((bits.asInt >> 63) ? -0.0 : 0.0));
uint64_t mask = 0xfffffFFFFffffULL >> exponent;
uint64_t a = mantissa & mask;
uint64_t b = mantissa & (mask >> 1);
if (a & ~b) {
bits.asInt += mask;
bits.asInt &= ~mask;
return bits.asFloat;
}
bits.asInt &= ~mask;
return bits.asFloat;
}
float ceilf(float x) {
return ceil(x);
}
float roundf(float x) {
return round(x);
}
long lroundf(float x) {
return round(x);
}