Skip to content

V
V8
Commit b01622c3 authored by bmeurer's avatar bmeurer Committed by Commit bot
Browse files
Options

[ieee754] Import ANSIfied msun log from FreeBSD. 

Instead of manually adopting the ancient fdlibm sources, import the msun
versions from FreeBSD instead, which were already adopted to ANSI C.
Still under the same copyright.

R=yangguo@chromium.org
BUG=v8:5065,v8:5086

Review-Url: https://codereview.chromium.org/2065473002
Cr-Commit-Position: refs/heads/master@{#36913}
parent 8e1ccba3
Hide whitespace changes
Inline Side-by-side
Showing with 174 additions and 72 deletions
src/base/ieee754.cc
View file @ b01622c3
......@@ -26,52 +26,142 @@ namespace ieee754 {
namespace {
union Float64 {
double v;
uint64_t w;
struct {
/* Fix-up typedefs so we can use the FreeBSD msun code mostly unmodified. */
#if V8_OS_WIN
typedef uint32_t u_int32_t;
typedef uint64_t u_int64_t;
#endif
/* Disable "potential divide by 0" warning in Visual Studio compiler. */
#if V8_CC_MSVC
#pragma warning(disable : 4723)
#endif
/*
* The original fdlibm code used statements like:
* n0 = ((*(int*)&one)>>29)^1; * index of high word *
* ix0 = *(n0+(int*)&x); * high word of x *
* ix1 = *((1-n0)+(int*)&x); * low word of x *
* to dig two 32 bit words out of the 64 bit IEEE floating point
* value. That is non-ANSI, and, moreover, the gcc instruction
* scheduler gets it wrong. We instead use the following macros.
* Unlike the original code, we determine the endianness at compile
* time, not at run time; I don't see much benefit to selecting
* endianness at run time.
*/
/*
* A union which permits us to convert between a double and two 32 bit
* ints.
*/
#if V8_TARGET_LITTLE_ENDIAN
uint32_t lw;
uint32_t hw;
typedef union {
double value;
struct {
u_int32_t lsw;
u_int32_t msw;
} parts;
struct {
u_int64_t w;
} xparts;
} ieee_double_shape_type;
#else
uint32_t hw;
uint32_t lw;
typedef union {
double value;
struct {
u_int32_t msw;
u_int32_t lsw;
} parts;
struct {
u_int64_t w;
} xparts;
} ieee_double_shape_type;
#endif
} words;
};
// Extract the less significant 32-bit word from a double.
V8_INLINE uint32_t extractLowWord32(double v) {
Float64 f;
f.v = v;
return f.words.lw;
}
// Extract the most significant 32-bit word from a double.
V8_INLINE uint32_t extractHighWord32(double v) {
Float64 f;
f.v = v;
return f.words.hw;
}
/* Get two 32 bit ints from a double. */
// Insert the most significant 32-bit word into a double.
V8_INLINE double insertHighWord32(double v, uint32_t hw) {
Float64 f;
f.v = v;
f.words.hw = hw;
return f.v;
}
#define EXTRACT_WORDS(ix0, ix1, d) \
do { \
ieee_double_shape_type ew_u; \
ew_u.value = (d); \
(ix0) = ew_u.parts.msw; \
(ix1) = ew_u.parts.lsw; \
} while (0)
/* Get a 64-bit int from a double. */
#define EXTRACT_WORD64(ix, d) \
do { \
ieee_double_shape_type ew_u; \
ew_u.value = (d); \
(ix) = ew_u.xparts.w; \
} while (0)
/* Get the more significant 32 bit int from a double. */
#define GET_HIGH_WORD(i, d) \
do { \
ieee_double_shape_type gh_u; \
gh_u.value = (d); \
(i) = gh_u.parts.msw; \
} while (0)
/* Get the less significant 32 bit int from a double. */
#define GET_LOW_WORD(i, d) \
do { \
ieee_double_shape_type gl_u; \
gl_u.value = (d); \
(i) = gl_u.parts.lsw; \
} while (0)
/* Set a double from two 32 bit ints. */
#define INSERT_WORDS(d, ix0, ix1) \
do { \
ieee_double_shape_type iw_u; \
iw_u.parts.msw = (ix0); \
iw_u.parts.lsw = (ix1); \
(d) = iw_u.value; \
} while (0)
/* Set a double from a 64-bit int. */
#define INSERT_WORD64(d, ix) \
do { \
ieee_double_shape_type iw_u; \
iw_u.xparts.w = (ix); \
(d) = iw_u.value; \
} while (0)
/* Set the more significant 32 bits of a double from an int. */
#define SET_HIGH_WORD(d, v) \
do { \
ieee_double_shape_type sh_u; \
sh_u.value = (d); \
sh_u.parts.msw = (v); \
(d) = sh_u.value; \
} while (0)
double const kLn2Hi = 6.93147180369123816490e-01; // 3fe62e42 fee00000
double const kLn2Lo = 1.90821492927058770002e-10; // 3dea39ef 35793c76
double const kTwo54 = 1.80143985094819840000e+16; // 43500000 00000000
double const kLg1 = 6.666666666666735130e-01; // 3FE55555 55555593
double const kLg2 = 3.999999999940941908e-01; // 3FD99999 9997FA04
double const kLg3 = 2.857142874366239149e-01; // 3FD24924 94229359
double const kLg4 = 2.222219843214978396e-01; // 3FCC71C5 1D8E78AF
double const kLg5 = 1.818357216161805012e-01; // 3FC74664 96CB03DE
double const kLg6 = 1.531383769920937332e-01; // 3FC39A09 D078C69F
double const kLg7 = 1.479819860511658591e-01; // 3FC2F112 DF3E5244
/* Set the less significant 32 bits of a double from an int. */
#define SET_LOW_WORD(d, v) \
do { \
ieee_double_shape_type sl_u; \
sl_u.value = (d); \
sl_u.parts.lsw = (v); \
(d) = sl_u.value; \
} while (0)
} // namespace
......@@ -126,44 +216,58 @@ double const kLg7 = 1.479819860511658591e-01; // 3FC2F112 DF3E5244
* to produce the hexadecimal values shown.
*/
double log(double x) {
double hfsq, f, s, z, r, w, t1, t2, dk;
int32_t k = 0, i, j;
int32_t hx = extractHighWord32(x);
uint32_t lx = extractLowWord32(x);
static const double /* -- */
ln2_hi = 6.93147180369123816490e-01, /* 3fe62e42 fee00000 */
ln2_lo = 1.90821492927058770002e-10, /* 3dea39ef 35793c76 */
two54 = 1.80143985094819840000e+16, /* 43500000 00000000 */
Lg1 = 6.666666666666735130e-01, /* 3FE55555 55555593 */
Lg2 = 3.999999999940941908e-01, /* 3FD99999 9997FA04 */
Lg3 = 2.857142874366239149e-01, /* 3FD24924 94229359 */
Lg4 = 2.222219843214978396e-01, /* 3FCC71C5 1D8E78AF */
Lg5 = 1.818357216161805012e-01, /* 3FC74664 96CB03DE */
Lg6 = 1.531383769920937332e-01, /* 3FC39A09 D078C69F */
Lg7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */
static const double zero = 0.0;
static volatile double vzero = 0.0;
double hfsq, f, s, z, R, w, t1, t2, dk;
int32_t k, hx, i, j;
u_int32_t lx;
EXTRACT_WORDS(hx, lx, x);
k = 0;
if (hx < 0x00100000) { /* x < 2**-1022 */
if (((hx & 0x7fffffff) | lx) == 0) {
return -std::numeric_limits<double>::infinity();
}
if (hx < 0) {
return std::numeric_limits<double>::quiet_NaN();
}
if (((hx & 0x7fffffff) | lx) == 0)
return -two54 / vzero; /* log(+-0)=-inf */
if (hx < 0) return (x - x) / zero; /* log(-#) = NaN */
k -= 54;
x *= kTwo54; /* subnormal number, scale up x */
hx = extractHighWord32(x);
x *= two54; /* subnormal number, scale up x */
GET_HIGH_WORD(hx, x);
}
if (hx >= 0x7ff00000) return x + x;
k += (hx >> 20) - 1023;
hx &= 0x000fffff;
i = (hx + 0x95f64) & 0x100000;
x = insertHighWord32(x, hx | (i ^ 0x3ff00000)); /* normalize x or x/2 */
SET_HIGH_WORD(x, hx | (i ^ 0x3ff00000)); /* normalize x or x/2 */
k += (i >> 20);
f = x - 1.0;
if ((0x000fffff & (2 + hx)) < 3) { /* -2**-20 <= f < 2**-20 */
if (f == 0.0) {
if (f == zero) {
if (k == 0) {
return 0.0;
return zero;
} else {
dk = static_cast<double>(k);
return dk * kLn2Hi + dk * kLn2Lo;
return dk * ln2_hi + dk * ln2_lo;
}
}
r = f * f * (0.5 - 0.33333333333333333 * f);
R = f * f * (0.5 - 0.33333333333333333 * f);
if (k == 0) {
return f - r;
return f - R;
} else {
dk = static_cast<double>(k);
return dk * kLn2Hi - ((r - dk * kLn2Lo) - f);
return dk * ln2_hi - ((R - dk * ln2_lo) - f);
}
}
s = f / (2.0 + f);
......@@ -172,23 +276,21 @@ double log(double x) {
i = hx - 0x6147a;
w = z * z;
j = 0x6b851 - hx;
t1 = w * (kLg2 + w * (kLg4 + w * kLg6));
t2 = z * (kLg1 + w * (kLg3 + w * (kLg5 + w * kLg7)));
t1 = w * (Lg2 + w * (Lg4 + w * Lg6));
t2 = z * (Lg1 + w * (Lg3 + w * (Lg5 + w * Lg7)));
i |= j;
r = t2 + t1;
R = t2 + t1;
if (i > 0) {
hfsq = 0.5 * f * f;
if (k == 0) {
return f - (hfsq - s * (hfsq + r));
} else {
return dk * kLn2Hi - ((hfsq - (s * (hfsq + r) + dk * kLn2Lo)) - f);
}
if (k == 0)
return f - (hfsq - s * (hfsq + R));
else
return dk * ln2_hi - ((hfsq - (s * (hfsq + R) + dk * ln2_lo)) - f);
} else {
if (k == 0) {
return f - s * (f - r);
} else {
return dk * kLn2Hi - ((s * (f - r) - dk * kLn2Lo) - f);
}
if (k == 0)
return f - s * (f - R);
else
return dk * ln2_hi - ((s * (f - R) - dk * ln2_lo) - f);
}
}
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment