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Inline DoubleToECMAInt32 (512049, r=dmandelin).

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This commit is contained in:
Andreas Gal 2009-08-24 18:46:21 -07:00
parent f808b9ca98
commit 7644588864
2 changed files with 103 additions and 106 deletions
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104
js/src/jsnum.cpp
View File

@ -1012,110 +1012,6 @@ js_ValueToECMAInt32(JSContext *cx, jsval *vp)
return js_DoubleToECMAInt32(d);
}
/*
* From the ES3 spec, 9.5
* 2. If Result(1) is NaN, +0, -0, +Inf, or -Inf, return +0.
* 3. Compute sign(Result(1)) * floor(abs(Result(1))).
* 4. Compute Result(3) modulo 2^32; that is, a finite integer value k of Number
* type with positive sign and less than 2^32 in magnitude such the mathematical
* difference of Result(3) and k is mathematically an integer multiple of 2^32.
* 5. If Result(4) is greater than or equal to 2^31, return Result(4)- 2^32,
* otherwise return Result(4).
*/
int32
js_DoubleToECMAInt32(jsdouble d)
{
#ifdef __i386__
jsdpun du, duh, two32;
uint32 di_h, u_tmp, expon, shift_amount;
int32 mask32;
/*
* Algorithm Outline
* Step 1. If d is NaN, +/-Inf or |d|>=2^84 or |d|<1, then return 0
* All of this is implemented based on an exponent comparison.
* Step 2. If |d|<2^31, then return (int)d
* The cast to integer (conversion in RZ mode) returns the correct result.
* Step 3. If |d|>=2^32, d:=fmod(d, 2^32) is taken -- but without a call
* Step 4. If |d|>=2^31, then the fractional bits are cleared before
* applying the correction by 2^32: d - sign(d)*2^32
* Step 5. Return (int)d
*/
du.d = d;
di_h = du.s.hi;
u_tmp = (di_h & 0x7ff00000) - 0x3ff00000;
if (u_tmp >= (0x45300000-0x3ff00000)) {
// d is Nan, +/-Inf or +/-0, or |d|>=2^(32+52) or |d|<1, in which case result=0
return 0;
}
if (u_tmp < 0x01f00000) {
// |d|<2^31
return int32_t(d);
}
if (u_tmp > 0x01f00000) {
// |d|>=2^32
expon = u_tmp >> 20;
shift_amount = expon - 21;
duh.u64 = du.u64;
mask32 = 0x80000000;
if (shift_amount < 32) {
mask32 >>= shift_amount;
duh.s.hi = du.s.hi & mask32;
duh.s.lo = 0;
} else {
mask32 >>= (shift_amount-32);
duh.s.hi = du.s.hi;
duh.s.lo = du.s.lo & mask32;
}
du.d -= duh.d;
}
di_h = du.s.hi;
// eliminate fractional bits
u_tmp = (di_h & 0x7ff00000);
if (u_tmp >= 0x41e00000) {
// |d|>=2^31
expon = u_tmp >> 20;
shift_amount = expon - (0x3ff - 11);
mask32 = 0x80000000;
if (shift_amount < 32) {
mask32 >>= shift_amount;
du.s.hi &= mask32;
du.s.lo = 0;
} else {
mask32 >>= (shift_amount-32);
du.s.lo &= mask32;
}
two32.s.hi = 0x41f00000 ^ (du.s.hi & 0x80000000);
two32.s.lo = 0;
du.d -= two32.d;
}
return int32(du.d);
#else
int32 i;
jsdouble two32, two31;
if (!JSDOUBLE_IS_FINITE(d))
return 0;
i = (int32) d;
if ((jsdouble) i == d)
return i;
two32 = 4294967296.0;
two31 = 2147483648.0;
d = fmod(d, two32);
d = (d >= 0) ? floor(d) : ceil(d) + two32;
return (int32) (d >= two31 ? d - two32 : d);
#endif
}
uint32
js_ValueToECMAUint32(JSContext *cx, jsval *vp)
{

105
js/src/jsnum.h
View File

@ -223,8 +223,109 @@ js_ValueToECMAUint32(JSContext *cx, jsval *vp);
/*
* Specialized ToInt32 and ToUint32 converters for doubles.
*/
extern int32
js_DoubleToECMAInt32(jsdouble d);
/*
* From the ES3 spec, 9.5
* 2. If Result(1) is NaN, +0, -0, +Inf, or -Inf, return +0.
* 3. Compute sign(Result(1)) * floor(abs(Result(1))).
* 4. Compute Result(3) modulo 2^32; that is, a finite integer value k of Number
* type with positive sign and less than 2^32 in magnitude such the mathematical
* difference of Result(3) and k is mathematically an integer multiple of 2^32.
* 5. If Result(4) is greater than or equal to 2^31, return Result(4)- 2^32,
* otherwise return Result(4).
*/
static inline int32
js_DoubleToECMAInt32(jsdouble d)
{
#ifdef __i386__
jsdpun du, duh, two32;
uint32 di_h, u_tmp, expon, shift_amount;
int32 mask32;
/*
* Algorithm Outline
* Step 1. If d is NaN, +/-Inf or |d|>=2^84 or |d|<1, then return 0
* All of this is implemented based on an exponent comparison.
* Step 2. If |d|<2^31, then return (int)d
* The cast to integer (conversion in RZ mode) returns the correct result.
* Step 3. If |d|>=2^32, d:=fmod(d, 2^32) is taken -- but without a call
* Step 4. If |d|>=2^31, then the fractional bits are cleared before
* applying the correction by 2^32: d - sign(d)*2^32
* Step 5. Return (int)d
*/
du.d = d;
di_h = du.s.hi;
u_tmp = (di_h & 0x7ff00000) - 0x3ff00000;
if (u_tmp >= (0x45300000-0x3ff00000)) {
// d is Nan, +/-Inf or +/-0, or |d|>=2^(32+52) or |d|<1, in which case result=0
return 0;
}
if (u_tmp < 0x01f00000) {
// |d|<2^31
return int32_t(d);
}
if (u_tmp > 0x01f00000) {
// |d|>=2^32
expon = u_tmp >> 20;
shift_amount = expon - 21;
duh.u64 = du.u64;
mask32 = 0x80000000;
if (shift_amount < 32) {
mask32 >>= shift_amount;
duh.s.hi = du.s.hi & mask32;
duh.s.lo = 0;
} else {
mask32 >>= (shift_amount-32);
duh.s.hi = du.s.hi;
duh.s.lo = du.s.lo & mask32;
}
du.d -= duh.d;
}
di_h = du.s.hi;
// eliminate fractional bits
u_tmp = (di_h & 0x7ff00000);
if (u_tmp >= 0x41e00000) {
// |d|>=2^31
expon = u_tmp >> 20;
shift_amount = expon - (0x3ff - 11);
mask32 = 0x80000000;
if (shift_amount < 32) {
mask32 >>= shift_amount;
du.s.hi &= mask32;
du.s.lo = 0;
} else {
mask32 >>= (shift_amount-32);
du.s.lo &= mask32;
}
two32.s.hi = 0x41f00000 ^ (du.s.hi & 0x80000000);
two32.s.lo = 0;
du.d -= two32.d;
}
return int32(du.d);
#else
int32 i;
jsdouble two32, two31;
if (!JSDOUBLE_IS_FINITE(d))
return 0;
i = (int32) d;
if ((jsdouble) i == d)
return i;
two32 = 4294967296.0;
two31 = 2147483648.0;
d = fmod(d, two32);
d = (d >= 0) ? floor(d) : ceil(d) + two32;
return (int32) (d >= two31 ? d - two32 : d);
#endif
}
extern uint32
js_DoubleToECMAUint32(jsdouble d);