mirrors/qemu
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

softfloat: add float32_exp2()

Browse Source 
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Aurelien Jarno 2009-02-05 12:04:05 +01:00
parent f077caa99c
commit 8229c9913a
2 changed files with 82 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

79
fpu/softfloat.c
View File

@ -2055,6 +2055,85 @@ float32 float32_sqrt( float32 a STATUS_PARAM )
}
/*----------------------------------------------------------------------------
| Returns the binary exponential of the single-precision floating-point value
| `a'. The operation is performed according to the IEC/IEEE Standard for
| Binary Floating-Point Arithmetic.
|
| Uses the following identities:
|
| 1. -------------------------------------------------------------------------
| x x*ln(2)
| 2 = e
|
| 2. -------------------------------------------------------------------------
| 2 3 4 5 n
| x x x x x x x
| e = 1 + --- + --- + --- + --- + --- + ... + --- + ...
| 1! 2! 3! 4! 5! n!
*----------------------------------------------------------------------------*/
static const float64 float32_exp2_coefficients[15] =
{
make_float64( 0x3ff0000000000000ll ), /* 1 */
make_float64( 0x3fe0000000000000ll ), /* 2 */
make_float64( 0x3fc5555555555555ll ), /* 3 */
make_float64( 0x3fa5555555555555ll ), /* 4 */
make_float64( 0x3f81111111111111ll ), /* 5 */
make_float64( 0x3f56c16c16c16c17ll ), /* 6 */
make_float64( 0x3f2a01a01a01a01all ), /* 7 */
make_float64( 0x3efa01a01a01a01all ), /* 8 */
make_float64( 0x3ec71de3a556c734ll ), /* 9 */
make_float64( 0x3e927e4fb7789f5cll ), /* 10 */
make_float64( 0x3e5ae64567f544e4ll ), /* 11 */
make_float64( 0x3e21eed8eff8d898ll ), /* 12 */
make_float64( 0x3de6124613a86d09ll ), /* 13 */
make_float64( 0x3da93974a8c07c9dll ), /* 14 */
make_float64( 0x3d6ae7f3e733b81fll ), /* 15 */
};
float32 float32_exp2( float32 a STATUS_PARAM )
{
flag aSign;
int16 aExp;
bits32 aSig;
float64 r, x, xn;
int i;
aSig = extractFloat32Frac( a );
aExp = extractFloat32Exp( a );
aSign = extractFloat32Sign( a );
if ( aExp == 0xFF) {
if ( aSig ) return propagateFloat32NaN( a, float32_zero STATUS_VAR );
return (aSign) ? float32_zero : a;
}
if (aExp == 0) {
if (aSig == 0) return float32_one;
}
float_raise( float_flag_inexact STATUS_VAR);
/* ******************************* */
/* using float64 for approximation */
/* ******************************* */
x = float32_to_float64(a STATUS_VAR);
x = float64_mul(x, float64_ln2 STATUS_VAR);
xn = x;
r = float64_one;
for (i = 0 ; i < 15 ; i++) {
float64 f;
f = float64_mul(xn, float32_exp2_coefficients[i] STATUS_VAR);
r = float64_add(r, f STATUS_VAR);
xn = float64_mul(xn, x STATUS_VAR);
}
return float64_to_float32(r, status);
}
/*----------------------------------------------------------------------------
| Returns the binary log of the single-precision floating-point value `a'.
| The operation is performed according to the IEC/IEEE Standard for Binary

3
fpu/softfloat.h
View File

@ -275,6 +275,7 @@ float32 float32_mul( float32, float32 STATUS_PARAM );
float32 float32_div( float32, float32 STATUS_PARAM );
float32 float32_rem( float32, float32 STATUS_PARAM );
float32 float32_sqrt( float32 STATUS_PARAM );
float32 float32_exp2( float32 STATUS_PARAM );
float32 float32_log2( float32 STATUS_PARAM );
int float32_eq( float32, float32 STATUS_PARAM );
int float32_le( float32, float32 STATUS_PARAM );
@ -315,6 +316,7 @@ INLINE int float32_is_zero(float32 a)
#define float32_zero make_float32(0)
#define float32_one make_float32(0x3f800000)
#define float32_ln2 make_float32(0x3f317218)
/*----------------------------------------------------------------------------
| Software IEC/IEEE double-precision conversion routines.
@ -386,6 +388,7 @@ INLINE int float64_is_zero(float64 a)
#define float64_zero make_float64(0)
#define float64_one make_float64(0x3ff0000000000000LL)
#define float64_ln2 make_float64(0x3fe62e42fefa39efLL)
#ifdef FLOATX80