diff options
Diffstat (limited to 'sysdeps/i386/fpu/e_exp.S')
| -rw-r--r-- | sysdeps/i386/fpu/e_exp.S | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/sysdeps/i386/fpu/e_exp.S b/sysdeps/i386/fpu/e_exp.S new file mode 100644 index 0000000000..4a75fa1d1c --- /dev/null +++ b/sysdeps/i386/fpu/e_exp.S @@ -0,0 +1,41 @@ +/* + * Written by J.T. Conklin <jtc@netbsd.org>. + * Public domain. + */ + +#include <machine/asm.h> + +RCSID("$NetBSD: e_exp.S,v 1.7 1996/07/03 17:31:28 jtc Exp $") + +/* e^x = 2^(x * log2(e)) */ +ENTRY(__ieee754_exp) + fldl 4(%esp) +/* I added the following ugly construct because exp(+-Inf) resulted + in NaN. The ugliness results from the bright minds at Intel. + For the i686 the code can be written better. + -- drepper@cygnus.com. */ + fxam /* Is NaN or +-Inf? */ + fstsw %ax + movb $0x45, %dh + andb %ah, %dh + cmpb $0x05, %dh + je 1f /* Is +-Inf, jump. */ + fldl2e + fmulp /* x * log2(e) */ + fld %st + frndint /* int(x * log2(e)) */ + fsubr %st,%st(1) /* fract(x * log2(e)) */ + fxch + f2xm1 /* 2^(fract(x * log2(e))) - 1 */ + fld1 + faddp /* 2^(fract(x * log2(e))) */ + fscale /* e^x */ + fstp %st(1) + ret + +1: testl $0x200, %eax /* Test sign. */ + jz 2f /* If positive, jump. */ + fstp %st + fldz /* Set result to 0. */ +2: ret +END (__ieee754_exp) |