diff options
Diffstat (limited to 'sysdeps/libm-i387/e_expf.S')
| -rw-r--r-- | sysdeps/libm-i387/e_expf.S | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/sysdeps/libm-i387/e_expf.S b/sysdeps/libm-i387/e_expf.S new file mode 100644 index 0000000000..c8233eba50 --- /dev/null +++ b/sysdeps/libm-i387/e_expf.S @@ -0,0 +1,42 @@ +/* + * Written by J.T. Conklin <jtc@netbsd.org>. + * Public domain. + * Adapted for float type by Ulrich Drepper <drepper@cygnus.com>. + */ + +#include <machine/asm.h> + +RCSID("$NetBSD: $") + +/* e^x = 2^(x * log2(e)) */ +ENTRY(__ieee754_expf) + flds 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 + sahf + jnc .LnoInfNaN /* No, jump. */ + jp .LisInf /* Is +-Inf, jump. */ +.LnoInfNaN: + fldl2e + fmulp /* x * log2(e) */ + fstl %st(1) + frndint /* int(x * log2(e)) */ + fstl %st(2) + fsubrp /* fract(x * log2(e)) */ + f2xm1 /* 2^(fract(x * log2(e))) - 1 */ + fld1 + faddp /* 2^(fract(x * log2(e))) */ + fscale /* e^x */ + fstp %st(1) + ret + +.LisInf: + andb $2, %ah /* Test sign. */ + jz .LpInf /* If positive, jump. */ + fldz /* Set result to 0. */ +.LpInf: ret +END (__ieee754_expf) |