i386 exp2l implementation.
authordrepper <drepper>
Sat, 17 Feb 2001 16:47:51 +0000 (16:47 +0000)
committerdrepper <drepper>
Sat, 17 Feb 2001 16:47:51 +0000 (16:47 +0000)
sysdeps/i386/fpu/e_exp2l.S [new file with mode: 0644]

diff --git a/sysdeps/i386/fpu/e_exp2l.S b/sysdeps/i386/fpu/e_exp2l.S
new file mode 100644 (file)
index 0000000..fa1fdc9
--- /dev/null
@@ -0,0 +1,37 @@
+/*
+ * Written by J.T. Conklin <jtc@netbsd.org>.
+ * Adapted for exp2 by Ulrich Drepper <drepper@cygnus.com>.
+ * Public domain.
+ */
+
+#include <machine/asm.h>
+
+ENTRY(__ieee754_exp2l)
+       fldt    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.  */
+       fld     %st
+       frndint                         /* int(x) */
+       fsubr   %st,%st(1)              /* fract(x) */
+       fxch
+       f2xm1                           /* 2^(fract(x)) - 1 */
+       fld1
+       faddp                           /* 2^(fract(x)) */
+       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_exp2l)