about summary refs log tree commit diff
path: root/sysdeps/i386/fpu/e_log.S
diff options
context:
space:
mode:
authorUlrich Drepper <drepper@redhat.com>1999-07-14 00:54:57 +0000
committerUlrich Drepper <drepper@redhat.com>1999-07-14 00:54:57 +0000
commitabfbdde177c3a7155070dda1b2cdc8292054cc26 (patch)
treee021306b596381fbf8311d2b7eb294e918ff17c8 /sysdeps/i386/fpu/e_log.S
parent86421aa57ecfd70963ae66848bd6a6dd3b8e0fe6 (diff)
downloadglibc-abfbdde177c3a7155070dda1b2cdc8292054cc26.tar.gz
glibc-abfbdde177c3a7155070dda1b2cdc8292054cc26.tar.xz
glibc-abfbdde177c3a7155070dda1b2cdc8292054cc26.zip
Update.
Diffstat (limited to 'sysdeps/i386/fpu/e_log.S')
-rw-r--r--sysdeps/i386/fpu/e_log.S59
1 files changed, 59 insertions, 0 deletions
diff --git a/sysdeps/i386/fpu/e_log.S b/sysdeps/i386/fpu/e_log.S
new file mode 100644
index 0000000000..c7cacdfb0a
--- /dev/null
+++ b/sysdeps/i386/fpu/e_log.S
@@ -0,0 +1,59 @@
+/*
+ * Written by J.T. Conklin <jtc@netbsd.org>.
+ * Public domain.
+ *
+ * Changed to use fyl2xp1 for values near 1, <drepper@cygnus.com>.
+ */
+
+#include <machine/asm.h>
+
+RCSID("$NetBSD: e_log.S,v 1.4 1995/05/08 23:48:39 jtc Exp $")
+
+#ifdef __ELF__
+	.section .rodata
+#else
+	.text
+#endif
+	.align ALIGNARG(4)
+	ASM_TYPE_DIRECTIVE(one,@object)
+one:	.double 1.0
+	ASM_SIZE_DIRECTIVE(one)
+	/* It is not important that this constant is precise.  It is only
+	   a value which is known to be on the safe side for using the
+	   fyl2xp1 instruction.  */
+	ASM_TYPE_DIRECTIVE(limit,@object)
+limit:	.double 0.29
+	ASM_SIZE_DIRECTIVE(limit)
+
+
+#ifdef PIC
+#define MO(op) op##@GOTOFF(%edx)
+#else
+#define MO(op) op
+#endif
+
+	.text
+ENTRY(__ieee754_log)
+	fldln2			// log(2)
+	fldl	4(%esp)		// x : log(2)
+#ifdef PIC
+	call	1f
+1:	popl	%edx
+	addl	$_GLOBAL_OFFSET_TABLE_+[.-1b], %edx
+#endif
+	fld	%st		// x : x : log(2)
+	fsubl	MO(one)		// x-1 : x : log(2)
+	fld	%st		// x-1 : x-1 : x : log(2)
+	fabs			// |x-1| : x-1 : x : log(2)
+	fcompl	MO(limit)	// x-1 : x : log(2)
+	fnstsw			// x-1 : x : log(2)
+	andb	$0x45, %ah
+	jz	2f
+	fstp	%st(1)		// x-1 : log(2)
+	fyl2xp1			// log(x)
+	ret
+
+2:	fstp	%st(0)		// x : log(2)
+	fyl2x			// log(x)
+	ret
+END (__ieee754_log)