about summary refs log tree commit diff
path: root/sysdeps/i386/fpu/e_log10.S
diff options
context:
space:
mode:
Diffstat (limited to 'sysdeps/i386/fpu/e_log10.S')
-rw-r--r--sysdeps/i386/fpu/e_log10.S59
1 files changed, 59 insertions, 0 deletions
diff --git a/sysdeps/i386/fpu/e_log10.S b/sysdeps/i386/fpu/e_log10.S
new file mode 100644
index 0000000000..2c8488c3a9
--- /dev/null
+++ b/sysdeps/i386/fpu/e_log10.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_log10.S,v 1.4 1995/05/08 23:49:24 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_log10)
+	fldlg2			// log10(2)
+	fldl	4(%esp)		// x : log10(2)
+#ifdef PIC
+	call	1f
+1:	popl	%edx
+	addl	$_GLOBAL_OFFSET_TABLE_+[.-1b], %edx
+#endif
+	fld	%st		// x : x : log10(2)
+	fsubl	MO(one)		// x-1 : x : log10(2)
+	fld	%st		// x-1 : x-1 : x : log10(2)
+	fabs			// |x-1| : x-1 : x : log10(2)
+	fcompl	MO(limit)	// x-1 : x : log10(2)
+	fnstsw			// x-1 : x : log10(2)
+	andb	$0x45, %ah
+	jz	2f
+	fstp	%st(1)		// x-1 : log10(2)
+	fyl2xp1			// log10(x)
+	ret
+
+2:	fstp	%st(0)		// x : log10(2)
+	fyl2x			// log10(x)
+	ret
+END (__ieee754_log10)