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-rw-r--r--sysdeps/i386/fpu/s_log2.S59
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diff --git a/sysdeps/i386/fpu/s_log2.S b/sysdeps/i386/fpu/s_log2.S
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+/*
+ * Written by J.T. Conklin <jtc@netbsd.org>.
+ * Adapted for use as log2 by Ulrich Drepper <drepper@cygnus.com>.
+ * Public domain.
+ *
+ * Changed to use fyl2xp1 for values near 1, <drepper@cygnus.com>.
+ */
+
+#include <machine/asm.h>
+
+#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(__log2)
+#ifdef PIC
+ call 1f
+1: popl %edx
+ addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %edx
+#endif
+ fldl MO(one)
+ fldl 4(%esp) // x : 1
+ fld %st // x : x : 1
+ fsub %st(2), %st // x-1 : x : 1
+ fld %st // x-1 : x-1 : x : 1
+ fabs // |x-1| : x-1 : x : 1
+ fcompl MO(limit) // x-1 : x : 1
+ fnstsw // x-1 : x : 1
+ andb $0x45, %ah
+ jz 2f
+ fstp %st(1) // x-1 : 1
+ fyl2xp1 // log(x)
+ ret
+
+2: fstp %st(0) // x : 1
+ fyl2x // log(x)
+ ret
+END (__log2)
+weak_alias (__log2, log2)