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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/s_expm1.S
parent86421aa57ecfd70963ae66848bd6a6dd3b8e0fe6 (diff)
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+/* ix87 specific implementation of exp(x)-1.
+   Copyright (C) 1996, 1997 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
+   Based on code by John C. Bowman <bowman@ipp-garching.mpg.de>.
+   Corrections by H.J. Lu (hjl@gnu.ai.mit.edu), 1997.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+	/* Using: e^x - 1 = 2^(x * log2(e)) - 1 */
+
+#include <machine/asm.h>
+
+#ifdef __ELF__
+	.section .rodata
+#else
+	.text
+#endif
+	.align ALIGNARG(4)
+	ASM_TYPE_DIRECTIVE(minus1,@object)
+minus1:	.double -1.0
+	ASM_SIZE_DIRECTIVE(minus1)
+	ASM_TYPE_DIRECTIVE(one,@object)
+one:	.double 1.0
+	ASM_SIZE_DIRECTIVE(one)
+	ASM_TYPE_DIRECTIVE(l2e,@object)
+l2e:	.tfloat 1.442695040888963407359924681002
+	ASM_SIZE_DIRECTIVE(l2e)
+
+#ifdef PIC
+#define MO(op) op##@GOTOFF(%edx)
+#else
+#define MO(op) op
+#endif
+
+	.text
+ENTRY(__expm1)
+	fldl	4(%esp)		// x
+	fxam			// Is NaN or +-Inf?
+	fstsw	%ax
+	movb	$0x45, %ch
+	andb	%ah, %ch
+	cmpb	$0x40, %ch
+	je	3f		// If +-0, jump.
+#ifdef	PIC
+	call	1f
+1:	popl	%edx
+	addl	$_GLOBAL_OFFSET_TABLE_+[.-1b], %edx
+#endif
+	cmpb	$0x05, %ch
+	je	2f		// If +-Inf, jump.
+
+	fldt	MO(l2e)		// log2(e) : x
+	fmulp			// log2(e)*x
+	fld	%st		// log2(e)*x : log2(e)*x
+	frndint			// int(log2(e)*x) : log2(e)*x
+	fsubr	%st, %st(1)	// int(log2(e)*x) : fract(log2(e)*x)
+	fxch			// fract(log2(e)*x) : int(log2(e)*x)
+	f2xm1			// 2^fract(log2(e)*x)-1 : int(log2(e)*x)
+	fscale			// 2^(log2(e)*x)-2^int(log2(e)*x) : int(log2(e)*x)
+	fxch			// int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
+	fldl	MO(one)		// 1 : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
+	fscale			// 2^int(log2(e)*x) : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
+	fsubrl	MO(one)		// 1-2^int(log2(e)*x) : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
+	fstp	%st(1)		// 1-2^int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
+	fsubrp	%st, %st(1)	// 2^(log2(e)*x)
+	ret
+
+2:	testl	$0x200, %eax	// Test sign.
+	jz	3f		// If positive, jump.
+	fstp	%st
+	fldl	MO(minus1)	// Set result to -1.0.
+3:	ret
+END(__expm1)
+weak_alias (__expm1, expm1)