reg_u_add.s

freebsd v4.4内核源码

	.file	"reg_u_add.S"
/*
 *  reg_u_add.S
 *
 * Add two valid (TW_Valid) FPU_REG numbers, of the same sign, and put the
 *   result in a destination FPU_REG.
 *
 * Call from C as:
 *   void reg_u_add(FPU_REG *arg1, FPU_REG *arg2, FPU_REG *answ,
 *                                                int control_w)
 *
 *
 * Copyright (C) 1992,1993,1994
 *                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,
 *                       Australia.  E-mail   [e-mail]
 * All rights reserved.
 *
 * This copyright notice covers the redistribution and use of the
 * FPU emulator developed by W. Metzenthen. It covers only its use
 * in the 386BSD, FreeBSD and NetBSD operating systems. Any other
 * use is not permitted under this copyright.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must include information specifying
 *    that source code for the emulator is freely available and include
 *    either:
 *      a) an offer to provide the source code for a nominal distribution
 *         fee, or
 *      b) list at least two alternative methods whereby the source
 *         can be obtained, e.g. a publically accessible bulletin board
 *         and an anonymous ftp site from which the software can be
 *         downloaded.
 * 3. All advertising materials specifically mentioning features or use of
 *    this emulator must acknowledge that it was developed by W. Metzenthen.
 * 4. The name of W. Metzenthen may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * W. METZENTHEN BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 * The purpose of this copyright, based upon the Berkeley copyright, is to
 * ensure that the covered software remains freely available to everyone.
 *
 * The software (with necessary differences) is also available, but under
 * the terms of the GNU copyleft, for the Linux operating system and for
 * the djgpp ms-dos extender.
 *
 * W. Metzenthen   June 1994.
 *
 *
 * $FreeBSD: src/sys/gnu/i386/fpemul/reg_u_add.s,v 1.4.2.1 1999/09/05 08:09:56 peter Exp $
 *
 */


/*
 |    Kernel addition routine reg_u_add(reg *arg1, reg *arg2, reg *answ).
 |    Takes two valid reg f.p. numbers (TW_Valid), which are
 |    treated as unsigned numbers,
 |    and returns their sum as a TW_Valid or TW_S f.p. number.
 |    The returned number is normalized.
 |    Basic checks are performed if PARANOID is defined.
 */

#include <gnu/i386/fpemul/exception.h>
#include <gnu/i386/fpemul/fpu_asm.h>
#include <gnu/i386/fpemul/control_w.h>

.text
	.align 2,144
.globl _reg_u_add
_reg_u_add:
	pushl	%ebp
	movl	%esp,%ebp
/*	subl	$16,%esp*/
	pushl	%esi
	pushl	%edi
	pushl	%ebx

	movl	PARAM1,%esi		/* source 1 */
	movl	PARAM2,%edi		/* source 2 */

#ifdef DENORM_OPERAND
	cmpl	EXP_UNDER,EXP(%esi)
	jg	xOp1_not_denorm

	call	_denormal_operand
	orl	%eax,%eax
	jnz	FPU_Arith_exit

xOp1_not_denorm:
	cmpl	EXP_UNDER,EXP(%edi)
	jg	xOp2_not_denorm

	call	_denormal_operand
	orl	%eax,%eax
	jnz	FPU_Arith_exit

xOp2_not_denorm:
#endif DENORM_OPERAND

/*	xorl	%ecx,%ecx*/
	movl	EXP(%esi),%ecx
	subl	EXP(%edi),%ecx		/* exp1 - exp2 */
/*	jnc	L_arg1_larger*/
	jge	L_arg1_larger

	/* num1 is smaller */
	movl	SIGL(%esi),%ebx
	movl	SIGH(%esi),%eax

	movl	%edi,%esi
	negw	%cx
	jmp	L_accum_loaded

L_arg1_larger:
	/* num1 has larger or equal exponent */
	movl	SIGL(%edi),%ebx
	movl	SIGH(%edi),%eax

L_accum_loaded:
	movl	PARAM3,%edi		/* destination */
	movb	SIGN(%esi),%dl
	movb	%dl,SIGN(%edi)		/* Copy the sign from the first arg */


	movl	EXP(%esi),%edx
	movl	%edx,EXP(%edi)	/* Copy exponent to destination */

	xorl	%edx,%edx		/* clear the extension */

#ifdef PARANOID
	testl	$0x80000000,%eax
	je	L_bugged

	testl	$0x80000000,SIGH(%esi)
	je	L_bugged
#endif PARANOID

/* The number to be shifted is in %eax:%ebx:%edx*/
	cmpw	$32,%cx		/* shrd only works for 0..31 bits */
	jnc	L_more_than_31

/* less than 32 bits */
	shrd	%cl,%ebx,%edx
	shrd	%cl,%eax,%ebx
	shr	%cl,%eax
	jmp	L_shift_done

L_more_than_31:
	cmpw	$64,%cx
	jnc	L_more_than_63

	subb	$32,%cl
	jz	L_exactly_32

	shrd	%cl,%eax,%edx
	shr	%cl,%eax
	orl	%ebx,%ebx
	jz	L_more_31_no_low	/* none of the lowest bits is set*/

	orl	$1,%edx			/* record the fact in the extension*/

L_more_31_no_low:
	movl	%eax,%ebx
	xorl	%eax,%eax
	jmp	L_shift_done

L_exactly_32:
	movl	%ebx,%edx
	movl	%eax,%ebx
	xorl	%eax,%eax
	jmp	L_shift_done

L_more_than_63:
	cmpw	$65,%cx
	jnc	L_more_than_64

	movl	%eax,%edx
	orl	%ebx,%ebx
	jz	L_more_63_no_low

	orl	$1,%edx
	jmp	L_more_63_no_low

L_more_than_64:
	movl	$1,%edx		/* The shifted nr always at least one '1'*/

L_more_63_no_low:
	xorl	%ebx,%ebx
	xorl	%eax,%eax

L_shift_done:
	/* Now do the addition */
	addl	SIGL(%esi),%ebx
	adcl	SIGH(%esi),%eax
	jnc	L_round_the_result

	/* Overflow, adjust the result */
	rcrl	$1,%eax
	rcrl	$1,%ebx
	rcrl	$1,%edx
	jnc	L_no_bit_lost

	orl	$1,%edx

L_no_bit_lost:
	incl	EXP(%edi)

L_round_the_result:
	jmp	FPU_round	/* Round the result*/



#ifdef PARANOID
/* If we ever get here then we have problems! */
L_bugged:
	pushl	EX_INTERNAL|0x201
	call	EXCEPTION
	pop	%ebx
	jmp	L_exit
#endif PARANOID


L_exit:
	popl	%ebx
	popl	%edi
	popl	%esi
	leave
	ret