xref: /csrg-svn/sys/tahoe/align/Asbwc.c (revision 45760)
1*45760Sbostic /*-
2*45760Sbostic  * Copyright (c) 1986 The Regents of the University of California.
3*45760Sbostic  * All rights reserved.
4*45760Sbostic  *
5*45760Sbostic  * This code is derived from software contributed to Berkeley by
6*45760Sbostic  * Computer Consoles Inc.
7*45760Sbostic  *
8*45760Sbostic  * %sccs.include.redist.c%
9*45760Sbostic  *
10*45760Sbostic  *	@(#)Asbwc.c	7.1 (Berkeley) 12/06/90
11*45760Sbostic  */
1229631Ssam 
1345699Sbostic #include "align.h"
sbwc(infop)1429631Ssam sbwc(infop)	process_info *infop;
1529631Ssam /*
1629631Ssam /*	Subtract with carry.
1729631Ssam /*	Note : the play with 'tmp' just before the 'asm' line makes
1829631Ssam /*		sure that when the sbwc opcode is executed, the current
1929631Ssam /*		carry in psl is the same as the 'offending' process'.
2029631Ssam /*		Don't change unless you know exactly what you're doing.
2129631Ssam /*
2229631Ssam /*****************************/
2329631Ssam {
2429631Ssam 	register	long	Register_12;	/* Has to be first reg ! */
2529631Ssam 	register	long	Register_11;
2629631Ssam 	register	long	Register_10;
2729631Ssam 	register 	long	tmp;
2829631Ssam 
2929631Ssam 	Register_12 = operand(infop,0)->data;
3029631Ssam 	Register_11 = operand(infop,1)->data;
3129631Ssam 	if (carry)	/* If process' carry set */
3229631Ssam 		tmp = -1;
3329631Ssam 	else tmp = 0;
3429631Ssam 	tmp++;		/* 0 => carry set.  1 => carry clear */
3529631Ssam 
3629631Ssam 	Register_10=psl;
3729631Ssam 	Set_psl(r10);	/* restore the user psl */
3829631Ssam 	asm("	sbwc	r12,r11");
3929631Ssam 	asm("	movpsl	r12");
4029631Ssam 	New_cc (Register_12);
4129631Ssam 
4229631Ssam 	write_back(infop, Register_11, operand(infop,1) );
4329631Ssam }
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