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Annotation of 43BSDTahoe/ucb/lisp/franz/tahoe/exarith.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * exarith(mul1,mul2,add,hi,lo)
                      3:  *
                      4:  * (hi,lo) gets 64 bit product + sum of mul1*mul2+add;
                      5:  * routine returns non-zero if product is bigger than 30 bits
                      6:  *
                      7:  * Copyright (c) 1982, Regents, University of California
                      8:  *
                      9:  * stolen from 68k by P. S. Housel 04/29/86, with minor mods
                     10:  *     (replaced call to emul with asm("emul..."))
                     11:  */
                     12: 
                     13: struct vl
                     14:        {long high;
                     15:        long low;
                     16:        };
                     17: 
                     18: long exarith(mul1,mul2,add,hi,lo)
                     19: long *hi, *lo;
                     20: register long add;
                     21: {
                     22:        register long rlo;
                     23:        struct vl work;
                     24: 
                     25:             asm("      emul    4(fp),8(fp),r12,-60(fp)");
                     26: 
                     27:            add = work.high;
                     28:            add <<= 2;
                     29:            if((rlo = work.low) < 0) add += 2;
                     30:            if(rlo & 0x40000000) add += 1;
                     31:            *lo = rlo &0x3fffffff;
                     32:            (*hi = add);
                     33:            if((add==0) || (add!=-1)) return(add);
                     34:            *lo = rlo;
                     35:            return(0);
                     36: }

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