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Annotation of 41BSD/cmd/as/asexpr.h, revision 1.1

1.1     ! root        1: /* Copyright (c) 1980 Regents of the University of California */
        !             2: /* "@(#)asexpr.h 4.2 8/15/80" */
        !             3: /*
        !             4:  *     Definitions to parse tokens
        !             5:  */
        !             6: 
        !             7: #define ERROR(string)          yyerror(string); goto errorfix
        !             8: 
        !             9: #define peekahead (*tokptr)
        !            10: 
        !            11: #define shift                  val = yylex()
        !            12: #define advance        shift
        !            13: 
        !            14: #define shiftover(token)       if (val != token) { \
        !            15:                                        yyerror("token expected"); \
        !            16:                                        goto errorfix; \
        !            17:                                } \
        !            18:                                shift
        !            19: 
        !            20: #define advanceover    shiftover
        !            21: 
        !            22: /*
        !            23:  *     To speed up the expression processing, we class the input tokens
        !            24:  *     into various sets.
        !            25:  *
        !            26:  *     We don't call the recursive descent expression analyzer if we can
        !            27:  *     determine by looking at the next token after the first token in
        !            28:  *     an expression that the expression is simple (name, integer or floating
        !            29:  *     point value).  Expressions with operators are parsed using the recursive
        !            30:  *     descent method.
        !            31:  */
        !            32: 
        !            33: /*
        !            34:  *     Functional forwards for expression utility routines
        !            35:  */
        !            36: struct exp     *combine();
        !            37: struct exp     *boolterm();
        !            38: struct exp     *term();
        !            39: struct exp     *factor();
        !            40: struct exp     *yukkyexpr();
        !            41: 
        !            42: /*
        !            43:  *     The set definitions
        !            44:  */
        !            45: 
        !            46: extern char    tokensets[(LASTTOKEN) - (FIRSTTOKEN) + 1];
        !            47: 
        !            48: #define        LINSTBEGIN      01      /*SEMI, NL, NAME*/
        !            49: #define        EBEGOPS         02      /*LP, MINUS, TILDE*/
        !            50: #define        YUKKYEXPRBEG    04      /*NAME, INSTn, INST0, REG, BFINT*/
        !            51: #define        SAFEEXPRBEG     010     /*INT, FLTNUM*/
        !            52: #define        ADDOPS          020     /*PLUS, MINUS*/
        !            53: #define        BOOLOPS         040     /*IOR, XOR, AND*/
        !            54: #define        MULOPS          0100    /*LSH, RSH, MUL, DIV, TILDE*/
        !            55: 
        !            56: #define        INTOKSET(val, set)      (tokensets[(val)] & (set) )
        !            57: 
        !            58: #define expr(xp, val) { \
        !            59:        if ( (!INTOKSET(val, EBEGOPS)) && (!INTOKSET(peekahead, ADDOPS+BOOLOPS+MULOPS))) { \
        !            60:                if (INTOKSET(val, YUKKYEXPRBEG)) xp = yukkyexpr(val, yylval); \
        !            61:                else xp = (struct exp *) yylval; \
        !            62:                shift; \
        !            63:        } else { \
        !            64:                val = exprparse(val, ptrloc1xp); \
        !            65:                xp = loc1xp; \
        !            66:        } \
        !            67:     }
        !            68: 
        !            69: /*
        !            70:  *     Registers can be either of the form r0...pc, or
        !            71:  *     of the form % <expression>
        !            72:  *     NOTE:   Reizers documentation on the assembler says that it
        !            73:  *     can be of the form r0 + <expression>.. That's not true.
        !            74:  *
        !            75:  *     NOTE:   Reizer's yacc grammar would seem to allow an expression
        !            76:  *     to be: (This is undocumented)
        !            77:  *             a)      a register
        !            78:  *             b)      an Instruction (INSTn or INST0)
        !            79:  */
        !            80: 
        !            81: #define findreg(regno) \
        !            82:        if (val == REG) { \
        !            83:                regno = yylval; \
        !            84:                shift; \
        !            85:        } else \
        !            86:        if (val == REGOP) { \
        !            87:                shift;  /*over the REGOP*/ \
        !            88:                val = funnyreg(val, ptrregno); \
        !            89:        } \
        !            90:        else { ERROR ("register expected"); }

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