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Annotation of 40BSD/cmd/as/asexpr.h, revision 1.1.1.1

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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