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Annotation of 3BSD/cmd/as/asexpr.h, revision 1.1.1.1

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

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