git.sur5r.net Git - cc65/blob - src/ca65/easw16.c

   1 /*****************************************************************************/
   2 /*                                                                           */
   3 /*                                 easw16.c                                  */
   4 /*                                                                           */
   5 /*       SWEET16 effective address parsing for the ca65 macroassembler       */
   6 /*                                                                           */
   7 /*                                                                           */
   8 /*                                                                           */
   9 /* (C) 2004-2011, Ullrich von Bassewitz                                      */
  10 /*                Roemerstrasse 52                                           */
  11 /*                D-70794 Filderstadt                                        */
  12 /* EMail:         uz@cc65.org                                                */
  13 /*                                                                           */
  14 /*                                                                           */
  15 /* This software is provided 'as-is', without any expressed or implied       */
  16 /* warranty.  In no event will the authors be held liable for any damages    */
  17 /* arising from the use of this software.                                    */
  18 /*                                                                           */
  19 /* Permission is granted to anyone to use this software for any purpose,     */
  20 /* including commercial applications, and to alter it and redistribute it    */
  21 /* freely, subject to the following restrictions:                            */
  22 /*                                                                           */
  23 /* 1. The origin of this software must not be misrepresented; you must not   */
  24 /*    claim that you wrote the original software. If you use this software   */
  25 /*    in a product, an acknowledgment in the product documentation would be  */
  26 /*    appreciated but is not required.                                       */
  27 /* 2. Altered source versions must be plainly marked as such, and must not   */
  28 /*    be misrepresented as being the original software.                      */
  29 /* 3. This notice may not be removed or altered from any source              */
  30 /*    distribution.                                                          */
  31 /*                                                                           */
  32 /*****************************************************************************/
  33
  34
  35
  36 /* ca65 */
  37 #include "ea.h"
  38 #include "ea65.h"
  39 #include "error.h"
  40 #include "expr.h"
  41 #include "instr.h"
  42 #include "nexttok.h"
  43
  44
  45
  46 /*****************************************************************************/
  47 /*                                   Code                                    */
  48 /*****************************************************************************/
  49
  50
  51
  52 static long RegNum ()
  53 /* Try to read a register number specified not as a register (Rx) but as a
  54  * numeric value between 0 and 15. Return the register number or -1 on
  55  * failure.
  56  */
  57 {
  58     long Val;
  59     ExprNode* Expr = Expression ();
  60     if (!IsConstExpr (Expr, &Val) || Val < 0 || Val > 15) {
  61         /* Invalid register */
  62         Val = -1L;
  63     }
  64
  65     /* Free the expression and return the register number */
  66     FreeExpr (Expr);
  67     return Val;
  68 }
  69
  70
  71
  72 void GetSweet16EA (EffAddr* A)
  73 /* Parse an effective address, return the result in A */
  74 {
  75     long Reg;
  76
  77     /* Clear the output struct */
  78     A->AddrModeSet = 0;
  79     A->Expr = 0;
  80     A->Reg  = 0;
  81
  82     /* Parse the effective address */
  83     if (TokIsSep (CurTok.Tok)) {
  84
  85         A->AddrModeSet = AMSW16_IMP;
  86
  87     } else if (CurTok.Tok == TOK_AT) {
  88
  89         /* @reg or @regnumber */
  90         A->AddrModeSet = AMSW16_IND;
  91         NextTok ();
  92         if (CurTok.Tok == TOK_REG) {
  93             A->Reg = (unsigned) CurTok.IVal;
  94             NextTok ();
  95         } else if ((Reg = RegNum ()) >= 0) {
  96             /* Register number */
  97             A->Reg = (unsigned) Reg;
  98         } else {
  99             ErrorSkip ("Register or register number expected");
 100             A->Reg = 0;
 101         }
 102
 103     } else if (CurTok.Tok == TOK_REG) {
 104
 105         A->Reg = (unsigned) CurTok.IVal;
 106         NextTok ();
 107
 108         if (CurTok.Tok == TOK_COMMA) {
 109
 110             /* Rx, constant */
 111             NextTok ();
 112             A->Expr = Expression ();
 113
 114             A->AddrModeSet = AMSW16_IMM;
 115
 116         } else {
 117
 118             A->AddrModeSet = AMSW16_REG;
 119
 120         }
 121
 122     } else {
 123
 124         /* OPC ea  or: OPC regnum, constant */
 125         A->Expr = Expression ();
 126         A->AddrModeSet = AMSW16_BRA;
 127
 128         /* If the value is a constant between 0 and 15, it may also be a
 129          * register number.
 130          */
 131         if (IsConstExpr (A->Expr, &Reg) && Reg >= 0 && Reg <= 15) {
 132             FreeExpr (A->Expr);
 133             A->Reg = (unsigned) Reg;
 134
 135             /* If a comma follows, it is: OPC Rx, constant */
 136             if (CurTok.Tok == TOK_COMMA) {
 137                 NextTok ();
 138                 A->Expr = Expression ();
 139                 A->AddrModeSet = AMSW16_IMM;
 140             } else {
 141                 A->Expr = 0;
 142                 A->AddrModeSet |= AMSW16_REG;
 143             }
 144         }
 145
 146     }
 147 }
 148
 149
 150