Q59374: FIX: Incorrect Code With TYPE and SI Index Register

Article: Q59374
Product(s): Microsoft Macro Assembler
Version(s): 5.1,5.1a
Operating System(s): 
Keyword(s): 
Last Modified: 06-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Macro Assembler (MASM), versions 5.1, 5.1a 
-------------------------------------------------------------------------------

SYMPTOMS
========

An incorrect opcode is generated by the Microsoft Macro Assembler (MASM)
versions 5.1 and 5.1a when using the TYPE operator and the SI register are used
in an indirect memory operand.

STATUS
======

Microsoft has confirmed this to be a problem in MASM versions 5.1 and 5.1a. This
problem was corrected in MASM version 6.0.

MORE INFORMATION
================

The type operator returns a number that represents the type of an expression.
This is normally the size of the variable. For example, a variable declared as
dw will cause TYPE to return the number 2.

Each of the CMP instructions in the sample below should produce the exact same
encoding. Verify with a listing file that an incorrect encoding is produced. The
opcode portion of the instruction is 3b84 in the correct examples and 3b06 in
the incorrect examples.

Sample Code
-----------

  ; Assemble options needed: none

  .MODEL small
  .STACK 4096                       ; Allocate 4K stack space
  .DATA
   var1 dw 0

  .CODE
   main proc
        MOV ax, @data               ; Set up the DS register
        MOV ds, ax                  ;

        CMP ax,var1[si]+type var1   ; Incorrect code generated
        CMP ax,var1[si]+(type var1) ; Incorrect code generated
        CMP ax,var1[si]+[type var1] ; Incorrect code generated
        CMP ax,type var1+var1[si]   ; correct code generated
        CMP ax,var1[si+type var1]   ; correct code generated
        CMP ax,var1[si]+2           ; correct code generated
        CMP ax,var1[si+2]           ; correct code generated

  main  ENDP
  END main

Additional query words: 5.10 5.10a buglist5.10 buglist5.10a fixlist6.00

======================================================================
Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM510 kbMASM510a
Version           : :5.1,5.1a
Solution Type     : kbfix

=============================================================================

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