FIX: Incorrect Code With TYPE and SI Index Register (59374)

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