Question

Possible Duplicates:
error A2070:invalid instruction operands with MASM
Need help understanding conditional directives with MASM

I am trying to implement the following basic codeblock. I am trying to implement a basic if, elseif, elseif block to learn to use the conditional directives in MASM, but can’t seem to make the logic work.

.if a > b
sub a, 1
.elseif b >= c1
sub b, 2
.elseif c1 > d
mov eax, d
add c1, eax
.else
mov eax, d
cdq
mov ebx, 2
idiv ebx
mov d, eax
.endif

On the .if and .elseif lines I get the above error A2070.

Why? What is the actualy problem with my code?

Answer 1

Most likely MASM expects the compared entities to be directly encodable in a single CMP instruction. CMP supports the following pairs of operands:

• reg/mem, reg
• reg, reg/mem
• reg/mem, imm

Where reg is a register, mem is a memory location, imm is a numeric constant, reg/mem is either reg or mem. Thus, you can’t compare directly two memory locations or two constants, such an operand combination isn’t supported by the CMP instruction.