Transformation of based indexed mode into indirect addressing mode (x86 assembly)

Question

I\'m corrently working on changing examples from complex indirect addresssing mode into simple indirect addressing mode pieces. However, I\'ve come across an example from the B

Answer 1

Example 1:

This:

addl    $28, %esp
movl    (%eax), %esp

doesn't do the same thing as move %eax, 28(%esp). What you're looking for is something like:

addl    $28, %esp
movl    %eax, (%esp)

But note that your version modifies the value of esp, while the original instruction does not.

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Example 2:

Again, this:

addl    $28, %esp
cmpl    $4, %esp

doesn't do the same thing as cmpl $4, 28(%esp). The original instruction compares the 32-bit value in memory at address esp+28 with the value 4. Your version compares the value esp+28 with the value 4 (i.e. there's no memory access).