CODEWITHSUNDEEP
assemblyx86inline-assembly
Dmitry
Dmitry

Reputation: 119

Assembler packing data

I need write assebler code for write 3 letter's word in minimal cell memory this picture, that illustrated what I need:

enter image description here

I'm starting writing code:

    mov eax, dword ptr str[0]
    bsr cl, eax
    inc cl
    shl eax, cl
    push eax
    //
    mov eax, dword ptr str[1]
    pop ebx
    or eax, ebx
    push eax // unshifted
    //
    mov eax, dword ptr str[2]
    bsr cl, eax
    inc cl
    pop ebx
    shl ebx, cl
    or eax, ebx
    mov result, ebx

But I get -934608896 (‭00110111101101010000000000000000‬ after negate)
instead of 1304526 (0100111110011111001110)

Upvotes: 1

Views: 277

Answers (1)

Sep Roland
Sep Roland

Reputation: 39166

The result is in EAX after the final or eax, ebx.
Why do you put EBX in result? Is this the wrong value that you inspect?

This is a code that inserts 3 bitpatterns in the same register:

movzx eax, byte ptr str[0]
movzx ebx, byte ptr str[1]
bsr   ecx, ebx
inc   ecx
shl   eax, cl
or    eax, ebx
movzx ebx, byte ptr str[2]
bsr   ecx, ebx
inc   ecx
shl   eax, cl
or    eax, ebx
mov   result, eax

Upvotes: 5

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