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ia32 assembly to c

Posted on 2013-12-13
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Last Modified: 2013-12-13
The following is a function that returns either 1 or 0 based on the provided input.
_test:
       pushl       %ebp
       movl       %esp,      %ebp
       subl       $24,      %esp
       movl       8(%ebp),      %eax
       movl       %eax,      -4(%ebp)
       movl       -4(%ebp),      %eax
       movl       %eax,      (%esp)
       call       _strlen
       movl       %eax,      -16(%ebp)
       movl       -16(%ebp),      %eax
       cmpl       $1,      %eax
       jg       LBB1_2
       movl       $1,      -12(%ebp)
       jmp       LBB1_5
LBB1_2:
       movl       -4(%ebp),      %eax
       movb       (%eax),      %al
       movl       -16(%ebp),      %ecx
       subl       $1,      %ecx
       movl       -4(%ebp),      %edx
       movb       (%edx,%ecx),      %cl
       cmpb       %cl,      %al
       je       LBB1_4
       movl       $0,      -12(%ebp)
       jmp       LBB1_5
LBB1_4:
       movl       -16(%ebp),      %eax
       subl       $1,      %eax
       movl       -4(%ebp),      %ecx
       movb       $0,      (%ecx,%eax)
       movl       -4(%ebp),      %eax
       addl       $1,      %eax
       movl       %eax,      (%esp)
       call       _test
       movl       %eax,      -12(%ebp)
LBB1_5:
       movl       -12(%ebp),      %eax
       movl       %eax,      -8(%ebp)
       movl       -8(%ebp),      %eax
       addl       $24,      %esp
       popl       %ebp
       ret
a. Provide an input for which this function will return 1. What does this function do?
b. Write the equivalent C function.
c. The performance of this function will be abysmal. There are two major issues with the code.
Identify them and rewrite the function to perform better.
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Question by:KeithStone
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3 Comments
 

Author Comment

by:KeithStone
ID: 39716932
I believe that the program is checking for palindromes, but im not really sure about parts b and c
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Accepted Solution

by:
Kent Olsen earned 500 total points
ID: 39717115
Hi Keith,

This is clearly an assignment of some sort, probably class/school work.  As such, out ability to help is limited so that we all maintain a high degree of academic integrity.

One thing that we can't do is rewrite this for you.  Short of that, how can we help?


Kent
0
 

Author Closing Comment

by:KeithStone
ID: 39717233
You're right, ill get it done myself
0

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