Name:

Note: Post your submission to ICS$232$ D$2$L site on or before the due date.

Programming Assignment $2$:

The purpose of this project is to gain a greater understanding of the Intel $32-$bit instruction set and understand how a compiler translates C code into assembly language. By compiling the program in unoptimized mode you will hopefully see a fairly clear translation. When running in optimization mode, you will see how well compilers can optimize your code.

To compile an unoptimized version use:

gcc $-$Wa$,-$adhln $-$g $-$masm$=$intel $-$m$32$ "Project $2.$c$">$ "Project $2-$g$.$asm"

This will write the unoptimized inter$-$mixed source and assembly code Project $2-$g$.$asm.

To compile an optimized version use:

gcc $-$Wa$,-$adhln $-$O $-$masm$=$intel $-$m$32$ "Project $2.$c$">$ "Project $2-$o$.$asm"

This will write the optimized inter$-$mixed source and assembly code Project $2-$o$.$asm.

The $-$Wa$,-$adhln option causes gcc to generate intermixed source and assembly code.

The $-$masm$=$intel option causes gcc to generate assembly code in intel format.

The $-$m$32$ generates $32-$bit code.

The $-$g option generates unoptimized code while $-$O generates optimized code.

The web site Godbolt.org can also be used to compile the program. Make sure you use the correct compiler options as shown above.

The generated code includes quite a few directives that can be ignored. Most of the directives begin with a period $(.).$ There are also a few call instructions to procedures that you may not know what they mean that can be ignored. For example:

call $\_\_$x$86.$get$\_$pc$\_$thunk.bx

add ebx, OFFSET FLAT:$\_$GLOBAL$\_$OFFSET$\_$TABLE$\_$

In all of the following questions, the line numbers refer the line numbers in the C code.

The following questions should be answered using the unoptimized code.

$1.$ Describe the stack at line $25($return $($sum$)$;$).$ The bottom of the stack is the first row below. The top of the stack will be the last item. The first few items are provided. You will probably need to add some additional rows to the table below.

Description Value

First argument to main argv

Second argument to main argc

Return address of main Caller$$s return address

C runtime value of bp Caller$$s bp register

Local variable i in main $[$bp$-12]5$

$2.$ In detail explain the code generated for line $105($k $=$ function$1($i$,$ j$)$;$).$ For this and all further questions in which you are asked to explain the code generated in detail, I expect you to copy the generated code and add a comment for each line. For example:

$006$e C$745$FC$00$ mov DWORD PTR $-4[$ebp$],0$ ; initialize i

You can also refer to Week$9-$CAssembly$-$g$.$asm for examples of what you should submit.

$3.$ In detail explain the code generated for function$2($line $29$ through $49).$

$4.$ In detail explain the code generated for function$5($line $80$ through $93).$

The following questions should be answered using the optimized code.

$5.$ In detail explain the code generated for function$1($line $12$ through $27).$ Why does this work?

$6.$ How are function calls optimized? For example, see lines $114$ and $117.$

The following questions should be answered using by comparing the unoptimized code and the optimized code.

$7.$ Compare the code generated by function$4$ in the unoptimized and optimized versions. Explain the optimizations.

Bonus $10$ points

In detail explain the code generated for function$3.$ This a hard. Try your best. Why is the compiler doing this? You need to explain the purpose of each line of the generated assembly code.

Bonus $10$ points

The file strlen.asm contains the Microsoft Visual Studio source code for the strlen$()$ function. You need to explain the purpose of each line of the assembly code particularly lines $81$ through $88.$

Grading Criteria By Project Items:

$1.$ Stack contents not defined well enough $(-5->-10$ points$).$

$2.$ Call functon$1$ description $(-5->-10$ points$).$

$3.$ Code description for function$2$ not complete enough $(-5->-10$ points$).$

$4.$ Code description for function$5$ not complete enough $(-5->-10$ points$).$

$5.$ Optimized function$1$ description incomplete $(-5->-10$ points$).$

$6.$ Optimized function call description incomplete $(-5->-10$ points$).$

$7.$ Function$4$ optimized description incomplete $(-5->-10$ points$).$

Late Submission Policy:

$-10$ points if submitted after the due date and an extension has been granted.

$-20$ points if submitted after the due date and an extension has not been granted.