ASSIGNMENT 2 Solution

Remember that you only need to do one of the assignments below.




In each of these assignments, you will be asked to write a "math library"

function. You will be writing the function in assembly language, using gcc's

inline assembler. Class code files asm.c and cpuid.c are good models for how to

write assembly code for gcc.




You can use a mixture of C code and assembly code for these assignments, but all

floating point calculations (including comparisons) must be done in assembly

language. You should use C only for support tasks like defining and initializing

local variables, returning a value from the function, etc.




Your assembly code should work in the following way:




1. Load values from the function's arguments and local variables onto the

floating point stack (local variables can be initialized first by C code

as long as no calculations are performed).

2. Perform the required calculation entirely within the floating point

stack. Using stack comments in this code will help you keep track of

what's going on. (A stack comment is a comment that specifies what is

supposed to be on the floating point stack after that instruction has

executed. Or you can write stack comments to specify the situation

before the instruction executes if you prefer.)

3. Store the calculated result from the floating point stack to a local

variable

4. Return that the value of that local variable with a C 'return' statement.




The IA-32 Architecture includes the floating point instructions needed to

implement these functions (they all start with the letter 'F'). You will save

yourself a lot of work if you carefully choose the right instructions. This is a

large and powerful instruction set, and you should make use of that power

instead of "re-inventing the wheel." In other words, don't spend a lot of time

writing a lot of dumb code. Instead, spend your time thinking first, and you

will be able to write a smaller amount of smart code.




In your assembly code, you are required to use only the syntax demonstrated in

course file objectCode/asm.c. You are not allowed to use any other GAS syntax,

such as %0, or any specifier other than "=m" in an "output" or "m" in an

"input."




**********************************************************

* THE USE OF ANY PROHIBITED SYNTAX IN YOUR ASSEMBLY CODE *

* WILL RESULT IN A SIGNIFICANT LOSS OF POINTS. *

**********************************************************




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REGULAR VERSION




In hullSpeed(), write FPU assembly code to calculate the "hull speed" of a boat

according to the formula 1.34*sqrt(lgth) where lgth is the length in feet of the

boat at the waterline, and the computed speed is specified in knots.




Start with the provided code file a02.c. Upload your code as a02.c.




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PREMIUM VERSION




This assignment includes all of the work from the Regular version plus this

additional task:




In the function named roundD write assembly code that rounds its first argument

to an integer value according to the rounding mode specified by its second

argument. The function prototype is:




double roundD(double n, RoundingMode roundingMode);




RoundingMode is defined in the starter code.




You will need to set the Rounding Control field of the FPU Control Word in

accordance with the roundingMode argument. You need to do this with assembly

code -- do not use library functions.




You will also need to restore the original value of the FPU's Rounding Control

field before roundD returns. Do not use finit or fninit for this. The original

value is whatever the value was when roundD was called, which could have been

set by the calling function to some arbitrary value, not necessarily what finit

produces.




Start with the provided code file a02p.c. Upload your code as a02p.c.




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HOW TO COMPILE THE CODE FOR ASSIGNMENT 2




Because the code for both versions of this assignment calls the sqrt() function

from math.h, you will need to compile it as follows:




gcc <required flags a02p.c -lm -o a02p




You can use file ~michael.trigoboff/bin/gclm to avoid having to type this.




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REQUIRED PLATFORM




I grade your code on syccuxas01.pcc.edu. Your code is required to compile and

run correctly on that machine.




COMPILING YOUR CODE




You are required to compile your code with the same flags that are used by

the 'gc' bash script in ~michael.trigoboff/bin.




GRADING YOUR CODE




Your code needs to compile without errors or warnings and run correctly. Code

that does not compile will receive zero points. Code that crashes will receive

zero points.




I use bash scripts to grade your code. Because of this, it is very important

that you submit your code with the file name that was requested. If you change

the file name, my scripts will crash, your work will not be graded, you will

have to resubmit a corrected version of your work, and you will lose points.




My scripts produce a log file containing your code, compiler warnings and errors

(if any), your code's output, and some statistics that are useful to me. I then

personally go through that log file to produce your grade. In other words, the

scripts don't generate your grade, they just make it more convenient for me to

generate your grade.




TO SUBMIT THIS ASSIGNMENT




Submit the requested file to Desire2Learn.




* Be certain to check that you completed the upload successfully. After you

click the Upload File button, you must also click the SUBMIT ASSIGNMENT

button. This is very easy to forget. If you do not do this, I will not

see your work and you will get a grade of zero for the assignment. I

would recommend entering an email address so you can be notified that

the upload was completed successfully.

* You may upload as many versions as you wish prior to the due date. I will

only see and grade the final one. You will not be able to upload

assignments after the due date.




Points will be deducted for uploading a file with a name that is not as

specified. Every term I get a few students whose approach to following

directions is, shall we say, "creative." I encourage creativity in general, but

there are places where it is not appropriate.