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Case Conversion a la Stack

In this assignment, you will convert the solution of the case conversion homework to use local variables on the stack. You will write a function called to_upper that converts a string from lowercase to uppercase and prints the string. It should not modify the original string--it should instead create a copy the original string and convert the copy to uppercase. The copy will be stored in a local array allocated on the function's stack. I have drawn a stack diagram below.

Stack frame for to_upper:

|------------------------------|
| Return address to main (LR)  |  4 bytes
|------------------------------|
| Pointer to original string   |  4 bytes
|------------------------------|
|                              |  Variable
| Copy of original string      |
|                              |
|------------------------------|

0. Create your main function. Write a prologue and epilogue for main to stash and restore the link register. Your main function will call to_upper
1. Create a string to be converted to uppercase. The string should be located in the .data segment.
2. Create a new function called to_upper. Write a prologue and epilogue for to_upper to stash and restore the link register (see stack diagram above). This function will have one input: a pointer to the string to convert from lowercase to uppercase. The parameter will be passed to to_upper in register r0. In your prologue, save the input parameter on the stack frame by pushing r0. to_upper should do the following things:
   1. Compute the length of the original string by calling strlen, which takes one parameter, the string pointer in r0. It returns the length of the string in r0.
   2. Allocate space on your stack frame to store a copy of the original string. Do this by subtracting the string length from your stack pointer.
   3. Copy the original string into local array using strcpy, which takes two parameters: destination pointer in r0 and source pointer in r1.
   4. Convert the copy to uppercase. You can use the same code from your last homework assignment.
   5. Print the uppercase string by calling puts.
   6. Collapse the stack frame (epilogue) and return.