Homework Assignment 4
                               CS 340d
                         Unique Number: 50960
                             Spring, 2019

                       Given:  February 18, 2019
                        Due:  February 27, 2019


1.  This problem is an evolution of Problem 1 from HW #3.  Our specification
    remains the same:

    char *dst, *src;
    // Set src and dst pointers
    *dst++ = *src++;

    This program fragment copies memory bytes from *src to *dst one
    byte at a time.

    Unlike Problem 1 from HW #3, we no longer know that the initial
    value of pointer ``src'' is long-word (8-byte) aligned.  If it is,
    then the solution you produced for Problem 1 of HW #3 should
    (hopefully) work.  But, if the starting point of ``src'' is not
    8-byte aligned, then you will need to do some additional work.

    Your solution should not read each word from the ``src'' more than
    once.


2.  Write C code that performs the x86 function shown.  The assembler
    code below was produced by running ``gcc -O2 -S hw4-re-problems.c''
    on a UTCS Linux system.  Your task is to produce C-language code
    that the compiler might have received to produce this output.

      fun_1:
              leaq    (%rdi,%rdi,8), %rax
              ret

3.  Write C code that performs the x86 function shown.

      fun_2:
              .cfi_startproc
              movq    %rdi, %rdx
              movq    %rdi, %rax
              salq    $56, %rdx
              shrq    $56, %rax
              orq     %rdx, %rax
              movq    %rdi, %rdx
              andl    $65280, %edx
              salq    $40, %rdx
              orq     %rdx, %rax
              movq    %rdi, %rdx
              andl    $16711680, %edx
              salq    $24, %rdx
              orq     %rdx, %rax
              movq    %rdi, %rdx
              andq    $-16777216, %rdx
              salq    $8, %rdx
              orq     %rdx, %rax
              movq    %rdi, %rdx
              shrq    $8, %rdx
              andl    $4278190080, %edx
              orq     %rdx, %rax
              movq    %rdi, %rdx
              shrq    $40, %rdi
              shrq    $24, %rdx
              andl    $65280, %edi
              andl    $16711680, %edx
              orq     %rdx, %rax
              orq     %rdi, %rax
              ret


4.  Write C code that performs the x86 function shown.

      fun_3:
              .cfi_startproc
              cmpq    %rcx, %rdx
              movq    %rdi, %rax
              cmovl   %rcx, %rdx
              cmpq    %rsi, %rdx
              cmovge  %rdx, %rsi
              cmpq    %rdi, %rsi
              cmovge  %rsi, %rax
              ret

5.  Turn in your C-language code for Part A of Lab #1.  This is a way
    for you to get early feedback on your Lab #1 effort.