The program division.c is available for download as part of this assignment. It is a binary division program which works for signed integers. It contains a function, div32, which does the signed division; and a main() program which tests division for several pairs of numbers. You should download, compile, and run it to see the output. Now, re-implement the binary division function, div32, in MIPS assembly code, assuming the following convention for passing arguments:
Register Argument Mechanism
$4 dividend pass by value
$5 divisor pass by value
$6 quotient pass by value
$7 remainder pass by value
Although this is not quite the convention used by a "C" compiler (quotient and remainder are pointers and would otherwise by passed by reference), we will use it here since argument passing mechanisms have not been dealt with in detail at this point in the course. In coding your function it is absolutely essential that the context of the calling program is fully preserved.
Then, re-implement the main() program in MIPS assembly code to test the binary division function. The SPIM environment includes a number of SYSCALL functions for printing strings and integers. Test your functions with the same arrays of test cases given. Your results should be identical. Your assembly program must be fully documented, as follows:
First, at the start of each procedure (main and div32) you should have a list of all the registers that you use, and what each is used for. For example, you should have something like the following at the start of your div32 code (you will have many more registers, probably allocated differently; this is just to give the idea):
#--------------------------------------------------------------------------
# Procedure Name: int div32(long dividend, long divisor,
# long quotient, long remainder)
#
# Description:
#
# Register Allocation: $4: dividend (changed)
# $5: divisor (changed)
# ...
# $10: scratch
# ...
# $17: dividend_sign
# $18: divisor_sign
#--------------------------------------------------------------------------
Second, you should have a comment containing the "C" code that you are translating just before the assembly code implementing that "C" code. You should also have a comment at the end of every line of the assembly code. Here's an example:
#--------------------------------------------------------------------------
# if (dividend < 0) {
# dividend_sign = 1;
# dividend = -dividend;
# }
#--------------------------------------------------------------------------
slt $10, $4, $0 # Check if dividend less than 0
beq $10, $0, div20 # If not, skip to next case
li $17, 1 # dividend_sign = 1
negu $4, $4 # negate dividend
#--------------------------------------------------------------------------
# if (divisor < 0) {
# divisor_sign = 1;
# divisor = -divisor;
# }
#--------------------------------------------------------------------------
div20: slt $10, $5, $0 # Check if divisor less than 0
beq $10, $0, div30 # If not, skip ahead
li $18, 1 # divisor_sign = 1
negu $5, $5 # negate dividend