projects / ned1 / blame
| Commit | Line | Data |
|---|---|---|
| bc5b63cf AT |
1 | # Operands |
| 2 | WORD_174 | |
| 3 | WORD_186 | |
| 4 | ||
| 5 | # Multiplication routine | |
| 6 | # Restrictions: | |
| 7 | # Positive numbers only (31 shifts max since operands are twos-complement) | |
| 8 | # No overflow checking | |
| 9 | ||
| 10 | multiply | |
| 11 | WORD_2147483648 # For use in setting sign for left shifts. | |
| 12 | IM_0 # For magnitude of left/right shifts. | |
| 13 | LDSP+0 # Sets up stack location to build/store result. | |
| 14 | #----- | |
| 15 | testbit # | |
| 16 | LDSP+3 # | |
| 17 | LDSP+2 # | |
| 18 | SHIFT # Check Nth bit of second operand. | |
| 19 | IM_1 # | |
| 20 | AND # | |
| 21 | TEST # | |
| 22 | #----- | |
| 23 | BRZ>skipadd # | |
| 24 | LDSP+4 # | |
| 25 | LDSP+3 # | |
| 26 | LDSP+3 # | |
| 27 | OR # Shift and add first operand to result if indicated. | |
| 28 | SHIFT # | |
| 29 | ADD # | |
| 30 | skipadd # | |
| 31 | #----- | |
| 32 | LDSP+1 # | |
| 33 | IM_1 # Increment counter for shift magnitude | |
| 34 | ADD # | |
| 35 | STSP+1 # | |
| 36 | #----- | |
| 37 | IM_30 # | |
| 38 | NOT # | |
| 39 | IM_1 # | |
| 40 | ADD # Test for completion of multiplication subroutine (31 shifts). | |
| 41 | LDSP+2 # | |
| 42 | ADD # | |
| 43 | TEST # | |
| 44 | BRZ>cleanup # If finished, cleanup and return from subroutine with result on TOS. | |
| 45 | #----- | |
| 46 | IM_0 # | |
| 47 | TEST # If not finished, repeat this process on the next bit. | |
| 48 | BRZ>testbit # | |
| 49 | #----- | |
| 50 | cleanup # | |
| 51 | STSP+0 # | |
| 52 | STSP+0 # | |
| 53 | STSP+0 # Remove all subroutine temporaries from stack and return result on TOS. | |
| 54 | STSP+0 # | |
| 55 | HALT # |