ITEC 352 Lecture 14 ISA(6)

Review Questions? Beginning / End Memory locations Variable / Memory syntax PSR Loops / Branches

ISA(6) More assembly What does the program I show you do? How important are comments in assembly? How would we write a JAVA program that would produce similar assembly? What are the benefits / downsides of each approach to writing the software? Why are the memory locations offset by 4?

ISA(6) Conditionals ba –Always branch bne –Brach when Z is not 0 be –Branch when Z is 0 bg /bge ble –Branch when not (Z or (N xor V)) bpos / bneg –Branch when negative bit is on or off bv(c/s) –Overflow bit cleared or set How would you use these conditionals?

ISA(6) Jumping call –Goto a specific label in the program (memory where label is must be within 30 bits of the call statement) –Saves location of where call is in %r15 jmpl –Goto a specific address and store the location of the jmpl in %r15

ISA(6) Shifty Shift right (srl) –Shift a register by a certain % of bits and store the result in another register (0s are padded) –Syntax? Shift left (sll) –Instead of the right, go left Why is shifting bits important?

ISA(6) Summary Assembly instructions / simple program