PDP-8 Code Optimization (was Re: HP-35/45 Simulator for PDP-8)

From: Kyle Owen: Tuesday, September 13, 2016 7:12 PM Sigh. There seems to be an issue with my implementation of XOR. Before the CMA IAC there needs to be CLL RAL, to reposition the carries before subtracting them. Both XORs are affected. Since all we are interested in is the sign of the XOR results, only some of the sums end up wrong. Mostly where both operands are negative; there will be a carry out of the sign bit when we add them together. Kyle: I wrote to code to exhaustively enumerate the operand space, and some Perl to generate "correct" answers. Wrote the results to simulated paper tape. With the modification described, the 250Mb result files match. Good thing that paper tape was a simulated one :-). Vince