Charles I stand corrected!
Edit: it *should be* all the same to the compiler (if the compiler knew what it was doing).. Brian -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Charles Stevenson Sent: 20 April 2012 14:28 To: U2 Users List Subject: Re: [U2] Case Statement with only two cases A respectful correction, Brian. On 4/20/2012 4:50 AM, Brian Leach wrote: > it's all the same to the compiler. > -----Original Message----- > BEGIN CASE > CASE A = "TEST"; GOSUB DO.SOMETHING > CASE 1; GOSUB DO.SOMETHING.ELSE > END CASE > versus this > IF A = "TEST" THEN GOSUB DO.SOMETHING ELSE GOSUB DO.SOMETHING.ELSE ----- Since we seem to be finding every nit in the bottom of this empty barrel, here's one more. There are 2 compiler difference as shown by VLIST (UV10.2): 00001: BEGIN CASE 00002: CASE A = "TEST"; GOSUB DO.SOMETHING 00002 00000 : 06E eq A "TEST" => $R0 00002 00008 : 2DE testfw $R0 00020: 00002 00010 : 0A4 gosub 00060: 00003: CASE 1; GOSUB DO.SOMETHING.ELSE 00003 00018 : 0C2 jump 00038: 00003 00020 : 2DE testfw 1 00038: <-------------- Extra worthless test 00003 00028 : 0A4 gosub 00062: 00004: END CASE 00004 00030 : 0C2 jump 00038: <-------------- Extra worthless jump (to next line) (Source lineup is goofy. This jump is really part of source line 3. RAID is confusing, too. A discussion for a different thread.) 00005: IF A = "TEST" THEN GOSUB DO.SOMETHING ELSE GOSUB DO.SOMETHING.ELSE 00005 00038 : 06E eq A "TEST" => $R0 00005 00040 : 2DE testfw $R0 00058: 00005 00048 : 0A4 gosub 00060: 00005 00050 : 0C2 jump 00060: 00005 00058 : 0A4 gosub 00062: 00006: STOP 00006 00060 : 190 stop With the speed of today's machines it would be hard to find a place where that performance makes a difference. Rocket could theoretically clean up both (or either independently) if the compiler was smart enough: 1. to know that a logical test outcome was predestined at compile time (It already does that sort of thing in other situations.). Then it could compile only 1 of the 2 paths the testfw takes. (e.g. 0020x). Same for IF, WHILE, or UNTIL constructs. 2. To recognize the final CASE before the END CASE never needs to jump (e.g., 0030x). I wonder if we've already wasted more electrical & biological energy by me writing this email, dispersing it around the globe, and you reading it, than all the machine cycles wasted executing the 2 worthless tests in all the object scattered around the universe that Rocket could theoretically optimize. cds _______________________________________________ U2-Users mailing list [email protected] http://listserver.u2ug.org/mailman/listinfo/u2-users _______________________________________________ U2-Users mailing list [email protected] http://listserver.u2ug.org/mailman/listinfo/u2-users
