Email: Password: Remember Me | Create Account (Free)

Back to Subject List

Old thread has been locked -- no new posts accepted in this thread
???
02/16/07 09:45
Read: times


 		 #133114 - SDCC peephole optimiser conflict
Responding to: ???'s previous message
I had a closer look at that last example, as I think this is quite a simple case (djnz).

I found out that this is exactly the case, when one of the strengths of SDCC - the peephole optimizer - turned into its weakness. The trouble is, that the peephole optimisations do interact.

In this case, there is a peephole optimisation (#257.b) which is supposed to turn a dec/jnz pair into djnz; but it is "spoiled" by peephole #160.c, which turns jnz (and subsequent jmp) into jz...

JW


List of 68 messages in thread
TopicAuthorDate
Speed Recommendation            01/01/70 00:00      
   Time for processing            01/01/70 00:00      
   Get a 1X Chip            01/01/70 00:00      
      another 485 issue            01/01/70 00:00      
         slightly less            01/01/70 00:00      
            who gives a hoot            01/01/70 00:00      
               maybe yes, maybe not...            01/01/70 00:00      
   Choose the appropriate tool!            01/01/70 00:00      
      Don't have much of a choice!            01/01/70 00:00      
         drop the "coding standards"            01/01/70 00:00      
         Yikes.            01/01/70 00:00      
            down memory lane            01/01/70 00:00      
               a possible compromise...            01/01/70 00:00      
                  Well...            01/01/70 00:00      
               The other end of the spectrum ...            01/01/70 00:00      
                  afer quite a few iterations....            01/01/70 00:00      
                     The guide to writing unmaintainable code says:            01/01/70 00:00      
         That's the kind of nonsense...            01/01/70 00:00      
   put some load on the hardware            01/01/70 00:00      
      Jan, oh Jan            01/01/70 00:00      
      9-bit - more work for the hardware!            01/01/70 00:00      
         true, but...            01/01/70 00:00      
            It is...            01/01/70 00:00      
               calculate the ISR after making the ISR skip            01/01/70 00:00      
   Optimizing C            01/01/70 00:00      
      just one example            01/01/70 00:00      
         The advantage is...            01/01/70 00:00      
            If the thinking had preceded the coding ...            01/01/70 00:00      
               you miss the point            01/01/70 00:00      
                  then what's the chance of having him to C-craft?            01/01/70 00:00      
                     zero            01/01/70 00:00      
                     Job security, of course.            01/01/70 00:00      
      Examples are not equivalent            01/01/70 00:00      
         Wasn\'t saying that they were.            01/01/70 00:00      
            I just tried SDCC...            01/01/70 00:00      
               Hm, can you post the assembly output ?            01/01/70 00:00      
                  Keil does this            01/01/70 00:00      
                     Interesting.            01/01/70 00:00      
                     Optimizing and Keil/SDCC/Raisonance            01/01/70 00:00      
                        Retort            01/01/70 00:00      
                           Register Banks...            01/01/70 00:00      
                              benchmarks            01/01/70 00:00      
                              tools differ            01/01/70 00:00      
                              Clarification            01/01/70 00:00      
                                 comments            01/01/70 00:00      
                                    not to write things twice            01/01/70 00:00      
                                       no need            01/01/70 00:00      
                                          And how does this produce two incarnations?            01/01/70 00:00      
                                             like this            01/01/70 00:00      
                                                hehe            01/01/70 00:00      
                                                   this is no better confusion-wise            01/01/70 00:00      
                                                      what is "efficient"            01/01/70 00:00      
                                                         ok is \'safe\' better?            01/01/70 00:00      
                                                            How to convey our ideas to the mcu?            01/01/70 00:00      
                                                               Carefull now, you could end with Prolog :)            01/01/70 00:00      
                                                                  my kids            01/01/70 00:00      
                                                            Huge code != huge time            01/01/70 00:00      
                                                               This comes under the heading of "famous last words            01/01/70 00:00      
                        the question I always raise on this            01/01/70 00:00      
                           Here's Why...            01/01/70 00:00      
                  SDCC            01/01/70 00:00      
                     Thanks. Also interesting.            01/01/70 00:00      
                     SDCC peephole optimiser conflict            01/01/70 00:00      
                  Raisonance            01/01/70 00:00      
   help me ,I NEED SOME HELP ON MY PROJECT            01/01/70 00:00      
      that is NOT 'help'            01/01/70 00:00      
      Well that is not the way to get it!            01/01/70 00:00      
      start a new thread!            01/01/70 00:00      

Back to Subject List