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???
08/06/09 12:58
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#168215 - If you can ignore those features
Responding to: ???'s previous message
Christoph Franck said:
Richard Erlacher said:
My app's don't have any time to waste either.

I've yet to see/evaluate a 'C' compiler that could keep up with ASM. I've yet to see/evaluate a 'C' compiler that I had time to fool with. They're either time-limited, or they're going to have too small a memory range to be "evaluatable." Now, that's a real waste of time!


4k should be plenty to evaluate the performance-critical parts of most applications for a '51 (usually, the CPU spends 90% of its time executing a handful of percent of the code).

It would be if 4K were all that the MCU had, as the original 8051 had, but ... if tables are in the upper half of the 64KB code space, and the code resides in the lower portion, things can't be evaluated so easily. If you attempt to "evaluate" piece by piece, you get one result. If you evaluate as the end-product will be configured, you get another. If that's good enough for you, well ... fine. It's not good enough for me, though. Most of my ASM code is based on lookup tables, dispatch tables, and table-driven decision trees. It's not unusual for half of my code space to be consumed by tables. Often it's 10% code and 90% tables. At times, it's faster to perform arithmetic by lookup rather than by computation. I could go on ... None of those tasks can be evaluated in their 'C' form with so limited an evaluation version.

And as soon as you look at pipelined architectures (or, even worse, quirks like instructions with delayed execution), writing anything in assembly will become a royal pain in the neck. And after that, you're not faster than the compiler yet, you merely have code that doesn't mess up because of pipeline conflicts - beating the compiler will take another round of work.


If those features were properly and fully documented so that one actually could determine precisely what their effects under various circumstances really are, it would be practical. Cut-and-try approaches aren't sufficiently rigorous to suit me. Architectures that approach non-determinism, or are documented as though they do, don't interest me. The SiLabs parts are entirely deterministic. Consequently, their behavior can be precisely predicted. The lack of a precise simulator is not SiLabs' fault ... it's the fault of those who claim they can simulate the output from their compiler. That's the thing about which the KEIL support folks have repeatedly attempted to mislead me. They've lied about that, saying that timing of the Dallas parts can't be predicted, and they've said the same about the SiLabs parts. The real fact is that their simulator isn't written to simulate a specific core. That would be too much trouble for them.

Letting the compiler "handle" the various deviations from the "standard" core simply ignores those things you say are difficult in ASM. It doesn't solve the problem. That's consistent with relying on 'C' to do the work. It simply means one can proceed with inadequate attention to detail. If you do that, you get what you deserve.

RE




List of 131 messages in thread
TopicAuthorDate
Article: "Real engineers program in C"            01/01/70 00:00      
   C and Latin            01/01/70 00:00      
      similarities between English and C            01/01/70 00:00      
         all sorts of similarities            01/01/70 00:00      
      NOT engineers.....            01/01/70 00:00      
         I think that was his point?            01/01/70 00:00      
            I know            01/01/70 00:00      
               I also don't know if his diagram on Page 3 is right            01/01/70 00:00      
   fewer ASM developers            01/01/70 00:00      
   languages            01/01/70 00:00      
   Muscle Vs Fat            01/01/70 00:00      
      apples vs bears            01/01/70 00:00      
         Wait a minute, pilgrim!            01/01/70 00:00      
            pilgrim has arrived            01/01/70 00:00      
            Break out that DOS Computer            01/01/70 00:00      
               I do that quite often!            01/01/70 00:00      
            blame drivers            01/01/70 00:00      
               Equip them right and they seem to work ... sort-of            01/01/70 00:00      
                  Engineers and Marketing guys            01/01/70 00:00      
            jeeziz x kryst            01/01/70 00:00      
               So ... Why do you do all that?            01/01/70 00:00      
                  wrong choice of word            01/01/70 00:00      
                     It's just a millstone ...            01/01/70 00:00      
                  re: why?            01/01/70 00:00      
      My computer _boots_ faster than that.            01/01/70 00:00      
         DMA?            01/01/70 00:00      
      Maybe it's the amount of memory            01/01/70 00:00      
         The cost of mutlitasking..            01/01/70 00:00      
         haven't any time to waste            01/01/70 00:00      
            That would be too slow!            01/01/70 00:00      
               I see no ships!            01/01/70 00:00      
               Isn't 4k plenty for a '51?            01/01/70 00:00      
                  which '51 does have that?            01/01/70 00:00      
                     Erik would call those "deviates".            01/01/70 00:00      
                        nope            01/01/70 00:00      
                        pipelines, cars, and real engineers            01/01/70 00:00      
                           It's also pipelined.            01/01/70 00:00      
                              then it's irrelevant            01/01/70 00:00      
                  If you can ignore those features            01/01/70 00:00      
               keeping up            01/01/70 00:00      
                  I feel your pain ...            01/01/70 00:00      
                     Don't see problems - see possibilities            01/01/70 00:00      
                        Do you really want to hide from reality?            01/01/70 00:00      
                           Always hiding behind excuses            01/01/70 00:00      
                              What excuses?            01/01/70 00:00      
                                 Your excuses            01/01/70 00:00      
                                    Do you directly or indirectly work for Keil?            01/01/70 00:00      
                                       BULL!!            01/01/70 00:00      
                                          I don't harbor any animosity, but I don't like being lied-to            01/01/70 00:00      
                                             you "understand well enough"            01/01/70 00:00      
                                                I have to agree ... evaluation takes time ...            01/01/70 00:00      
                                                   this is where I think I'm the realist            01/01/70 00:00      
                                                      If only the pieces were separately available ...            01/01/70 00:00      
                                                         I can't and would never            01/01/70 00:00      
                                                            So ... Who's a simulator specialist?            01/01/70 00:00      
                                                               don't know, don't care            01/01/70 00:00      
                                                                  So why even mention it?            01/01/70 00:00      
                                                                     because someone (you?) brought it up            01/01/70 00:00      
                                       Tangential Richard at work            01/01/70 00:00      
                           the pot calling the kettle black            01/01/70 00:00      
                     that's the crux            01/01/70 00:00      
                        It's a matter of realism            01/01/70 00:00      
                           well, if you do not have the time to evaluate, your points            01/01/70 00:00      
                              I have to disagree ...            01/01/70 00:00      
                                 no need            01/01/70 00:00      
                                    That would be an ideal fix!            01/01/70 00:00      
                  no way            01/01/70 00:00      
                     but only if we both define a project            01/01/70 00:00      
                        oh, that's no proof then...            01/01/70 00:00      
                           It would be a nice idea, but how would you time it?            01/01/70 00:00      
                           you did not read what I said            01/01/70 00:00      
                              implication and how to challenge it            01/01/70 00:00      
                                 disassembly            01/01/70 00:00      
                                    Encryption module?            01/01/70 00:00      
                                    not at all            01/01/70 00:00      
                                       It's clear to see that some folks really like 'C'            01/01/70 00:00      
                                          can you only like one thing?            01/01/70 00:00      
                                             Yes, but ...            01/01/70 00:00      
                                                you can boil steak too            01/01/70 00:00      
                                                   but you don't have to do that            01/01/70 00:00      
                                                      but you just said            01/01/70 00:00      
                                       no praise, just not hate            01/01/70 00:00      
                                          That makes sense            01/01/70 00:00      
                                          not that claim            01/01/70 00:00      
                                             again you miss 'usually', 'mostly', 'often', etc            01/01/70 00:00      
                                                Not so ... exactly            01/01/70 00:00      
                                                   Based on what experience?            01/01/70 00:00      
                                                      That's not how it works            01/01/70 00:00      
                                                         maintenance is a totally different issue            01/01/70 00:00      
                                                         apples to pears?            01/01/70 00:00      
                                                            I don't need to compare/contrast apples and pears            01/01/70 00:00      
                                                               The embedded world is larger than your tiny island            01/01/70 00:00      
                                                   IF            01/01/70 00:00      
                                                      It's all about initial hardware cost, not maintenance cost.            01/01/70 00:00      
                                                         Value of investment            01/01/70 00:00      
                                                         Not Here            01/01/70 00:00      
                                                         Whose business?            01/01/70 00:00      
                                                            What do you mean by "code analysis tools"?            01/01/70 00:00      
                                                               Some important tests            01/01/70 00:00      
                                                                  Yes, those come up in HLL, but ...            01/01/70 00:00      
                                                                     Memory leaks nothing to do with HLL            01/01/70 00:00      
                                                                        Yeah, you can do that ... but it's not recommended            01/01/70 00:00      
                                                                           More way than one to create memory leaks            01/01/70 00:00      
                                                                           that is not applicable to small embedded            01/01/70 00:00      
                                                                     Way easier to analyse non-goto code            01/01/70 00:00      
                                                                        and why would that be?            01/01/70 00:00      
                                                                           General purpose languages normally allows dangers            01/01/70 00:00      
                                                                              You still don't get the point, Per            01/01/70 00:00      
                                                                                 Wrong question            01/01/70 00:00      
                                                                                    what view?            01/01/70 00:00      
                                                                                       and the answer is            01/01/70 00:00      
                                                                                       can be seen as a leading question            01/01/70 00:00      
                                                                        Careful now! Some folks like Pascal for the '51            01/01/70 00:00      
                                                                           Why?            01/01/70 00:00      
                                                                        Some things depend on your point of view            01/01/70 00:00      
                                                                           Richard has never, ever, in his whole life implemented a bug            01/01/70 00:00      
                                                                              I may have written 'em, but I've never shipped 'em            01/01/70 00:00      
                                                               QAC and Polyspace            01/01/70 00:00      
                                                                  thanks, Oliver            01/01/70 00:00      
                                                                     MISRA and assembly don't mix well.            01/01/70 00:00      
                                                                        you can write FORTRAN in any language            01/01/70 00:00      
                                                                           I know ... but MISRA rules are explicit.            01/01/70 00:00      
                                                                              Not happy will all parts of MISRA            01/01/70 00:00      
                                                                                 Interesting discussion of MISRA C:            01/01/70 00:00      
                                                                                 Flawed but useful            01/01/70 00:00      
                                                                              Nested comments can produce different results            01/01/70 00:00      
                                                                           That's the thing with rules            01/01/70 00:00      
                                                                     Polyspace            01/01/70 00:00      
            Also in VB            01/01/70 00:00      
               Amazing!            01/01/70 00:00      
   You really are very naughty Andy            01/01/70 00:00      

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