Testing Clang + LLVM

Article: Bulldozer Benchmarks, What Do They Mean?
By: Vincent Diepeveen (diep.delete@this.xs4all.nl), April 20, 2011 6:31 am
Room: Moderated Discussions
Brett (ggtgp@yahoo.com) on 4/7/11 wrote:
---------------------------
>Vincent Diepeveen (diep@xs4all.nl) on 4/7/11 wrote:
>---------------------------
>>none (none@none.com) on 4/6/11 wrote:
>>---------------------------
>>>Vincent Diepeveen (diep@xs4all.nl) on 4/6/11 wrote:
>>>---------------------------
>>As for GCC, I've already posted something before here on inefficiency with assembler
>>output attached and clear proof of sabotage of the GCC compiler in order to keep it slow.
>>
>>GCC isn't getting sold and therefore always will be kept slow.
>>GCC really is a disaster at integer codes.
>>
>>Not because it lacks brilliancy; it's not even at beginners level; it's doing all
>>sorts of things that are not necessary generating either too many branches and generating too many instructions.
>
>Apple is dumping GCC for Clang with LLVM, in another ~5 years no one that cares about performance will care about GCC.
>(People with broken legacy code will of course still care.)
>
>Have you taken a look at Clang and how it compares with commercial compilers?
>Would like to know your opinion.
>

Hi, i have just downloaded clang + llvm.

First impression is that someone cut'n pasted the GCC compiler, put a new logo in front of it: "this is clang".

I call that cloning actually. It's gcc 4.2.1 and from the compile options it's obvious it doesn't know all kind of stuff more recent GCC's do know (without that it produces faster code for GCC but that's another issue).

First i compiled with GCC. And ran my code directly parallel at 16 cores (barcelona).

Clang is older GCC compiler so doesn't know the -march=barcelona -mtune=barcelona.

No big deal i replaced it by -march=k8 and -mtune=k8
Just simple -O2 compile. No fancy other stuff yet.

I start clang compiled version, which not surprisingly in size is not much different from the version a newer GCC version produces.

CRASH

It's crashing on me Brett. It's like open64 there.
What you download for free crashes and i bet the version apple is gonna spread isn't crashing.

But now from a meta viewpoint.

a) it isn't compiling faster at all
b) it's crashing and i'm 100% sure it won't be faster than a later GCC version in terms of execution speed of code.

For users there are 2 things that matters, as opposed to programmers.

1) it must not crash
2) it must do what they want and in my case what i do must be faster than elsewhere. A big problem of apple in general, and realize i write this at an apple macbookpro, is that they have crap software.

Want to copy more than 1 file at once? Ever tried it at os/x?

You select say 2 files, click right mouse button. DANG and it just selected 1 file, the one you rightclicked.
What works so easily in *nix and windows it just doesn't work like that in apple. In apple you need to move MORE with the mouse to get the SAME thing done. Bad for your wrists man.

You have a TFT attached to your laptop (which in many companies many dudes do)? BAD IDEA with apple. the pulldown menu is not where your program is, but in most cases you must manoeuvre with the mouse back to the other TFT to select the function you want in the pulldown menu. Really childish to still use some 'feature' from the 80s even in todays multitasked and multithreaded environment where every kid has more than 1 TFT; modern gpu's support half a dozen TFT's already for 'em.

Now we remember the crap thing called cloud computing. It's utter crap, yet some companies manage to sell it a tad to persons who are bad in moneymath.

If you throw enough cash into some slogans, it always works.

In case of LLVM, i don't really see the advantage of it over GCC so far.

It's true that if apple would pay 1 guy to optimize the GCC compiler, that for many generic programs it will produce way way faster code (i mean of course programs NOT in specint) than GCC. Yet the strategy of clang+llvm seems to be to cut'n paste existing compilers.

Nothing new there.

But in this case in fact it crashes on me. I added debug code, still crashes. It can't multithread or something?

Figuring all this out in order to find out it isn't generating code that executes faster is going to be a focking waste of time of course.

clang to me seems like: have a buzzword, cut'n paste years of hard work (gcc compiler) and then throw it on the market as being your own.

Sometimes works. But i'm guessing we soon have to pay for it in order to not crash, just like open64? You need to pay for the pgi compiler in order to have a non-crashing copy of open64; in order to find out it's lightyears slower (50% default - too much to even seriously measure) than GCC and with PGO code it's still considerable slower (yet a lot less than 50%, like 10% or so than gcc; so it profits bigtime there from pgo unlike gcc as this feature has been BROKEN in gcc for as long as they implemented it).

Regards,
Vincent


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TopicPosted ByDate
New article: Bulldozer benchmark analysisDavid Kanter2011/03/30 02:27 AM
  New article: Bulldozer benchmark analysisNaN2011/03/30 07:47 AM
    New article: Bulldozer benchmark analysisDavid Kanter2011/03/30 09:25 AM
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                  Post removedDavid Kanter2011/04/02 12:39 PM
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              New article: Bulldozer benchmark analysisNaN2011/04/02 09:24 AM
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                      AMD's Open64 compiler ?Richard Cownie2011/04/04 09:52 AM
                        AMD's Open64 compiler ?David Kanter2011/04/04 01:20 PM
                          AMD's Open64 compiler ?none2011/04/04 02:25 PM
                        AMD's Open64 compiler ?gallier22011/04/04 11:06 PM
                          thanks, very interesting (NT)Richard Cownie2011/04/05 03:44 AM
                          AMD's Open64 compiler ?Andreas Stiller2011/04/05 08:23 AM
                        AMD's Open64 compiler ?Vincent Diepeveen2011/04/06 01:11 AM
                      AMD's Open64 compiler ?Vincent Diepeveen2011/04/06 01:01 AM
                        AMD's Open64 compiler ?none2011/04/06 01:41 AM
                          AMD's Open64 compiler ?Vincent Diepeveen2011/04/07 02:02 PM
                            AMD's Open64 compiler ?Brett2011/04/07 04:55 PM
                              AMD's Open64 compiler ?Megol2011/04/09 11:03 AM
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                                            Clang+LLVMLinus Torvalds2011/04/13 04:40 PM
                                              Clang+LLVManon2011/04/13 07:31 PM
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                                                      Clang+LLVM?2011/04/15 10:11 PM
                                                        Clang+LLVMLinus Torvalds2011/04/16 08:10 AM
                                                          Clang+LLVMLinus Torvalds2011/04/16 08:32 AM
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                                                            Clang+LLVMEduardoS2011/04/17 12:38 PM
                                                              Clang+LLVMLinus Torvalds2011/04/17 02:00 PM
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                                                                  Competing for speedLinus Torvalds2011/04/18 09:07 AM
                                                                    Competing for speedanon2011/04/18 05:38 PM
                                                                      Competing for speedLinus Torvalds2011/04/18 07:24 PM
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                                                                    Competing for speed?2011/04/18 11:45 PM
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                                                                        Competing for speedLinus Torvalds2011/04/19 07:46 AM
                                                                        Oh ... the irony?2011/04/19 10:36 AM
                                                                          Oh ... the ironyLinus Torvalds2011/04/19 01:49 PM
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                                                                          Oh ... the ironyDougal2011/04/20 06:23 AM
                                                                            Oh ... the irony?2011/04/25 12:05 PM
                                                                              Oh ... the ironyDougal2011/04/26 05:22 AM
                                                                                Oh ... the irony?2011/04/27 12:14 AM
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                                                        Clang+LLVManon2011/04/18 05:28 PM
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                              AMD's Open64 compiler ?Paul2011/04/10 02:50 AM
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                                  C++ front-endsPaul2011/04/10 07:19 AM
                                    C++ front-endsanonymous2011/04/10 07:28 AM
                                      C++ front-endsnone2011/04/10 07:36 AM
                                      C++ front-endsPaul2011/04/10 07:44 AM
                                    C++ front-endsMichael S2011/04/10 07:47 AM
                                      C++ front-endsnone2011/04/10 07:51 AM
                                      C++ front-endsRob Thorpe2011/04/10 11:13 AM
                                        C++ front-endsPaul2011/04/11 10:07 AM
                                AMD's Open64 compiler ?Konrad Schwarz2011/04/14 01:06 AM
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                                        Testing Clang + LLVMnone2011/04/21 02:36 AM
                                        Testing Clang + LLVMahnoun2011/04/21 11:02 AM
                                          Testing Clang + LLVMMichael S2011/04/21 12:01 PM
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                              Imperative compilers (and the lack of it)?2011/04/10 12:36 AM
                                Imperative compilers (and the lack of it)?2011/04/10 12:43 AM
                                Imperative compilers (and the lack of it)Paul2011/04/10 02:37 AM
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                                          U+269B?2011/04/13 03:52 AM
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                                              U+269BMichael S2011/04/20 09:11 AM
                                                U+269BHeath Provost2011/04/20 10:26 AM
                                                  You are right, Heath. Sorry, Brannon.Michael S2011/04/20 10:42 AM
                                                    Sorry again, Brendan (NT)Michael S2011/04/20 10:43 AM
                                                    Testing western non-us letters.Jouni Osmala2011/04/20 09:41 PM
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                                                      Testing western non-us letters.Heath Provost2011/04/21 11:15 AM
                                                        Testing western non-us letters.EduardoS2011/04/22 02:14 PM
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                                                                We actually upgraded to 2008 R2rwessel2011/04/22 11:11 PM
                                                                  We actually upgraded to 2008 R2David Kanter2011/04/22 11:28 PM
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                                                                      We actually upgraded to 2008 R2David Kanter2011/04/24 03:36 PM
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                                                                        We actually upgraded to 2008 R2EduardoS2011/04/24 08:10 PM
                                                                          We actually upgraded to 2008 R2David Kanter2011/04/24 11:04 PM
                                                                        We actually upgraded to 2008 R2anonymous2011/04/24 08:44 PM
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                                                                          File size optimizationsRicardo B2011/04/25 07:14 AM
                                                                            File size optimizationsjrl2011/04/25 05:52 PM
                                                                          File size optimizationsDavid Kanter2011/04/25 07:49 AM
                                                                            File size optimizationsRicardo B2011/04/25 08:22 AM
                                                                              ContinuationRicardo B2011/04/25 08:25 AM
                                                                              File size optimizationsChristian Packmann2011/04/25 09:56 AM
                                                                                File size optimizationsEduardoS2011/04/25 11:57 AM
                                                                                  File size optimizationsRicardo B2011/04/25 01:01 PM
                                                                            File size optimizationsEduardoS2011/04/25 12:01 PM
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                                                                          File size optimizationsEduardoS2011/04/25 12:14 PM
                                                                            File size optimizationsrwessel2011/04/25 12:49 PM
                                                                              File size optimizationsEduardoS2011/04/25 12:57 PM
                                                                            File size optimizationsjrl2011/04/25 05:54 PM
                                                                              A simple approachSilent2011/04/25 09:24 PM
                                                                                Show Thread exists but the default is Yes (NT)Silent2011/04/25 09:26 PM
                                                                          File size optimizationsHeath Provost2011/04/25 02:02 PM
                                    Imperative compilers (and the lack of it)Azazel2011/04/12 08:23 PM
                                Imperative compilers (and the lack of it)none2011/04/10 06:00 AM
                                  Imperative compilers (and the lack of it)dmsc2011/04/10 06:39 AM
                                  Imperative compilers (and the lack of it)EduardoS2011/04/10 12:55 PM
                                compiler failure rateshobold2011/04/10 10:55 AM
                                  compiler failure rates?2011/04/10 11:13 PM
                                    compiler failure rateshobold2011/04/11 05:07 AM
                                Imperative compilers (and the lack of it)EduardoS2011/04/10 12:55 PM
                                  Imperative compilers (and the lack of it)?2011/04/10 11:13 PM
                                    Imperative compilers (and the lack of it)Konrad Schwarz2011/04/14 01:28 AM
                                      Imperative compilers (and the lack of it)gallier22011/04/14 04:47 AM
                                      Imperative compilers (and the lack of it)EduardoS2011/04/14 02:04 PM
                                        Imperative compilers (and the lack of it)Konrad Schwarz2011/04/15 03:43 AM
                                Hard register problemsRob Thorpe2011/04/11 12:14 AM
                                  Hard register problemsMax2011/04/11 03:05 PM
                                    Hard register problemsRob Thorpe2011/04/11 03:28 PM
                                Imperative compilers (and the lack of it)gallier22011/04/11 09:26 AM
                                  I wonder why.j2011/04/11 10:39 PM
                                    I wonder why.?2011/04/11 11:44 PM
                                Imperative compilers (and the lack of it)nksingh2011/04/12 11:00 PM
                                  Imperative compilers (and the lack of it)?2011/04/12 11:23 PM
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                                AMD's Open64 compiler ?none2011/04/10 07:23 AM
                                  AMD's Open64 compiler ?Eugene Nalimov2011/04/11 03:57 PM
                                    AMD's Open64 compiler ?EduardoS2011/04/12 02:55 PM
                                AMD's Open64 compiler ?Megol2011/04/10 11:05 PM
                                  AMD's Open64 compiler ?Vincent Diepeveen2011/04/20 12:52 PM
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                                      Yap transform? What is it? (NT)Vincent Diepeveen2011/04/22 02:56 AM
                    AMD's Open64 compiler ?Vincent Diepeveen2011/04/05 12:02 PM
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        AMD's memory controllers are fineDavid Kanter2011/03/31 09:27 AM
          AMD's memory controllers are fineanon2011/04/05 11:24 AM
            AMD's memory controllers are fineanon2011/04/05 04:52 PM
              AMD's memory controllers are fineVincent Diepeveen2011/04/06 01:36 AM
                AMD's memory controllers are fineanon2011/04/06 06:59 AM
                  AMD's memory controllers are fineVincent Diepeveen2011/04/07 02:15 PM
                    AMD's memory controllers are fineVincent Diepeveen2011/04/07 02:27 PM
                      AMD's memory controllers are fineanon2011/04/07 02:57 PM
                    AMD's memory controllers are fineanon2011/04/07 02:54 PM
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      a waste of timeDavid Kanter2011/04/09 06:56 PM
        a waste of timehorsefly2011/04/10 05:13 AM
          InvestorsDavid Kanter2011/04/10 06:27 AM
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