Clang+LLVM

Article: Bulldozer Benchmarks, What Do They Mean?
By: Linus Torvalds (torvalds.delete@this.linux-foundation.org), April 13, 2011 4:40 pm
Room: Moderated Discussions
Rob Thorpe (rthorpe@robertthorpeconsulting.com) on 4/13/11 wrote:
>
>>So for fast compilation, you really do end up wanting a
>>tokenization/preprocessing/semantic parsing all very much
>>tied into each other. Automated tools tend to suck for
>>that. The generated parsers all tend to be about just one
>>level, and tying them together is a fools errand.
>
>I'm not sure that's really so difficult.

I suspect it's one of those problems that aren't all
that difficult in theory, but in practice you end up
fighting all the silly impedance issues because the
tools expect one model, and mixing generated code with
the non-generated gets ugly really quickly.

>Take the Yacc/Bison approach for example. Bison asks a lexer function to supply
>a token.

Sure. And the end result tends to be very messy and not
very maintainable, because you have to mix the bison
code with your own complex code, and the bison code has
to (obviously) follow the bison rules.

And it all works fine if the language is very simple and
regular, and the syntax is very close to the parsing
language. Then you don't have a lot of impedance issues,
and so bison works fine for a language grammar that really
is context-free.

But that is seldom the case. It's certainly not the case
for C (much less C++). C is close enough to context-free
that you can do things within the confines of something
like bison without it being too painful, but when
you get to C++, you're going to be in real pain.

So then you need a new generator language that matches the
language semantics more closely, and in practice that means
that you are likely not working with a generic parser
generator any more, but a language-specific one.

At which point you're now writing your own generator, or
hope somebody else already did it.

You might as well just write the parser yourself instead.
Usually using a trivial recursive-descent model, which is
dead simple, rather than even trying to do anything fancy.

The downsides of that "stupid" approach would tend to be
totally outweighed by then being able to avoid all the
mismatches between the parser generator and the language
you're parsing.

And don't get me wrong: I think yacc/bison are great for
what they do well - simple, very regular parsers. And I'm
also sure that writing even a rather specialized parser
generator can actually be a great idea.

But I do think that in the end, it turns out that most
parsers aren't all that complicated. I think there's a
good reason all the major compiler projects for C-like
languages end up doing their own hand-written recursive
descent parsers.

(I think gcc _used_ to use bison for C parsing, but afaik
it hasn't done that for many years now - it was just too
damn painful to have different parsers, and the hacks for
bison to do C++ are just too horrid)

Linus
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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
      New article: Bulldozer benchmark analysisdc2011/03/30 12:07 PM
      New article: Bulldozer benchmark analysisFoo_2011/03/30 12:17 PM
        New article: Bulldozer benchmark analysisDavid Kanter2011/03/30 01:34 PM
          BD won't "kick in" until 2.5GHzBaronMAtrix2011/03/31 08:37 AM
            BD won't "kick in" until 2.5GHzDavid Kanter2011/03/31 09:21 AM
              He is an AMDZone lunaticNIKOLAS2011/04/01 06:40 AM
                See how he behaves hereDavid Kanter2011/04/01 08:08 AM
                He is an AMDZone lunatichorsefly2011/04/02 05:46 AM
                  This is not relevantDavid Kanter2011/04/02 09:16 AM
                  Post removedDavid Kanter2011/04/02 12:39 PM
          New article: Bulldozer benchmark analysisanonymous2011/04/04 05:08 AM
      New article: Bulldozer benchmark analysisinterested2011/04/01 03:28 PM
        New article: Bulldozer benchmark analysisDavid Kanter2011/04/01 03:53 PM
          New article: Bulldozer benchmark analysisNaN2011/04/02 07:12 AM
            New article: Bulldozer benchmark analysisDavid Kanter2011/04/02 09:05 AM
              New article: Bulldozer benchmark analysisNaN2011/04/02 09:24 AM
                New article: Bulldozer benchmark analysisDavid Kanter2011/04/02 12:36 PM
                  AMD's Open64 compiler ?Alex2011/04/04 02:23 AM
                    AMD's Open64 compiler ?David Kanter2011/04/04 08:19 AM
                      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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                                          Life is not about money, but about power (and informational asymetry)?2011/04/18 01:14 AM
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                                                    Clang+LLVMJouni Osmala2011/04/14 09:54 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+LLVMLinus Torvalds2011/04/17 02:00 PM
                                                                Competing for speed?2011/04/17 10:57 PM
                                                                  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
                                                                        Competing for speedanon2011/04/19 05:05 AM
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                                                                            Competing for speedLinus Torvalds2011/04/22 11:09 AM
                                                                    Competing for speed?2011/04/18 11:45 PM
                                                                      Competing for speedLinus Torvalds2011/04/19 06:41 AM
                                                                        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
                                                                            What's the speedup?iz2011/04/19 10:54 PM
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                                                                            Oh ... the irony?2011/04/23 05:52 AM
                                                                          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
                                                  Clang+LLVMRob Thorpe2011/04/16 01:23 PM
                                                    Clang+LLVManon2011/04/16 03:01 PM
                                                      Clang+LLVMRob Thorpe2011/04/18 04:53 AM
                                                        Clang+LLVManon2011/04/18 05:28 PM
                                        Clang+LLVMPaul2011/04/14 10:43 AM
                                  Clang+LLVMFoo_2011/04/12 05:36 AM
                              AMD's Open64 compiler ?Paul2011/04/10 02:50 AM
                                C++ front-endsDavid Kanter2011/04/10 06:29 AM
                                  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
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                            AMD's Open64 compiler ?Megol2011/04/09 10:49 AM
                              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
                                  Imperative compilers (and the lack of it)?2011/04/10 05:30 AM
                                  Imperative compilers (and the lack of it)Vincent Diepeveen2011/04/10 06:20 AM
                                  Imperative compilers (and the lack of it)Gabriele Svelto2011/04/11 08:24 AM
                                  Imperative compilers (and the lack of it)Michael S2011/04/12 12:12 AM
                                    Imperative compilers (and the lack of it)?2011/04/12 01:41 AM
                                      Imperative compilers (and the lack of it)EduardoS2011/04/12 03:13 PM
                                        U+269BMichael S2011/04/13 12:45 AM
                                          U+269B?2011/04/13 03:52 AM
                                            U+269BBrendan2011/04/20 07:18 AM
                                              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
                                                      Those show up fine to me (NT)David Kanter2011/04/21 07:48 AM
                                                      Testing western non-us letters.Heath Provost2011/04/21 11:15 AM
                                                        Testing western non-us letters.EduardoS2011/04/22 02:14 PM
                                                          Testing western non-us letters.Heath Provost2011/04/22 03:21 PM
                                                            Testing western non-us letters.EduardoS2011/04/22 04:24 PM
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                                                              We actually upgraded to 2008 R2EduardoS2011/04/22 10:33 PM
                                                                We actually upgraded to 2008 R2rwessel2011/04/22 11:11 PM
                                                                  We actually upgraded to 2008 R2David Kanter2011/04/22 11:28 PM
                                                                    We actually upgraded to 2008 R2Ricardo B2011/04/23 09:43 AM
                                                                      We actually upgraded to 2008 R2David Kanter2011/04/23 10:31 AM
                                                                    We actually upgraded to 2008 R2sparkplug2011/04/23 08:25 PM
                                                                      We actually upgraded to 2008 R2David Kanter2011/04/24 03:36 PM
                                                                        We actually upgraded to 2008 R2anon2011/04/24 06:32 PM
                                                                          We actually upgraded to 2008 R2David Kanter2011/04/24 11:12 PM
                                                                        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
                                                                          We actually upgraded to 2008 R2David Kanter2011/04/24 10:57 PM
                                                                        File size optimizationsjrl2011/04/25 02:03 AM
                                                                          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
                                                                            Javascript is at the root of the latency problemjrl2011/04/25 06:03 PM
                                                                          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
                              AMD's Open64 compiler ?Vincent Diepeveen2011/04/10 06:06 AM
                                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
    New article: Bulldozer benchmark analysisNaN2011/03/30 05:24 PM
      New article: Bulldozer benchmark analysisChris2011/04/05 03:33 AM
  New article: Bulldozer benchmark analysisdc2011/03/30 08:09 AM
    New article: Bulldozer benchmark analysisMS2011/03/30 08:53 AM
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        New article: Bulldozer benchmark analysisanun2011/03/31 02:48 AM
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      New article: Bulldozer benchmark analysisanon2011/03/31 08:29 AM
        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
        New article: Bulldozer benchmark analysisAzazel2011/03/31 09:54 AM
        New article: Bulldozer benchmark analysisAlex2011/03/31 11:38 PM
      New article: Bulldozer benchmark analysisanon2011/04/01 03:23 AM
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  a waste of timeMoritz2011/04/09 07:01 AM
    a waste of timehorsefly2011/04/09 03:34 PM
      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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