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Comment by evmar | Hacker News Reader

I'm curious whether the performance varies if you used a C compiler from the last five years -- GCC 4.2.1 was released in July 2007. (I'm not claimed the author of the post is unfairly biasing the results, I'm just honestly curious.)

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To answer my own question, I got:

  gcc 4.6.3: 3.554688 +/- 4.786550
  clang trunk: 3.593750 +/- 4.798172  
  Chrome: 41.03515625 +/- 9.331709130062185

Which puts Chrome at about 11x these native compilers, consistent with the blog post.

FWIW, I just ran it through Clang 4.1 (the standard on XCode these days), and got roughly identical performance. I'm still compiling gcc 4.8 just to be sure, but it seems unlikely to make much of a difference.

There's no Clang 4.1, though. You probably mean "the Clang that comes with version 4.1 of XCode"?

Clang 3.3 will be released soon.

Good point. Apple helpfully reports the rather confusing version string "Apple clang version 4.1 (tags/Apple/clang-421.11.65) (based on LLVM 3.1svn)" :P

Ditto for gcc-4.8. Roughly the same (ever so slightly worse) performance.

    gcc 4.8.0: 1.640625 +/- 3.703323
    clang 3.2: 1.718750 +/- 3.772718
    chrome   : 23.28515625 +/- 3.636932727324763

So chrome is about ~14x the native compilers.

Changing gcc to use -O2 instead of -O3 gets: 1.562500 +/- 3.630922.

What about -Ofast which enables -ffast-math?

The makefile supplied with the repo specifies -ffast-math. It uses these CFLAGS:

    CFLAGS=-s -O3 -msse -mfpmath=sse -ffast-math -fomit-frame-pointer -IBox2D_v2.2.1 -DNDEBUG=1

Using -Ofast gets the same results as -O2.

Thanks for the info, I should have guessed that he enabled -ffast-math manually.

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