[llvm-commits] [PATCH] Make Path::GetMainExecutable faster on OSX

[Daniel Dunbar]

On Tue, Sep 8, 2009 at 3:02 PM, Chris Lattner<clattner at apple.com> wrote:
>
> On Sep 8, 2009, at 2:58 PM, Daniel Dunbar wrote:
>
>> Wow, nice catch -- I've known something was wrong because of the
>> amount of system time it consumes, but hadn't dug in. This makes your
>> patch an even bigger win w/ more threads, its almost 50% faster for
>> me.
>>
>> Looking at the code now I'm wondering if it is even right that
>> clang-cc uses the main executable path to resolve headers. I think
>> this change got made to accommodate symlinked binaries, but I'm not
>> sure that "GetMainExecutablePath" is really the right way to find
>> this. Chris?
>
> I don't really know either.  Nick, do you have an opinion about this?

The question of how to resolve headers is different from
GetMainExecutable (which I think we should fix).

I think we should probably resolve headers by taking the realpath of
the abspath of the argv[0], but I'm not sure if there was a good
reason we didn't do this. I think it was because you decided readlink
was evil. :)

 - Daniel

>> On Tue, Sep 8, 2009 at 11:52 AM, Benjamin
>> Kramer<benny.kra at googlemail.com> wrote:
>>>
>>> Playing around with shark shows that much of the startup time of clang-cc
>>> is
>>> spent in dladdr looking for the executable path. There is another dyld
>>> API
>>> called _NSGetExecutablePath which does the same thing much faster. The
>>> function is available since 10.2 and documented in "man 3 dyld" (I don't
>>> know why it has a leading underscore though).
>>>
>>> benchmark: clang testsuite on my 2007 macbook pro (debug build, best of 3
>>> runs)
>>>
>>> dladdr:
>>> --- Running clang tests for i686-apple-darwin10.0.0 ---
>>> Testing Time: 57.76s
>>>
>>> _NSGetExecutablePath:
>>> --- Running clang tests for i686-apple-darwin10.0.0 ---
>>> Testing Time: 48.71s
>>>
>>>
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>
>