[cfe-dev] strace clang refers files from lib/tls/x86_64 multiple times

[mats petersson via cfe-dev]

Are you saying that these "find something in a directory that doesn't
exist" steps are taking a majority of the difference between 30 and 100
seconds? That does seem very unlikely to me, as `stat` in Linux/Unix is a
fairly well optimised function, and a lot of caching is done to ensure that
it doesn't take much time.

I'm not sure what the difference is, and nor what project you are working
on, but I doubt the searching through various paths for shared libraries is
the big problem.

--
Mats

On 8 February 2016 at 10:41, Oza, Hiral via cfe-dev <cfe-dev at lists.llvm.org>
wrote:

> Greetings!
>
>
>
> Sample program:
>
> int main(int argc, char **argv)
>
> {
>
>     int myLocal=0xAA;
>
>     return 0;
>
> }
>
>
>
> Command: clang t.c –o a.o –c
>
>
>
> With above simple program we are observing that clang is stat-ing and
> trying to open various files from lib/tls location. Eventually all calls to
> “lib/tls” leads to ENOENT (No such file or directory)!
>
>
>
> <sample_strace>
>
> open("path/lib/tls/x86_64/libpthread.so.0", O_RDONLY) = -1 ENOENT
> (No such file or directory)
>
> …
>
> open("path/lib/tls/libpthread.so.0", O_RDONLY) = -1 ENOENT (No such
> file or directory)
>
> …
>
> </sample_strace>
>
>
>
> The same behavior is not observed with GCC. With gcc we could build above
> sample program under 30 seconds while it takes more than 100 seconds when
> using clang!!!
>
> Any pointer on how to reduce unnecessary stat/open is appreciated.
>
>
>
> My local installation paths are…
>
>                 somepath/gcc-4.9.x/{bin,lib}
>
>                 somepath/llvm-3.7.1/{bin,lib}
>
>                 somepath/{bin,lib}
>
>
>
> In above installation path we don’t have “tls” directory.
>
>
>
> In this regards I have following questions…
>
> - We are not seeing present of “tls” directory under
> “somepath/llvm-3.7.1/{bin,lib}” – is anything missing in our installation?
>
> - Why clang refers to “lib/tls”?
>
> - Why clang refers to “lib/x86_64” ? And why not just using “lib/”
>
>
>
> Thank you in advance for your help.
>
>
>
> Regards,
>
> -Hiral
>
>
>
> _______________________________________________
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>
>
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