llvm dev - Aug 2010 - [LLVMdev] Is -O4 supposed to work on linux ?

Hello all,

Just a quick question for which I think the answer is "NO". I am
currently
experiencing clang on a RHE linux x86_64 server. It seems to work very fine
(great news, and thank you), but when I try to build using -O4 flag, I get
an error telling me that it is "not possible to emit LLVM bit-code files to
linker". I came across some post in this mailing list that made me think
that it was because all system linker did not support LTO and that the
feature is essentially supported on Mac os X.
However, when using the online demo, LTO is enabled and the results says
among other things:
target triple = "x86_64-linux-gnu"

Can you explain me why it does not work in my case and why it does in others
?

Best regards,

-Romain
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Romain Pechayre wrote:
>   Hello all,
>
> Just a quick question for which I think the answer is "NO". I am
> currently experiencing clang on a RHE linux x86_64 server. It seems to
> work very fine (great news, and thank you), but when I try to build
> using -O4 flag, I get an error telling me that it is "not possible to
> emit LLVM bit-code files to linker". I came across some post in this
> mailing list that made me think that it was because all system linker
> did not support LTO and that the feature is essentially supported on Mac
> os X.
> However, when using the online demo, LTO is enabled and the results says
> among other things:
> target triple = " x86_64-linux-gnu"
>
> Can you explain me why it does not work in my case and why it does in
> others ?
The online demo doesn't use the system linker, it just runs the LTO 
optimizations.

As for getting a binutils ld which can use LLVM, see 
http://llvm.org/docs/GoldPlugin.html

Nick