[cfe-dev] Using Clang -O4 with CMake

[Toralf Niebuhr]

Am 19.06.2010 um 06:15 schrieb Chris Lattner:

> 
> On Jun 18, 2010, at 8:47 PM, Clark Gaebel wrote:
> 
>> I'm running...
>> 
>> clark at clark-laptop ~/dev/cpp/GoGo/build $ clang++ --version
>> clang version 1.5 (trunk 101682)
>> Target: x86_64-unknown-linux-gnu
>> Thread model: posix
> 
> For LTO to work on linux, you need to use the gold linker and set up the gold lto plugin.  Please see:
> http://llvm.org/docs/GoldPlugin.html
I had the same problem too. Is there such a plugin for Mac OS X too?
> 
> -Chris
> 
>> 
>> On 06/18/10 23:07, Eric Christopher wrote:
>>> On Jun 18, 2010, at 8:01 PM, Clark Gaebel wrote:
>>> 
>>> 
>>>> When trying out -O4 instead of my usual -O3 on my C++ code using CMake,
>>>> I got this error...
>>>> 
>>>> Linking CXX executable test_memory
>>>> cd /home/clark/dev/cpp/GoGo/build/util/test && /usr/bin/cmake -E
>>>> cmake_link_script CMakeFiles/test_memory.dir/link.txt --verbose=1
>>>> /usr/local/bin/clang++     
>>>> CMakeFiles/test_memory.dir/test_memory.cpp.o  -o test_memory -rdynamic
>>>> -lboost_filesystem-mt-1_42 -lboost_iostreams-mt-1_42
>>>> -lboost_program_options-mt-1_42 -lboost_regex-mt-1_42
>>>> -lboost_serialization-mt-1_42 -lboost_signals-mt-1_42
>>>> -lboost_thread-mt-1_42 -lboost_wave-mt-1_42
>>>> CMakeFiles/test_memory.dir/test_memory.cpp.o: file not recognized: File
>>>> format not recognized
>>>> collect2: ld returned 1 exit status
>>>> 
>>>> What am I doing wrong? This works fine on every other optimization
>>>> setting. Literally, the only thing I did differently was -O4 instead of -O3.
>>>> 
>>> O4 means use lto.  What platform are you on? Does it support llvm lto? :)
>>> 
>>> And I have no idea if the cmake files are set up for that either.
>>> 
>>> -eric
>> 
>> -- 
>> Regards,
>> -Clark
>> 
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