[LLVMdev] Replace gcc with llvm-gcc

[John Criswell]

罗勇刚(Yonggang Luo) wrote:
> Just set llvm-ld as the default ld .
> Such as LD = llvm-ld in makefile, if it's not working, then there is no solution
>   
Some Makefiles use the C compiler (e.g., gcc or llvm-gcc) as the
linker.  For such Makefiles, the above will not work because llvm-gcc
runs ld.  What you need is a linker that can link LLVM bitcode files
together.

If that is the case, then an alternative is to use the LLVM plugin for
the gold linker (http://llvm.org/docs/GoldPlugin.html).  If gold is your
system linker (or you can make llvm-gcc use it instead of ld), then (I
believe) you can get the Makefiles to transparently link LLVM bitcode
files together into a single bitcode file.

The above is for Linux.  On Mac OS X, I think the linker with Xcode can
link bitcode files together, but I'm not sure.

Please note that I haven't tried this myself yet; it's one of the things
I will try the next time I need to create a single bitcode file for an
executable.

-- John T.

> 2009/9/15, zhunan <zhunansjtu at gmail.com>:
>   
>> I truly get the bytecode file for each souce file,but can I use
>> llvm-link to link them into a whole-program one automatically through
>> some scripts?
>>
>>
>>     
>>> Message: 27
>>> Date: Tue, 15 Sep 2009 03:16:10 +0200
>>> From: ?scar Fuentes <ofv at wanadoo.es>
>>> Subject: Re: [LLVMdev] Replace gcc with llvm-gcc???
>>> To: llvmdev at cs.uiuc.edu
>>> Message-ID: <87vdjlnh2d.fsf at telefonica.net>
>>> Content-Type: text/plain; charset=windows-1252
>>>
>>> zhunan <zhunansjtu at gmail.com> writes:
>>>
>>>       
>>>> Recently I met a question when I want to replace gcc with llvm-gcc
>>>> through configure script(command).
>>>>
>>>> For simply,described like that
>>>>
>>>> I typed as following
>>>>
>>>> 1.zhunan at sjtu:~/workplace/$ ./configure CC=llvm-gcc CFLAGS="-S
>>>> -emit-llvm"
>>>>
>>>> configure will failed when it checks whether C compiler is working
>>>>
>>>> 2.zhunan at sjtu:~/workplace/$ ./configure CC=llvm-gcc CFLAGS="-c
>>>> -emit-llvm"
>>>>
>>>> configure will failed when it checks the default output filename,just
>>>> means the C compiler cannot create executables.
>>>>
>>>>
>>>> I would like to know what's the matter with this replacing attempt?and
>>>> any possibility to overcome the trouble?
>>>>         
>>> Your CFLAGS is telling llvm-gcc that it must not produce an object code
>>> file nor an executable file, but something else (llvm assembler on your
>>> first attempt and llvm bitcode on your second attempt).
>>>
>>> `configure' needs a fully working compiler toolset, which means that the
>>> compiler must be able to produce executable files. Your CFLAGS setting
>>> is preventing this.
>>>
>>> Execute `configure' with just CC=llvm-gcc and then try
>>>
>>> make CFLAGS="-emit-llvm"
>>>
>>> if you want LLVM bitcode or
>>>
>>> make CFLAGS="-S -emit-llvm"
>>>
>>> if you want LLVM assembler.
>>>
>>> `make' will fail at the linking phase, but you will have a set of LLVM
>>> bitcode/assembler files for each of your C source files.
>>>
>>> If you simply want to replace gcc with llvm-gcc for building your
>>> software, forget about CFLAGS and just do
>>>
>>> ./configure CC=llvm-gcc && make
>>>
>>>       
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>>     
>
>