[LLVMdev] llvm-ar llvm-link

[ankur deshwal]

Hi Ahmad,

Yes, merging works good.

However, my problem is like this - I have a C library which consists of
1000's of functions spread through various files. The functions do not have
dependency amoung each other. I want to link only relavant files( files
which have functions called from my application). Since ar has a global
symbol table, I believe it should be faster to look for a symol in the
table and pull out and link the file to .bc of my application.

Is my understand regarding llvm-ar correct? Or is there a better way to
achieve it?

One not-so-great solution I can think of is compile the library into
separate .bc files and write llvm pass which has a predefined hash mapping
of the names of functions these bc files. So while compiling, I look for
only relavant files and link them using code form llvm-link.

OR. rather than linking the files, only extract the function from the
library .bc file and insert it into module of application .bc.

Does any of the idea make sense ? Which one will be doable+preferable?


Thanks a lot,
Ankur






On Thu, Feb 21, 2013 at 11:51 PM, Hassan, Ahmad <ahmad.hassan at sap.com>wrote:

>  Hi Ankur,****
>
> ** **
>
> ** **
>
> Why do you need archive in this case? The other way of doing this is to
> merge all bitcode files into single file:****
>
> ** **
>
>  $ clang -c -emit-llvm abc.c –o abc.bc****
>
>  $  clang -c -emit-llvm bcd.c –o bcd.bc****
>
> llvm-link bcd.bc abc.bc –o merged.bc****
>
> ** **
>
> Cheers,****
>
> Ahmad****
>
> ** **
>
> *From:* llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] *On
> Behalf Of *ankur deshwal
> *Sent:* 21 February 2013 17:54
> *To:* llvmdev at cs.uiuc.edu; ankur deshwal
> *Subject:* [LLVMdev] llvm-ar llvm-link****
>
> ** **
>
> Hi,****
>
> ** **
>
> I tried to build an llvm archive and link it against an llvm bc file.
> However, it fails. Following is the procedure I followed ( abc.c is file
> which calls a function whose definition is present in bcd.c)****
>
> ** **
>
>  $ clang -c -emit-llvm abc.c ****
>
>  $  clang -c -emit-llvm bcd.c ****
>
>  $  llvm-ar cr bsd.ar bcd.o ****
>
>  $  llvm-link abc.o bsd.ar****
>
> ** **
>
> llvm-link: bsd.ar:1:2: error: expected integer****
>
> !<arch>****
>
>  ^****
>
> llvm-link: error loading file 'bsd.ar'****
>
> ** **
>
> What am I missing here ? ****
>
> ** **
>
> Regards,****
>
> Ankur****
>
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