llvm dev - Jun 2012 - [LLVMdev] How to use LLVM optimizations with clang

Hello everyone

I am trying to use some LLVM optimizations like -die or -adce. Is it
possible to use them along clang?

Or is there a way where these optimization can be passed on to "opt"
tool through clang, if opt is being used by clang behind the scenes?

Thanks alot

Regards

Shahzad

On Jun 7, 2012, at 10:59 AM, Abdul Wahid Memon wrote:
> Hello everyone
> 
> I am trying to use some LLVM optimizations like -die or -adce. Is it
> possible to use them along clang?
> 
> Or is there a way where these optimization can be passed on to
"opt"
> tool through clang, if opt is being used by clang behind the scenes?
> 
No, opt only works on llvm IR/bitcode.  You can generate it like this:
clang -c foo.c -emit-llvm -o foo.bc
or
clang -S foo.c -emit-llvm -o foo.ll

Then you can run the optimization(s):
opt -adce foo.bc -o foo-adce.bc

Then you can compile using clang
clang -c foo-adce.bc -o foo-adce.o

 Chad
> Thanks alot
> 
> Regards
> 
> Shahzad
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Thanks alot Chad for quick response. Does this means that, we can not
use LLVM optimizations except O1, O2, O3, O4 and unroll-loops with
clang?

One more thing I would like to know that If I want to process multiple
modules with opt at the same time like

opt -adce *.bc

then how is it possible with opt in one go, if I process all the
bytecode files within Makefile.

Thanks.

Shahzad

On Thu, Jun 7, 2012 at 9:22 PM, Chad Rosier <mcrosier at apple.com>
wrote:
>
> On Jun 7, 2012, at 10:59 AM, Abdul Wahid Memon wrote:
>
>> Hello everyone
>>
>> I am trying to use some LLVM optimizations like -die or -adce. Is it
>> possible to use them along clang?
>>
>> Or is there a way where these optimization can be passed on to
"opt"
>> tool through clang, if opt is being used by clang behind the scenes?
>>
>
> No, opt only works on llvm IR/bitcode.  You can generate it like this:
> clang -c foo.c -emit-llvm -o foo.bc
> or
> clang -S foo.c -emit-llvm -o foo.ll
>
> Then you can run the optimization(s):
> opt -adce foo.bc -o foo-adce.bc
>
> Then you can compile using clang
> clang -c foo-adce.bc -o foo-adce.o
>
>  Chad
>
>> Thanks alot
>>
>> Regards
>>
>> Shahzad
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>