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

Hi

Yes. But how exactly code generation (optimized one) be done without
clang. Is it possible that we can specify those optimization
(individual ones instead of standard ones like -O3) some how when
generating code as is done by clang or llc?

Regards

Shahzad

On Tue, Jun 12, 2012 at 12:42 PM, Duncan Sands <baldrick at free.fr>
wrote:
> Hi, the reason is that lli does optimized code generation by default, while
> clang does unoptimized codegen by default.  Use this
>  clang -O2 comb.ll
> instead.
>
> Ciao, Duncan.

> Yes. But how exactly code generation (optimized one) be done without
> clang. Is it possible that we can specify those optimization
> (individual ones instead of standard ones like -O3) some how when
> generating code as is done by clang or llc?
llc comb.ll
gcc -o comb comb.s

Variants:
   llc -O0 comb.ll
   llc -O3 comb.ll
etc

Note that the codegen level optimizations done by llc have nothing to do with
the IR level optimizations of the kind performed by opt.

Ciao, Duncan.

Thanks alot. How can we view those optimization which are enabled when we do

llc -O3 comb.ll

Are these the same as the ones produced by the following command line

llvm-as < /dev/null | opt -O3 -disable-output -debug-pass=Arguments

Regards

Shahzad

On Tue, Jun 12, 2012 at 1:01 PM, Duncan Sands <baldrick at free.fr>
wrote:
>> Yes. But how exactly code generation (optimized one) be done without
>> clang. Is it possible that we can specify those optimization
>> (individual ones instead of standard ones like -O3) some how when
>> generating code as is done by clang or llc?
>
>
> llc comb.ll
> gcc -o comb comb.s
>
> Variants:
>  llc -O0 comb.ll
>  llc -O3 comb.ll
> etc
>
> Note that the codegen level optimizations done by llc have nothing to do
> with
> the IR level optimizations of the kind performed by opt.
>
> Ciao, Duncan.