[LLVMdev] How to use LLVM optimizations with clang

[Abdul Wahid Memon]

Thanks again.

I executed the following command line

llc -O3 comb.ll.bc -debug-pass=Arguments

and got

Pass Arguments:  -targetdata -targetpassconfig -no-aa -tbaa
-targetlibinfo -basicaa -collector-metadata -machinemoduleinfo
-machine-branch-prob -preverify -domtree -verify -loops -loop-simplify
-scalar-evolution -loop-simplify -iv-users -loop-reduce -gc-lowering
-unreachableblockelim -codegenprepare -stack-protector -preverify
-domtree -verify -loops -branch-prob -expand-isel-pseudos
-tailduplication -opt-phis -localstackalloc -dead-mi-elimination
-machinedomtree -machine-loops -machinelicm -machine-cse -machine-sink
-peephole-opts -unreachable-mbb-elimination -livevars
-phi-node-elimination -twoaddressinstruction -processimpdefs
-slotindexes -liveintervals -livedebugvars -simple-register-coalescing
-calcspillweights -livestacks -virtregmap -edge-bundles
-spill-code-placement -stack-slot-coloring -machinelicm -edge-bundles
-prologepilog -branch-folder -tailduplication -machine-cp
-postrapseudos -machinedomtree -machine-loops -post-RA-sched
-gc-analysis -machine-block-freq -block-placement2 -machinedomtree
-machine-loops

Now, how can I specify these optimization manually along with llc like
we did with opt tool?

Regards

Shahzad

On Tue, Jun 12, 2012 at 1:23 PM, Duncan Sands <baldrick at free.fr> wrote:
> Hi,
>
>
> On 12/06/12 13:09, Abdul Wahid Memon wrote:
>>
>> Thanks alot. How can we view those optimization which are enabled when we
>> do
>>
>> llc -O3 comb.ll
>
>
> llc -O3 comb.ll -debug-pass=Arguments
>
>
>>
>> Are these the same as the ones produced by the following command line
>
>
> no, as I mentioned before they are of a completely different nature
> to the optimizations that opt does.
>
> Ciao, Duncan.
>
>
>>
>> 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.
>
>