llvm dev - Mar 2012 - [LLVMdev] Execution Engine: CodeGenOpt level

Hi,

How can I dynamically change the code generation optimization level (e.g.,
None) of a JIT in other to recompile a function with a new optimization
level (e.g., Default)?

Thank you.

Best regards,
Nurudeen.

> How can I dynamically change the code generation optimization level (e.g.,
> None) of a JIT in other to recompile a function with a new optimization
> level (e.g., Default)?
  From the source code I'm reading, you might have to creat another JIT with
different opt level.

Regards,
chenwj

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj

Hi Chenwj,

Thank you for your response.

The problem with this approach is that global mappings have to be
recreated in the new JIT. Can this be somehow avoided?

Best regards,
Nurudeen.

On Thu, March 22, 2012 10:15 pm, 陳韋任 wrote:
>> How can I dynamically change the code generation optimization level
>> (e.g.,
>> None) of a JIT in other to recompile a function with a new optimization
>> level (e.g., Default)?
>
> From the source code I'm reading, you might have to creat another JIT
> with different opt level.
>
> Regards,
> chenwj
>
> --
> Wei-Ren Chen (陳韋任)
> Computer Systems Lab, Institute of Information Science,
> Academia Sinica, Taiwan (R.O.C.)
> Tel:886-2-2788-3799 #1667
> Homepage: http://people.cs.nctu.edu.tw/~chenwj
>
>

> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at
cs.uiuc.edu] On Behalf Of nlamee at cs.mcgill.ca
> Subject: [LLVMdev] Execution Engine: CodeGenOpt level
> How can I dynamically change the code generation optimization level (e.g.,
> None) of a JIT in other to recompile a function with a new optimization
> level (e.g., Default)?
We set the optimization level with a PassManagerBuilder, which is initialized
for each function compilation:

    PassManagerBuilder PMBuilder;
...
    PMBuilder.OptLevel = conf.value_of(CF_OPTLEVEL);
    PMBuilder.SizeLevel = conf.is_set(CF_OPTSIZE) ? 1 : 0;
    PMBuilder.DisableUnitAtATime = !conf.is_set(CF_OPTUNIT);
    PMBuilder.DisableUnrollLoops = !conf.is_set(CF_UNROLL);
    PMBuilder.DisableSimplifyLibCalls = !conf.is_set(CF_SIMPLIB);
    if (Opt != CodeGenOpt::None) {
        PMBuilder.Inliner = createFunctionInliningPass(Opt ==
CodeGenOpt::Aggressive ? 250 : 200);
    }
    pFPasses = new FunctionPassManager(pMod);
    pFPasses->add(new TargetData(*TD));
    PMBuilder.populateFunctionPassManager(*pFPasses);
    pFPasses->doInitialization();
    pFPasses->run(*pFun);
    pFPasses->doFinalization();
    delete pFPasses;
    pMPasses = new PassManager();
    pMPasses->add(new TargetData(*TD));
    pMPasses->add(createCFGSimplificationPass());
    pMPasses->add(createBlockPlacementPass());
    PMBuilder.populateModulePassManager(*pMPasses);
    pMPasses->run(*pMod);
    delete pMPasses;

(There is likely some redundancy and unnecessary steps in the above.)

 - Chuck


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Neat approach, I think. So you set PassManagers's Opt level rather
then ExecutionEngine's one?

Regards,
chenwj

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj