[llvm-dev] JIT Optimization Levels

[hameeza ahmed via llvm-dev]

I have already applied opt. so here my lli has IR emitted from opt which is
optimized.

On Thu, Aug 24, 2017 at 12:31 PM, Paweł Bylica <chfast at gmail.com> wrote:

> On Thu, Aug 24, 2017 at 9:21 AM, hameeza ahmed via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hello,
>> there are several optimization levels in lli like O0, O1, O2, O3. What
>> does they mean? how the run time optimization is performed in LLVM JIT?
>>
>> I am working on a project where my goal is to study the impact of lli
>> optimizations. here my IR is already optimized through opt. now i have to
>> perform lli optimizations provided i am giving varying inputs at run time.
>> so i suppose here my optimization level also depends on runtime input. like,
>> i am using following command.
>>
>> time lli -O3 sum-vec03.ll  5 2
>>
>
> If I'm not wrong, there are 2 distinct subsystems were optimizations can
> be applied. In case of lli, JIT, llc, and others the optimization level is
> applied to the CodeGen. The LLVM IR is the input for them and is not
> optimized. If you need both you have to run opt to optimize IR first. Then
> lli.
>
>
>>
>> also after acquiring the execution time at different scenarios i plan to
>> use some machine learning algorithm in order to predict the appropriate
>> flag setting for given program and run time input.
>>
>> Please help. Does this look appropriate approach? is my methodology
>> correct?
>>
>> Thank You
>>
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>>
>
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