[llvm-dev] LLVMTargetMachine with optimization level passed from clang.

[Ryan Taylor via llvm-dev]

My mistake, u want a code gen opt, not IR, so a backend pass?

On Jan 4, 2017 7:05 PM, "Ryan Taylor" <ryta1203 at gmail.com> wrote:

> If I understand you correctly, you should look at putting your pass in the
> pass manager at the opt level u want.
>
> Ryan
>
> On Jan 4, 2017 7:03 PM, "Sumanth Gundapaneni via llvm-dev" <
> llvm-dev at lists.llvm.org> wrote:
>
>> I see the BackendUtil.cpp of Clang creates the TargetMachine with the
>> optimization level based on below mentioned logic
>>
>>
>>
>>   CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
>>
>>   switch (CodeGenOpts.OptimizationLevel) {
>>
>>   default: break;
>>
>>   case 0: OptLevel = CodeGenOpt::None; break;
>>
>>   case 3: OptLevel = CodeGenOpt::Aggressive; break;
>>
>>   }
>>
>>
>>
>> As per my understanding, the correspondence between optimization level
>> and CodeGenOpt is as below
>>
>> O0  -  none
>>
>> O1  -  less
>>
>> O2 -   default
>>
>> O3  -  aggressive
>>
>>
>>
>> My goal is to turn on a target dependent codegen optimization at
>> –O1(less). The TargetMachine is constructed with “CodeGenOpt::Default”. Is
>> there a way I could do this in LLVM ? What is the standard way of doing
>> this ? Also, the code in BackendUtil.cpp seem somewhat offbeat to me.
>>
>>
>>
>> --Sumanth G
>>
>>
>>
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>>
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