[cfe-dev] Question about size optimization and PRE

[jingu@codeplay.com via cfe-dev]

Thanks for the helpful comment Hal.

Do you agree the PRE makes code size bigger?

JinGu Kang


On 27/06/18 17:08, Hal Finkel wrote:
> On 06/27/2018 04:15 AM, jingu at codeplay.com via cfe-dev wrote:
>> Hi All,
>>
>> I have a question about the opportunity of size optimization in clang.
>> As you know, the PRE(partial redundancy elimination) copies partially
>> available instructions to paths in which the instruction is not
>> available. I think it makes code size bigger. I can see the PRE
>> implementation in llvm's GVN pass. However, I can not see the options
>> like '-enable-pre=false' or '-enable-load-pre=fasle' on clang with
>> size optimization. How do you think about disabling PRE with clang's
>> size optimization? If I missed something, please let me know.
> The right way to do this would be to have the pass itself check
> F->optForSize() (or F->optForMinSize(), as the case may be). Clang
> itself should essentially never set pass command-line options for anything.
>
>   -Hal
>
>> Thanks,
>>
>> JinGu Kang
>>
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>> cfe-dev at lists.llvm.org
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-- 
JINGU KANG
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