g++ optimization

U.Mutlu for-gmane@mutluit.com
Mon Jun 19 19:12:00 GMT 2017


Jonathan Wakely wrote on 06/19/2017 08:52 PM:
> On 19 June 2017 at 18:28, U.Mutlu wrote:
>> Andrew Haley wrote on 06/19/2017 07:08 PM:
>>>
>>> On 19/06/17 18:00, U.Mutlu wrote:
>>>>
>>>> In a c++ file inside a loop I have the following snippet:
>>>>       const bool f = func();
>>>> // if (f) break;
>>>>
>>>> If I activate the line with "if (f) break;" then the performance
>>>> very much degrades.
>>>>
>>>> Which g++ optimization parameter should I disable (or enable) to keep the
>>>> performance?
>>>
>>>
>>> That depends on how f() is defined.  We need to see a test that we
>>> can reproduce.
>>
>>
>> It's a simple class member function returning bool:
>>
>> inline bool func() const
>> {
>> //...
>> }
>>
>>
>>
>
> Try again. We need to see a test that we can reproduce.
>
> Incomplete snippets of code hinting at what you mean do not count.

Luckily in the meantime I've been able to solve the problem by splitting
the code into 2 files and compiling each with slightly different switches
(tried many combinations :-), and of course linking the .o together.
Code now an unbelievable ~15 times faster! :-)

Thx everybody
cu




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