Please review writeup for fixing PR 78809 (inline strcmp for small constant strings)

[Jeff Law]

On 11/17/2017 03:50 PM, Qing Zhao wrote:

>>
>> The difficulty is tracking when exposure leads to these secondary
>> opportunities.  I often end up looking for this kind of stuff by first
>> identifying many source files where the transformation applies.  Then I
>> generate dumps & assembly code for the transformation in each candidate
>> location.  I first analyze the assembly files for differences.  If an
>> assembly file shows a difference, then I look more closely to try and
>> characterize the difference and if it looks interesting, then I work
>> backwards to the dump files for more details.
> 
> usually, what kind of benchmarks or test cases are you recommending? 
> I used to work a lot with SPEC, not sure whether that’s the same for working in GCC?
SPEC is always good.  Many of us also work with GCC's sources themselves
to help determine if a particluar transformation is helpful.

Jeff