Re: RFC: Patch for switch elimination (PR 54742)

[Jeff Law <law@redhat.com>]

On 08/15/14 04:07, Richard Biener wrote:
> On Thu, Aug 14, 2014 at 8:45 PM, Sebastian Pop <sebpop@gmail.com> wrote:
>> Steve Ellcey wrote:
>>> I understand the desire not to add optimizations just for benchmarks but
>>> we do know other compilers have added this optimization for coremark
>>> (See
>>> http://community.arm.com/groups/embedded/blog/2013/02/21/coremark-and-compiler-performance)
>>> and the 13 people on the CC list for this bug certainly shows interest in
>>> having it even if it is just for a benchmark.  Does 'competing against other
>>> compilers' sound better then 'optimizing for a benchmark'?
>>
>> I definitely would like to see GCC trunk do this transform.  What about we
>> integrate the new pass, and then when jump-threading manages to catch the
>> coremark loop, we remove the pass?
>
> It never worked that way.
>
> A new pass takes compile-time, if we disable it by default it won't help
> coremark (and it will bitrot quickly).
>
> So - please fix DOM instead.
Steve's work is highly likely to be faster than further extending the 
threading code -- that's one of the primary reasons I suggested Steve 
resurrect his work.



Jeff