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


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


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