[llvm-dev] [test-suite] making polybench/symm succeed with "-Ofast" and "-ffp-contract=on"

[Sebastian Pop via llvm-dev]

On Wed, Oct 12, 2016 at 4:38 AM, Renato Golin <renato.golin at linaro.org> wrote:
> On 12 October 2016 at 05:20, Sebastian Pop <sebpop.llvm at gmail.com> wrote:
>>   /*
>>   LLVM: This change ensures we do not calculate nan values, which are
>>         formatted differently on different platforms and which may also
>>         be optimized unexpectedly.
>
> This comment is there since it was originally introduced by Tobias.
> We'll have to ask him what changes were done to understand how this is
> relevant to your current proposal.
>

The code before is in the comments: we know exactly what Tobi has changed.
Most of these changes are in the initialization of the arrays, though
there are also
changes to the computational kernel.

Polybench was designed to stress loop optimizations in the polyhedral model.
The intent of adding Polybench to the test-suite was to stress loop
optimizations in Polly.
Those initial changes by Tobi reflect this intent: neither the FP
computation, nor the initial values matter much.
I would appreciate if Tobi could share his point of view on Polybench:
I added him to the CC list.

We are currently trying to modify Polybench to test something
different than what it was designed for.
This goes along with my earlier comment about the SPEC benchmarks:
there are benchmarks that have been designed to test FP computations.
If we need more FP benchmarks in the test-suite, we should try to
identify and add benchmarks in which "FP expert" people put thought in
correctly designing the tests to check FP computations.

Sebastian