Function Parameters vs. Prologue (fastcall + O1 + -fschedule-insns2)

[Ian Lance Taylor]

On Wed, Jun 19, 2013 at 8:21 AM, Geyslan Gregório Bem <geyslan@gmail.com> wrote:
>
> About technicalities of the option and whether reordering is not really
> optimizing as demonstrated in the benchmark.

Every complex optimization has cases where it will actually make code
worse.  All optimizations rely on heuristics, and those heuristics
sometimes fail.  You have very likely found such a case, which is why
I suggested filing a missed-optimization bug report.  It may be
possible to fix it; I don't know.

Since the differences are subtle you should make sure you are using
the correct -mtune option for the machine on which you are running
your benchmarks.

Ian