[Bug tree-optimization/80155] [7 regression] Performance regression with code hoisting enabled

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80155

--- Comment #17 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
(In reply to rguenther@suse.de from comment #16)
> On Thu, 23 Mar 2017, thopre01 at gcc dot gnu.org wrote:
> > 
> > Funnily this led back to the Cortex-M0+ reduced testcase. With the patch in
> > comment #13 applied we can still see a difference in the push (one register
> > pushed Vs 0).
> 
> I can't reproduce zero pushes here I get three with/without 
> -fno-code-hoisting.  code hoisting hoists the two loads inside
> the switch before it so we have

Ooops my apologize, it needs more flags indeed. -O2 -funroll-all-loops shows 2
registers pushed Vs 1 when -fno-code-hoisting is added.