[Bug rtl-optimization/90378] [9/10 regression] -Os -flto miscompiles 454.calculix after r266385 on Arm

rearnsha at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Tue Feb 18 15:41:00 GMT 2020


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90378

--- Comment #6 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
(In reply to Richard Earnshaw from comment #5)
> (In reply to Vladimir Makarov from comment #4)
> > > Miscompilation occurs in same configuration: arm-linux-gnueabihf at -O2
> > > -flto.
> > > 
> > 
> > I don't see how these two patches *directly* resulted in miscompilation. 
> > Although it might trigger some latent bug.
> > 
> > 
> > > I'll try to narrow this down to a single object.
> > 
> > Thank you, Maxim.  Unfortunately I have no arm machine with spec2006 to
> > reproduce it by myself. You help here would be much appreciated.
> 
> While I don't see a 1% regression, I did notice a measurable code size
> increase when building CSiBE for thumb-2 and -Os.  It's hard to put my
> finger on what is causing this, beyond the fact that the compiler is making
> more use of 'high' registers and this results in using more 32-bit rather
> than 16-bit instructions.

Err, ignore that.  Wrong bug.


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