libgcc: strange optimization

[Richard Guenther]

On Tue, Aug 2, 2011 at 10:48 AM, Mikael Pettersson <mikpe@it.uu.se> wrote:
> Hans-Peter Nilsson writes:
>  > On Mon, 1 Aug 2011, Richard Henderson wrote:
>  >
>  > > On 08/01/2011 01:30 PM, Michael Walle wrote:
>  > > >  1) function inlining
>  > > >  2) deferred argument evaluation
>  > > >  3) because our target has no barrel shifter, (arg >> 10) is emitted as a
>  > > > function call to libgcc's __ashrsi3 (_in place_!)
>  > > >  4) BAM! dead code elimination optimizes r8 assignment away because calli
>  > > > may clobber r1-r10 (callee saved registers on lm32).
>  > >
>  > > I'm afraid the only solution I can think of is to force F1 out-of-line.
>  >
>  > Or another temporary - but the parameter should already have
>  > that effect.
>
> It should, but doesn't.  See PR48863 for similar breakage on ARM.

On GIMPLE we don't see either the libcall nor those "dependencies".

Don't use register vars.

Richard.

> /Mikael
>