PR63633: May middle-end come up width hard regs for insn expanders?

[Segher Boessenkool]

On Tue, Apr 21, 2015 at 12:27:40AM +0200, Steven Bosscher wrote:
> On Mon, Apr 20, 2015 at 10:11 PM, Vladimir Makarov wrote:
> > I might be wrong but I think you have a bloated code because you use
> > scratches.  I already told several times that usage of scratch is always a
> > bad idea.  It was a bad idea for an old RA and is still a bad idea for IRA.
> > The usage of scratches should be prohibited, probably we should write it
> > somewhere.  It is better to use just a regular pseudo instead.
> 
> Thanks Vladimir, I didn't know this.
> Does this mean that, for example, extendsidi in i386.md would be
> better if it did not use match_scratch?

The combiner can add or remove clobbers of scratches whenever needed,
but it cannot do that for clobbers of pseudos.


Segher