Re: [patch] MIPS/gcc: Revert removal of DImode shifts for 32-bit targets

[Nigel Stephens <nigel@mips.com>]

Richard Sandiford wrote:

> Nigel Stephens <nigel@mips.com> writes:
>  
>
> > I have a patch against gcc-3.4 
> > <snip>
> > If people really don't like the inline expansion, then maybe it could be
> > enabled or disabled by a new -m option.
> >    
> IMO, controlling with optimize_size would be enough.  
Yes, that sounds right.

> But it sounds from
> your description like the patch just adds a new hard-coded multi-insn
> asm string.  Is that right?  If so, I'd really like to avoid that.
>
>  
Yes, and I totally agree with you.

> It would much better IMO if we handle this in the target-independent
> parts of the compiler.  We can already open-code certain non-native
> operations, it's "just" that wide shifts are a missing case.
>
>  
> If we handle it in a target-independent way, with each insn exposed
> separately, we will be able to optimize special cases better.
> We'll also get the usual scheduling benefits.
>  
I agree that we should open-code it for the obvious reasons, but does it 
have to be target independent, or could/should we prototype it with 
define_expand?
Nigel