Re: [PATCH 8/8] Add a common .md file and define standard constraints there

[Jeff Law <law@redhat.com>]

On 06/05/14 15:43, Richard Sandiford wrote:
> This final patch uses a common .md file to define all standard
> constraints except 'g'.  It then gets rid of explicit case statements
> for the standard constraints, except in two cases:
>
> (1) recog.c:asm_operand_ok still needs to handle 'o' specially for
>      targets like ia64 that don't have offsettable addresses.  See the
>      comment there for justification.
>
> (2) the trickier cases in reload.  I'm not changing those more than I have to.
Can't argue with #2 ;-)  reload gets less and less important every day, 
so I see less and less value hacking too much on it.

>
> I did wonder about defining a new rtl construct that could be used for 'g',
> so that even that special case goes away.  In the end I think it would be
> a false abstraction though.  No other constraint allows (or IMO should allow)
> all three of a register class, a base-reloadable memory and a constant,
> so handling it in the lookup_constraint paths would make things more
> complicated rather than less.
OK.

>
> Note that the s390 'e' constraint is TARGET_MEM_CONSTRAINT, which is now
> defined in the common file.
>
> I put the common .md file in the main gcc/ directory by analogy with
> defaults.h and common.opt.  It could instead go in config/ or config/common/,
> if those sound better.
Seems fine to me, I don't feel a need to bikeshed here.


Does the comment before indep_constraints in genoutput need updating? 
The constraints in common.md are machine independent, but aren't listed 
in indep_constraints in genoutput.c

Approved with whatever language you want to use for that comment.

Jeff