Re: [PATCH 2/5] recog: Handle register filters

[Jeff Law <jeffreyalaw@gmail.com>]

On 11/12/23 07:52, Richard Sandiford wrote:
> The main (but simplest) part of this patch makes constrain_operands
> take register filters into account.
> 
> The rest of the patch adds register filter information to
> operand_alternative.  Generally, if two register constraints
> have different register filters, it's better if they're in separate
> alternatives.  However, the syntax doesn't enforce that, and we can't
> assert it due to inline asms.  So it's a choice between (a) adding
> code to enforce consistent filters or (b) dealing with mixes of filters
> in a conservatively correct way (in the sense of not allowing invalid
> operands).  The latter seems much easier.
> 
> The patch therefore adds a mask of the filters that apply
> to at least one constraint in a given operand alternative.
> A register is OK if it passes all of the filters in the mask.
> 
> gcc/
> 	* recog.h (operand_alternative): Add a register_filters field.
> 	(alternative_register_filters): New function.
> 	* recog.cc (preprocess_constraints): Calculate the filters field.
> 	(constrain_operands): Check register filters.
OK
jeff