Re: [PING] Target hook for rewriting inline asm constraints

[Richard Sandiford <rsandifo@nildram.co.uk>]

"Andreas Krebbel" <Andreas.Krebbel@de.ibm.com> writes:
>> I don't understand.  What I'm saying is that we should look through
>> gcc/*.c for cases where the C construct "'m'" refers to "the constraint
>> associated with legitimate addresses", and replace those cases with some
>> target macro that is 'm' by default.  E.g.:
> ...
>> and other places would change similarly.  If we do that consistently,
>> there would no longer be a connection between 'm' and
>> GO_IF_LEGITIMATE_ADDRESS.
>
> Ok I see.  The new TARGET_MEM_CONSTRAINT would have to be a hook
> returning a new constraint letter for the architecture introducing the
> new address format and 'm' otherwise - right ?!

Well, I was thinking of making it a macro constant; I should have picked
a name other than TARGET_MEM_CONSTRAINT, sorry.

It might be nice to define the macro indirectly using a new constraints.md
construct (define_general_memory_constraint?).  I.e. have genpreds define
the macro for you based on the .md file.  The implementation could then
move away from macros at the same time as the rest of the constraints
stuff does[*].  I think that'd still be easier than converting gcc/*.c
to treat 'm' as a hook (and easier than rewriting asms).  But personally,
I'd be happy enough if the macro was defined in the target .h file.

Richard

[*] E.g. we might eventually generate a constraints parser from the
    .md file.  I can't remember now if that was an explicit goal of
    the constraints.md stuff.