Understanding Predicate and Constrains

[Omar]

Jim,
 After further reading, the Internals document answered my question.
 I realized that CONST_OK_FOR_LETTER_P is under the "Obsolete Macros
for Defining Constraints" section, which states:
 "Machine-specific constraints can be defined with these macros
instead of the machine description
constructs described in Section 14.8.6 [Define Constraints], page 274.
This mechanism is obsolete. New ports should not use it..."

So, to answer myself: Yes, define_constraint definitions are used
instead of the CONST_OK_FOR_LETTER_P macro.

Thanks for your patience!
-Omar

On Tue, Apr 8, 2008 at 1:33 PM, Omar <gcc.omar@gmail.com> wrote:
>
> Jim,
>    First, thanks a lot for your comments.
>
>  > It current sources, you want to define a
>  > $target/constraints.md file that has a (define_contraint "I" ...) pattern.
>  I have been looking at other targets, and they seem to use the
>  CONST_OK_FOR_LETTER_P macro for this purpose.
>  Is the define_constraint equivalent to what the macro CONST_OK_FOR
>  _LETTER_P used to stand for?
>  I am trying to understand is define_constraint replaces this macro's
>  functionality.
>
>  Your comment confirms my suspicion:
>  > Most gcc internals stuff like this is not well documented.
>  > You just try it, and if it works fine, if
>  > it doesn't, then change it.
>
>  -Omar
>