Re: i370 port

["Ulrich Weigand" <uweigand@de.ibm.com>]

Paul Edwards wrote:

> I then found out that even with old versions of the machine definition,
> I can have the warning removed by simply not defining CONST_INT
> in the PREDICATE_CODES, even though it is allowed when the
> function is called.  ie it seems to have no effect on the code
> generation, but succeeds in eliminating the warning, and without
> needing to define an extra constraint for non-constant situations.

Actually PREDICATE_CODES does have to match the predicate definitions.
If it does not, you can run into subtle bugs, as the code in genrecog.c
that generates the finite state automaton matching an RTX pattern
against the .md insn definitions *does* make use of PREDICATE_CODES;
for example, it will assume that two predicates with disjoint sets
of PREDICATE_CODES can never both match the same RTX.

This may or may not lead to visible differences when compiling simple
test cases, but I'd expect effects to be visible in more complex
scenarios.

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  GNU Toolchain for Linux on System z and Cell BE
  Ulrich.Weigand@de.ibm.com