RFC: Change rules for adding/changing test cases

[DJ Delorie <dj at redhat dot com>]

Given that the preprocessor is integrated into cc1, and that there are
more and more people helping with gcc, and more and more ports to new
chips, I would like to propose changing the rules for approving new
test cases and maintaining old ones as follows:

  All test cases must have comments indicating what type of failure
  they are testing (i.e. the conditions that indicated the need for a
  test case, location of the abort, whatever), and when fixed,
  comments indicating what/how it was fixed.

This way, if a new port sees a failure in a specific test, the porter
can read the comments to see if they've repeated that mistake in their
port, and thus correct the bug quickly.

So I see these three cases:

1. New testcase for a bug that's not yet fixed.  Should include a
   comment saying what failure was seen in gcc (like "caused abort in
   foo.c:bar() on for blat-elf").  That way, if someone wants to fix
   the bug, they can reproduce the original bug easily, rather than
   hunting for a failure and perhaps tripping over some unrelated
   failure and missing the original one.

2. New testcase for a recently fixed bug.  Should include a comment as
   in #1, and one saying how it was fixed (like "caused by wrong
   constraints in addsi3 for foo-elf chip").

3. Fix a bug tested by an existing testcase.  Should add comment to
   existing testcase as in #2 above, even if there's already a comment
   or two in there (assuming it's saying something new).

This way, each testcase will contain a history of how people dealt
with that failure, so that others won't have to search the mail
archives or web to try to figure out what a given failure means.