Re: [WWW] simtest-howto.html clarifications, additions

[Janis Johnson <janis187 at us dot ibm dot com>]

On Wed, Jun 11, 2003 at 06:36:52PM -0400, Hans-Peter Nilsson wrote:
> On Wed, 11 Jun 2003, Janis Johnson wrote:
> 
> > On Wed, Jun 11, 2003 at 01:54:59PM -0700, Dan Kegel wrote:
> > > Janis Johnson wrote:
> > > > +    <p>The target characteristic can help you determine which targets to
> > > > +    use to broaden the scope of your testing.  A CC0 target causes
> > > > +    significantly different code to be generated and can matter more
> > > > +    than word size and endianness in terms of detecting new breakage.</p>
> > >
> > > What's a CC0 target?  I've googled and googled, and can't find a clue.
> 
> You mean you found no references to GCC internals?
> 
> > I changed it from "CC0" to "cc0", which is how it's used in the GCC
> > internals manual.
> 
> Very well.  I used capitals because... I don't remember.
> It just looked better at the time.
> 
> >  It has to do with condition codes, but most of the
> > documentation assumes you already know what it means and talks about
> > machines that do or do not use cc0.  If someone provides a good, short
> > description I'll add it here.
> 
> Here's goes: A "cc0 target" is one that describes setting
> condition codes as side-effects of most instructions on a single
> fixed register, cc0.

How's this, which is a combination of what Hans-Peter and Michael wrote.
(Something like this would be nice in the Condition Codes section of
the internals manual, too.)

Index: simtest-howto.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/simtest-howto.html,v
retrieving revision 1.15
diff -u -p -r1.15 simtest-howto.html
--- simtest-howto.html	11 Jun 2003 21:37:33 -0000	1.15
+++ simtest-howto.html	11 Jun 2003 22:57:22 -0000
@@ -133,7 +133,11 @@ make check-gcc RUNTESTFLAGS=--target_boa
     a patch you should compare your results with and without the patch.</p>
 
     <p>The target characteristic can help you determine which targets to
-    use to broaden the scope of your testing.  A cc0 target causes
+    use to broaden the scope of your testing.  A `cc0 target' uses a
+    single condition code register, cc0, which is set as a side effect
+    of most instructions.  The compiler cannot insert other instructions
+    between the instruction that sets cc0 and the one that uses it.
+    Because of this, a cc0 target causes
     significantly different code to be generated and can matter more
     than word size and endianness in terms of detecting new breakage.</p>