[PATCH] C++ space optimization: de-cloning con/de/structors

[Stuart Hastings]

On Tuesday, Aug 6, 2002, at 16:02 US/Pacific, Richard Henderson wrote:

> On Tue, Aug 06, 2002 at 11:41:49AM -0700, Stuart Hastings wrote:
>> There is a related patch coming soon that recognizes these thunk-esque
>> clones and omits the EH info for them, saving more space.
>
> You realize this can only happen when you know for
> absolute certain that these thunks actually do get
> generated with tail-calls, right?  The target can
> reject the tail-call with FUNCTION_OK_FOR_SIBCALL.

I got this wrong, twice.  Ask me how I know.  :-P

However, it was clearly worth the effort; with the de-cloner operating, 
this shaved another 10% off the diskfile size of a certain, critical OS 
X framework.  Combined, the de-cloner and the EH-info change shaved 
15-16% off the projects we measured.  This didn't get us back to the 
sizes we got with GCC2, but our management was nonetheless pleased.

>> +   /* If constructor expects vector (e.g. AltiVec) arguments, give 
>> up.  */
>
> Why?

Laziness; if I support it, I'm obligated to test it, and AltiVec C++ 
codes are rare and not trivial to debug.

It's likely that the de-cloner would work fine with C++ constructors 
that take AltiVec parameters (or their x86 counterparts), and I believe 
this restriction could be relaxed.

stuart hastings
Apple Computer