Re: Potential fix for rdar://4658012

[kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)]

> I completely agree.  But only up to the point defining "proper analysis" -
> bootstrapping and regtesting is required for a patch to be accepted and
> I think it is a valid request from your side to require testing of Ada on
> Sparc for this patch as you remember problems on that platform.  Given that
> this succeeds, requiring further "proper analysis" or proof or whatever is
> putting the burden on the wrong side and not reasonable. 

I disagree.  Testing is not, and should never be, a substitute for analysis.

A patch is proposed because we have a reason to believe it's correct.  Then
we test to increase our confidence that it is, indeed, correct.  But both
parts are essential for any patch.

Here we have a situation where we'd like to see some optimization done (the
merging of temporaries).  There's some code that suppresses that optimization
in one case because that optimization was unsafe in that case.  It is not
acceptable to find out whether that code is still needed by merely running
a test suite: there has to be some analysis that says what changed to
make that code no longer needed.  The burden of proof on that analysis has
to be on the person who's proposing that the code is no longer needed.