On Thu, Nov 13, 2014 at 06:46:23AM -0800, Teresa Johnson wrote:
> >> --- tree.c (revision 217190)
> >> +++ tree.c (working copy)
> >> @@ -10330,6 +10330,8 @@ initializer_zerop (const_tree init)
> >> {
> >> unsigned HOST_WIDE_INT idx;
> >>
> >> + if (TREE_CLOBBER_P (init))
> >> + return false;
> >
> > Wrong formatting.
>
> Sorry, not sure I understand why? My mailer does tend to eat spaces,
> but it is indented the correct amount and I think has the right spaces
> within the line.
I meant that you are using spaces instead of tabs and the unsigned line
above it being one char off suggested to me visually it has the tab in there
(apparently it is eaten too). Use MUA that doesn't eat it, or convince your
employer that tabs are important in e-mails? ;)
If you commit tabs in there, it is fine with me.
> Ok, I have held off on my commit for now. I considered fixing this in
> tree-ssa-strlen, but thought this was a potentially larger problem
> with initializer_zerop, where it shouldn't be considering a clobber to
> be a zero init and might be affecting other callers as well.
As I said, I think your tree.c change is useful, but perhaps too risky
for the release branches, because we don't know what all it will affect?
> If we make the change to initializer_zerop is it still useful to
> change tree-strlen?
I think it is better to be clear on it that right now we want clobbers
to clobber the memory for strlen pass purposes, maybe in the future we want
to perform some optimizations for them as Richard suggested in the PR
(though, extending the lifetime in that case by removing the clobber
shouldn't be done unconditionally (i.e. limited to when we'd actually want
to benefit from the known length) and assuming we are close to the clobber
(i.e. it is fine to extend it a little bit, but not extend the lifetime
across multi-megabyte function e.g.).
And for release branches I'd really prefer tree-ssa-strlen.c change.
Jakub
