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[Bug tree-optimization/40073] Vector short/char shifts generate sub-optimal code
- From: "glisse at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 12 Jun 2015 12:01:48 +0000
- Subject: [Bug tree-optimization/40073] Vector short/char shifts generate sub-optimal code
- Auto-submitted: auto-generated
- References: <bug-40073-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40073
Marc Glisse <glisse at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |law at gcc dot gnu.org
--- Comment #9 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to alalaw01 from comment #8)
> Is there a case where the result is different with vs without all the
> extending/truncating?
>
> It seems we should need the extending/truncating on vectors exactly iff we
> need it on scalars?
The extending/truncating is what the standard requires. Then we can start
optimizing (since indeed in many cases it isn't necessary), and Jeff is working
on exactly that (shortening). This seems like a rather straightforward case,
but who knows...