On 19 Jun 2012, at 22:41, Mike Stump wrote: > On Jun 19, 2012, at 12:22 PM, Iain Sandoe <i...@codesourcery.com> wrote: >> On 19 Jun 2012, at 13:53, Dominique Dhumieres wrote: >> >>> On Tue, 19 Jun 2012, Richard Guenther wrote: >>>> >>>>> Richard Guenther <rguent...@suse.de> writes: >>>>>> We are too eager to bump alignment of some decls when vectorizing. >>>>>> The fix is to not bump alignment of decls the user explicitely >>>>>> aligned or that are used in an unknown way. >>>>> >>>>> I thought attribute((__aligned__)) only set a minimum alignment for >>>>> variables? Most usees I've seen have been trying to get better >>>>> performance from higher alignment, so it might not go down well if the >>>>> attribute stopped the vectoriser from increasing the alignment still >>>>> further. >>>> >>>> That's what the documentation says indeed. I'm not sure which part of >>>> the patch fixes the ObjC failures where the alignment is part of the ABI >>>> (and I suppose ObjC then mis-uses the aligned attribute?). >>> >>> A quick test shows that >>> >>> if (DECL_PRESERVE_P (decl)) >>> >>> alone is enough to fix the objc failures, while they are still there if >>> one uses only >>> >>> if (DECL_USER_ALIGN (decl)) >> >> That makes sense, I had a quick look at the ObjC code, and it appears that >> the explicit ALIGNs were never committed to trunk. >> >> Thus, the question becomes; what should ObjC (or any other) FE do to ensure >> that specific ABI (upper) alignment constraints are met? > > Hum, upper is easy... I thought the issue was that extra alignment would > kill it? I know that extra alignment does kill some of the objc metadata.
clearly, ambiguous phrasing on my part. I mean when we want to say "no more than this much".
