[PATCH] Fix unaligned access generated by IVOPTS
Fri Jan 10 23:43:00 GMT 2014
[Sorry for dropping the ball here]
> I think that may_be_unaligned_p is just seriously out-dated ... shouldn't it
> be sth like
> get_object_alignment_1 (ref, &align, &bitpos);
> if step * BITS_PER_UNIT + bitpos is misaligned
> or rather all this may_be_unaligned_p stuff should be dropped and IVOPTs
> should finally generate proper [TARGET_]MEM_REFs instead? That is,
> we already handle aliasing fine:
> ref = create_mem_ref (&bsi, TREE_TYPE (*use->op_p), &aff,
> reference_alias_ptr_type (*use->op_p),
> iv, base_hint, data->speed);
> so just also handle alignment properly by passing down
> get_object_alignment (*use->op_p) and in create_mem_ref_raw
> do at the end do the
> if (TYPE_MODE (type) != BLKmode
> && GET_MODE_ALIGNMENT (TYPE_MODE (type)) > align)
> type = build_aligned_type (type, align);
> for BLKmode we already look at TYPE_ALIGN and as we do not change
> the access type(?) either the previous code was already wrong or it was
> fine, so there is nothing to do.
> So - if you want to give it a try...?
After a bit of pondering, I'm not really thrilled, as this would mean changing
TARGET_MEM_REF to accept invalid (unaligned) memory references for the target.
But I agree that may_be_unaligned_p is seriously outdated, so the attached
patch entirely rewrites it, fixing the bug in the process.
Tested on SPARC, SPARC64, IA-64 and ARM, OK for the mainline?
2014-01-10 Eric Botcazou <email@example.com>
* builtins.c (get_object_alignment_2): Minor tweak.
* tree-ssa-loop-ivopts.c (may_be_unaligned_p): Rewrite.
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