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Re: alias.c:nonoverlapping_component_refs_p
- From: Geert Bosch <bosch at gnat dot com>
- To: Richard Henderson <rth at redhat dot com>
- Cc: Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>,gcc-patches at gcc dot gnu dot org
- Date: Mon, 3 Dec 2001 21:02:53 -0500
- Subject: Re: alias.c:nonoverlapping_component_refs_p
On Monday, December 3, 2001, at 08:50 , Richard Henderson wrote:
> At the same place, I also note that we can derive some information
> if we make some assumptions about which bits insert/extract_bit_field
> will touch for a given field. For instance, it's unlikely that a
> bit at position 0 will be manipulated concurrently with a bit at
> position 1000, and in general I'd suspect (but don't know for sure)
> that we could bound the check by bit_position/bits_per_word being
> equal.
At some day we may well decide to use 128-bit vector registers for
operating on fields of a packed struct, if the struct has proper
alignment. So the bound should depend on the known alignment and
the widest mode that can be used for that alignment.
-Geert