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Re: Handling aliasing memory accesses in gimple/ssa


On Tue, May 10, 2016 at 3:41 PM, Kyrill Tkachov
<kyrylo.tkachov@foss.arm.com> wrote:
> Hi all,
>
> I'm taking a stab at fixing PR 22141 by merging adjacent stores into wider
> stores in a late gimple pass.
>
> My current plan is to go through all the assignments in a basic block and
> keep track of
> LHS expressions that are COMPONENT_REF, BIT_FIELD_REF, ARRAY_REF or
> ARRAY_RANGE_REF until
> we encounter an expression that affects the recorded stores or a mergeable
> store that aliases with
> any of the preceeding loads. My question is how to express that question in
> gimple/tree-ssa?
>
> Is taking get_alias_set of the two expressions that I want to compare and
> checking alias_sets_conflict_p enough?

That's too conservative.  You want to use stmt_may_clobber_ref_p /
ref_maybe_used_by_stmt_p
and likely feed both with the "base" you want to perform the merging with.

Richard.

> Thanks,
> Kyrill
>


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