[PATCH] D19821: [EarlyCSE] Port to use MemorySSA (disabled by default). NFC.

[Daniel Berlin via llvm-commits]

On Tue, May 17, 2016 at 8:23 AM, Geoff Berry <gberry at codeaurora.org> wrote:

> gberry added a comment.
>
> @reames I've attempted to resolved most of your individual concerns (or at
> least made them explicit in the change).  The bigger question of whether
> this is worth the compile time remains to be determined.  Do you think more
> tests need to be added in addition to the already existing EarlyCSE tests?
> Adding additional run lines to those tests to enable
> -early-cse-use-memoryssa seems like overkill to me, but I don't feel to
> strongly about it.  Or are you more concerned about adding new tests for
> cases that are only caught by MemorySSA (both positive and negative)?
>
> @dberlin, @george.burgess.iv There are a couple of FIXME comments in this
> change that identify cases where MemorySSA is maybe being too conservative
> (e.g. when dealing with fence release instructions and load atomic
> instructions).


This is known :)


> Do you think it is reasonable to refine these cases in MemorySSA


Yes, it's one of george's goals.


>

or is the conservatism restricted to EarlyCSE's usage, in which case we
> should deal with it in EarlyCSE?


No, we should make memoryssa work well.


>   Similarly, what do you think of Phillip's suggestion to look at using
> ValueHandles in MemorySSA to make removal invalidating more automated?
>
>
Already suggested this to george a few weeks ago.


>
> http://reviews.llvm.org/D19821
>
>
>
>
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