[llvm] r290816 - NewGVN: Add UnknownExpression and create them for things we can't symbolize. Kill fragile machinery for handling null expressions.

[Davide Italiano via llvm-commits]

On Mon, Jan 2, 2017 at 10:00 AM, Daniel Berlin via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: dannyb
> Date: Mon Jan  2 12:00:53 2017
> New Revision: 290816
>
> URL: http://llvm.org/viewvc/llvm-project?rev=290816&view=rev
> Log:
> NewGVN: Add UnknownExpression and create them for things we can't symbolize. Kill fragile machinery for handling null expressions.
>
> Summary:
> This avoids the very fragile code for null expressions. We could also use a denseset that tracks which things have null expressions instead, but that seems pretty fragile and premature optimization.
>
> This resolves a number of infinite loop cases, test reductions coming.
>

Note for archive archelogists: this is already tested (see comment in
the review).

-- 
Davide