[PATCH] D28193: NewGVN: Add UnknownExpression and create them for things we can't symbolize. Kill fragile machinery for handling null expressions.

[Daniel Berlin via Phabricator via llvm-commits]

dberlin created this revision.
dberlin added a reviewer: davide.
dberlin added a subscriber: llvm-commits.

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.


https://reviews.llvm.org/D28193

Files:
  include/llvm/Transforms/Scalar/GVNExpression.h
  lib/Transforms/Scalar/NewGVN.cpp

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