[llvm] [GVN] Track visited nodes in equality propagation to avoid OOM (PR #212265)

[Antonio Frighetto via llvm-commits]

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+; RUN: opt < %s -passes=gvn -disable-output
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antoniofrighetto wrote:

Hang/OOM regression tests are expected to include check lines nowadays. We should reduce the test to a minimal reproducer (possibly that exhibits the exponential behavior) and autogenerate check lines via `./llvm/utils/update_test_checks.py`. Please also use named values below.

https://github.com/llvm/llvm-project/pull/212265