[PATCH] D126337: [pseudo] WIP: GSS node refcounting (dumb pointers)

[Sam McCall via Phabricator via cfe-commits]

sammccall created this revision.
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This adds a refcount to GSS::Node, and uses a freelist to reuse nodes rather
than reallocating.

The freelist works well (on AST.cpp, 35K nodes created but only 74 allocated),
but it's not the only point here. Tracking the lifetime of GSS nodes is going to
be useful for error handling: when a node dies having never been successfully
reduced, we can capture it to run recovery on it.

This version of the patch continues to use Node*, with calls to GSS::ref() and
GSS::unref() to manipulate the count. I don't think this is workable - it
took me a depressingly long time to track down the bugs, and the code is hard
to reason about.
I think we want a smart pointer here to make the code clearer. Unfortunately
this is a bit tricky: the destructor needs the GSS to do the destruction, but
we don't want to pay the cost of storing an extra pointer to the GSS everywhere.
I can't think of a better alternative than (ick) thread-local storage.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D126337

Files:
  clang-tools-extra/pseudo/include/clang-pseudo/GLR.h
  clang-tools-extra/pseudo/lib/GLR.cpp
  clang-tools-extra/pseudo/unittests/GLRTest.cpp

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