[all-commits] [llvm/llvm-project] 8bc298: [NewPM][Inliner] Check if deleted function is in c...

[aeubanks via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8bc298d041fbe8ec2cabe8a05c6cb06beff5527f
      https://github.com/llvm/llvm-project/commit/8bc298d041fbe8ec2cabe8a05c6cb06beff5527f
  Author: Arthur Eubanks <aeubanks at google.com>
  Date:   2021-07-21 (Wed, 21 Jul 2021)

  Changed paths:
    M llvm/lib/Transforms/IPO/Inliner.cpp
    A llvm/test/Transforms/Inline/deleted-scc.ll

  Log Message:
  -----------
  [NewPM][Inliner] Check if deleted function is in current SCC

In weird cases, the inliner will inline internal recursive functions,
sometimes causing them to have no more uses, in which case the
inliner will mark the function to be deleted. The function is
actually deleted after the call to
updateCGAndAnalysisManagerForCGSCCPass(). In
updateCGAndAnalysisManagerForCGSCCPass(), UR.UpdatedC may be set to
the SCC containing the function to be deleted. Then the inliner calls
CG.removeDeadFunction() which can cause that SCC to be deleted, even
though it's still stored in UR.UpdatedC.

We could potentially check in the wrappers/pass managers if UR.UpdatedC
is in UR.InvalidatedSCCs before doing anything with it, but it's safer
to do this as close to possible to the call to CG.removeDeadFunction()
to avoid issues with allocating a new SCC in the same address as
the deleted one.

It's hard to find a small test case since we need to have recursive
internal functions be reachable from non-internal functions, yet they
need to become non-recursive and not referenced by other functions when
inlined.

Similar to https://reviews.llvm.org/D106306.

Fixes PR50788.

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D106405