[PATCH] D104870: [SimplifyCFG] Tail-merging all blocks with `unreachable` terminator

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: rnk, dmgreen, fhahn, nikic, hans.
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lebedev.ri requested review of this revision.

Unlike `ret`/`resume`, for `unreachable` currently no such tail-merging is being performed.
There has been at least one previous attempt at this - D29428 <https://reviews.llvm.org/D29428>.

As @rnk notes in D104445 <https://reviews.llvm.org/D104445>, this may be somewhat problematic for certain backends
that "form regions later in the backend". But then, surely they already have to
deal with such IR, because even if transforms don't create it,
can it not have been created by the user?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D104870

Files:
  llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
  llvm/test/CodeGen/Thumb2/setjmp_longjmp.ll
  llvm/test/Transforms/SimplifyCFG/tail-merge-noreturn.ll

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