[PATCH] D104598: [NFCI-ish][SimplifyCFGPass] Rework and generalize `ret` block tail-merging

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: rnk, fhahn, hans, nikic, spatel.
lebedev.ri added a project: LLVM.
Herald added subscribers: zzheng, hiraditya.
lebedev.ri requested review of this revision.

This changes the approach taken to tail-merge the blocks
to always create a new block instead of trying to reuse some block,
and generalizes it to support dealing not with just the `ret` in the future.

This effectively lifts the CallBr restriction, although this isn't really intentional.
That showed that we miscompile blocks with their addresses taken in at least two places,
so two fixes had to be applied.

Other restrictions of the transform remain.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D104598

Files:
  llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
  llvm/lib/Transforms/Utils/SimplifyCFG.cpp
  llvm/test/Transforms/LoopUnroll/ARM/upperbound.ll
  llvm/test/Transforms/SimplifyCFG/2003-08-17-FoldSwitch.ll
  llvm/test/Transforms/SimplifyCFG/ConditionalTrappingConstantExpr.ll
  llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-domtree-preservation-edgecase.ll
  llvm/test/Transforms/SimplifyCFG/FoldValueComparisonIntoPredecessors-no-new-successors.ll
  llvm/test/Transforms/SimplifyCFG/SimplifyEqualityComparisonWithOnlyPredecessor-domtree-preservation-edgecase.ll
  llvm/test/Transforms/SimplifyCFG/basictest.ll
  llvm/test/Transforms/SimplifyCFG/hoist-dbgvalue.ll
  llvm/test/Transforms/SimplifyCFG/pr48778-sdiv-speculation.ll
  llvm/test/Transforms/SimplifyCFG/rangereduce.ll
  llvm/test/Transforms/SimplifyCFG/suppress-zero-branch-weights.ll
  llvm/test/Transforms/SimplifyCFG/switch-masked-bits.ll

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