[all-commits] [llvm/llvm-project] 0e84bf: [CIR] Handle the 'before case' block of a switch s...

[Erich Keane via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0e84bfa79f1121b65609013175c6515159e3cdec
      https://github.com/llvm/llvm-project/commit/0e84bfa79f1121b65609013175c6515159e3cdec
  Author: Erich Keane <ekeane at nvidia.com>
  Date:   2026-05-27 (Wed, 27 May 2026)

  Changed paths:
    M clang/lib/CIR/CodeGen/CIRGenStmt.cpp
    M clang/lib/CIR/Dialect/Transforms/FlattenCFG.cpp
    A clang/test/CIR/CodeGen/switch-pre-case-stmts.cpp

  Log Message:
  -----------
  [CIR] Handle the 'before case' block of a switch statement. (#199752)

Before this patch, we would fail any time there was a block with
entry/exit (in this case, one with successors thanks to a label) with a
verification error. This patch adds special handling for that first
block.

This patch DOES choose to not trim them however. Unless there is a label
inside of the block, there isn't any way to get there, and it is dead
code. I've opted to NOT do that optimization, as I suspect that might be
valuable to future passes/something we may wish to warn about in some
sort of CFG analysis.

Additionally, there is some minor changes to FlattenCFG, first to make
sure we skip the switch ONLY if it is truly empty, and second to make
sure we transform any 'break' in the pre-case region.



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