[KeyInstr][SimplifyCFG] Remap atoms when folding br to common succ into pred (#133482)

SimplifyCFG folds `d` into preds `b` and `c`.

              +---------------+
              |               |
         +--> b --+           |
         |        v           v
     --> a        d --> e --> f -->
         |        ^           ^
         +--> c --+           |
              |               |
              +---------------+
    
Remap source atoms so that the duplicated instructions are analysed
independently to determine is_stmt positions.

The pull request contains a discussion covering various edge cases here:
https://github.com/llvm/llvm-project/pull/133482/files#r2039519348

The summary of the discussion is that we could avoid remapping when there's a
single pred, but we decided that it's still a trade off, and not worth the
additional complexity right now.

RFC:
https://discourse.llvm.org/t/rfc-improving-is-stmt-placement-for-better-interactive-debugging/82668

0 files changed, 0 insertions, 0 deletions