Yevgeny Rouban e901b0295d [BasicBlockUtils] Fixed LoopInfo update in UpdateAnalysisInformation() (#177147) ...

SplitLandingPadPredecessors() results in an irreducible loop
and makes LoopInfo invalid. Verification results in a crash:
Assertion `CB != OutsideLoopPreds[i] && "Loop has multiple entry
points!"' failed.

Created a new test with a broken LoopInfo after
SplitLandingPadPredecessors().
The test @split-lp-predecessors-test() after
SplitBlockPredecessors(catch_dest, { loop }, "", DT, LI) changes to
the following IR where the loop {%catch_dest} gets into irreducible
loop {%catch_dest.split-lp, %catch_dest}:

```
define void @split-lp-predecessors-test() personality ptr null {
entry:
  invoke void @foo()
          to label %loop unwind label %catch_dest.split-lp

loop:                                             ; preds = %latch, %entry
  invoke void @foo()
          to label %latch unwind label %catch_dest1

latch:                                            ; preds = %loop
  br label %loop

catch_dest1:                                      ; preds = %loop
  %lpad = landingpad i32
          cleanup
  br label %catch_dest

catch_dest.split-lp:                              ; preds = %entry, %catch_dest
  %lpad.split-lp = landingpad i32
          cleanup
  br label %catch_dest

catch_dest:                                       ; preds = %catch_dest.split-lp, %catch_dest1
  invoke void @foo()
          to label %exit unwind label %catch_dest.split-lp

exit:                                             ; preds = %catch_dest
  ret void
}
```

Irreducible loops must be removed from LoopInfo.

When UpdateAnalysisInformation() detects an irreducible loop created
then the loop is erased from LoopInfo.

See the issue #163922 for details.

2026-03-30 10:53:52 +00:00

71 KiB

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