[llvm] [MachineSink] Check predecessor/successor relationship between two basic blocks involved in critical edge splitting (PR #98540)

[Min-Yih Hsu via llvm-commits]

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+; RUN: llc < %s
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mshockwave wrote:

Despite the fact that this test is checking whether llc crashes, I would prefer using FileCheck + UTC (Update Test Check) to check against the output just like other codegen tests, for the sake of uniformity.

https://github.com/llvm/llvm-project/pull/98540