[llvm] [AMDGPU] Improve isBasicBlockPrologue helper function (PR #69924)

[Piotr Sobczak via llvm-commits]

piotrAMD wrote:

Starting from this commit we are hitting the following assertion when running Vulkan CTS:

lib/CodeGen/SplitKit.cpp:1648: void llvm::SplitEditor::splitLiveThroughBlock(unsigned int, unsigned int, llvm::SlotIndex, unsigned int, llvm::SlotIndex): Assertion `(!LeaveBefore || Idx <= LeaveBefore) && "Interference"' failed.

I'll prepare a reproducer.

https://github.com/llvm/llvm-project/pull/69924