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

[via llvm-commits]

ruiling wrote:

> This patch passed in our internal testing (PSDB) and landing it would unblock my ongoing work related to wwm-allocation and a major issue observed in a customer code.

ok, sounds fine to me to solve the liverange-issue separately.

> Like I said earlier, we don't have a ready .ll test. I will try to get one forcing some reg-constraints.

But I think you should have a test that would fail without this change (not the liverange-split related issue) and pass with this change?



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