[llvm] SimplifyCFG: fold trivial non-empty blocks with safe instructions (PR #180350)

[Ridham Khurana via llvm-commits]

rmkhurana28 wrote:

Pushed an update commit addressing:
- Debug and lifetime markers are now preserved during the splice.
- The side-effect safety comment has been clarified.
- A single-predecessor store folding test has been added for completeness.

All changes have been tested locally and pass the full `check-llvm` suite.


https://github.com/llvm/llvm-project/pull/180350