[clang] [llvm] [mlir] Enforce single-operand form for llvm.loop.distribute metadata (PR #201077)

[Madhur Amilkanthwar via cfe-commits]

madhur13490 wrote:

> [critical] With this change, there will be an hard error with metadata with the old format. We will need the AutoUpgrade otherwise older .bc files will be rejected, violating the IR backwards compatibility guarantee
> 
> > The current LLVM version supports loading any bitcode since version 3.0.
> 
> > Non-debug metadata is defined to be safe to drop, so a valid way to upgrade it is to drop it. That is not very user friendly and a bit more effort is expected, but no promises are made.
> 
> https://llvm.org/docs/DeveloperPolicy.html#ir-backwards-compatibility

Done changes in AutoUpgrade.

https://github.com/llvm/llvm-project/pull/201077