[llvm] [DAGCombiner] Fold subtraction if above threshold to `umin` (PR #134235)

[Piotr Fusik via llvm-commits]

pfusik wrote:

> Build failed with:
> 
> ```
> # | error: 'expected-note' diagnostics expected but not seen: 
> # |   File C:\ws\src\clang\test\CXX\temp\temp.arg\temp.arg.type\p2.cpp Line 17 (directive at C:\ws\src\clang\test\CXX\temp\temp.arg\temp.arg.type\p2.cpp:18): unnamed type used in template argument was declared here
> ```
> 
> I don't believe this is caused by my change.

Rebasing should fix this.

https://github.com/llvm/llvm-project/pull/134235