[llvm] [X86] Truncates i64 add arithmetic to i32 when known zeroes in upper 33 bits (PR #191619)

[via llvm-commits]

2elliti wrote:

> Ping — I've addressed all the review feedback: applied the style fixes, simplified the NSW logic per @Takashiidobe's suggestion, added a guard for ConstantSDNode operands to prevent promoteExtBeforeAdd from reverting the fold, and regenerated the affected tests. PTAL when you have a moment.

@RKSimon 

https://github.com/llvm/llvm-project/pull/191619