[llvm] [X86] Truncate i64 add/sub/mul arithmetic to i32 with known zeros in upper 32 bits (PR #143313)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon requested changes to this pull request.

(style) Only clang-format the diff - not the entire file - you've made review of X86ISelLowering.cpp impossible :( 

https://github.com/llvm/llvm-project/pull/143313