[llvm] [WebAssembly] Fix lowering of (extending) loads from addrspace(1) globals (PR #155937)

[Jasmine Tang via llvm-commits]

badumbatish wrote:

>  Is there something in particular you need explained further?

I think I grasp the general idea now after taking some time to review. Ty!

looks good to me, one thing i noticed locally is yes, the combine of  `i32.load8_u +  i32.extend8_s`  into `i32.load8_s` and the like is being left out. The default dag combiner must have run before lowerload, you can probably add a combine to PerformDAGCombine (same file) to help reduce code size, maybe `llvm-project/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:15728` for inspiration?

You can run the update test check again on simd.ll to show that CI actually passes all check for now, and redo it after you have added PerformDAGCombine. 

Tagging @sparker-arm @dschuff for some reviews 


https://github.com/llvm/llvm-project/pull/155937