[llvm] [WebAssembly] Add more lowerings for wide-arithmetic (PR #132430)

[Alex Crichton via llvm-commits]

================
@@ -1109,6 +1110,18 @@ void WebAssemblyTargetLowering::computeKnownBitsForTargetNode(
     }
     }
   }
+
+  // For 128-bit addition if the upper bits are all zero then it's known that
+  // the upper bits of the result will have all bits guaranteed zero except the
+  // first.
+  case WebAssemblyISD::I64_ADD128:
----------------
alexcrichton wrote:

Oh the previous case is supposed to break, it's not supposed to fall through. Sorry about that!

I've sent https://github.com/llvm/llvm-project/pull/133783 to fix this

https://github.com/llvm/llvm-project/pull/132430