[llvm] [GlobalISel] Add G_ADD for computeNumSignBits (PR #159202)

[Yatao Wang via llvm-commits]

================
@@ -1959,6 +1959,41 @@ unsigned GISelValueTracking::computeNumSignBits(Register R,
 
     break;
   }
+  case TargetOpcode::G_ADD: {
+    Register Src2 = MI.getOperand(2).getReg();
+    unsigned Src2NumSignBits =
+        computeNumSignBits(Src2, DemandedElts, Depth + 1);
+    if (Src2NumSignBits == 1)
----------------
ningxinr wrote:

@jayfoad @arsenm Gentle ping for any comments/feedbacks on RHS check location, please. 

https://github.com/llvm/llvm-project/pull/159202