[llvm] [GlobalISel] Support GISelValueTracking for G_FREEZE. (PR #223696)

[Matt Arsenault via llvm-commits]

================
@@ -2253,6 +2261,13 @@ void GISelValueTracking::computeKnownFPClass(Register R,
     }
     break;
   }
+  case TargetOpcode::G_FREEZE: {
+    Register Src = MI.getOperand(1).getReg();
+    if (isGuaranteedNotToBeUndefOrPoison(Src, MRI, Depth + 1))
+      computeKnownFPClass(Src, DemandedElts, InterestedClasses, Known,
+                          Depth + 1);
+    break;
----------------
arsenm wrote:

Not sure what value there is in falling to the base case 

https://github.com/llvm/llvm-project/pull/223696