[ptr-compr][turbofan] Remove unneeded CheckedTaggedToTaggedPointer conversion

In some cases, we end up with a ChangeCompressedPointerToTaggedPointer next
to a CheckedTaggedToTaggedPointer. In this case, the checked one is not
needed since we are sure we are dealing with a pointer (and not a Smi).

This doesn't get resolved in the simplfied lowering phase due to having a
Phi[Tagged] in the middle of those two nodes.

Cq-Include-Trybots: luci.v8.try:v8_linux64_pointer_compression_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_linux64_arm64_pointer_compression_rel_ng
Bug: v8:7703
Change-Id: Ia4a44b36423c2242d5c663f9b93b09924190fe8e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1709426
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62941}

src/compiler/simplified-operator-reducer.cc

@@ -179,6 +179,14 @@ Reduction SimplifiedOperatorReducer::Reduce(Node* node) {
       }
       break;
     }
+    case IrOpcode::kCheckedTaggedToTaggedPointer: {
+      NodeMatcher m(node->InputAt(0));
+      if (m.IsChangeCompressedPointerToTaggedPointer()) {
+        RelaxEffectsAndControls(node);
+        return Replace(m.node());
+      }
+      break;
+    }
     case IrOpcode::kCheckIf: {
       HeapObjectMatcher m(node->InputAt(0));
       if (m.Is(factory()->true_value())) {