A64: Port LGapResolver::Verify().

src/a64/lithium-gap-resolver-a64.cc

Index: src/a64/lithium-gap-resolver-a64.cc
diff --git a/src/a64/lithium-gap-resolver-a64.cc b/src/a64/lithium-gap-resolver-a64.cc
index f924805d741c3a258cb31498e31afa7ad7631e9a..54378c5ba2d807efcc2831eb932978ebdac40f59 100644
--- a/src/a64/lithium-gap-resolver-a64.cc
+++ b/src/a64/lithium-gap-resolver-a64.cc
@@ -153,7 +153,15 @@ void LGapResolver::PerformMove(int index) {
 
 
 void LGapResolver::Verify() {
-  TODO_UNIMPLEMENTED("LGapResolver::Verify");
+#ifdef ENABLE_SLOW_ASSERTS
+  // No operand should be the destination for more than one move.
+  for (int i = 0; i < moves_.length(); ++i) {
+    LOperand* destination = moves_[i].destination();
+    for (int j = i + 1; j < moves_.length(); ++j) {
+      SLOW_ASSERT(!destination->Equals(moves_[j].destination()));
+    }
+  }
+#endif
 }