Ignore redundant parallel moves when checking if a block is empty.

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
diff --git a/runtime/vm/intermediate_language.h b/runtime/vm/intermediate_language.h
index 7733ba3edf4d89ff707bbfe3c29dad21686f0bbd..1f4201a09b8fdd94ebc2ccd2e7a997fc9a766925 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -1078,6 +1078,8 @@ class ParallelMoveInstr : public TemplateInstruction<0> {
 
   intptr_t NumMoves() const { return moves_.length(); }
 
+  bool IsRedundant() const;
+
   virtual void PrintTo(BufferFormatter* f) const;
 
   virtual bool MayThrow() const { return false; }
@@ -1138,6 +1140,10 @@ class BlockEntryInstr : public Instruction {
     return parallel_move_ != NULL;
   }
 
+  bool HasNonRedundantParallelMove() const {
+    return HasParallelMove() && !parallel_move()->IsRedundant();
+  }
+
   ParallelMoveInstr* GetParallelMove() {
     if (parallel_move_ == NULL) {
       parallel_move_ = new ParallelMoveInstr();
@@ -2167,6 +2173,10 @@ class GotoInstr : public TemplateInstruction<0> {
     return parallel_move_ != NULL;
   }
 
+  bool HasNonRedundantParallelMove() const {
+    return HasParallelMove() && !parallel_move()->IsRedundant();
+  }
+
   ParallelMoveInstr* GetParallelMove() {
     if (parallel_move_ == NULL) {
       parallel_move_ = new ParallelMoveInstr();