1 files changed, 10 insertions, 1 deletions
diff --git a/include/llvm/Transforms/Scalar/GVNExpression.h b/include/llvm/Transforms/Scalar/GVNExpression.h
index a971df975b6fa..324ebca46de20 100644
--- a/include/llvm/Transforms/Scalar/GVNExpression.h
+++ b/include/llvm/Transforms/Scalar/GVNExpression.h
@@ -58,10 +58,11 @@ class Expression {
 private:
   ExpressionType EType;
   unsigned Opcode;
+  mutable hash_code HashVal;
 
 public:
   Expression(ExpressionType ET = ET_Base, unsigned O = ~2U)
-      : EType(ET), Opcode(O) {}
+      : EType(ET), Opcode(O), HashVal(0) {}
   Expression(const Expression &) = delete;
   Expression &operator=(const Expression &) = delete;
   virtual ~Expression();
@@ -82,6 +83,14 @@ public:
 
     return equals(Other);
   }
+  hash_code getComputedHash() const {
+    // It's theoretically possible for a thing to hash to zero.  In that case,
+    // we will just compute the hash a few extra times, which is no worse that
+    // we did before, which was to compute it always.
+    if (static_cast<unsigned>(HashVal) == 0)
+      HashVal = getHashValue();
+    return HashVal;
+  }
 
   virtual bool equals(const Expression &Other) const { return true; }