Assign APValues by swapping from a temporary. Removes a bunch of unnecessary

copy-construction, which Daniel Dunbar reports as giving a 0.75% speedup on
403.gcc/combine.c. The performance differences on my constexpr torture tests
are below the noise floor.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152455 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 4 deletions

diff --git a/include/clang/AST/APValue.h b/include/clang/AST/APValue.h
index b7e588fba4..1b6e90cf4a 100644
--- a/include/clang/AST/APValue.h
+++ b/include/clang/AST/APValue.h
@@ -135,9 +135,7 @@ public:
   APValue(const APFloat &R, const APFloat &I) : Kind(Uninitialized) {
     MakeComplexFloat(); setComplexFloat(R, I);
   }
-  APValue(const APValue &RHS) : Kind(Uninitialized) {
-    *this = RHS;
-  }
+  APValue(const APValue &RHS);
   APValue(LValueBase B, const CharUnits &O, NoLValuePath N, unsigned CallIndex)
       : Kind(Uninitialized) {
     MakeLValue(); setLValue(B, O, N, CallIndex);
@@ -170,6 +168,9 @@ public:
     MakeUninit();
   }
 
+  /// \brief Swaps the contents of this and the given APValue.
+  void swap(APValue &RHS);
+
   ValueKind getKind() const { return Kind; }
   bool isUninit() const { return Kind == Uninitialized; }
   bool isInt() const { return Kind == Int; }
@@ -382,7 +383,11 @@ public:
     ((AddrLabelDiffData*)(char*)Data)->RHSExpr = RHSExpr;
   }
 
-  const APValue &operator=(const APValue &RHS);
+  /// Assign by swapping from a copy of the RHS.
+  APValue &operator=(APValue RHS) {
+    swap(RHS);
+    return *this;
+  }
 
 private:
   void DestroyDataAndMakeUninit();