[Basic] Change DiagnosticBuilder to use a separate status variable to track whether the builder is active.

 - This may seem superflous, but actually this allows the optimizer to more
   easily eliminate the isActive() checks needed by the SemaDiagnosticBuilder
   and DiagnosticBuilder dtors. And by more easily, I mean the current LLVM is
   actually able to do one and not the other. :)

This is good for another 20k code size reduction.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152709 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 8 deletions

diff --git a/include/clang/Basic/Diagnostic.h b/include/clang/Basic/Diagnostic.h
index 43747a1810..1634306fc3 100644
--- a/include/clang/Basic/Diagnostic.h
+++ b/include/clang/Basic/Diagnostic.h
@@ -772,10 +772,17 @@ class DiagnosticBuilder {
   mutable DiagnosticsEngine *DiagObj;
   mutable unsigned NumArgs, NumRanges, NumFixits;
 
+  /// \brief Status variable indicating if this diagnostic is still active.
+  ///
+  // NOTE: This field is redundant with DiagObj (IsActive iff (DiagObj == 0)),
+  // but LLVM is not currently smart enough to eliminate the null check that
+  // Emit() would end up with if we used that as our status variable.
+  mutable bool IsActive;
+
   void operator=(const DiagnosticBuilder&); // DO NOT IMPLEMENT
   friend class DiagnosticsEngine;
   explicit DiagnosticBuilder(DiagnosticsEngine *diagObj)
-    : DiagObj(diagObj), NumArgs(0), NumRanges(0), NumFixits(0) {
+    : DiagObj(diagObj), NumArgs(0), NumRanges(0), NumFixits(0), IsActive(true) {
     assert(diagObj && "DiagnosticBuilder requires a valid DiagnosticsEngine!");
   }
 
@@ -789,10 +796,13 @@ protected:
   }
 
   /// \brief Clear out the current diagnostic.
-  void Clear() { DiagObj = 0; }
+  void Clear() const {
+    DiagObj = 0;
+    IsActive = false;
+  }
 
   /// isActive - Determine whether this diagnostic is still active.
-  bool isActive() const { return DiagObj != 0; }
+  bool isActive() const { return IsActive; }
 
   /// \brief Force the diagnostic builder to emit the diagnostic now.
   ///
@@ -802,9 +812,9 @@ protected:
   /// \returns true if a diagnostic was emitted, false if the
   /// diagnostic was suppressed.
   bool Emit() {
-    // If DiagObj is null, then its soul was stolen by the copy ctor
-    // or the user called Emit().
-    if (DiagObj == 0) return false;
+    // If this diagnostic is inactive, then its soul was stolen by the copy ctor
+    // (or by a subclass, as in SemaDiagnosticBuilder).
+    if (!isActive()) return false;
 
     // When emitting diagnostics, we set the final argument count into
     // the DiagnosticsEngine object.
@@ -814,7 +824,7 @@ protected:
     bool Result = DiagObj->EmitCurrentDiagnostic();
 
     // This diagnostic is dead.
-    DiagObj = 0;
+    Clear();
 
     return Result;
   }
@@ -824,7 +834,8 @@ public:
   /// input and neuters it.
   DiagnosticBuilder(const DiagnosticBuilder &D) {
     DiagObj = D.DiagObj;
-    D.DiagObj = 0;
+    IsActive = D.IsActive;
+    D.Clear();
     NumArgs = D.NumArgs;
     NumRanges = D.NumRanges;
     NumFixits = D.NumFixits;