patch for PR9027 and // rdar://11861085

Title: [PR9027] volatile struct bug: member is not loaded at -O;
This is caused by last flag passed to @llvm.memcpy being false, 
not honoring that aggregate has at least one 'volatile' data member 
(even though aggregate itself has not been qualified as 'volatile'. 
As a result, optimization optimizes away the memcpy altogether.
Patch review by John MaCall (I still need to fix up a test though).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173535 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 22 insertions, 3 deletions

diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp
index a35ef0c931..8c64e8a6e7 100644
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@@ -792,6 +792,11 @@ void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
     AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed, 
                             needsGC(E->getLHS()->getType()),
                             AggValueSlot::IsAliased);
+  // A non-volatile aggregate destination might have volatile member.
+  if (!LHSSlot.isVolatile() &&
+      CGF.hasVolatileMember(E->getLHS()->getType()))
+    LHSSlot.setVolatile(true);
+      
   CGF.EmitAggExpr(E->getRHS(), LHSSlot);
 
   // Copy into the destination if the assignment isn't ignored.
diff --git a/lib/CodeGen/CGValue.h b/lib/CodeGen/CGValue.h
index 7a2b8e30b1..01dee1f628 100644
--- a/lib/CodeGen/CGValue.h
+++ b/lib/CodeGen/CGValue.h
@@ -412,6 +412,10 @@ public:
     return Quals.hasVolatile();
   }
 
+  void setVolatile(bool flag) {
+    Quals.setVolatile(flag);
+  }
+  
   Qualifiers::ObjCLifetime getObjCLifetime() const {
     return Quals.getObjCLifetime();
   }
diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index afe99381ae..bfcc77a3fd 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -1665,14 +1665,24 @@ public:
   void EmitExprAsInit(const Expr *init, const ValueDecl *D,
                       LValue lvalue, bool capturedByInit);
 
+  /// hasVolatileMember - returns true if aggregate type has a volatile
+  /// member.
+  bool hasVolatileMember(QualType T) {
+    if (const RecordType *RT = T->getAs<RecordType>()) {
+      const RecordDecl *RD = cast<RecordDecl>(RT->getDecl());
+      return RD->hasVolatileMember();
+    }
+    return false;
+  }
   /// EmitAggregateCopy - Emit an aggrate assignment.
   ///
   /// The difference to EmitAggregateCopy is that tail padding is not copied.
   /// This is required for correctness when assigning non-POD structures in C++.
   void EmitAggregateAssign(llvm::Value *DestPtr, llvm::Value *SrcPtr,
-                           QualType EltTy, bool isVolatile=false,
-                           CharUnits Alignment = CharUnits::Zero()) {
-    EmitAggregateCopy(DestPtr, SrcPtr, EltTy, isVolatile, Alignment, true);
+                           QualType EltTy) {
+    bool IsVolatile = hasVolatileMember(EltTy);
+    EmitAggregateCopy(DestPtr, SrcPtr, EltTy, IsVolatile, CharUnits::Zero(),
+                      true);
   }
 
   /// EmitAggregateCopy - Emit an aggrate copy.