CodeGen: Copy tail padding when we're not dealing with a trivial copy assign or move assign operator.
This fixes a regression from r162254, the optimizer has problems reasoning
about the smaller memcpy as it's often not safe to widen a store but making it
smaller is.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@164917 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp
index c9ffc19..200b43a 100644
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@@ -1274,7 +1274,8 @@
void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
llvm::Value *SrcPtr, QualType Ty,
bool isVolatile,
- CharUnits alignment) {
+ CharUnits alignment,
+ bool isAssignment) {
assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
if (getContext().getLangOpts().CPlusPlus) {
@@ -1303,9 +1304,13 @@
// implementation handles this case safely. If there is a libc that does not
// safely handle this, we can add a target hook.
- // Get data size and alignment info for this aggregate.
- std::pair<CharUnits, CharUnits> TypeInfo =
- getContext().getTypeInfoDataSizeInChars(Ty);
+ // Get data size and alignment info for this aggregate. If this is an
+ // assignment don't copy the tail padding. Otherwise copying it is fine.
+ std::pair<CharUnits, CharUnits> TypeInfo;
+ if (isAssignment)
+ TypeInfo = getContext().getTypeInfoDataSizeInChars(Ty);
+ else
+ TypeInfo = getContext().getTypeInfoInChars(Ty);
if (alignment.isZero())
alignment = TypeInfo.second;
diff --git a/lib/CodeGen/CGExprCXX.cpp b/lib/CodeGen/CGExprCXX.cpp
index 7276440..1631196 100644
--- a/lib/CodeGen/CGExprCXX.cpp
+++ b/lib/CodeGen/CGExprCXX.cpp
@@ -241,7 +241,7 @@
// We don't like to generate the trivial copy/move assignment operator
// when it isn't necessary; just produce the proper effect here.
llvm::Value *RHS = EmitLValue(*CE->arg_begin()).getAddress();
- EmitAggregateCopy(This, RHS, CE->getType());
+ EmitAggregateAssign(This, RHS, CE->getType());
return RValue::get(This);
}
@@ -378,7 +378,7 @@
MD->isTrivial()) {
llvm::Value *Src = EmitLValue(E->getArg(1)).getAddress();
QualType Ty = E->getType();
- EmitAggregateCopy(This, Src, Ty);
+ EmitAggregateAssign(This, Src, Ty);
return RValue::get(This);
}
diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index fc930ec..4a0c35b 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -1653,13 +1653,26 @@
void EmitExprAsInit(const Expr *init, const ValueDecl *D,
LValue lvalue, bool capturedByInit);
+ /// 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);
+ }
+
/// EmitAggregateCopy - Emit an aggrate copy.
///
/// \param isVolatile - True iff either the source or the destination is
/// volatile.
+ /// \param isAssignment - If false, allow padding to be copied. This often
+ /// yields more efficient.
void EmitAggregateCopy(llvm::Value *DestPtr, llvm::Value *SrcPtr,
QualType EltTy, bool isVolatile=false,
- CharUnits Alignment = CharUnits::Zero());
+ CharUnits Alignment = CharUnits::Zero(),
+ bool isAssignment = false);
/// StartBlock - Start new block named N. If insert block is a dummy block
/// then reuse it.