PR36992: do not store beyond the dsize of a class object unless we know
the tail padding is not reused.
We track on the AggValueSlot (and through a couple of other
initialization actions) whether we're dealing with an object that might
share its tail padding with some other object, so that we can avoid
emitting stores into the tail padding if that's the case. We still
widen stores into tail padding when we can do so.
Differential Revision: https://reviews.llvm.org/D45306
llvm-svn: 329342
diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp
index 4ba5c06..fb09b4d 100644
--- a/clang/lib/CodeGen/CGClass.cpp
+++ b/clang/lib/CodeGen/CGClass.cpp
@@ -555,10 +555,12 @@
BaseClassDecl,
isBaseVirtual);
AggValueSlot AggSlot =
- AggValueSlot::forAddr(V, Qualifiers(),
- AggValueSlot::IsDestructed,
- AggValueSlot::DoesNotNeedGCBarriers,
- AggValueSlot::IsNotAliased);
+ AggValueSlot::forAddr(
+ V, Qualifiers(),
+ AggValueSlot::IsDestructed,
+ AggValueSlot::DoesNotNeedGCBarriers,
+ AggValueSlot::IsNotAliased,
+ CGF.overlapForBaseInit(ClassDecl, BaseClassDecl, isBaseVirtual));
CGF.EmitAggExpr(BaseInit->getInit(), AggSlot);
@@ -647,7 +649,8 @@
LValue Src = CGF.EmitLValueForFieldInitialization(ThisRHSLV, Field);
// Copy the aggregate.
- CGF.EmitAggregateCopy(LHS, Src, FieldType, LHS.isVolatileQualified());
+ CGF.EmitAggregateCopy(LHS, Src, FieldType, CGF.overlapForFieldInit(Field),
+ LHS.isVolatileQualified());
// Ensure that we destroy the objects if an exception is thrown later in
// the constructor.
QualType::DestructionKind dtorKind = FieldType.isDestructedType();
@@ -677,10 +680,12 @@
break;
case TEK_Aggregate: {
AggValueSlot Slot =
- AggValueSlot::forLValue(LHS,
- AggValueSlot::IsDestructed,
- AggValueSlot::DoesNotNeedGCBarriers,
- AggValueSlot::IsNotAliased);
+ AggValueSlot::forLValue(
+ LHS,
+ AggValueSlot::IsDestructed,
+ AggValueSlot::DoesNotNeedGCBarriers,
+ AggValueSlot::IsNotAliased,
+ overlapForFieldInit(Field));
EmitAggExpr(Init, Slot);
break;
}
@@ -911,15 +916,15 @@
}
CharUnits getMemcpySize(uint64_t FirstByteOffset) const {
+ ASTContext &Ctx = CGF.getContext();
unsigned LastFieldSize =
- LastField->isBitField() ?
- LastField->getBitWidthValue(CGF.getContext()) :
- CGF.getContext().getTypeSize(LastField->getType());
- uint64_t MemcpySizeBits =
- LastFieldOffset + LastFieldSize - FirstByteOffset +
- CGF.getContext().getCharWidth() - 1;
- CharUnits MemcpySize =
- CGF.getContext().toCharUnitsFromBits(MemcpySizeBits);
+ LastField->isBitField()
+ ? LastField->getBitWidthValue(Ctx)
+ : Ctx.toBits(
+ Ctx.getTypeInfoDataSizeInChars(LastField->getType()).first);
+ uint64_t MemcpySizeBits = LastFieldOffset + LastFieldSize -
+ FirstByteOffset + Ctx.getCharWidth() - 1;
+ CharUnits MemcpySize = Ctx.toCharUnitsFromBits(MemcpySizeBits);
return MemcpySize;
}
@@ -1960,7 +1965,8 @@
}
EmitCXXConstructorCall(ctor, Ctor_Complete, /*ForVirtualBase=*/false,
- /*Delegating=*/false, curAddr, E);
+ /*Delegating=*/false, curAddr, E,
+ AggValueSlot::DoesNotOverlap);
}
// Go to the next element.
@@ -1995,7 +2001,8 @@
CXXCtorType Type,
bool ForVirtualBase,
bool Delegating, Address This,
- const CXXConstructExpr *E) {
+ const CXXConstructExpr *E,
+ AggValueSlot::Overlap_t Overlap) {
CallArgList Args;
// Push the this ptr.
@@ -2011,7 +2018,7 @@
LValue Src = EmitLValue(Arg);
QualType DestTy = getContext().getTypeDeclType(D->getParent());
LValue Dest = MakeAddrLValue(This, DestTy);
- EmitAggregateCopyCtor(Dest, Src);
+ EmitAggregateCopyCtor(Dest, Src, Overlap);
return;
}
@@ -2023,7 +2030,8 @@
EmitCallArgs(Args, FPT, E->arguments(), E->getConstructor(),
/*ParamsToSkip*/ 0, Order);
- EmitCXXConstructorCall(D, Type, ForVirtualBase, Delegating, This, Args);
+ EmitCXXConstructorCall(D, Type, ForVirtualBase, Delegating, This, Args,
+ Overlap);
}
static bool canEmitDelegateCallArgs(CodeGenFunction &CGF,
@@ -2055,7 +2063,8 @@
bool ForVirtualBase,
bool Delegating,
Address This,
- CallArgList &Args) {
+ CallArgList &Args,
+ AggValueSlot::Overlap_t Overlap) {
const CXXRecordDecl *ClassDecl = D->getParent();
// C++11 [class.mfct.non-static]p2:
@@ -2082,7 +2091,7 @@
LValue SrcLVal = MakeAddrLValue(Src, SrcTy);
QualType DestTy = getContext().getTypeDeclType(ClassDecl);
LValue DestLVal = MakeAddrLValue(This, DestTy);
- EmitAggregateCopyCtor(DestLVal, SrcLVal);
+ EmitAggregateCopyCtor(DestLVal, SrcLVal, Overlap);
return;
}
@@ -2171,7 +2180,7 @@
}
EmitCXXConstructorCall(D, Ctor_Base, ForVirtualBase, /*Delegating*/false,
- This, Args);
+ This, Args, AggValueSlot::MayOverlap);
}
void CodeGenFunction::EmitInlinedInheritingCXXConstructorCall(
@@ -2267,7 +2276,8 @@
EmitCallArgs(Args, FPT, drop_begin(E->arguments(), 1), E->getConstructor(),
/*ParamsToSkip*/ 1);
- EmitCXXConstructorCall(D, Ctor_Complete, false, false, This, Args);
+ EmitCXXConstructorCall(D, Ctor_Complete, false, false, This, Args,
+ AggValueSlot::MayOverlap);
}
void
@@ -2302,7 +2312,8 @@
}
EmitCXXConstructorCall(Ctor, CtorType, /*ForVirtualBase=*/false,
- /*Delegating=*/true, This, DelegateArgs);
+ /*Delegating=*/true, This, DelegateArgs,
+ AggValueSlot::MayOverlap);
}
namespace {
@@ -2333,7 +2344,8 @@
AggValueSlot::forAddr(ThisPtr, Qualifiers(),
AggValueSlot::IsDestructed,
AggValueSlot::DoesNotNeedGCBarriers,
- AggValueSlot::IsNotAliased);
+ AggValueSlot::IsNotAliased,
+ AggValueSlot::MayOverlap);
EmitAggExpr(Ctor->init_begin()[0]->getInit(), AggSlot);