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Stub out IsOverriderUsed. 

llvm-svn: 96883
This commit is contained in:
Anders Carlsson 2010-02-23 04:26:39 +00:00
parent 0570f71255
commit a8796c692c
1 changed files with 50 additions and 4 deletions
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54
clang/lib/CodeGen/CGVtable.cpp
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@ -992,9 +992,33 @@ private:
void AddMethod(const CXXMethodDecl *MD, ReturnAdjustment ReturnAdjustment,
ThisAdjustment ThisAdjustment);
/// IsOverriderUsed - Returns whether the overrider will ever be used in this
/// part of the vtable.
///
/// Itanium C++ ABI 2.5.2:
///
/// struct A { virtual void f(); };
/// struct B : virtual public A { int i; };
/// struct C : virtual public A { int j; };
/// struct D : public B, public C {};
///
/// When B and C are declared, A is a primary base in each case, so although
/// vcall offsets are allocated in the A-in-B and A-in-C vtables, no this
/// adjustment is required and no thunk is generated. However, inside D
/// objects, A is no longer a primary base of C, so if we allowed calls to
/// C::f() to use the copy of A's vtable in the C subobject, we would need
/// to adjust this from C* to B::A*, which would require a third-party
/// thunk. Since we require that a call to C::f() first convert to A*,
/// C-in-D's copy of A's vtable is never referenced, so this is not
/// necessary.
bool IsOverriderUsed(BaseSubobject Base,
BaseSubobject FirstBaseInPrimaryBaseChain,
FinalOverriders::OverriderInfo Overrider) const;
/// AddMethods - Add the methods of this base subobject and all its
/// primary bases to the vtable components vector.
void AddMethods(BaseSubobject Base, PrimaryBasesSetTy &PrimaryBases);
void AddMethods(BaseSubobject Base, BaseSubobject FirstBaseInPrimaryBaseChain,
PrimaryBasesSetTy &PrimaryBases);
// LayoutVtable - Layout the vtable for the most derived class, including its
// secondary vtables and any vtables for virtual bases.
@ -1257,8 +1281,22 @@ VtableBuilder::AddMethod(const CXXMethodDecl *MD,
}
}
bool
VtableBuilder::IsOverriderUsed(BaseSubobject Base,
BaseSubobject FirstBaseInPrimaryBaseChain,
FinalOverriders::OverriderInfo Overrider) const {
// If the base and the first base in the primary base chain have the same
// offsets, then this overrider will be used.
if (Base.getBaseOffset() == FirstBaseInPrimaryBaseChain.getBaseOffset())
return true;
return true;
}
void
VtableBuilder::AddMethods(BaseSubobject Base, PrimaryBasesSetTy &PrimaryBases) {
VtableBuilder::AddMethods(BaseSubobject Base,
BaseSubobject FirstBaseInPrimaryBaseChain,
PrimaryBasesSetTy &PrimaryBases) {
const CXXRecordDecl *RD = Base.getBase();
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
@ -1283,7 +1321,8 @@ VtableBuilder::AddMethods(BaseSubobject Base, PrimaryBasesSetTy &PrimaryBases) {
BaseOffset = Base.getBaseOffset();
}
AddMethods(BaseSubobject(PrimaryBase, BaseOffset), PrimaryBases);
AddMethods(BaseSubobject(PrimaryBase, BaseOffset),
FirstBaseInPrimaryBaseChain, PrimaryBases);
if (!PrimaryBases.insert(PrimaryBase))
assert(false && "Found a duplicate primary base!");
@ -1311,6 +1350,13 @@ VtableBuilder::AddMethods(BaseSubobject Base, PrimaryBasesSetTy &PrimaryBases) {
continue;
}
// Check if this overrider is going to be used.
if (!IsOverriderUsed(Base, FirstBaseInPrimaryBaseChain, Overrider)) {
const CXXMethodDecl *OverriderMD = Overrider.Method;
Components.push_back(VtableComponent::MakeUnusedFunction(OverriderMD));
continue;
}
// Check if this overrider needs a return adjustment.
BaseOffset ReturnAdjustmentOffset =
Overriders.getReturnAdjustmentOffset(Base, MD);
@ -1363,7 +1409,7 @@ void VtableBuilder::LayoutPrimaryAndAndSecondaryVtables(BaseSubobject Base,
// Now go through all virtual member functions and add them.
PrimaryBasesSetTy PrimaryBases;
AddMethods(Base, PrimaryBases);
AddMethods(Base, Base, PrimaryBases);
// Record the address point.
AddressPoints.insert(std::make_pair(Base, AddressPoint));