[ms-cxxabi] Correctly compute the size of member pointers
Summary:
This also relaxes the requirement on Windows that the member pointer
class type be a complete type (http://llvm.org/PR12070). We still ask
for a complete type to instantiate any templates (MSVC does this), but
if that fails we continue as normal, relying on any inheritance
attributes on the declaration.
Reviewers: rjmccall
CC: triton, timurrrr, cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D568
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178283 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/MicrosoftCXXABI.cpp b/lib/AST/MicrosoftCXXABI.cpp
index 51308ea..2f41cec 100644
--- a/lib/AST/MicrosoftCXXABI.cpp
+++ b/lib/AST/MicrosoftCXXABI.cpp
@@ -13,6 +13,7 @@
//===----------------------------------------------------------------------===//
#include "CXXABI.h"
+#include "clang/AST/Attr.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/RecordLayout.h"
@@ -27,7 +28,8 @@
public:
MicrosoftCXXABI(ASTContext &Ctx) : Context(Ctx) { }
- unsigned getMemberPointerSize(const MemberPointerType *MPT) const;
+ std::pair<uint64_t, unsigned>
+ getMemberPointerWidthAndAlign(const MemberPointerType *MPT) const;
CallingConv getDefaultMethodCallConv(bool isVariadic) const {
if (!isVariadic && Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)
@@ -52,17 +54,77 @@
};
}
-unsigned MicrosoftCXXABI::getMemberPointerSize(const MemberPointerType *MPT) const {
- QualType Pointee = MPT->getPointeeType();
- CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
- if (RD->getNumVBases() > 0) {
- if (Pointee->isFunctionType())
- return 3;
- else
- return 2;
- } else if (RD->getNumBases() > 1 && Pointee->isFunctionType())
- return 2;
- return 1;
+// getNumBases() seems to only give us the number of direct bases, and not the
+// total. This function tells us if we inherit from anybody that uses MI, or if
+// we have a non-primary base class, which uses the multiple inheritance model.
+static bool usesMultipleInheritanceModel(const CXXRecordDecl *RD) {
+ while (RD->getNumBases() > 0) {
+ if (RD->getNumBases() > 1)
+ return true;
+ assert(RD->getNumBases() == 1);
+ const CXXRecordDecl *Base = RD->bases_begin()->getType()->getAsCXXRecordDecl();
+ if (RD->isPolymorphic() && !Base->isPolymorphic())
+ return true;
+ RD = Base;
+ }
+ return false;
+}
+
+std::pair<uint64_t, unsigned>
+MicrosoftCXXABI::getMemberPointerWidthAndAlign(const MemberPointerType *MPT) const {
+ const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
+ const TargetInfo &Target = Context.getTargetInfo();
+
+ assert(Target.getTriple().getArch() == llvm::Triple::x86 ||
+ Target.getTriple().getArch() == llvm::Triple::x86_64);
+
+ Attr *IA = RD->getAttr<MSInheritanceAttr>();
+ attr::Kind Inheritance;
+ if (IA) {
+ Inheritance = IA->getKind();
+ } else if (RD->getNumVBases() > 0) {
+ Inheritance = attr::VirtualInheritance;
+ } else if (MPT->getPointeeType()->isFunctionType() &&
+ usesMultipleInheritanceModel(RD)) {
+ Inheritance = attr::MultipleInheritance;
+ } else {
+ Inheritance = attr::SingleInheritance;
+ }
+
+ unsigned PtrSize = Target.getPointerWidth(0);
+ unsigned IntSize = Target.getIntWidth();
+ uint64_t Width;
+ unsigned Align;
+ if (MPT->getPointeeType()->isFunctionType()) {
+ // Member function pointers are a struct of a function pointer followed by a
+ // variable number of ints depending on the inheritance model used. The
+ // function pointer is a real function if it is non-virtual and a vftable
+ // slot thunk if it is virtual. The ints select the object base passed for
+ // the 'this' pointer.
+ Align = Target.getPointerAlign(0);
+ switch (Inheritance) {
+ case attr::SingleInheritance: Width = PtrSize; break;
+ case attr::MultipleInheritance: Width = PtrSize + 1 * IntSize; break;
+ case attr::VirtualInheritance: Width = PtrSize + 2 * IntSize; break;
+ case attr::UnspecifiedInheritance: Width = PtrSize + 3 * IntSize; break;
+ default: llvm_unreachable("unknown inheritance model");
+ }
+ } else {
+ // Data pointers are an aggregate of ints. The first int is an offset
+ // followed by vbtable-related offsets.
+ Align = Target.getIntAlign();
+ switch (Inheritance) {
+ case attr::SingleInheritance: // Same as multiple inheritance.
+ case attr::MultipleInheritance: Width = 1 * IntSize; break;
+ case attr::VirtualInheritance: Width = 2 * IntSize; break;
+ case attr::UnspecifiedInheritance: Width = 3 * IntSize; break;
+ default: llvm_unreachable("unknown inheritance model");
+ }
+ }
+ Width = llvm::RoundUpToAlignment(Width, Align);
+
+ // FIXME: Verify that our alignment matches MSVC.
+ return std::make_pair(Width, Align);
}
CXXABI *clang::CreateMicrosoftCXXABI(ASTContext &Ctx) {