commit b0f533e716ae5a21ca5682ea235a68082fd5ed28
author Reid Kleckner <reid@kleckner.net> Wed May 29 18:02:47 2013 +0000
committer Reid Kleckner <reid@kleckner.net> Wed May 29 18:02:47 2013 +0000
tree 6e981fc0eeb609a4c4b6f73cb089774f33e09f2b
parent c72ff4f71833c46702fbfc64a3b7743c4f2002a9

[ms-cxxabi] Implement MSVC virtual base adjustment

While we can't yet emit vbtables, this allows us to find virtual bases
of objects constructed in other TUs.

This make iostream hello world work, since basic_ostream virtually
inherits from basic_ios.

Differential Revision: http://llvm-reviews.chandlerc.com/D795

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182870 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/ItaniumCXXABI.cpp

diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index f786956..6cf95b5 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -98,6 +98,11 @@
                                       llvm::Value *ptr,
                                       QualType type);
 
+  llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
+                                         llvm::Value *This,
+                                         const CXXRecordDecl *ClassDecl,
+                                         const CXXRecordDecl *BaseClassDecl);
+
   void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
                                  CXXCtorType T,
                                  CanQualType &ResTy,
@@ -720,6 +725,27 @@
   return CGF.Builder.CreateInBoundsGEP(ptr, offset);
 }
 
+llvm::Value *
+ItaniumCXXABI::GetVirtualBaseClassOffset(CodeGenFunction &CGF,
+                                         llvm::Value *This,
+                                         const CXXRecordDecl *ClassDecl,
+                                         const CXXRecordDecl *BaseClassDecl) {
+  llvm::Value *VTablePtr = CGF.GetVTablePtr(This, CGM.Int8PtrTy);
+  CharUnits VBaseOffsetOffset =
+    CGM.getVTableContext().getVirtualBaseOffsetOffset(ClassDecl, BaseClassDecl);
+
+  llvm::Value *VBaseOffsetPtr =
+    CGF.Builder.CreateConstGEP1_64(VTablePtr, VBaseOffsetOffset.getQuantity(),
+                                   "vbase.offset.ptr");
+  VBaseOffsetPtr = CGF.Builder.CreateBitCast(VBaseOffsetPtr,
+                                             CGM.PtrDiffTy->getPointerTo());
+
+  llvm::Value *VBaseOffset =
+    CGF.Builder.CreateLoad(VBaseOffsetPtr, "vbase.offset");
+
+  return VBaseOffset;
+}
+
 /// The generic ABI passes 'this', plus a VTT if it's initializing a
 /// base subobject.
 void ItaniumCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,