Generating assumption loads of vptr after ctor call (fixed)

Generating call assume(icmp %vtable, %global_vtable) after constructor
call for devirtualization purposes.

For more info go to:
http://lists.llvm.org/pipermail/cfe-dev/2015-July/044227.html

Edit:
Fixed version because of PR24479.
After this patch got reverted because of ScalarEvolution bug (D12719)
Merged after John McCall big patch (Added Address).

http://reviews.llvm.org/D11859

llvm-svn: 247199

1 files changed, 37 insertions, 17 deletions

diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 5cefc72ed0c..74c8774ba21 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -127,8 +127,7 @@ public:
                                      QualType DestTy) override;
 
   bool EmitBadCastCall(CodeGenFunction &CGF) override;
-  bool canEmitAvailableExternallyVTable(
-      const CXXRecordDecl *RD) const override {
+  bool canSpeculativelyEmitVTable(const CXXRecordDecl *RD) const override {
     return false;
   }
 
@@ -236,10 +235,22 @@ public:
   void emitVTableDefinitions(CodeGenVTables &CGVT,
                              const CXXRecordDecl *RD) override;
 
+  bool isVirtualOffsetNeededForVTableField(CodeGenFunction &CGF,
+                                           CodeGenFunction::VPtr Vptr) override;
+
+  /// Don't initialize vptrs if dynamic class
+  /// is marked with with the 'novtable' attribute.
+  bool doStructorsInitializeVPtrs(const CXXRecordDecl *VTableClass) override {
+    return !VTableClass->hasAttr<MSNoVTableAttr>();
+  }
+
+  llvm::Constant *
+  getVTableAddressPoint(BaseSubobject Base,
+                        const CXXRecordDecl *VTableClass) override;
+
   llvm::Value *getVTableAddressPointInStructor(
       CodeGenFunction &CGF, const CXXRecordDecl *VTableClass,
-      BaseSubobject Base, const CXXRecordDecl *NearestVBase,
-      bool &NeedsVirtualOffset) override;
+      BaseSubobject Base, const CXXRecordDecl *NearestVBase) override;
 
   llvm::Constant *
   getVTableAddressPointForConstExpr(BaseSubobject Base,
@@ -1608,14 +1619,15 @@ void MicrosoftCXXABI::emitVTableDefinitions(CodeGenVTables &CGVT,
   }
 }
 
+bool MicrosoftCXXABI::isVirtualOffsetNeededForVTableField(
+    CodeGenFunction &CGF, CodeGenFunction::VPtr Vptr) {
+  return Vptr.NearestVBase != nullptr;
+}
+
 llvm::Value *MicrosoftCXXABI::getVTableAddressPointInStructor(
     CodeGenFunction &CGF, const CXXRecordDecl *VTableClass, BaseSubobject Base,
-    const CXXRecordDecl *NearestVBase, bool &NeedsVirtualOffset) {
-  NeedsVirtualOffset = (NearestVBase != nullptr);
-
-  (void)getAddrOfVTable(VTableClass, Base.getBaseOffset());
-  VFTableIdTy ID(VTableClass, Base.getBaseOffset());
-  llvm::GlobalValue *VTableAddressPoint = VFTablesMap[ID];
+    const CXXRecordDecl *NearestVBase) {
+  llvm::Constant *VTableAddressPoint = getVTableAddressPoint(Base, VTableClass);
   if (!VTableAddressPoint) {
     assert(Base.getBase()->getNumVBases() &&
            !getContext().getASTRecordLayout(Base.getBase()).hasOwnVFPtr());
@@ -1630,11 +1642,17 @@ static void mangleVFTableName(MicrosoftMangleContext &MangleContext,
   MangleContext.mangleCXXVFTable(RD, VFPtr->MangledPath, Out);
 }
 
-llvm::Constant *MicrosoftCXXABI::getVTableAddressPointForConstExpr(
-    BaseSubobject Base, const CXXRecordDecl *VTableClass) {
+llvm::Constant *
+MicrosoftCXXABI::getVTableAddressPoint(BaseSubobject Base,
+                                       const CXXRecordDecl *VTableClass) {
   (void)getAddrOfVTable(VTableClass, Base.getBaseOffset());
   VFTableIdTy ID(VTableClass, Base.getBaseOffset());
-  llvm::GlobalValue *VFTable = VFTablesMap[ID];
+  return VFTablesMap[ID];
+}
+
+llvm::Constant *MicrosoftCXXABI::getVTableAddressPointForConstExpr(
+    BaseSubobject Base, const CXXRecordDecl *VTableClass) {
+  llvm::Constant *VFTable = getVTableAddressPoint(Base, VTableClass);
   assert(VFTable && "Couldn't find a vftable for the given base?");
   return VFTable;
 }
@@ -1644,6 +1662,7 @@ llvm::GlobalVariable *MicrosoftCXXABI::getAddrOfVTable(const CXXRecordDecl *RD,
   // getAddrOfVTable may return 0 if asked to get an address of a vtable which
   // shouldn't be used in the given record type. We want to cache this result in
   // VFTablesMap, thus a simple zero check is not sufficient.
+
   VFTableIdTy ID(RD, VPtrOffset);
   VTablesMapTy::iterator I;
   bool Inserted;
@@ -1697,10 +1716,11 @@ llvm::GlobalVariable *MicrosoftCXXABI::getAddrOfVTable(const CXXRecordDecl *RD,
   if (llvm::GlobalValue *VFTable =
           CGM.getModule().getNamedGlobal(VFTableName)) {
     VFTablesMap[ID] = VFTable;
-    return VTableAliasIsRequred
-               ? cast<llvm::GlobalVariable>(
-                     cast<llvm::GlobalAlias>(VFTable)->getBaseObject())
-               : cast<llvm::GlobalVariable>(VFTable);
+    VTable = VTableAliasIsRequred
+                 ? cast<llvm::GlobalVariable>(
+                       cast<llvm::GlobalAlias>(VFTable)->getBaseObject())
+                 : cast<llvm::GlobalVariable>(VFTable);
+    return VTable;
   }
 
   uint64_t NumVTableSlots =