r195168 - Add a mangler entry point for TBAA rather than using RTTI directly

Reid Kleckner reid at kleckner.net
Tue Nov 19 15:23:00 PST 2013


Author: rnk
Date: Tue Nov 19 17:23:00 2013
New Revision: 195168

URL: http://llvm.org/viewvc/llvm-project?rev=195168&view=rev
Log:
Add a mangler entry point for TBAA rather than using RTTI directly

Summary:
RTTI is not yet implemented for the Microsoft C++ ABI and isn't expected
soon.  We could easily add the mangling, but the error is what prevents
us from silently miscompiling code that expects RTTI.

Instead, add a new mangleTypeName entry point that simply forwards to
mangleName or mangleType to produce a string that isn't part of the ABI.
Itanium can continue to use RTTI names to avoid unecessary test
breakage.

This also seems like the right design.  The fact that TBAA names happen
to be RTTI names is now an implementation detail of the mangler, rather
than part of TBAA.

Differential Revision: http://llvm-reviews.chandlerc.com/D2153

Added:
    cfe/trunk/test/CodeGen/tbaa-ms-abi.cpp
Modified:
    cfe/trunk/include/clang/AST/Mangle.h
    cfe/trunk/lib/AST/ItaniumMangle.cpp
    cfe/trunk/lib/AST/MicrosoftMangle.cpp
    cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp

Modified: cfe/trunk/include/clang/AST/Mangle.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/Mangle.h?rev=195168&r1=195167&r2=195168&view=diff
==============================================================================
--- cfe/trunk/include/clang/AST/Mangle.h (original)
+++ cfe/trunk/include/clang/AST/Mangle.h Tue Nov 19 17:23:00 2013
@@ -148,6 +148,12 @@ public:
   virtual void mangleDynamicAtExitDestructor(const VarDecl *D,
                                              raw_ostream &) = 0;
 
+  /// Generates a unique string for an externally visible type for use with TBAA
+  /// or type uniquing.
+  /// TODO: Extend this to internal types by generating names that are unique
+  /// across translation units so it can be used with LTO.
+  virtual void mangleTypeName(QualType T, raw_ostream &) = 0;
+
   /// @}
 };
 

Modified: cfe/trunk/lib/AST/ItaniumMangle.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ItaniumMangle.cpp?rev=195168&r1=195167&r2=195168&view=diff
==============================================================================
--- cfe/trunk/lib/AST/ItaniumMangle.cpp (original)
+++ cfe/trunk/lib/AST/ItaniumMangle.cpp Tue Nov 19 17:23:00 2013
@@ -144,6 +144,7 @@ public:
                            raw_ostream &);
   void mangleCXXRTTI(QualType T, raw_ostream &);
   void mangleCXXRTTIName(QualType T, raw_ostream &);
+  void mangleTypeName(QualType T, raw_ostream &);
   void mangleCXXCtor(const CXXConstructorDecl *D, CXXCtorType Type,
                      raw_ostream &);
   void mangleCXXDtor(const CXXDestructorDecl *D, CXXDtorType Type,
@@ -3784,6 +3785,10 @@ void ItaniumMangleContextImpl::mangleCXX
   Mangler.mangleType(Ty);
 }
 
+void ItaniumMangleContextImpl::mangleTypeName(QualType Ty, raw_ostream &Out) {
+  mangleCXXRTTIName(Ty, Out);
+}
+
 ItaniumMangleContext *
 ItaniumMangleContext::create(ASTContext &Context, DiagnosticsEngine &Diags) {
   return new ItaniumMangleContextImpl(Context, Diags);

Modified: cfe/trunk/lib/AST/MicrosoftMangle.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/MicrosoftMangle.cpp?rev=195168&r1=195167&r2=195168&view=diff
==============================================================================
--- cfe/trunk/lib/AST/MicrosoftMangle.cpp (original)
+++ cfe/trunk/lib/AST/MicrosoftMangle.cpp Tue Nov 19 17:23:00 2013
@@ -197,6 +197,7 @@ public:
                                 raw_ostream &Out);
   virtual void mangleCXXRTTI(QualType T, raw_ostream &);
   virtual void mangleCXXRTTIName(QualType T, raw_ostream &);
+  virtual void mangleTypeName(QualType T, raw_ostream &);
   virtual void mangleCXXCtor(const CXXConstructorDecl *D, CXXCtorType Type,
                              raw_ostream &);
   virtual void mangleCXXDtor(const CXXDestructorDecl *D, CXXDtorType Type,
@@ -2019,6 +2020,14 @@ void MicrosoftMangleContextImpl::mangleC
     << T.getBaseTypeIdentifier();
 }
 
+void MicrosoftMangleContextImpl::mangleTypeName(QualType T, raw_ostream &Out) {
+  // This is just a made up unique string for the purposes of tbaa.  undname
+  // does *not* know how to demangle it.
+  MicrosoftCXXNameMangler Mangler(*this, Out);
+  Mangler.getStream() << '?';
+  Mangler.mangleType(T, SourceRange());
+}
+
 void MicrosoftMangleContextImpl::mangleCXXCtor(const CXXConstructorDecl *D,
                                                CXXCtorType Type,
                                                raw_ostream &Out) {

Modified: cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp?rev=195168&r1=195167&r2=195168&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp (original)
+++ cfe/trunk/lib/CodeGen/CodeGenTBAA.cpp Tue Nov 19 17:23:00 2013
@@ -152,11 +152,9 @@ CodeGenTBAA::getTBAAInfo(QualType QTy) {
     if (!Features.CPlusPlus || !ETy->getDecl()->isExternallyVisible())
       return MetadataCache[Ty] = getChar();
 
-    // TODO: This is using the RTTI name. Is there a better way to get
-    // a unique string for a type?
     SmallString<256> OutName;
     llvm::raw_svector_ostream Out(OutName);
-    MContext.mangleCXXRTTIName(QualType(ETy, 0), Out);
+    MContext.mangleTypeName(QualType(ETy, 0), Out);
     Out.flush();
     return MetadataCache[Ty] = createTBAAScalarType(OutName, getChar());
   }
@@ -268,13 +266,11 @@ CodeGenTBAA::getTBAAStructTypeInfo(QualT
           FieldNode, Layout.getFieldOffset(idx) / Context.getCharWidth()));
     }
 
-    // TODO: This is using the RTTI name. Is there a better way to get
-    // a unique string for a type?
     SmallString<256> OutName;
     if (Features.CPlusPlus) {
-      // Don't use mangleCXXRTTIName for C code.
+      // Don't use the mangler for C code.
       llvm::raw_svector_ostream Out(OutName);
-      MContext.mangleCXXRTTIName(QualType(Ty, 0), Out);
+      MContext.mangleTypeName(QualType(Ty, 0), Out);
       Out.flush();
     } else {
       OutName = RD->getName();

Added: cfe/trunk/test/CodeGen/tbaa-ms-abi.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/tbaa-ms-abi.cpp?rev=195168&view=auto
==============================================================================
--- cfe/trunk/test/CodeGen/tbaa-ms-abi.cpp (added)
+++ cfe/trunk/test/CodeGen/tbaa-ms-abi.cpp Tue Nov 19 17:23:00 2013
@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 -cxx-abi microsoft -triple i686-pc-win32 -disable-llvm-optzns -emit-llvm -o - -O1 %s | FileCheck %s
+//
+// Test that TBAA works in the Microsoft C++ ABI.  We used to error out while
+// attempting to mangle RTTI.
+
+struct StructA {
+  int a;
+};
+
+struct StructB : virtual StructA {
+  StructB();
+};
+
+StructB::StructB() {
+  a = 42;
+// CHECK: store i32 42, i32* {{.*}}, !tbaa [[TAG_A_i32:!.*]]
+}
+
+// CHECK: [[TYPE_CHAR:!.*]] = metadata !{metadata !"omnipotent char", metadata
+// CHECK: [[TYPE_INT:!.*]] = metadata !{metadata !"int", metadata [[TYPE_CHAR]], i64 0}
+// CHECK: [[TAG_A_i32]] = metadata !{metadata [[TYPE_A:!.*]], metadata [[TYPE_INT]], i64 0}
+// CHECK: [[TYPE_A]] = metadata !{metadata !"?AUStructA@@", metadata [[TYPE_INT]], i64 0}





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