[Itanium] Emit type info names with external linkage.

Summary:
The Itanium ABI requires that the type info for pointer-to-incomplete types to have internal linkage, so that it doesn't interfere with the type info once completed.  Currently it also marks the type info name as internal as well. However, this causes a bug with the STL implementations, which use the type info name pointer to perform ordering and hashing of type infos.
For example:

```
// header.h
struct T;
extern std::type_info const& Info;

// tu_one.cpp
#include "header.h"
std::type_info const& Info = typeid(T*);

// tu_two.cpp
#include "header.h"
struct T {};
int main() {
  auto &TI1 = Info;
  auto &TI2 = typeid(T*);
  assert(TI1 == TI2); // Fails
  assert(TI1.hash_code() == TI2.hash_code()); // Fails
}
```

This patch fixes the STL bug by emitting the type info name as linkonce_odr when the type-info is for a pointer-to-incomplete type.

Note that libc++ could fix this without a compiler change, but the quality of fix would be poor. The library would either have to:

(A) Always perform strcmp/string hashes.
(B) Determine if we have a pointer-to-incomplete type, and only do strcmp then. This would require an ABI break for libc++.


Reviewers: rsmith, rjmccall, majnemer, vsapsai

Reviewed By: rjmccall

Subscribers: smeenai, cfe-commits

Differential Revision: https://reviews.llvm.org/D46665

llvm-svn: 331957

1 files changed, 34 insertions, 22 deletions

diff --git a/clang/test/CodeGenCXX/rtti-linkage.cpp b/clang/test/CodeGenCXX/rtti-linkage.cpp
index b6b72aa04aa..38483953bbb 100644
--- a/clang/test/CodeGenCXX/rtti-linkage.cpp
+++ b/clang/test/CodeGenCXX/rtti-linkage.cpp
@@ -1,29 +1,31 @@
-// RUN: %clang_cc1 %s -I%S -triple=x86_64-apple-darwin10 -emit-llvm -o - | FileCheck %s -check-prefix=CHECK -check-prefix=CHECK-BOTH
-// RUN: %clang_cc1 %s -I%S -triple=x86_64-apple-darwin10 -fvisibility hidden -emit-llvm -o - | FileCheck -check-prefix=CHECK-WITH-HIDDEN -check-prefix=CHECK-BOTH %s
+// RUN: %clang_cc1 %s -I%S -triple=x86_64-apple-darwin10 -emit-llvm -o - | \
+// RUN:    FileCheck %s -check-prefix=CHECK -check-prefix=CHECK-BOTH \
+// RUN:   -DLINKONCE_VIS_CONSTANT='linkonce_odr constant'
+// RUN: %clang_cc1 %s -I%S -triple=x86_64-apple-darwin10 -fvisibility hidden -emit-llvm -o - | \
+// RUN:    FileCheck %s -check-prefix=CHECK-WITH-HIDDEN -check-prefix=CHECK-BOTH \
+// RUN:   -DLINKONCE_VIS_CONSTANT='linkonce_odr hidden constant'
 
 #include <typeinfo>
 
-// CHECK-BOTH: _ZTSP1C = internal constant
-// CHECK-BOTH: _ZTS1C = internal constant
+// CHECK-BOTH: _ZTSP1C = [[LINKONCE_VIS_CONSTANT]]
+// CHECK-BOTH: _ZTS1C = [[LINKONCE_VIS_CONSTANT]]
 // CHECK-BOTH: _ZTI1C = internal constant
 // CHECK-BOTH: _ZTIP1C = internal constant
-// CHECK-BOTH: _ZTSPP1C = internal constant
+// CHECK-BOTH: _ZTSPP1C = [[LINKONCE_VIS_CONSTANT]]
 // CHECK-BOTH: _ZTIPP1C = internal constant
-// CHECK-BOTH: _ZTSM1Ci = internal constant
+// CHECK-BOTH: _ZTSM1Ci = [[LINKONCE_VIS_CONSTANT]]
 // CHECK-BOTH: _ZTIM1Ci = internal constant
-// CHECK-BOTH: _ZTSPM1Ci = internal constant
+// CHECK-BOTH: _ZTSPM1Ci = [[LINKONCE_VIS_CONSTANT]]
 // CHECK-BOTH: _ZTIPM1Ci = internal constant
-// CHECK-BOTH: _ZTSM1CS_ = internal constant
+// CHECK-BOTH: _ZTSM1CS_ = [[LINKONCE_VIS_CONSTANT]]
 // CHECK-BOTH: _ZTIM1CS_ = internal constant
-// CHECK-BOTH: _ZTSM1CPS_ = internal constant
+// CHECK-BOTH: _ZTSM1CPS_ = [[LINKONCE_VIS_CONSTANT]]
 // CHECK-BOTH: _ZTIM1CPS_ = internal constant
-// CHECK-BOTH: _ZTSM1A1C = internal constant
-// CHECK: _ZTS1A = linkonce_odr constant
-// CHECK-WITH-HIDDEN: _ZTS1A = linkonce_odr hidden constant
-// CHECK: _ZTI1A = linkonce_odr constant
-// CHECK-WITH-HIDDEN: _ZTI1A = linkonce_odr hidden constant
+// CHECK-BOTH: _ZTSM1A1C = [[LINKONCE_VIS_CONSTANT]]
+// CHECK-BOTH: _ZTS1A = [[LINKONCE_VIS_CONSTANT]]
+// CHECK-BOTH: _ZTI1A = [[LINKONCE_VIS_CONSTANT]]
 // CHECK-BOTH: _ZTIM1A1C = internal constant
-// CHECK-BOTH: _ZTSM1AP1C = internal constant
+// CHECK-BOTH: _ZTSM1AP1C = [[LINKONCE_VIS_CONSTANT]]
 // CHECK-BOTH: _ZTIM1AP1C = internal constant
 
 // CHECK-WITH-HIDDEN: _ZTSFN12_GLOBAL__N_11DEvE = internal constant
@@ -52,6 +54,12 @@
 // CHECK: _ZTSFvvE = linkonce_odr constant
 // CHECK: _ZTIFvvE = linkonce_odr constant
 // CHECK: _ZTIPFvvE = linkonce_odr constant
+// CHECK: _ZTSPN12_GLOBAL__N_12DIE = internal constant
+// CHECK: _ZTSN12_GLOBAL__N_12DIE = internal constant
+// CHECK: _ZTIN12_GLOBAL__N_12DIE = internal constant
+// CHECK: _ZTIPN12_GLOBAL__N_12DIE = internal constant
+// CHECK: _ZTSMN12_GLOBAL__N_12DIEFvvE = internal constant
+// CHECK: _ZTIMN12_GLOBAL__N_12DIEFvvE = internal constant
 // CHECK: _ZTSN12_GLOBAL__N_11EE = internal constant
 // CHECK: _ZTIN12_GLOBAL__N_11EE = internal constant
 // CHECK: _ZTSA10_i = linkonce_odr constant
@@ -99,12 +107,13 @@ void t1() {
 }
 
 namespace {
-  // D is inside an anonymous namespace, so all type information related to D should have
-  // internal linkage.
-  struct D { };
-  
-  // E is also inside an anonymous namespace.
-  enum E { };
+// D and DI are inside an anonymous namespace, so all type information related
+// to both should have internal linkage.
+struct D {};
+struct DI;
+
+// E is also inside an anonymous namespace.
+enum E {};
   
 };
 
@@ -126,7 +135,10 @@ const std::type_info &t2() {
   // The exception specification is not part of the RTTI descriptor, so it should not have
   // internal linkage.
   (void)typeid(void (*)() throw (D));
-  
+
+  (void)typeid(DI *);
+  (void)typeid(void (DI::*)());
+
   (void)typeid(E);
   
   return typeid(getD());