[PATCH] D13954: CodeGen: Fix LLVM assertion if Swift and Clang emit Objective-C class reference in same LLVM module

[Slava Pestov via cfe-commits]

slavapestov added a subscriber: slavapestov.
slavapestov added a comment.

Unfortunately the asm label attribute doesn’t seem to work in this case, at least on Darwin. I get two symbols in the IR, with the asm label having the \01 prefix from MangleContext::mangleName():

@"\01OBJC_CLASS_$_NSNumber" = common global %struct.art_class* null, align 8                          
@"OBJC_CLASS_$_NSNumber" = external global %struct._class_t

As for the diagnostic, is this what you had in mind?

commit 4d4f15ffc4d6a72357fa4cee8e2197a03afe6b51
Author: Slava Pestov <spestov at apple.com>
Date:   Fri Oct 23 23:57:56 2015 -0700

  CodeGen: More robust handling of type conflicts in GetClassGlobal()

diff --git a/lib/CodeGen/CGObjCMac.cpp b/lib/CodeGen/CGObjCMac.cpp
index 31e98b9..e5ef767 100644

- a/lib/CodeGen/CGObjCMac.cpp

+++ b/lib/CodeGen/CGObjCMac.cpp
@@ -6692,16 +6692,31 @@ CGObjCNonFragileABIMac::GetClassGlobal(const std::string &Name,

  llvm::GlobalVariable *GV = CGM.getModule().getGlobalVariable(Name);
   

- if (!GV)
- GV = new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ClassnfABITy,
- false, L, nullptr, Name);

+  // If it doesn't exist, create it with the right type.
+  if (!GV) {
+    return new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ClassnfABITy,
+                                    false, L, nullptr, Name);
+  }

  assert(GV->getLinkage() == L);
   

- if (ForDefinition ||
- GV->getValueType() == ObjCTypes.ClassnfABITy)

+  // If it already exists, we might need to bitcast.
+  if (GV->getValueType() == ObjCTypes.ClassnfABITy)

  return GV;
   

+  if (ForDefinition) {
+    DiagnosticsEngine &Diags = CGM.getDiags();
+    unsigned DiagID = Diags.getCustomDiagID(
+        DiagnosticsEngine::Error,
+        "global variable %0 already defined with wrong type");
+    Diags.Report(SourceLocation(), DiagID) << Name;
+
+    // Return a new global in this case, with the right type, since the caller
+    // doesn't expect a constexpr
+    return new llvm::GlobalVariable(CGM.getModule(), ObjCTypes.ClassnfABITy,
+                                    false, L, nullptr, Name);
+  }
+

  return llvm::ConstantExpr::getBitCast(GV, ObjCTypes.ClassnfABIPtrTy);

}


Repository:
  rL LLVM

http://reviews.llvm.org/D13954