Revert r312224: "[ItaniumCXXABI] Always use linkonce_odr linkage for RTTI data on MinGW"

Breaks on buildbot:
http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/4548/steps/test-check-all/logs/stdio

The test in CodeGenCXX/virt-dtor-key.cpp tests using %itanium_abi_triple;
on non-windows platforms, this resolves to the current platform triple
(where there was no behaviour change), while on windows, it resolves to
a mingw triple (where the behaviour was intentionally changed).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@312229 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 7 deletions

diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index e07dbdd3ab..d78c032cec 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2998,13 +2998,15 @@ static llvm::GlobalVariable::LinkageTypes getTypeInfoLinkage(CodeGenModule &CGM,
         if (RD->hasAttr<DLLImportAttr>() &&
             ShouldUseExternalRTTIDescriptor(CGM, Ty))
           return llvm::GlobalValue::ExternalLinkage;
-      // MinGW always uses LinkOnceODRLinkage for type info.
-      if (RD->isDynamicClass() &&
-          !CGM.getContext()
-               .getTargetInfo()
-               .getTriple()
-               .isWindowsGNUEnvironment())
-        return CGM.getVTableLinkage(RD);
+      if (RD->isDynamicClass()) {
+        llvm::GlobalValue::LinkageTypes LT = CGM.getVTableLinkage(RD);
+        // MinGW won't export the RTTI information when there is a key function.
+        // Make sure we emit our own copy instead of attempting to dllimport it.
+        if (RD->hasAttr<DLLImportAttr>() &&
+            llvm::GlobalValue::isAvailableExternallyLinkage(LT))
+          LT = llvm::GlobalValue::LinkOnceODRLinkage;
+        return LT;
+      }
     }
 
     return llvm::GlobalValue::LinkOnceODRLinkage;