[ThinLTO] Remove dllimport attribute from locally defined symbols

Summary:
The LTO/ThinLTO driver currently creates invalid bitcode by setting 
symbols marked dllimport as dso_local. The compiler often has access 
to the definition (often dllexport) and the declaration (often 
dllimport) of an object at link-time, leading to a conflicting 
declaration. This patch resolves the inconsistency by removing the
dllimport attribute.

Reviewers: tejohnson, pcc, rnk, echristo

Reviewed By: rnk

Subscribers: dmikulin, wristow, mehdi_amini, inglorion, eraman, steven_wu, dexonsmith, dang, llvm-commits

Differential Revision: https://reviews.llvm.org/D55627

llvm-svn: 349667

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index 08924fb92dd..f736ef8b7f9 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -693,8 +693,12 @@ LTO::addRegularLTO(BitcodeModule BM, ArrayRef<InputFile::Symbol> Syms,
       }
 
       // Set the 'local' flag based on the linker resolution for this symbol.
-      if (Res.FinalDefinitionInLinkageUnit)
+      if (Res.FinalDefinitionInLinkageUnit) {
         GV->setDSOLocal(true);
+        if (GV->hasDLLImportStorageClass())
+          GV->setDLLStorageClass(GlobalValue::DLLStorageClassTypes::
+                                 DefaultStorageClass);
+      }
     }
     // Common resolution: collect the maximum size/alignment over all commons.
     // We also record if we see an instance of a common as prevailing, so that