[Orc] Fix common symbol support in ORC.

Common symbol support in ORC was broken in r270716 when the symbol resolution
rules in RuntimeDyld were changed. With the switch to lazily materialized
symbols in r277386, common symbols can be supported by having
RuntimeDyld::emitCommonSymbols search for (but not materialize!) definitions
elsewhere in the logical dylib.

This patch adds the 'Common' flag to JITSymbolFlags, and the necessary check
to RuntimeDyld::emitCommonSymbols.

llvm-svn: 277397

1 files changed, 8 insertions, 2 deletions

diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
index 1e0903349ef..1b40329eb19 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
@@ -584,13 +584,19 @@ Error RuntimeDyldImpl::emitCommonSymbols(const ObjectFile &Obj,
       return NameOrErr.takeError();
 
     // Skip common symbols already elsewhere.
-    if (GlobalSymbolTable.count(Name) ||
-        Resolver.findSymbolInLogicalDylib(Name)) {
+    if (GlobalSymbolTable.count(Name)) {
       DEBUG(dbgs() << "\tSkipping already emitted common symbol '" << Name
                    << "'\n");
       continue;
     }
 
+    if (auto Sym = Resolver.findSymbolInLogicalDylib(Name)) {
+      if (!Sym.isCommon()) {
+        DEBUG(dbgs() << "\tSkipping common symbol '" << Name
+                     << "' in favor of stronger definition.\n");
+        continue;
+      }
+    }
     uint32_t Align = Sym.getAlignment();
     uint64_t Size = Sym.getCommonSize();