[ORC] Drop Comdat when discarding IR symbol

According to the IR verifier, "Declaration[s] may not be in a Comdat!"

This is a re-commit of 76b3f0b4d5a0b8c54147c4c73a30892bbca76467 with
updates to the test:
 * Force emission of the extra-module, to trigger the bug after D138264,
   by providing a second symbol @g, and making the comdat nodeduplicate.
   (Technically only one is needed, but two should be safer.)
 * Name the comdat $f to avoid failure on Windows:
   LLVM ERROR: Associative COMDAT symbol 'c' does not exist.

Differential Revision: https://reviews.llvm.org/D142443

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/ExecutionEngine/Orc/Layer.cpp b/llvm/lib/ExecutionEngine/Orc/Layer.cpp
index 95380d91..3368d32 100644
--- a/llvm/lib/ExecutionEngine/Orc/Layer.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/Layer.cpp
@@ -125,6 +125,10 @@ void IRMaterializationUnit::discard(const JITDylib &JD,
   assert(!I->second->isDeclaration() &&
          "Discard should only apply to definitions");
   I->second->setLinkage(GlobalValue::AvailableExternallyLinkage);
+  // According to the IR verifier, "Declaration[s] may not be in a Comdat!"
+  // Remove it, if this is a GlobalObject.
+  if (auto *GO = dyn_cast<GlobalObject>(I->second))
+    GO->setComdat(nullptr);
   SymbolToDefinition.erase(I);
 }