Do not destroy external linkage when deleting function body

The function deleteBody() converts the linkage to external and thus destroys
original linkage type value. Lack of correct linkage type causes wrong
relocations to be emitted later.
Calling dropAllReferences() instead of deleteBody() will fix the issue.

Differential Revision: http://reviews.llvm.org/D5415


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218302 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Bitcode/Reader/BitcodeReader.cpp

@@ -3347,7 +3347,7 @@ void BitcodeReader::Dematerialize(GlobalValue *GV) {
   assert(DeferredFunctionInfo.count(F) && "No info to read function later?");
 
   // Just forget the function body, we can remat it later.
-  F->deleteBody();
+  F->dropAllReferences();
 }
 
 std::error_code BitcodeReader::MaterializeModule(Module *M) {

unittests/Bitcode/BitReaderTest.cpp

@@ -58,6 +58,30 @@ static std::unique_ptr<Module> getLazyModuleFromAssembly(LLVMContext &Context,
   return std::unique_ptr<Module>(ModuleOrErr.get());
 }
 
+TEST(BitReaderTest, DematerializeFunctionPreservesLinkageType) {
+  SmallString<1024> Mem;
+
+  LLVMContext Context;
+  std::unique_ptr<Module> M = getLazyModuleFromAssembly(
+      Context, Mem, "define internal i32 @func() {\n"
+                      "ret i32 0\n"
+                    "}\n");
+
+  EXPECT_FALSE(verifyModule(*M, &dbgs()));
+
+  M->getFunction("func")->Materialize();
+  EXPECT_FALSE(M->getFunction("func")->empty());
+  EXPECT_TRUE(M->getFunction("func")->getLinkage() ==
+              GlobalValue::InternalLinkage);
+
+  // Check that the linkage type is preserved after dematerialization.
+  M->getFunction("func")->Dematerialize();
+  EXPECT_TRUE(M->getFunction("func")->empty());
+  EXPECT_TRUE(M->getFunction("func")->getLinkage() ==
+              GlobalValue::InternalLinkage);
+  EXPECT_FALSE(verifyModule(*M, &dbgs()));
+}
+
 TEST(BitReaderTest, MaterializeFunctionsForBlockAddr) { // PR11677
   SmallString<1024> Mem;