2 files changed, 83 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
index 8db7e1e142d..20f54ef53f7 100644
--- a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -956,6 +956,21 @@ void LowerTypeTestsModule::importFunction(Function *F, bool isDefinition) {
     FDecl = Function::Create(F->getFunctionType(), GlobalValue::ExternalLinkage,
                              Name, &M);
     FDecl->setVisibility(Visibility);
+
+    // Delete aliases pointing to this function, they'll be re-created in the
+    // merged output
+    SmallVector<GlobalAlias*, 4> ToErase;
+    for (auto &U : F->uses()) {
+      if (auto *A = dyn_cast<GlobalAlias>(U.getUser())) {
+        Function *AliasDecl = Function::Create(
+            F->getFunctionType(), GlobalValue::ExternalLinkage, "", &M);
+        AliasDecl->takeName(A);
+        A->replaceAllUsesWith(AliasDecl);
+        ToErase.push_back(A);
+      }
+    }
+    for (auto *A : ToErase)
+      A->eraseFromParent();
   } else {
     // Function definition without type metadata, where some other translation
     // unit contained a declaration with type metadata. This normally happens
@@ -1804,6 +1819,49 @@ bool LowerTypeTestsModule::lower() {
 
   allocateByteArrays();
 
+  // Parse alias data to replace stand-in function declarations for aliases
+  // with an alias to the intended target.
+  if (ExportSummary) {
+    if (NamedMDNode *AliasesMD = M.getNamedMetadata("aliases")) {
+      for (auto AliasMD : AliasesMD->operands()) {
+        assert(AliasMD->getNumOperands() >= 4);
+        StringRef AliasName =
+            cast<MDString>(AliasMD->getOperand(0))->getString();
+        StringRef Aliasee = cast<MDString>(AliasMD->getOperand(1))->getString();
+
+        if (!ExportedFunctions.count(Aliasee) ||
+            ExportedFunctions[Aliasee].Linkage != CFL_Definition ||
+            !M.getNamedAlias(Aliasee))
+          continue;
+
+        GlobalValue::VisibilityTypes Visibility =
+            static_cast<GlobalValue::VisibilityTypes>(
+                cast<ConstantAsMetadata>(AliasMD->getOperand(2))
+                    ->getValue()
+                    ->getUniqueInteger()
+                    .getZExtValue());
+        bool Weak =
+            static_cast<bool>(cast<ConstantAsMetadata>(AliasMD->getOperand(3))
+                                  ->getValue()
+                                  ->getUniqueInteger()
+                                  .getZExtValue());
+
+        auto *Alias = GlobalAlias::create("", M.getNamedAlias(Aliasee));
+        Alias->setVisibility(Visibility);
+        if (Weak)
+          Alias->setLinkage(GlobalValue::WeakAnyLinkage);
+
+        if (auto *F = M.getFunction(AliasName)) {
+          Alias->takeName(F);
+          F->replaceAllUsesWith(Alias);
+          F->eraseFromParent();
+        } else {
+          Alias->setName(AliasName);
+        }
+      }
+    }
+  }
+
   return true;
 }
 
diff --git a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
index caffc03339c..f5a3d4452c7 100644
--- a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
+++ b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
@@ -357,6 +357,31 @@ void splitAndWriteThinLTOBitcode(
       NMD->addOperand(MD);
   }
 
+  SmallVector<MDNode *, 8> FunctionAliases;
+  for (auto &A : M.aliases()) {
+    if (!isa<Function>(A.getAliasee()))
+      continue;
+
+    auto *F = cast<Function>(A.getAliasee());
+    auto &Ctx = MergedM->getContext();
+    SmallVector<Metadata *, 4> Elts;
+
+    Elts.push_back(MDString::get(Ctx, A.getName()));
+    Elts.push_back(MDString::get(Ctx, F->getName()));
+    Elts.push_back(ConstantAsMetadata::get(
+        llvm::ConstantInt::get(Type::getInt8Ty(Ctx), A.getVisibility())));
+    Elts.push_back(ConstantAsMetadata::get(
+        llvm::ConstantInt::get(Type::getInt8Ty(Ctx), A.isWeakForLinker())));
+
+    FunctionAliases.push_back(MDTuple::get(Ctx, Elts));
+  }
+
+  if (!FunctionAliases.empty()) {
+    NamedMDNode *NMD = MergedM->getOrInsertNamedMetadata("aliases");
+    for (auto MD : FunctionAliases)
+      NMD->addOperand(MD);
+  }
+
   simplifyExternals(*MergedM);
 
   // FIXME: Try to re-use BSI and PFI from the original module here.