[ThinLTO] Handle an external call from an import to an alias in dest

The findExternalCalls routine ignores calls to functions already
defined in the dest module. This was not handling the case where
the definition in the current module is actually an alias to a
function call.

llvm-svn: 257493

llvm/lib/Transforms/IPO/FunctionImport.cpp

@@ -133,6 +133,8 @@ static void findExternalCalls(const Module &DestModule, Function &F,
         // Ignore functions already present in the destination module
         auto *SrcGV = DestModule.getNamedValue(ImportedName);
         if (SrcGV) {
+          if (GlobalAlias *SGA = dyn_cast<GlobalAlias>(SrcGV))
+            SrcGV = SGA->getBaseObject();
           assert(isa<Function>(SrcGV) && "Name collision during import");
           if (!cast<Function>(SrcGV)->isDeclaration()) {
             DEBUG(dbgs() << DestModule.getModuleIdentifier() << ": Ignoring "

llvm/test/Transforms/FunctionImport/Inputs/funcimport_alias.ll

@@ -0,0 +1,7 @@
+declare void @analias()
+
+define void @callanalias() #0 {
+entry:
+  call void @analias()
+  ret void
+}

llvm/test/Transforms/FunctionImport/funcimport_alias.ll

@@ -0,0 +1,25 @@
+; Do setup work for all below tests: generate bitcode and combined index
+; RUN: llvm-as -function-summary %s -o %t.bc
+; RUN: llvm-as -function-summary %p/Inputs/funcimport_alias.ll -o %t2.bc
+; RUN: llvm-lto -thinlto -o %t3 %t.bc %t2.bc %t3.bc
+
+; Do the import now. Ensures that the importer handles an external call
+; from imported callanalias() to a function that is defined already in
+; the dest module, but as an alias.
+; RUN: opt -function-import -summary-file %t3.thinlto.bc %s -S | FileCheck %s
+
+define i32 @main() #0 {
+entry:
+  call void @callanalias()
+  ret i32 0
+}
+
+@analias = alias void (), void ()* @globalfunc
+
+define void @globalfunc() #0 {
+entry:
+  ret void
+}
+
+declare void @callanalias() #1
+; CHECK-DAG: define available_externally void @callanalias()