Implement call lowering without parameters on AIX

Summary:dd
This patch implements call lowering for calls without parameters
on AIX as initial support.

Reviewers: sfertile, hubert.reinterpretcast, aheejin, efriedma

Differential Revision: https://reviews.llvm.org/D61948

llvm-svn: 361669
diff --git a/llvm/lib/Target/TargetMachine.cpp b/llvm/lib/Target/TargetMachine.cpp
index fd70b83..634866d 100644
--- a/llvm/lib/Target/TargetMachine.cpp
+++ b/llvm/lib/Target/TargetMachine.cpp
@@ -173,6 +173,11 @@
     return GV && GV->isStrongDefinitionForLinker();
   }
 
+  // Due to the AIX linkage model, any global with default visibility is
+  // considered non-local.
+  if (TT.isOSBinFormatXCOFF())
+    return false;
+
   assert(TT.isOSBinFormatELF() || TT.isOSBinFormatWasm());
   assert(RM != Reloc::DynamicNoPIC);