fix a nasty bug where we were not treating available_externally
symbols as declarations in the X86 backend.  This would manifest
on darwin x86-32 as errors like this with -fvisibility=hidden:

symbol '__ZNSbIcED1Ev' can not be undefined in a subtraction expression

This fixes PR7353.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105954 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86Subtarget.cpp b/lib/Target/X86/X86Subtarget.cpp
index 4012b50..6eda20d 100644
--- a/lib/Target/X86/X86Subtarget.cpp
+++ b/lib/Target/X86/X86Subtarget.cpp
@@ -53,9 +53,12 @@
   if (GV->hasDLLImportLinkage())
     return X86II::MO_DLLIMPORT;
 
-  // Materializable GVs (in JIT lazy compilation mode) do not require an
-  // extra load from stub.
-  bool isDecl = GV->isDeclaration() && !GV->isMaterializable();
+  // Determine whether this is a reference to a definition or a declaration.
+  // Materializable GVs (in JIT lazy compilation mode) do not require an extra
+  // load from stub.
+  bool isDecl = GV->hasAvailableExternallyLinkage();
+  if (GV->isDeclaration() && !GV->isMaterializable())
+    isDecl = true;
 
   // X86-64 in PIC mode.
   if (isPICStyleRIPRel()) {