[PATCH] Fix asserts about emitting constexpr methods twice during dllexport explicit instantiation (PR21718)

[David Majnemer]

LGTM with nits.


================
Comment at: lib/CodeGen/CodeGenModule.cpp:1105-1108
@@ -1104,2 +1104,6 @@
 
-    assert(GV == GetGlobalValue(getMangledName(D)));
+    if (GV)
+      assert(GV == GetGlobalValue(getMangledName(D)));
+    else
+      GV = GetGlobalValue(getMangledName(D));
+
----------------
Maybe:
  assert(!GV || GV == GetGlobalValue(getMangledName(D)));
  if (!GV)
    GV = GetGlobalValue(getMangledName(D));

================
Comment at: lib/CodeGen/CodeGenModule.cpp:1389
@@ +1388,3 @@
+    assert(!MayBeEmittedEagerly(Global));
+    addDeferredDeclToEmit(nullptr, GD);
+  } else {
----------------
You may want to make this a little more clear:
  addDeferredDeclToEmit(/*GV=*/nullptr, GD);

http://reviews.llvm.org/D6674

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