[PATCH] Add support for __declspec(thread) under -fms-extensions

[Richard Smith]

LGTM

================
Comment at: lib/Sema/SemaDeclAttr.cpp:3700-3717
@@ -3699,1 +3699,20 @@
 
+static void handleDeclspecThreadAttr(Sema &S, Decl *D,
+                                     const AttributeList &Attr) {
+  VarDecl *VD = cast<VarDecl>(D);
+  if (!S.Context.getTargetInfo().isTLSSupported()) {
+    S.Diag(Attr.getLoc(), diag::err_thread_unsupported);
+    return;
+  }
+  if (VD->getTSCSpec() != TSCS_unspecified) {
+    S.Diag(Attr.getLoc(), diag::err_declspec_thread_on_thread_variable);
+    return;
+  }
+  if (VD->hasLocalStorage()) {
+    S.Diag(Attr.getLoc(), diag::err_thread_non_global) << "__declspec(thread)";
+    return;
+  }
+  VD->addAttr(::new (S.Context) ThreadAttr(
+      Attr.getRange(), S.Context, Attr.getAttributeSpellingListIndex()));
+}
+
----------------
Are you allowed to specify `__declspec(thread)` multiple times on the same declaration? This would appear to allow that.

================
Comment at: lib/Sema/SemaDeclAttr.cpp:3711-3714
@@ +3710,6 @@
+  }
+  if (VD->hasLocalStorage()) {
+    S.Diag(Attr.getLoc(), diag::err_thread_non_global) << "__declspec(thread)";
+    return;
+  }
+  VD->addAttr(::new (S.Context) ThreadAttr(
----------------
Can you move the `hasLocalStorage` check into the common attribute subject checking side of things? That'd be more in line with what we do elsewhere, but might make the diagnostic less consistent with other thread specifiers, so I'm on the fence.

http://reviews.llvm.org/D3551