[PATCH] CodeGen: Emit globals with a constant initializer but no definition as available_externally.

[Richard Smith]

  Seems like a great idea to me.


================
Comment at: lib/CodeGen/CodeGenModule.cpp:1591
@@ +1590,3 @@
+    if (D->hasInit() && !D->hasDefinition(Context)) {
+      assert(!D->getType().isVolatileQualified());
+      assert(GetLLVMLinkageVarDefinition(D, /*isConstant=*/true) ==
----------------
This is incorrect. The following is valid:

  struct S {
    static constexpr volatile int n = 0;
  };

================
Comment at: lib/CodeGen/CodeGenModule.cpp:1884-1885
@@ +1883,4 @@
+  if (D->hasInit() && !D->hasDefinition(Context)) {
+    assert(isTypeConstant(D->getType(), /*ExcludeCtor=*/true) &&
+           "Variable with init but no definition should be constant!");
+    return llvm::GlobalValue::AvailableExternallyLinkage;
----------------
This is incorrect. The following is valid:

  struct A {
    mutable int n;
  };
  struct B {
    static constexpr A a = { 0 };
  };


http://llvm-reviews.chandlerc.com/D1982