[clang] [Clang] Apply exclude_from_explicit_instantiation to dllimport/dllexport (PR #168171)

[Tomohiro Kashiwada via cfe-commits]

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@@ -0,0 +1,179 @@
+// RUN: %clang_cc1 -triple x86_64-win32 -fms-extensions -emit-llvm -o - %s | \
+// RUN:     FileCheck %s --check-prefixes=MSC --implicit-check-not=to_be_ --implicit-check-not=" dllexport"
+// RUN: %clang_cc1 -triple x86_64-mingw                 -emit-llvm -o - %s | \
+// RUN:     FileCheck %s --check-prefixes=GNU --implicit-check-not=to_be_ --implicit-check-not=" dllexport"
+// RUN: %clang_cc1 -triple x86_64-cygwin                -emit-llvm -o - %s | \
+// RUN:     FileCheck %s --check-prefixes=GNU --implicit-check-not=to_be_ --implicit-check-not=" dllexport"
+
+// Test that __declspec(dllexport) doesn't instantiate entities marked with
+// the exclude_from_explicit_instantiation attribute unless marked as dllexport explicitly.
+
+#define EXCLUDE_ATTR __attribute__((exclude_from_explicit_instantiation))
+
+struct NoAttrTag {};
+struct WithExportTag {};
+struct ImplicitTag {};
+
+template <class T>
+struct BasicCase {
+  // This will be instantiated explicitly as an exported function because it
+  // inherits dllexport from the class instantiation.
+  void to_be_exported();
+
+  // This will be instantiated implicitly as an exported function because it is
+  // marked as dllexport explicitly.
+  EXCLUDE_ATTR __declspec(dllexport) void to_be_memberwise_exported();
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kikairoya wrote:

I noticed that this method is instantiated by an explicit instantiation with dllexport, though emitted at the bottom of the module.
The logic should be revised further...

https://github.com/llvm/llvm-project/pull/168171