[MinGW] Ignore -fvisibility/-fvisibility-inlines-hidden for dllexport

[MaskRay]

Summary

Similar to 123ce97fac78bc4519afd5d2aba17c59c5717aad for dllimport: dllexport
expresses a non-hidden visibility intention. We can consider it explicit and
therefore it should override the global visibility setting (see AST/Decl.cpp
"NamedDecl Implementation").

Adding the exception to CodeGenModule::setGlobalVisibility is somewhat weird,
but allows us to add the code in one place instead of many in AST/Decl.cpp.

[MaskRay]

improve test

[mstorsjo]

This LGTM, but one question about the test. Thanks!

clang/test/CodeGenCXX/dllstorage-hidden.cpp

3 ↗

(On Diff #457483)

What parts of this test requires -fms-extensions?

[MaskRay]

rename test to dllstorage-visibility.cpp
use -fdeclspec instead of -fms-extensions

clang/lib/CodeGen/CodeGenModule.cpp

 }
 
 llvm::ConstantInt *CodeGenModule::getSize(CharUnits size) {
   return llvm::ConstantInt::get(SizeTy, size.getQuantity());
 }
 
 void CodeGenModule::setGlobalVisibility(llvm::GlobalValue *GV,
                                         const NamedDecl *D) const {
-  if (GV->hasDLLImportStorageClass())
+  if (GV->hasDLLExportStorageClass() || GV->hasDLLImportStorageClass())
     return;
   // Internal definitions always have default visibility.
   if (GV->hasLocalLinkage()) {
     GV->setVisibility(llvm::GlobalValue::DefaultVisibility);
     return;
   }
   if (!D)
     return;

clang/test/CodeGenCXX/dllstorage-visibility.cpp

+/// dllimport and dllexport express non-hidden intention. Don't apply hidden visibility.
+
+// RUN: %clang_cc1 -emit-llvm -triple x86_64-windows-msvc -fdeclspec -fvisibility-inlines-hidden -o - %s | FileCheck %s --check-prefix=MSVC
+// RUN: %clang_cc1 -emit-llvm -triple x86_64-windows-gnu -fdeclspec -fvisibility-inlines-hidden -o - %s | FileCheck %s --check-prefix=GNU
+// RUN: %clang_cc1 -emit-llvm -triple x86_64-windows-gnu -fdeclspec -fvisibility hidden -o - %s | FileCheck %s --check-prefix=GNU
+
+#define CONCAT2(x, y) x##y
+#define CONCAT(x, y) CONCAT2(x, y)
+#define USE(func) void CONCAT(use, __LINE__)() { func(); }
+
+// MSVC-DAG: declare dllimport void @"?bar@foo@@QEAAXXZ"(
+// GNU-DAG: define linkonce_odr hidden void @_ZN3foo3barEv(
+
+struct __attribute__((dllimport)) foo {
+  void bar() {}
+};
+void zed(foo *p) { p->bar(); }
+
+// MSVC-DAG: define dso_local dllexport void @"?exported@@YAXXZ"(
+// GNU-DAG: define dso_local dllexport void @_Z8exportedv(
+__attribute__((dllexport)) void exported() {}
+
+// MSVC-DAG: define weak_odr dso_local dllexport void @"?exported_inline@@YAXXZ"(
+// GNU-DAG: define weak_odr dso_local dllexport void @_Z15exported_inlinev(
+__declspec(dllexport) inline void exported_inline() {}
+USE(exported_inline)

clang/test/CodeGenCXX/hidden-dllimport.cpp

-// RUN: %clang_cc1 -no-opaque-pointers -triple x86_64-pc-windows-msvc -emit-llvm -fvisibility-inlines-hidden -o - %s | FileCheck %s
-
-// We used to declare this hidden dllimport, which is contradictory.
-
-// CHECK: declare dllimport void @"?bar@foo@@QEAAXXZ"(%struct.foo* {{[^,]*}})
-
-struct __attribute__((dllimport)) foo {
-  void bar() {}
-};
-void zed(foo *p) { p->bar(); }