[PS4] Support dllimport/export attributes

[bd1976llvm]

Summary

For PS4 development we support dllimport/export annotations in source code. This patch enables the dllimport/export attributes on PS4 by adding a new function to query the triple for whether dllimport/export are supported and using that function to decide whether these attributes are supported. This means we can drop the use of "TargetArch" in the .td file which is an improvement as dllimport/export support isn't really a function of the architecture.

I have included a simple codgen test to show that the attributes are accepted and have an effect on codegen. I have also enabled the DLLExportStaticLocal and DLLImportStaticLocal attributes, which we support downstream. However, I am unable to write a test for these attributes until other patches for PS4 dllimport/export handling land upstream. Whilst writing this patch I noticed that, as these attributes are internal, they do not need to be target specific (when these attributes are added internally in Clang the target specific checks have already been run); however, I think leaving them target specific is fine because it isn't harmful and they "really are" target specific even if that has no functional impact.

[hans]

Looks reasonable to me.

[aaron.ballman]

LGTM!

llvm/include/llvm/ADT/Triple.h

787

Indentation looks a bit off here

[bd1976llvm]

Fixed indentation.

[bd1976llvm]

llvm/include/llvm/ADT/Triple.h

787

Thanks!

clang/include/clang/Basic/Attr.td

 def TargetBPF : TargetArch<["bpfel", "bpfeb"]>;
 def TargetMips32 : TargetArch<["mips", "mipsel"]>;
 def TargetAnyMips : TargetArch<["mips", "mipsel", "mips64", "mips64el"]>;
 def TargetMSP430 : TargetArch<["msp430"]>;
 def TargetRISCV : TargetArch<["riscv32", "riscv64"]>;
 def TargetX86 : TargetArch<["x86"]>;
 def TargetAnyX86 : TargetArch<["x86", "x86_64"]>;
 def TargetWebAssembly : TargetArch<["wasm32", "wasm64"]>;
-def TargetWindows : TargetArch<["x86", "x86_64", "arm", "thumb", "aarch64"]> {
-  let OSes = ["Win32"];
+def TargetHasDLLImportExport : TargetSpec {
+  let CustomCode = [{ Target.getTriple().hasDLLImportExport() }];
 }
 def TargetItaniumCXXABI : TargetSpec {
   let CustomCode = [{ Target.getCXXABI().isItaniumFamily() }];
 }
 def TargetMicrosoftCXXABI : TargetArch<["x86", "x86_64", "arm", "thumb", "aarch64"]> {
   let CustomCode = [{ Target.getCXXABI().isMicrosoft() }];
 }
 def TargetELF : TargetSpec {

 
 def MSStruct : InheritableAttr {
   let Spellings = [GCC<"ms_struct">];
   let Subjects = SubjectList<[Record]>;
   let Documentation = [Undocumented];
   let SimpleHandler = 1;
 }
 
-def DLLExport : InheritableAttr, TargetSpecificAttr<TargetWindows> {
+def DLLExport : InheritableAttr, TargetSpecificAttr<TargetHasDLLImportExport> {
   let Spellings = [Declspec<"dllexport">, GCC<"dllexport">];
   let Subjects = SubjectList<[Function, Var, CXXRecord, ObjCInterface]>;
   let Documentation = [DLLExportDocs];
 }
 
-def DLLExportStaticLocal : InheritableAttr, TargetSpecificAttr<TargetWindows> {
+def DLLExportStaticLocal : InheritableAttr, TargetSpecificAttr<TargetHasDLLImportExport> {
   // This attribute is used internally only when -fno-dllexport-inlines is
-  // passed. This attribute is added to inline function of class having
-  // dllexport attribute. And if the function has static local variables, this
-  // attribute is used to whether the variables are exported or not. Also if
-  // function has local static variables, the function is dllexported too.
+  // passed. This attribute is added to inline functions of a class having the
+  // dllexport attribute. If the function has static local variables, this
+  // attribute is used to determine whether the variables are exported or not. If
+  // the function has local static variables, the function is dllexported too.
   let Spellings = [];
   let Subjects = SubjectList<[Function]>;
   let Documentation = [Undocumented];
 }
 
-def DLLImport : InheritableAttr, TargetSpecificAttr<TargetWindows> {
+def DLLImport : InheritableAttr, TargetSpecificAttr<TargetHasDLLImportExport> {
   let Spellings = [Declspec<"dllimport">, GCC<"dllimport">];
   let Subjects = SubjectList<[Function, Var, CXXRecord, ObjCInterface]>;
   let Documentation = [DLLImportDocs];
 
 
   let AdditionalMembers = [{
 private:
   bool PropagatedToBaseTemplate = false;
 
 public:
   void setPropagatedToBaseTemplate() { PropagatedToBaseTemplate = true; }
   bool wasPropagatedToBaseTemplate() { return PropagatedToBaseTemplate; }
   }];
 }
 
-def DLLImportStaticLocal : InheritableAttr, TargetSpecificAttr<TargetWindows> {
+def DLLImportStaticLocal : InheritableAttr, TargetSpecificAttr<TargetHasDLLImportExport> {
   // This attribute is used internally only when -fno-dllexport-inlines is
-  // passed. This attribute is added to inline function of class having
-  // dllimport attribute. And if the function has static local variables, this
-  // attribute is used to whether the variables are imported or not.
+  // passed. This attribute is added to inline functions of a class having the
+  // dllimport attribute. If the function has static local variables, this
+  // attribute is used to determine whether the variables are imported or not.
   let Spellings = [];
   let Subjects = SubjectList<[Function]>;
   let Documentation = [Undocumented];
 }
 
 def SelectAny : InheritableAttr {
   let Spellings = [Declspec<"selectany">, GCC<"selectany">];
   let Documentation = [SelectAnyDocs];

clang/test/CodeGen/ps4-dllimport-dllexport.c

+// RUN: %clang_cc1 \
+// RUN:     -triple x86_64-scei-ps4 \
+// RUN:     -fdeclspec \
+// RUN:     -Werror \
+// RUN:     -emit-llvm %s -o - | \
+// RUN:   FileCheck %s
+
+__declspec(dllexport) int export_int;
+
+__declspec(dllimport) int import_int;
+
+__declspec(dllexport) void export_declared_function();
+
+__declspec(dllexport) void export_implemented_function() {
+}
+
+__declspec(dllimport) void import_function(int);
+
+void call_imported_function() {
+  export_declared_function();
+  return import_function(import_int);
+}
+
+// CHECK-DAG: @import_int = external dllimport
+// CHECK-DAG: @export_int = dllexport global i32 0
+// CHECK-DAG: define dllexport void @export_implemented_function()
+// CHECK-DAG: declare dllimport void @import_function(i32)

llvm/include/llvm/ADT/Triple.h

bool hasDefaultEmulatedTLS() const {
     return isAndroid() || isOSOpenBSD() || isWindowsCygwinEnvironment();
   }
 
   /// Tests whether the target uses -data-sections as default.
   bool hasDefaultDataSections() const {
     return isOSBinFormatXCOFF() || isWasm();
   }
 
+  /// Tests if the environment supports dllimport/export annotations.
+  bool hasDLLImportExport() const { return isOSWindows() || isPS4CPU(); }
+
   /// @}
   /// @name Mutators
   /// @{
 
   /// setArch - Set the architecture (first) component of the triple
   /// to a known type.
   void setArch(ArchType Kind);