[AMDGPU] Enable overriding of OpenCL's default address space

`opencl-def-is-generic-addrspace` sets the default address space from
private to generic. This feature allows for building bitcode libraries
written in OpenCL that can then be linked against modules compiled from
sources written in languages that expect generic as the default address
space.

Author: Jakub Chlanda

clang/include/clang/Basic/TargetInfo.h

@@ -271,6 +271,9 @@ class TargetInfo : public TransferrableTargetInfo,
   LLVM_PREFERRED_TYPE(bool)
   unsigned AllowAMDGPUUnsafeFPAtomics : 1;
 
+  LLVM_PREFERRED_TYPE(bool)
+  unsigned OpenCLDefIsGenericAddrSpace : 1;
+
   LLVM_PREFERRED_TYPE(bool)
   unsigned HasUnalignedAccess : 1;
 

clang/include/clang/Basic/TargetOptions.h

@@ -78,6 +78,10 @@ class TargetOptions {
   /// \brief If enabled, allow AMDGPU unsafe floating point atomics.
   bool AllowAMDGPUUnsafeFPAtomics = false;
 
+  /// \brief If enabled, allow overriding of the default address space (from
+  /// private to generic).
+  bool OpenCLDefIsGenericAddrSpace = false;
+
   /// \brief Code object version for AMDGPU.
   llvm::CodeObjectVersionKind CodeObjectVersion =
       llvm::CodeObjectVersionKind::COV_None;

clang/include/clang/Driver/Options.td

@@ -5164,6 +5164,13 @@ defm unsafe_fp_atomics : BoolMOption<"unsafe-fp-atomics",
           "for certain memory destinations. (AMDGPU only)">,
   NegFlag<SetFalse>>;
 
+defm opencl_def_is_generic_addrspace: BoolMOption<"opencl-def-is-generic-addrspace",
+  TargetOpts<"OpenCLDefIsGenericAddrSpace">, DefaultFalse,
+  PosFlag<SetTrue, [], [ClangOption, CC1Option],
+          "Enable overriding of OpenCL's default address space: from private "
+          "to generic (AMDGPU only).">,
+  NegFlag<SetFalse>>;
+
 def faltivec : Flag<["-"], "faltivec">, Group<f_Group>;
 def fno_altivec : Flag<["-"], "fno-altivec">, Group<f_Group>;
 let Flags = [TargetSpecific] in {

clang/lib/Basic/TargetInfo.cpp

@@ -157,6 +157,7 @@ TargetInfo::TargetInfo(const llvm::Triple &T) : Triple(T) {
   HasAArch64SVETypes = false;
   HasRISCVVTypes = false;
   AllowAMDGPUUnsafeFPAtomics = false;
+  OpenCLDefIsGenericAddrSpace = false;
   HasUnalignedAccess = false;
   ARMCDECoprocMask = 0;
 

clang/lib/Basic/Targets/AMDGPU.cpp

@@ -240,6 +240,7 @@ AMDGPUTargetInfo::AMDGPUTargetInfo(const llvm::Triple &Triple,
   HasFloat16 = true;
   WavefrontSize = (GPUFeatures & llvm::AMDGPU::FEATURE_WAVE32) ? 32 : 64;
   AllowAMDGPUUnsafeFPAtomics = Opts.AllowAMDGPUUnsafeFPAtomics;
+  OpenCLDefIsGenericAddrSpace = Opts.OpenCLDefIsGenericAddrSpace;
 
   // Set pointer width and alignment for the generic address space.
   PointerWidth = PointerAlign = getPointerWidthV(LangAS::Default);
@@ -262,8 +263,13 @@ void AMDGPUTargetInfo::adjust(DiagnosticsEngine &Diags, LangOptions &Opts) {
   // ToDo: There are still a few places using default address space as private
   // address space in OpenCL, which needs to be cleaned up, then the references
   // to OpenCL can be removed from the following line.
-  setAddressSpaceMap((Opts.OpenCL && !Opts.OpenCLGenericAddressSpace) ||
-                     !isAMDGCN(getTriple()));
+  bool DefaultIsPrivate = (Opts.OpenCL && !Opts.OpenCLGenericAddressSpace) ||
+                          !isAMDGCN(getTriple());
+  // Allow for overriding of the default address space in OpenCL (from private
+  // to generic).
+  if (Opts.OpenCL && OpenCLDefIsGenericAddrSpace)
+    DefaultIsPrivate = false;
+  setAddressSpaceMap(DefaultIsPrivate);
 }
 
 ArrayRef<Builtin::Info> AMDGPUTargetInfo::getTargetBuiltins() const {

clang/lib/Driver/ToolChains/Clang.cpp

@@ -7888,6 +7888,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
     Args.addOptInFlag(CmdArgs, options::OPT_munsafe_fp_atomics,
                       options::OPT_mno_unsafe_fp_atomics);
+    Args.addOptInFlag(CmdArgs, options::OPT_mopencl_def_is_generic_addrspace,
+                      options::OPT_mno_opencl_def_is_generic_addrspace);
     Args.addOptOutFlag(CmdArgs, options::OPT_mamdgpu_ieee,
                        options::OPT_mno_amdgpu_ieee);
   }

clang/test/CodeGen/AMDGPU/opencl_def_is_generic_addrspace.cl

@@ -0,0 +1,18 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
+// RUN: %clang_cc1 -triple amdgcn-unknown-amdhsa -emit-llvm -target-cpu gfx900 -mopencl-def-is-generic-addrspace -cl-std=CL3.0 -cl-ext=+__opencl_c_generic_address_space -o - %s | FileCheck -check-prefix=CHECK-OPENCL-DEF-IS-GENERIC %s
+// RUN: %clang_cc1 -triple amdgcn-unknown-amdhsa -emit-llvm -target-cpu gfx900 -cl-std=CL3.0 -cl-ext=+__opencl_c_generic_address_space -o - %s | FileCheck -check-prefix=CHECK-NO-OPENCL-DEF-IS-GENERIC %s
+
+// CHECK-OPENCL-DEF-IS-GENERIC-LABEL: define dso_local void @_Z14funcGenericPtrfPf(
+// CHECK-OPENCL-DEF-IS-GENERIC-SAME: float noundef [[ARGS_0:%.*]], ptr nocapture noundef readnone [[ARGS_1:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
+// CHECK-OPENCL-DEF-IS-GENERIC-NEXT:  [[ENTRY:.*:]]
+// CHECK-OPENCL-DEF-IS-GENERIC-NEXT:    ret void
+//
+// CHECK-NO-OPENCL-DEF-IS-GENERIC-LABEL: define dso_local void @_Z14funcGenericPtrfPU3AS0f(
+// CHECK-NO-OPENCL-DEF-IS-GENERIC-SAME: float noundef [[ARGS_0:%.*]], ptr nocapture noundef readnone [[ARGS_1:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
+// CHECK-NO-OPENCL-DEF-IS-GENERIC-NEXT:  [[ENTRY:.*:]]
+// CHECK-NO-OPENCL-DEF-IS-GENERIC-NEXT:    ret void
+//
+__attribute__((overloadable)) void funcGenericPtr(float args_0,
+                                                  float __generic *args_1) {
+  return;
+}