[SYCL] Don't define SYCL_EXTERNAL if -fno-sycl-rdc is passed (#8537)

Please review this commit by commit because one of the commits affects a
ton of files. Thanks!

The SYCL [spec
](https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#subsec:syclexternal)allows
us to declare we don't support device function calls outside of the
current translation unit by not defining the `SYCL_EXTERNAL` macro.
With the `-fno-sycl-rdc` option, this is exactly that case: we do not
support calls outside of the TU, so don't define the macro.

However, we define and use the `SYCL_EXTERNAL` in the SYCL headers also,
so instead add `__DPCPP_SYCL_EXTERNAL` and use that. It is defined to
`SYCL_EXTERNAL` if `SYCL_EXTERNAL` is defined, and otherwise
`__attribute__((sycl_device))` for device code or empty for host. This
is fine because none of the uses here actually end up as cross-TU calls,
it's either linked in from the device libraries or replaced by the
SPIR-V translator to some SPIR-V intrinsic.

I added a test in `sycl/test/basic_tests/macros_no_rdc.cpp` to make sure
nobody uses `SYCL_EXTERNAL` directly in the SYCL headers in the future.

(UPDATE: This part has been removed) However, with the macro being
undefined, if a user tries to use it, they just get the classic `unknown
type name 'SYCL_EXTERNAL'` which is not super helpful. I added some
really gross code to give a better error message, but I'd like to hear
from the CFE folks if there's a better way to do it, and if not, if it's
so gross we should just drop it and rely on the normal error.


Relevant discussion: #8479

---------

Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>

Author: sarnex

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -11835,9 +11835,6 @@ def err_sycl_restrict : Error<
 def err_sycl_external_global : Error<
   "invalid reference to 'device_global' variable; external 'device_global'"
   " variable must be marked with SYCL_EXTERNAL macro">;
-def err_sycl_external_no_rdc : Error<
-  "invalid %select{declaration|definition}0 of SYCL_EXTERNAL function in non-relocatable "
-   "device code mode">;
 def warn_sycl_kernel_too_big_args : Warning<
   "size of kernel arguments (%0 bytes) may exceed the supported maximum "
   "of %1 bytes on some devices">, InGroup<SyclStrict>, ShowInSystemHeader;

clang/lib/Frontend/InitPreprocessor.cpp

@@ -1297,7 +1297,8 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
   // SYCL device compiler which doesn't produce host binary.
   if (LangOpts.SYCLIsDevice) {
     Builder.defineMacro("__SYCL_DEVICE_ONLY__");
-    Builder.defineMacro("SYCL_EXTERNAL", "__attribute__((sycl_device))");
+    if (LangOpts.GPURelocatableDeviceCode)
+      Builder.defineMacro("SYCL_EXTERNAL", "__attribute__((sycl_device))");
 
     const llvm::Triple &DeviceTriple = TI.getTriple();
     const llvm::Triple::SubArchType DeviceSubArch = DeviceTriple.getSubArch();

clang/lib/Sema/SemaDecl.cpp

@@ -10296,15 +10296,6 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     }
   }
 
-  if (getLangOpts().SYCLIsDevice && !getLangOpts().GPURelocatableDeviceCode &&
-      NewFD->hasAttr<SYCLDeviceAttr>() &&
-      !getSourceManager().isInSystemHeader(NewFD->getLocation())) {
-    Diag(NewFD->getLocation(), diag::err_sycl_external_no_rdc)
-        << (D.getFunctionDefinitionKind() ==
-            clang::FunctionDefinitionKind::Definition);
-    NewFD->setInvalidDecl();
-  }
-
   if (!getLangOpts().CPlusPlus) {
     // Perform semantic checking on the function declaration.
     if (!NewFD->isInvalidDecl() && NewFD->isMain())

clang/test/SemaSYCL/sycl-no-rdc.cpp

@@ -1,13 +1,10 @@
 // RUN: %clang_cc1 -fsycl-is-device -verify -fsyntax-only -fno-gpu-rdc -internal-isystem %S/Inputs %s
 
-// Check that declarations of SYCL_EXTERNAL functions throw an error if -fno-gpu-rdc is passed
+// Check that uses of SYCL_EXTERNAL throw an error if -fno-gpu-rdc is passed
 #include "sycl.hpp"
 
-// expected-error@+1{{invalid declaration of SYCL_EXTERNAL function in non-relocatable device code mode}}
-SYCL_EXTERNAL void syclExternalDecl();
-
-// expected-error@+1{{invalid definition of SYCL_EXTERNAL function in non-relocatable device code mode}}
-SYCL_EXTERNAL void syclExternalDefn() {}
+// expected-error@+1{{unknown type name 'SYCL_EXTERNAL'}}
+SYCL_EXTERNAL void syclExternal() {}
 
 using namespace sycl;
 queue q;

sycl/include/CL/__spirv/spirv_ops.hpp

@@ -17,39 +17,39 @@
 
 #if defined(__NVPTX__) || defined(__AMDGCN__)
 
-SYCL_EXTERNAL size_t __spirv_GlobalInvocationId_x();
-SYCL_EXTERNAL size_t __spirv_GlobalInvocationId_y();
-SYCL_EXTERNAL size_t __spirv_GlobalInvocationId_z();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_GlobalInvocationId_x();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_GlobalInvocationId_y();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_GlobalInvocationId_z();
 
-SYCL_EXTERNAL size_t __spirv_GlobalSize_x();
-SYCL_EXTERNAL size_t __spirv_GlobalSize_y();
-SYCL_EXTERNAL size_t __spirv_GlobalSize_z();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_GlobalSize_x();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_GlobalSize_y();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_GlobalSize_z();
 
-SYCL_EXTERNAL size_t __spirv_GlobalOffset_x();
-SYCL_EXTERNAL size_t __spirv_GlobalOffset_y();
-SYCL_EXTERNAL size_t __spirv_GlobalOffset_z();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_GlobalOffset_x();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_GlobalOffset_y();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_GlobalOffset_z();
 
-SYCL_EXTERNAL size_t __spirv_NumWorkgroups_x();
-SYCL_EXTERNAL size_t __spirv_NumWorkgroups_y();
-SYCL_EXTERNAL size_t __spirv_NumWorkgroups_z();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_NumWorkgroups_x();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_NumWorkgroups_y();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_NumWorkgroups_z();
 
-SYCL_EXTERNAL size_t __spirv_WorkgroupSize_x();
-SYCL_EXTERNAL size_t __spirv_WorkgroupSize_y();
-SYCL_EXTERNAL size_t __spirv_WorkgroupSize_z();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_WorkgroupSize_x();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_WorkgroupSize_y();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_WorkgroupSize_z();
 
-SYCL_EXTERNAL size_t __spirv_WorkgroupId_x();
-SYCL_EXTERNAL size_t __spirv_WorkgroupId_y();
-SYCL_EXTERNAL size_t __spirv_WorkgroupId_z();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_WorkgroupId_x();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_WorkgroupId_y();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_WorkgroupId_z();
 
-SYCL_EXTERNAL size_t __spirv_LocalInvocationId_x();
-SYCL_EXTERNAL size_t __spirv_LocalInvocationId_y();
-SYCL_EXTERNAL size_t __spirv_LocalInvocationId_z();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_LocalInvocationId_x();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_LocalInvocationId_y();
+__DPCPP_SYCL_EXTERNAL size_t __spirv_LocalInvocationId_z();
 
-SYCL_EXTERNAL uint32_t __spirv_SubgroupSize();
-SYCL_EXTERNAL uint32_t __spirv_SubgroupMaxSize();
-SYCL_EXTERNAL uint32_t __spirv_NumSubgroups();
-SYCL_EXTERNAL uint32_t __spirv_SubgroupId();
-SYCL_EXTERNAL uint32_t __spirv_SubgroupLocalInvocationId();
+__DPCPP_SYCL_EXTERNAL uint32_t __spirv_SubgroupSize();
+__DPCPP_SYCL_EXTERNAL uint32_t __spirv_SubgroupMaxSize();
+__DPCPP_SYCL_EXTERNAL uint32_t __spirv_NumSubgroups();
+__DPCPP_SYCL_EXTERNAL uint32_t __spirv_SubgroupId();
+__DPCPP_SYCL_EXTERNAL uint32_t __spirv_SubgroupLocalInvocationId();
 
 #else // defined(__NVPTX__) || defined(__AMDGCN__)
 
@@ -68,89 +68,89 @@ __SPIRV_VAR_QUALIFIERS uint32_t __spirv_BuiltInNumSubgroups;
 __SPIRV_VAR_QUALIFIERS uint32_t __spirv_BuiltInSubgroupId;
 __SPIRV_VAR_QUALIFIERS uint32_t __spirv_BuiltInSubgroupLocalInvocationId;
 
-SYCL_EXTERNAL inline size_t __spirv_GlobalInvocationId_x() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_GlobalInvocationId_x() {
   return __spirv_BuiltInGlobalInvocationId.x;
 }
-SYCL_EXTERNAL inline size_t __spirv_GlobalInvocationId_y() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_GlobalInvocationId_y() {
   return __spirv_BuiltInGlobalInvocationId.y;
 }
-SYCL_EXTERNAL inline size_t __spirv_GlobalInvocationId_z() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_GlobalInvocationId_z() {
   return __spirv_BuiltInGlobalInvocationId.z;
 }
 
-SYCL_EXTERNAL inline size_t __spirv_GlobalSize_x() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_GlobalSize_x() {
   return __spirv_BuiltInGlobalSize.x;
 }
-SYCL_EXTERNAL inline size_t __spirv_GlobalSize_y() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_GlobalSize_y() {
   return __spirv_BuiltInGlobalSize.y;
 }
-SYCL_EXTERNAL inline size_t __spirv_GlobalSize_z() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_GlobalSize_z() {
   return __spirv_BuiltInGlobalSize.z;
 }
 
-SYCL_EXTERNAL inline size_t __spirv_GlobalOffset_x() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_GlobalOffset_x() {
   return __spirv_BuiltInGlobalOffset.x;
 }
-SYCL_EXTERNAL inline size_t __spirv_GlobalOffset_y() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_GlobalOffset_y() {
   return __spirv_BuiltInGlobalOffset.y;
 }
-SYCL_EXTERNAL inline size_t __spirv_GlobalOffset_z() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_GlobalOffset_z() {
   return __spirv_BuiltInGlobalOffset.z;
 }
 
-SYCL_EXTERNAL inline size_t __spirv_NumWorkgroups_x() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_NumWorkgroups_x() {
   return __spirv_BuiltInNumWorkgroups.x;
 }
-SYCL_EXTERNAL inline size_t __spirv_NumWorkgroups_y() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_NumWorkgroups_y() {
   return __spirv_BuiltInNumWorkgroups.y;
 }
-SYCL_EXTERNAL inline size_t __spirv_NumWorkgroups_z() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_NumWorkgroups_z() {
   return __spirv_BuiltInNumWorkgroups.z;
 }
 
-SYCL_EXTERNAL inline size_t __spirv_WorkgroupSize_x() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_WorkgroupSize_x() {
   return __spirv_BuiltInWorkgroupSize.x;
 }
-SYCL_EXTERNAL inline size_t __spirv_WorkgroupSize_y() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_WorkgroupSize_y() {
   return __spirv_BuiltInWorkgroupSize.y;
 }
-SYCL_EXTERNAL inline size_t __spirv_WorkgroupSize_z() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_WorkgroupSize_z() {
   return __spirv_BuiltInWorkgroupSize.z;
 }
 
-SYCL_EXTERNAL inline size_t __spirv_WorkgroupId_x() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_WorkgroupId_x() {
   return __spirv_BuiltInWorkgroupId.x;
 }
-SYCL_EXTERNAL inline size_t __spirv_WorkgroupId_y() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_WorkgroupId_y() {
   return __spirv_BuiltInWorkgroupId.y;
 }
-SYCL_EXTERNAL inline size_t __spirv_WorkgroupId_z() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_WorkgroupId_z() {
   return __spirv_BuiltInWorkgroupId.z;
 }
 
-SYCL_EXTERNAL inline size_t __spirv_LocalInvocationId_x() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_LocalInvocationId_x() {
   return __spirv_BuiltInLocalInvocationId.x;
 }
-SYCL_EXTERNAL inline size_t __spirv_LocalInvocationId_y() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_LocalInvocationId_y() {
   return __spirv_BuiltInLocalInvocationId.y;
 }
-SYCL_EXTERNAL inline size_t __spirv_LocalInvocationId_z() {
+__DPCPP_SYCL_EXTERNAL inline size_t __spirv_LocalInvocationId_z() {
   return __spirv_BuiltInLocalInvocationId.z;
 }
 
-SYCL_EXTERNAL inline uint32_t __spirv_SubgroupSize() {
+__DPCPP_SYCL_EXTERNAL inline uint32_t __spirv_SubgroupSize() {
   return __spirv_BuiltInSubgroupSize;
 }
-SYCL_EXTERNAL inline uint32_t __spirv_SubgroupMaxSize() {
+__DPCPP_SYCL_EXTERNAL inline uint32_t __spirv_SubgroupMaxSize() {
   return __spirv_BuiltInSubgroupMaxSize;
 }
-SYCL_EXTERNAL inline uint32_t __spirv_NumSubgroups() {
+__DPCPP_SYCL_EXTERNAL inline uint32_t __spirv_NumSubgroups() {
   return __spirv_BuiltInNumSubgroups;
 }
-SYCL_EXTERNAL inline uint32_t __spirv_SubgroupId() {
+__DPCPP_SYCL_EXTERNAL inline uint32_t __spirv_SubgroupId() {
   return __spirv_BuiltInSubgroupId;
 }
-SYCL_EXTERNAL inline uint32_t __spirv_SubgroupLocalInvocationId() {
+__DPCPP_SYCL_EXTERNAL inline uint32_t __spirv_SubgroupLocalInvocationId() {
   return __spirv_BuiltInSubgroupLocalInvocationId;
 }