[OpenCL] Add clang extension for variadic functions.

Anastasia Stulova · Anastasia Stulova · commit 0e874fc014be · 2021-01-06T20:39:57.000Z
With the internal clang extension '__cl_clang_variadic_functions' variadic functions are accepted by the frontend. This is not a fully supported vendor/Khronos extension as it can only be used on targets with variadic prototype support or in metaprogramming to represent functions with generic prototype without calling such functions in the kernel code. Tags: #clang Differential Revision: https://reviews.llvm.org/D94027
diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
@@ -1773,6 +1773,31 @@ correctly in any circumstances. It can be used if:
     void (*fp)(); // error - pointers to function are not allowed
   }
 
+``__cl_clang_variadic_functions``
+---------------------------------
+
+With this extension it is possible to enable variadic arguments in functions
+using regular OpenCL extension pragma mechanism detailed in `the OpenCL
+Extension Specification, section 1.2
+<https://www.khronos.org/registry/OpenCL/specs/3.0-unified/html/OpenCL_Ext.html#extensions-overview>`_.
+
+This is not conformant behavior and it can only be used portably when the
+functions with variadic prototypes do not get generated in binary e.g. the
+variadic prototype is used to spesify a function type with any number of
+arguments in metaprogramming algorithms in C++ for OpenCL.
+
+This extensions can also be used when the kernel code is intended for targets
+supporting the variadic arguments e.g. majority of CPU targets.
+
+**Example of Use**:
+
+.. code-block:: c++
+
+  #pragma OPENCL EXTENSION __cl_clang_variadic_functions : enable
+  void foo(int a, ...); // compiled - no diagnostic generated
+
+  #pragma OPENCL EXTENSION __cl_clang_variadic_functions : disable
+  void bar(int a, ...); // error - variadic prototype is not allowed
 
 Builtin Functions
 =================
diff --git a/clang/include/clang/Basic/OpenCLExtensions.def b/clang/include/clang/Basic/OpenCLExtensions.def
@@ -70,6 +70,7 @@ OPENCLEXT_INTERNAL(cl_khr_subgroups, 200, ~0U)
 // Clang Extensions.
 OPENCLEXT_INTERNAL(cl_clang_storage_class_specifiers, 100, ~0U)
 OPENCLEXT_INTERNAL(__cl_clang_function_pointers, 100, ~0U)
+OPENCLEXT_INTERNAL(__cl_clang_variadic_functions, 100, ~0U)
 
 // AMD OpenCL extensions
 OPENCLEXT_INTERNAL(cl_amd_media_ops, 100, ~0U)
diff --git a/clang/lib/Basic/Targets/AMDGPU.h b/clang/lib/Basic/Targets/AMDGPU.h
@@ -286,6 +286,7 @@ class LLVM_LIBRARY_VISIBILITY AMDGPUTargetInfo final : public TargetInfo {
     auto &Opts = getSupportedOpenCLOpts();
     Opts.support("cl_clang_storage_class_specifiers");
     Opts.support("__cl_clang_function_pointers");
+    Opts.support("__cl_clang_variadic_functions");
 
     bool IsAMDGCN = isAMDGCN(getTriple());
 
diff --git a/clang/lib/Basic/Targets/NVPTX.h b/clang/lib/Basic/Targets/NVPTX.h
@@ -129,6 +129,7 @@ class LLVM_LIBRARY_VISIBILITY NVPTXTargetInfo : public TargetInfo {
     auto &Opts = getSupportedOpenCLOpts();
     Opts.support("cl_clang_storage_class_specifiers");
     Opts.support("__cl_clang_function_pointers");
+    Opts.support("__cl_clang_variadic_functions");
 
     Opts.support("cl_khr_fp64");
     Opts.support("cl_khr_byte_addressable_store");
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
@@ -5019,6 +5019,7 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state,
         // (s6.9.e and s6.12.5 OpenCL v2.0) except for printf.
         // We also allow here any toolchain reserved identifiers.
         if (FTI.isVariadic &&
+            !S.getOpenCLOptions().isEnabled("__cl_clang_variadic_functions") &&
             !(D.getIdentifier() &&
               ((D.getIdentifier()->getName() == "printf" &&
                 (LangOpts.OpenCLCPlusPlus || LangOpts.OpenCLVersion >= 120)) ||
diff --git a/clang/test/Misc/amdgcn.languageOptsOpenCL.cl b/clang/test/Misc/amdgcn.languageOptsOpenCL.cl
@@ -19,6 +19,11 @@
 #endif
 #pragma OPENCL EXTENSION __cl_clang_function_pointers : enable
 
+#ifndef __cl_clang_variadic_functions
+#error "Missing __cl_clang_variadic_functions define"
+#endif
+#pragma OPENCL EXTENSION __cl_clang_variadic_functions : enable
+
 #ifndef cl_khr_fp16
 #error "Missing cl_khr_fp16 define"
 #endif
diff --git a/clang/test/Misc/nvptx.languageOptsOpenCL.cl b/clang/test/Misc/nvptx.languageOptsOpenCL.cl
@@ -27,6 +27,11 @@
 #endif
 #pragma OPENCL EXTENSION __cl_clang_function_pointers : enable
 
+#ifndef __cl_clang_variadic_functions
+#error "Missing __cl_clang_variadic_functions define"
+#endif
+#pragma OPENCL EXTENSION __cl_clang_variadic_functions : enable
+
 #ifdef cl_khr_fp16
 #error "Incorrect cl_khr_fp16 define"
 #endif
diff --git a/clang/test/Misc/r600.languageOptsOpenCL.cl b/clang/test/Misc/r600.languageOptsOpenCL.cl
@@ -35,6 +35,11 @@
 #endif
 #pragma OPENCL EXTENSION __cl_clang_function_pointers : enable
 
+#ifndef __cl_clang_variadic_functions
+#error "Missing __cl_clang_variadic_functions define"
+#endif
+#pragma OPENCL EXTENSION __cl_clang_variadic_functions : enable
+
 #ifdef cl_khr_fp16
 #error "Incorrect cl_khr_fp16 define"
 #endif
diff --git a/clang/test/SemaOpenCL/extension-version.cl b/clang/test/SemaOpenCL/extension-version.cl
@@ -24,6 +24,11 @@
 #endif
 #pragma OPENCL EXTENSION __cl_clang_function_pointers : enable
 
+#ifndef __cl_clang_variadic_functions
+#error "Missing __cl_clang_variadic_functions define"
+#endif
+#pragma OPENCL EXTENSION __cl_clang_variadic_functions : enable
+
 #ifndef cl_khr_fp16
 #error "Missing cl_khr_fp16 define"
 #endif
diff --git a/clang/test/SemaOpenCL/func.cl b/clang/test/SemaOpenCL/func.cl
@@ -1,18 +1,31 @@
 // RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -triple spir-unknown-unknown
 // RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -triple spir-unknown-unknown -DFUNCPTREXT
+// RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -triple spir-unknown-unknown -DVARARG
 
 #ifdef FUNCPTREXT
 #pragma OPENCL EXTENSION __cl_clang_function_pointers : enable
 #endif
+#ifdef VARARGEXT
+#pragma OPENCL EXTENSION __cl_clang_variadic_functions : enable
+#endif
 
 // Variadic functions
-void vararg_f(int, ...);                    // expected-error {{invalid prototype, variadic arguments are not allowed in OpenCL}}
+void vararg_f(int, ...);
+#ifndef VARARGEXT
+// expected-error@-2 {{invalid prototype, variadic arguments are not allowed in OpenCL}}
+#endif
 void __vararg_f(int, ...);
-typedef void (*vararg_fptr_t)(int, ...);    // expected-error {{invalid prototype, variadic arguments are not allowed in OpenCL}}
+typedef void (*vararg_fptr_t)(int, ...);
+#ifndef VARARGEXT
+// expected-error@-2 {{invalid prototype, variadic arguments are not allowed in OpenCL}}
+#endif
 #ifndef FUNCPTREXT
-// expected-error@-2 {{pointers to functions are not allowed}}
+// expected-error@-5 {{pointers to functions are not allowed}}
+#endif
+int printf(__constant const char *st, ...);
+#ifndef VARARGEXT
+// expected-error@-2 {{invalid prototype, variadic arguments are not allowed in OpenCL}}
 #endif
-int printf(__constant const char *st, ...); // expected-error {{invalid prototype, variadic arguments are not allowed in OpenCL}}
 
 // Struct type with function pointer field
 typedef struct s
