Anastasia created this revision.
Anastasia added reviewers: svenvh, olestrohm.
Herald added subscribers: ebevhan, kerbowa, yaxunl, nhaehnle, jvesely,
jholewinski.
Anastasia requested review of this revision.
Bitfields result in struct/union layout that is implementation dependent and
therefore it was excluded from OpenCL originally for portability reasons. In
kernel prameters use of bitfields can result in functionality issues.
However, use of bitfields has been desirable feature for some applications,
there was a discussion about allowing this in the next standards
(https://github.com/KhronosGroup/OpenCL-Docs/issues/301) but regardless to that
clang can expose this functionality as a compiler extension for the application
that can take advanatge of it at the price of reduced portability.
This addresses PR45339!
https://reviews.llvm.org/D101843
Files:
clang/docs/LanguageExtensions.rst
clang/include/clang/Basic/OpenCLExtensions.def
clang/lib/Basic/Targets/AMDGPU.h
clang/lib/Basic/Targets/NVPTX.h
clang/lib/Sema/SemaDecl.cpp
clang/test/Misc/amdgcn.languageOptsOpenCL.cl
clang/test/Misc/nvptx.languageOptsOpenCL.cl
clang/test/Misc/r600.languageOptsOpenCL.cl
clang/test/SemaOpenCL/unsupported.cl
Index: clang/test/SemaOpenCL/unsupported.cl
===================================================================
--- clang/test/SemaOpenCL/unsupported.cl
+++ clang/test/SemaOpenCL/unsupported.cl
@@ -1,7 +1,15 @@
// RUN: %clang_cc1 -verify %s
+// RUN: %clang_cc1 -verify %s -DBITFIELDS_EXT
-struct {
- int a : 1; // expected-error {{bit-fields are not supported in OpenCL}}
+#ifdef BITFIELDS_EXT
+#pragma OPENCL EXTENSION __cl_clang_bitfields : enable
+#endif
+
+struct test {
+ int a : 1;
+#ifndef BITFIELDS_EXT
+// expected-error@-2 {{bit-fields are not supported in OpenCL}}
+#endif
};
void no_vla(int n) {
Index: clang/test/Misc/r600.languageOptsOpenCL.cl
===================================================================
--- clang/test/Misc/r600.languageOptsOpenCL.cl
+++ clang/test/Misc/r600.languageOptsOpenCL.cl
@@ -34,6 +34,11 @@
#endif
#pragma OPENCL EXTENSION __cl_clang_variadic_functions : enable
+#ifndef __cl_clang_bitfields
+#error "Missing __cl_clang_bitfields define"
+#endif
+#pragma OPENCL EXTENSION __cl_clang_bitfields : enable
+
#ifdef cl_khr_fp16
#error "Incorrect cl_khr_fp16 define"
#endif
Index: clang/test/Misc/nvptx.languageOptsOpenCL.cl
===================================================================
--- clang/test/Misc/nvptx.languageOptsOpenCL.cl
+++ clang/test/Misc/nvptx.languageOptsOpenCL.cl
@@ -28,6 +28,11 @@
#endif
#pragma OPENCL EXTENSION __cl_clang_variadic_functions : enable
+#ifndef __cl_clang_bitfields
+#error "Missing __cl_clang_bitfields define"
+#endif
+#pragma OPENCL EXTENSION __cl_clang_bitfields : enable
+
#ifdef cl_khr_fp16
#error "Incorrect cl_khr_fp16 define"
#endif
Index: clang/test/Misc/amdgcn.languageOptsOpenCL.cl
===================================================================
--- clang/test/Misc/amdgcn.languageOptsOpenCL.cl
+++ clang/test/Misc/amdgcn.languageOptsOpenCL.cl
@@ -24,6 +24,11 @@
#endif
#pragma OPENCL EXTENSION __cl_clang_variadic_functions : enable
+#ifndef __cl_clang_bitfields
+#error "Missing __cl_clang_bitfields define"
+#endif
+#pragma OPENCL EXTENSION __cl_clang_bitfields : enable
+
#ifndef cl_khr_fp16
#error "Missing cl_khr_fp16 define"
#endif
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -16796,7 +16796,8 @@
InvalidDecl = true;
}
// OpenCL v1.2 s6.9.c: bitfields are not supported.
- if (BitWidth) {
+ if (BitWidth && !getOpenCLOptions().isAvailableOption(
+ "__cl_clang_bitfields", LangOpts)) {
Diag(Loc, diag::err_opencl_bitfields);
InvalidDecl = true;
}
Index: clang/lib/Basic/Targets/NVPTX.h
===================================================================
--- clang/lib/Basic/Targets/NVPTX.h
+++ clang/lib/Basic/Targets/NVPTX.h
@@ -133,6 +133,7 @@
Opts["cl_clang_storage_class_specifiers"] = true;
Opts["__cl_clang_function_pointers"] = true;
Opts["__cl_clang_variadic_functions"] = true;
+ Opts["__cl_clang_bitfields"] = true;
Opts["cl_khr_fp64"] = true;
Opts["cl_khr_byte_addressable_store"] = true;
Index: clang/lib/Basic/Targets/AMDGPU.h
===================================================================
--- clang/lib/Basic/Targets/AMDGPU.h
+++ clang/lib/Basic/Targets/AMDGPU.h
@@ -287,6 +287,7 @@
Opts["cl_clang_storage_class_specifiers"] = true;
Opts["__cl_clang_variadic_functions"] = true;
Opts["__cl_clang_function_pointers"] = true;
+ Opts["__cl_clang_bitfields"] = true;
bool IsAMDGCN = isAMDGCN(getTriple());
Index: clang/include/clang/Basic/OpenCLExtensions.def
===================================================================
--- clang/include/clang/Basic/OpenCLExtensions.def
+++ clang/include/clang/Basic/OpenCLExtensions.def
@@ -87,6 +87,7 @@
OPENCL_EXTENSION(cl_clang_storage_class_specifiers, true, 100)
OPENCL_EXTENSION(__cl_clang_function_pointers, true, 100)
OPENCL_EXTENSION(__cl_clang_variadic_functions, true, 100)
+OPENCL_EXTENSION(__cl_clang_bitfields, true, 100)
// AMD OpenCL extensions
OPENCL_EXTENSION(cl_amd_media_ops, true, 100)
Index: clang/docs/LanguageExtensions.rst
===================================================================
--- clang/docs/LanguageExtensions.rst
+++ clang/docs/LanguageExtensions.rst
@@ -1741,6 +1741,34 @@
Clang supports internal OpenCL extensions documented below.
+``__cl_clang_bitfields``
+--------------------------------
+
+With this extension it is possible to enable bitfields in structs
+or unions 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>`_.
+
+Use of bitfields in OpenCL kernels can result in reduced portability as struct
+layout is not guaranteed to be consistent when compiled by different compilers.
+If structs with bitfields are used as kernel function parameters, it can result
+in incorrect functionality when the layout is different between the host and
+device code.
+
+**Example of Use**:
+
+.. code-block:: c++
+
+ #pragma OPENCL EXTENSION __cl_clang_bitfields : enable
+ struct with_bitfield {
+ unsigned int i : 5; // compiled - no diagnostic generated
+ };
+
+ #pragma OPENCL EXTENSION __cl_clang_bitfields : disable
+ struct without_bitfield {
+ unsigned int i : 5; // error - bitfields are not supported
+ };
+
``__cl_clang_function_pointers``
--------------------------------
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
