[OpenCL] Implement extended subgroups fully in headers

[Anastasia]

Summary

Extended subgroups extensions were added in https://reviews.llvm.org/D79781, however, in the unpublished spec there is no pragma mentioned anywhere and therefore adding it is incorrect. This should be fixed ideally before the spec is published to avoid a wide impact on the developers.

Considering that the extensions are implemented in headers and libraries there is no point to add it into the main Clang code. Therefore the macro definitions are now moved to the internal header. The macros should only be defined if the functionality is available. This makes the flow more consistent for developers as without the header the functions are not declared and therefore any kernel code calling them won't be compiled successfully.

More details about the effort on correcting the extension implementation can be found in: https://reviews.llvm.org/D91531

[svenvh]

LGTM.

[PiotrFusik]

The specification for these extensions was edited by Ben Ashbaugh @Intel. I've asked him about this change.

[Anastasia]

In D92231#2425305, @PiotrFusik wrote:

The specification for these extensions was edited by Ben Ashbaugh @Intel. I've asked him about this change.

Sure. Thanks! Happy to hold off committing for a few days to see if Ben has any feedback.

[Anastasia]

In D92231#2425323, @Anastasia wrote:

In D92231#2425305, @PiotrFusik wrote:

The specification for these extensions was edited by Ben Ashbaugh @Intel. I've asked him about this change.

Sure. Thanks! Happy to hold off committing for a few days to see if Ben has any feedback.

FYI, I have discussed this with Ben offline and he doesn't seem to have any objections on the approach. I will keep this open for another week to see if there is any detailed feedback from anyone.

[PiotrFusik]

clang/lib/Headers/opencl-c-base.h

17–23

These are currently defined as "1": https://godbolt.org/z/MnoWeo
Is the change to blank intentional?
This should be tested.

[Anastasia]

clang/lib/Headers/opencl-c-base.h

17–23

Thanks! I think the spec doesn't specify the values but only says that the macros are defined

Every extension which affects the OpenCL language semantics, syntax or adds built-in functions tothe language must create a preprocessor #define that matches the extension name string. This #define would be available in the language if and only if the extension is supported on a givenimplementation.

However, I think it makes sense to set the value 1 to align with the other extensions that are added by clang.

[PiotrFusik]

clang/lib/Headers/opencl-c-base.h

17–23

I think the spec doesn't specify the values but only says that the macros are defined

Yes, confirmed with Ben:

I don’t think we’ve said anything about the extension #defines, but for the OpenCL C 3.0 feature test macros we required that they are defined to a value for precisely this reason (#if used instead of #ifdef):

In OpenCL C 3.0 or newer, feature macros must expand to the value 1 if the feature macro is defined by the OpenCL C compiler. A feature macro must not be defined if the feature is not supported by the OpenCL C compiler. A feature macro may expand to a different value in the future, but if this occurs the value of the feature macro must compare greater than the prior value of the feature macro.

[Anastasia]

• Set all macros to value 1

[PiotrFusik]

LGTM

[Anastasia]

clang/lib/Headers/opencl-c-base.h

17–23

FYI, OpenCL 3.0 only determines the values for the feature macro but not the extension macro. Perhaps it's worth doing this for both?

clang/include/clang/Basic/OpenCLExtensions.def

 OPENCLEXT_INTERNAL(cl_khr_depth_images, 120, ~0U)
 OPENCLEXT_INTERNAL(cl_khr_gl_msaa_sharing, 120, ~0U)
 
 // OpenCL 2.0.
 OPENCLEXT_INTERNAL(cl_khr_mipmap_image, 200, ~0U)
 OPENCLEXT_INTERNAL(cl_khr_mipmap_image_writes, 200, ~0U)
 OPENCLEXT_INTERNAL(cl_khr_srgb_image_writes, 200, ~0U)
 OPENCLEXT_INTERNAL(cl_khr_subgroups, 200, ~0U)
-OPENCLEXT_INTERNAL(cl_khr_subgroup_extended_types, 200, ~0U)
-OPENCLEXT_INTERNAL(cl_khr_subgroup_non_uniform_vote, 200, ~0U)
-OPENCLEXT_INTERNAL(cl_khr_subgroup_ballot, 200, ~0U)
-OPENCLEXT_INTERNAL(cl_khr_subgroup_non_uniform_arithmetic, 200, ~0U)
-OPENCLEXT_INTERNAL(cl_khr_subgroup_shuffle, 200, ~0U)
-OPENCLEXT_INTERNAL(cl_khr_subgroup_shuffle_relative, 200, ~0U)
-OPENCLEXT_INTERNAL(cl_khr_subgroup_clustered_reduce, 200, ~0U)
 
 // Clang Extensions.
 OPENCLEXT_INTERNAL(cl_clang_storage_class_specifiers, 100, ~0U)
 
 // AMD OpenCL extensions
 OPENCLEXT_INTERNAL(cl_amd_media_ops, 100, ~0U)
 OPENCLEXT_INTERNAL(cl_amd_media_ops2, 100, ~0U)
 

clang/lib/Headers/opencl-c-base.h

 //===----- opencl-c-base.h - OpenCL C language base definitions -----------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _OPENCL_BASE_H_
 #define _OPENCL_BASE_H_
 
+// Define extension macros
+
+#if (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
+// For SPIR all extensions are supported.
+#if defined(__SPIR__)
+#define cl_khr_subgroup_extended_types 1
+#define cl_khr_subgroup_non_uniform_vote 1
+#define cl_khr_subgroup_ballot 1
+#define cl_khr_subgroup_non_uniform_arithmetic 1
+#define cl_khr_subgroup_shuffle 1
+#define cl_khr_subgroup_shuffle_relative 1
+#define cl_khr_subgroup_clustered_reduce 1
+#endif // defined(__SPIR__)
+#endif // (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
+
 // built-in scalar data types:
 
 /**
  * An unsigned 8-bit integer.
  */
 typedef unsigned char uchar;
 
 /**

clang/test/Headers/opencl-c-header.cl

void test_atomics(__generic volatile unsigned int* a) {
   atomic_add(a, 1);
 }
 #endif
 
 // Verify that ATOMIC_VAR_INIT is defined.
 #if defined(__OPENCL_CPP_VERSION__) || (__OPENCL_C_VERSION__ >= CL_VERSION_2_0)
 global atomic_int z = ATOMIC_VAR_INIT(99);
 #endif //__OPENCL_C_VERSION__
+// CHECK-MOD: Reading modules
+
+// Check that extension macros are defined correctly.
 
+// FIXME: this should not be defined for all targets
 // Verify that non-builtin cl_intel_planar_yuv extension is defined from
 // OpenCL 1.2 onwards.
 #if defined(__OPENCL_CPP_VERSION__) || (__OPENCL_C_VERSION__ >= CL_VERSION_1_2)
 // expected-no-diagnostics
 #else //__OPENCL_C_VERSION__
 // expected-warning@+2{{unknown OpenCL extension 'cl_intel_planar_yuv' - ignoring}}
 #endif //__OPENCL_C_VERSION__
 #pragma OPENCL EXTENSION cl_intel_planar_yuv : enable
 
-// CHECK-MOD: Reading modules
+// For SPIR all extensions are supported.
+#if defined(__SPIR__)
+
+#if (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
+
+#if cl_khr_subgroup_extended_types != 1
+#error "Incorrectly defined cl_khr_subgroup_extended_types"
+#endif
+#if cl_khr_subgroup_non_uniform_vote != 1
+#error "Incorrectly defined cl_khr_subgroup_non_uniform_vote"
+#endif
+#if cl_khr_subgroup_ballot != 1
+#error "Incorrectly defined cl_khr_subgroup_ballot"
+#endif
+#if cl_khr_subgroup_non_uniform_arithmetic != 1
+#error "Incorrectly defined cl_khr_subgroup_non_uniform_arithmetic"
+#endif
+#if cl_khr_subgroup_shuffle != 1
+#error "Incorrectly defined cl_khr_subgroup_shuffle"
+#endif
+#if cl_khr_subgroup_shuffle_relative != 1
+#error "Incorrectly defined cl_khr_subgroup_shuffle_relative"
+#endif
+#if cl_khr_subgroup_clustered_reduce != 1
+#error "Incorrectly defined cl_khr_subgroup_clustered_reduce"
+#endif
+
+#else
+
+#ifdef cl_khr_subgroup_extended_types
+#error "Incorrect cl_khr_subgroup_extended_types define"
+#endif
+#ifdef cl_khr_subgroup_non_uniform_vote
+#error "Incorrect cl_khr_subgroup_non_uniform_vote define"
+#endif
+#ifdef cl_khr_subgroup_ballot
+#error "Incorrect cl_khr_subgroup_ballot define"
+#endif
+#ifdef cl_khr_subgroup_non_uniform_arithmetic
+#error "Incorrect cl_khr_subgroup_non_uniform_arithmetic define"
+#endif
+#ifdef cl_khr_subgroup_shuffle
+#error "Incorrect cl_khr_subgroup_shuffle define"
+#endif
+#ifdef cl_khr_subgroup_shuffle_relative
+#error "Incorrect cl_khr_subgroup_shuffle_relative define"
+#endif
+#ifdef cl_khr_subgroup_clustered_reduce
+#error "Incorrect cl_khr_subgroup_clustered_reduce define"
+#endif
+
+#endif //(defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
+
+#endif // defined(__SPIR__)

clang/test/SemaOpenCL/extension-version.cl

 #if (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 120)
 #ifndef cl_intel_device_side_avc_motion_estimation
 #error "Missing cl_intel_device_side_avc_motion_estimation define"
 #endif
 #else
 // expected-warning@+2{{unsupported OpenCL extension 'cl_intel_device_side_avc_motion_estimation' - ignoring}}
 #endif
 #pragma OPENCL EXTENSION cl_intel_device_side_avc_motion_estimation : enable
-
-#if (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
-#ifndef cl_khr_subgroup_extended_types
-#error "Missing cl_khr_subgroup_extended_types"
-#endif
-#else
-#ifdef cl_khr_subgroup_extended_types
-#error "Incorrect cl_khr_subgroup_extended_types define"
-#endif
-// expected-warning@+2{{unsupported OpenCL extension 'cl_khr_subgroup_extended_types' - ignoring}}
-#endif
-#pragma OPENCL EXTENSION cl_khr_subgroup_extended_types : enable
-
-#if (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
-#ifndef cl_khr_subgroup_non_uniform_vote
-#error "Missing cl_khr_subgroup_non_uniform_vote"
-#endif
-#else
-#ifdef cl_khr_subgroup_non_uniform_vote
-#error "Incorrect cl_khr_subgroup_non_uniform_vote define"
-#endif
-// expected-warning@+2{{unsupported OpenCL extension 'cl_khr_subgroup_non_uniform_vote' - ignoring}}
-#endif
-#pragma OPENCL EXTENSION cl_khr_subgroup_non_uniform_vote : enable
-
-#if (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
-#ifndef cl_khr_subgroup_ballot
-#error "Missing cl_khr_subgroup_ballot"
-#endif
-#else
-#ifdef cl_khr_subgroup_ballot
-#error "Incorrect cl_khr_subgroup_ballot define"
-#endif
-// expected-warning@+2{{unsupported OpenCL extension 'cl_khr_subgroup_ballot' - ignoring}}
-#endif
-#pragma OPENCL EXTENSION cl_khr_subgroup_ballot : enable
-
-#if (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
-#ifndef cl_khr_subgroup_non_uniform_arithmetic
-#error "Missing cl_khr_subgroup_non_uniform_arithmetic"
-#endif
-#else
-#ifdef cl_khr_subgroup_non_uniform_arithmetic
-#error "Incorrect cl_khr_subgroup_non_uniform_arithmetic define"
-#endif
-// expected-warning@+2{{unsupported OpenCL extension 'cl_khr_subgroup_non_uniform_arithmetic' - ignoring}}
-#endif
-#pragma OPENCL EXTENSION cl_khr_subgroup_non_uniform_arithmetic : enable
-
-#if (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
-#ifndef cl_khr_subgroup_shuffle
-#error "Missing cl_khr_subgroup_shuffle"
-#endif
-#else
-#ifdef cl_khr_subgroup_shuffle
-#error "Incorrect cl_khr_subgroup_shuffle define"
-#endif
-// expected-warning@+2{{unsupported OpenCL extension 'cl_khr_subgroup_shuffle' - ignoring}}
-#endif
-#pragma OPENCL EXTENSION cl_khr_subgroup_shuffle : enable
-
-#if (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
-#ifndef cl_khr_subgroup_shuffle_relative
-#error "Missing cl_khr_subgroup_shuffle_relative"
-#endif
-#else
-#ifdef cl_khr_subgroup_shuffle_relative
-#error "Incorrect cl_khr_subgroup_shuffle_relative define"
-#endif
-// expected-warning@+2{{unsupported OpenCL extension 'cl_khr_subgroup_shuffle_relative' - ignoring}}
-#endif
-#pragma OPENCL EXTENSION cl_khr_subgroup_shuffle_relative : enable
-
-#if (defined(__OPENCL_CPP_VERSION__) || __OPENCL_C_VERSION__ >= 200)
-#ifndef cl_khr_subgroup_clustered_reduce
-#error "Missing cl_khr_subgroup_clustered_reduce"
-#endif
-#else
-#ifdef cl_khr_subgroup_clustered_reduce
-#error "Incorrect cl_khr_subgroup_clustered_reduce define"
-#endif
-// expected-warning@+2{{unsupported OpenCL extension 'cl_khr_subgroup_clustered_reduce' - ignoring}}
-#endif
-#pragma OPENCL EXTENSION cl_khr_subgroup_clustered_reduce : enable
-