Implementation design for “device_if” and “device_architecture”¶
This document describes the design for the DPC++ implementation of the sycl_ext_oneapi_device_if and sycl_ext_oneapi_device_architecture extensions.
Phased implementation¶
The implementation is divided into two phases. In the first phase, we support only sycl_ext_oneapi_device_architecture and it is supported only in AOT mode. The second phase adds support for both extensions in both AOT and JIT modes.
Changes to compiler driver¶
Both phases require changes to the -fsycl-targets
option that is recognized
by the compiler driver. The problem is that the current form of that option
does not identify a specific device name. As a reminder, the current command
line for AOT compilation on GPU looks like this:
$ clang++ -fsycl -fsycl-targets=spir64_gen -Xs "-device skl" ...
Notice that -fsycl-targets
option specifies only the generic name
spir64_gen
whereas the device name is passed directly to ocloc
(the Intel
GPU AOT compiler) via -Xs "-device skl"
. Since the compiler driver merely
passes the -Xs
options directly to the underlying ocloc
without
understanding them, the compiler driver does not currently know the target
device(s) of the AOT compilation.
To fix this, the -fsycl-targets
option should be changed to accept the
following GPU device names in addition to the target names it currently
recognizes:
intel_gpu_bdw
intel_gpu_skl
intel_gpu_kbl
intel_gpu_cfl
intel_gpu_apl
intel_gpu_glk
intel_gpu_whl
intel_gpu_aml
intel_gpu_cml
intel_gpu_icllp
intel_gpu_tgllp
intel_gpu_rkl
intel_gpu_adl_s
intel_gpu_rpl_s
intel_gpu_adl_p
intel_gpu_adl_n
intel_gpu_dg1
intel_gpu_acm_g10
intel_gpu_acm_g11
intel_gpu_acm_g12
intel_gpu_pvc
intel_gpu_8_0_0
(alias forintel_gpu_bdw
)intel_gpu_9_0_9
(alias forintel_gpu_skl
)intel_gpu_9_1_9
(alias forintel_gpu_kbl
)intel_gpu_9_2_9
(alias forintel_gpu_cfl
)intel_gpu_9_3_0
(alias forintel_gpu_apl
)intel_gpu_9_4_0
(alias forintel_gpu_glk
)intel_gpu_9_5_0
(alias forintel_gpu_whl
)intel_gpu_9_6_0
(alias forintel_gpu_aml
)intel_gpu_9_7_0
(alias forintel_gpu_cml
)intel_gpu_11_0_0
(alias forintel_gpu_icllp
)intel_gpu_12_0_0
(alias forintel_gpu_tgllp
)intel_gpu_12_10_0
(alias forintel_gpu_dg1
)nvidia_gpu_sm_50
nvidia_gpu_sm_52
nvidia_gpu_sm_53
nvidia_gpu_sm_60
nvidia_gpu_sm_61
nvidia_gpu_sm_62
nvidia_gpu_sm_70
nvidia_gpu_sm_72
nvidia_gpu_sm_75
nvidia_gpu_sm_80
nvidia_gpu_sm_86
nvidia_gpu_sm_87
nvidia_gpu_sm_89
nvidia_gpu_sm_90
amd_gpu_gfx700
amd_gpu_gfx701
amd_gpu_gfx702
amd_gpu_gfx801
amd_gpu_gfx802
amd_gpu_gfx803
amd_gpu_gfx805
amd_gpu_gfx810
amd_gpu_gfx900
amd_gpu_gfx902
amd_gpu_gfx904
amd_gpu_gfx906
amd_gpu_gfx908
amd_gpu_gfx909
amd_gpu_gfx90a
amd_gpu_gfx90c
amd_gpu_gfx940
amd_gpu_gfx941
amd_gpu_gfx942
amd_gpu_gfx1010
amd_gpu_gfx1011
amd_gpu_gfx1012
amd_gpu_gfx1013
amd_gpu_gfx1030
amd_gpu_gfx1031
amd_gpu_gfx1032
amd_gpu_gfx1033
amd_gpu_gfx1034
amd_gpu_gfx1035
amd_gpu_gfx1036
amd_gpu_gfx1100
amd_gpu_gfx1101
amd_gpu_gfx1102
amd_gpu_gfx1103
amd_gpu_gfx1150
amd_gpu_gfx1151
amd_gpu_gfx1200
amd_gpu_gfx1201
The above listed device names may not be mixed with the existing target name
spir64_gen
on the same command line. In addition, the user must not pass the
-device
option to ocloc
via -Xs
or related command line options because
the compiler driver will pass this option to ocloc
automatically.
Note that in the first phase of implementation, only one of the above listed GPU device names may appear on the command line. As a result, the first phase of implementation supports AOT compilation in this new mode only for a single GPU device.
Phase 1¶
The first phase requires changes only to the compiler driver and to the device headers.
Compiler driver macro predefines¶
Most of the changes to the compiler driver are described above, but there are
a few small additional changes that are specific to phase 1. If the user
invokes the compiler driver with -fsycl-targets=<device>
where <device>
is
one of the GPU device names listed above, the compiler driver must predefine
one of the following corresponding C++ macro names:
__SYCL_TARGET_INTEL_GPU_BDW__
__SYCL_TARGET_INTEL_GPU_SKL__
__SYCL_TARGET_INTEL_GPU_KBL__
__SYCL_TARGET_INTEL_GPU_CFL__
__SYCL_TARGET_INTEL_GPU_APL__
__SYCL_TARGET_INTEL_GPU_GLK__
__SYCL_TARGET_INTEL_GPU_WHL__
__SYCL_TARGET_INTEL_GPU_AML__
__SYCL_TARGET_INTEL_GPU_CML__
__SYCL_TARGET_INTEL_GPU_ICLLP__
__SYCL_TARGET_INTEL_GPU_TGLLP__
__SYCL_TARGET_INTEL_GPU_RKL__
__SYCL_TARGET_INTEL_GPU_ADL_S__
__SYCL_TARGET_INTEL_GPU_RPL_S__
__SYCL_TARGET_INTEL_GPU_ADL_P__
__SYCL_TARGET_INTEL_GPU_ADL_N__
__SYCL_TARGET_INTEL_GPU_DG1__
__SYCL_TARGET_INTEL_GPU_ACM_G10__
__SYCL_TARGET_INTEL_GPU_ACM_G11__
__SYCL_TARGET_INTEL_GPU_ACM_G12__
__SYCL_TARGET_INTEL_GPU_PVC__
__SYCL_TARGET_NVIDIA_GPU_SM50__
__SYCL_TARGET_NVIDIA_GPU_SM52__
__SYCL_TARGET_NVIDIA_GPU_SM53__
__SYCL_TARGET_NVIDIA_GPU_SM60__
__SYCL_TARGET_NVIDIA_GPU_SM61__
__SYCL_TARGET_NVIDIA_GPU_SM62__
__SYCL_TARGET_NVIDIA_GPU_SM70__
__SYCL_TARGET_NVIDIA_GPU_SM72__
__SYCL_TARGET_NVIDIA_GPU_SM75__
__SYCL_TARGET_NVIDIA_GPU_SM80__
__SYCL_TARGET_NVIDIA_GPU_SM86__
__SYCL_TARGET_NVIDIA_GPU_SM87__
__SYCL_TARGET_NVIDIA_GPU_SM89__
__SYCL_TARGET_NVIDIA_GPU_SM90__
__SYCL_TARGET_NVIDIA_GPU_SM90A__
__SYCL_TARGET_AMD_GPU_GFX700__
__SYCL_TARGET_AMD_GPU_GFX701__
__SYCL_TARGET_AMD_GPU_GFX702__
__SYCL_TARGET_AMD_GPU_GFX801__
__SYCL_TARGET_AMD_GPU_GFX802__
__SYCL_TARGET_AMD_GPU_GFX803__
__SYCL_TARGET_AMD_GPU_GFX805__
__SYCL_TARGET_AMD_GPU_GFX810__
__SYCL_TARGET_AMD_GPU_GFX900__
__SYCL_TARGET_AMD_GPU_GFX902__
__SYCL_TARGET_AMD_GPU_GFX904__
__SYCL_TARGET_AMD_GPU_GFX906__
__SYCL_TARGET_AMD_GPU_GFX908__
__SYCL_TARGET_AMD_GPU_GFX909__
__SYCL_TARGET_AMD_GPU_GFX90A__
__SYCL_TARGET_AMD_GPU_GFX90C__
__SYCL_TARGET_AMD_GPU_GFX940__
__SYCL_TARGET_AMD_GPU_GFX941__
__SYCL_TARGET_AMD_GPU_GFX942__
__SYCL_TARGET_AMD_GPU_GFX1010__
__SYCL_TARGET_AMD_GPU_GFX1011__
__SYCL_TARGET_AMD_GPU_GFX1012__
__SYCL_TARGET_AMD_GPU_GFX1013__
__SYCL_TARGET_AMD_GPU_GFX1030__
__SYCL_TARGET_AMD_GPU_GFX1031__
__SYCL_TARGET_AMD_GPU_GFX1032__
__SYCL_TARGET_AMD_GPU_GFX1033__
__SYCL_TARGET_AMD_GPU_GFX1034__
__SYCL_TARGET_AMD_GPU_GFX1035__
__SYCL_TARGET_AMD_GPU_GFX1036__
__SYCL_TARGET_AMD_GPU_GFX1100__
__SYCL_TARGET_AMD_GPU_GFX1101__
__SYCL_TARGET_AMD_GPU_GFX1102__
__SYCL_TARGET_AMD_GPU_GFX1103__
__SYCL_TARGET_AMD_GPU_GFX1150__
__SYCL_TARGET_AMD_GPU_GFX1151__
__SYCL_TARGET_AMD_GPU_GFX1200__
__SYCL_TARGET_AMD_GPU_GFX1201__
If the user invokes the compiler driver with -fsycl-targets=spir64_x86_64
,
the compiler driver must predefine the following C++ macro name:
__SYCL_TARGET_INTEL_X86_64__
These macros are an internal implementation detail, so they should not be documented to users, and user code should not make use of them.
Changes to the device headers¶
The device headers implement the sycl_ext_oneapi_device_architecture
extension using these predefined macros and leverage if constexpr
to discard
statements in the “if” or “else” body when the device does not match one of the
listed architectures. The following code snippet illustrates the technique:
namespace sycl {
namespace ext::oneapi::experimental {
enum class architecture {
x86_64,
intel_gpu_bdw,
intel_gpu_skl,
intel_gpu_kbl
// ...
};
} // namespace ext::oneapi::experimental
namespace detail {
#ifndef __SYCL_TARGET_INTEL_X86_64__
#define __SYCL_TARGET_INTEL_X86_64__ 0
#endif
#ifndef __SYCL_TARGET_INTEL_GPU_BDW__
#define __SYCL_TARGET_INTEL_GPU_BDW__ 0
#endif
#ifndef __SYCL_TARGET_INTEL_GPU_SKL__
#define __SYCL_TARGET_INTEL_GPU_SKL__ 0
#endif
#ifndef __SYCL_TARGET_INTEL_GPU_KBL__
#define __SYCL_TARGET_INTEL_GPU_KBL__ 0
#endif
// ...
// This is true when the translation unit is compiled in AOT mode with target
// names that supports the "if_architecture_is" features. If an unsupported
// target name is specified via "-fsycl-targets", the associated invocation of
// the device compiler will set this variable to false, and that will trigger
// an error for code that uses "if_architecture_is".
static constexpr bool is_allowable_aot_mode =
(__SYCL_TARGET_INTEL_X86_64__ == 1) ||
(__SYCL_TARGET_INTEL_GPU_BDW__ == 1) ||
(__SYCL_TARGET_INTEL_GPU_SKL__ == 1) ||
(__SYCL_TARGET_INTEL_GPU_KBL__ == 1)
// ...
;
// One entry for each enumerator in "architecture" telling whether the AOT
// target matches that architecture.
static constexpr bool is_aot_for_architecture[] = {
(__SYCL_TARGET_INTEL_X86_64__ == 1),
(__SYCL_TARGET_INTEL_GPU_BDW__ == 1),
(__SYCL_TARGET_INTEL_GPU_SKL__ == 1),
(__SYCL_TARGET_INTEL_GPU_KBL__ == 1)
// ...
};
// Read the value of "is_allowable_aot_mode" via a template to defer triggering
// static_assert() until template instantiation time.
template<ext::oneapi::experimental::architecture... Archs>
constexpr static bool allowable_aot_mode() {
return is_allowable_aot_mode;
}
// Tells if the current device has one of the architectures in the parameter
// pack.
template<ext::oneapi::experimental::architecture... Archs>
constexpr static bool device_architecture_is() {
return (is_aot_for_architecture[static_cast<int>(Archs)] || ...);
}
// Helper object used to implement "else_if_architecture_is" and "otherwise".
// The "MakeCall" template parameter tells whether a previous clause in the
// "if-elseif-elseif ..." chain was true. When "MakeCall" is false, some
// previous clause was true, so none of the subsequent
// "else_if_architecture_is" or "otherwise" member functions should call the
// user's function.
template<bool MakeCall>
class if_architecture_helper {
public:
template<ext::oneapi::experimental::architecture ...Archs, typename T>
constexpr auto else_if_architecture_is(T fnTrue) {
if constexpr (MakeCall && device_architecture_is<Archs...>()) {
fnTrue();
return if_architecture_helper<false>{};
} else {
return if_architecture_helper<MakeCall>{};
}
}
template<typename T>
constexpr void otherwise(T fn) {
if constexpr (MakeCall) {
fn();
}
}
};
} // namespace detail
namespace ext::oneapi::experimental {
template<architecture ...Archs, typename T>
constexpr static auto if_architecture_is(T fnTrue) {
static_assert(detail::allowable_aot_mode<Archs...>(),
"The if_architecture_is function may only be used when AOT "
"compiling with '-fsycl-targets=spir64_x86_64' or "
"'-fsycl-targets=intel_gpu_*'");
if constexpr (detail::device_architecture_is<Archs...>()) {
fnTrue();
return detail::if_architecture_helper<false>{};
} else {
return detail::if_architecture_helper<true>{};
}
}
} // namespace ext::oneapi::experimental
} // namespace sycl
Analysis of error checking for unsupported AOT modes¶
The header file code presented above triggers a static_assert
if the
if_architecture_is
function is used in a translation unit that is compiled
for an unsupported target. The supported targets are spir64_x86_64
,
the new intel_gpu_*
, nvidia_gpu_*
and amd_gpu_*
GPU device names.
The error checking relies on the fact that the device compiler is invoked
separately for each target listed in -fsycl-target
. If any target is
unsupported, the associated device compilation will compute
is_allowable_aot_mode
as false
, and this will trigger the static_assert
in that compilation phase.
Phase 2¶
TBD.