Dependencies
OpenCL 1.2 and support for cl_intel_subgroups is required.
This extension is written against version 8 of the cl_intel_subgroups specification.
This extension interacts with the cl_intel_subgroups_char, cl_intel_subgroups_short, cl_intel_subgroups_long, and cl_intel_spirv_subgroups extensions.
This extension requires OpenCL support for SPIR-V, either via OpenCL 2.1 or newer, or via the cl_khr_il_program extension.
Overview
This extension extends the subgroup block read and write functions defined by cl_intel_subgroups (and, when supported, cl_intel_subgroups_char, cl_intel_subgroups_short, and cl_intel_subgroups_long) to support reading from and writing to pointers to the __local memory address space in addition to pointers to the __global memory address space.
New OpenCL C Functions
Add variants of the uint subgroup block read and write functions that support loading from and storing to pointers to the __local address space:
uint intel_sub_group_block_read_ui( const __local uint* p )
uint2 intel_sub_group_block_read_ui2( const __local uint* p )
uint4 intel_sub_group_block_read_ui4( const __local uint* p )
uint8 intel_sub_group_block_read_ui8( const __local uint* p )
void intel_sub_group_block_write_ui( __local uint* p, uint data )
void intel_sub_group_block_write_ui2( __local uint* p, uint2 data )
void intel_sub_group_block_write_ui4( __local uint* p, uint4 data )
void intel_sub_group_block_write_ui8( __local uint* p, uint8 data )For naming consistency, also add un-suffixed aliases of the uint functions as originally described in the cl_intel_subgroups extension:
uint intel_sub_group_block_read( const __local uint* p )
uint2 intel_sub_group_block_read2( const __local uint* p )
uint4 intel_sub_group_block_read4( const __local uint* p )
uint8 intel_sub_group_block_read8( const __local uint* p )
void intel_sub_group_block_write( __local uint* p, uint data )
void intel_sub_group_block_write2( __local uint* p, uint2 data )
void intel_sub_group_block_write4( __local uint* p, uint4 data )
void intel_sub_group_block_write8( __local uint* p, uint8 data )If cl_intel_subgroups_char is supported, add variants of the uchar subgroup block read and write functions that support loading from and storing to pointers to the __local address space:
uchar intel_sub_group_block_read_uc( const __local uchar* p )
uchar2 intel_sub_group_block_read_uc2( const __local uchar* p )
uchar4 intel_sub_group_block_read_uc4( const __local uchar* p )
uchar8 intel_sub_group_block_read_uc8( const __local uchar* p )
uchar16 intel_sub_group_block_read_uc16( const __local uchar* p )
void intel_sub_group_block_write_uc( __local uchar* p, uchar data )
void intel_sub_group_block_write_uc2( __local uchar* p, uchar2 data )
void intel_sub_group_block_write_uc4( __local uchar* p, uchar4 data )
void intel_sub_group_block_write_uc8( __local uchar* p, uchar8 data )
void intel_sub_group_block_write_uc16( __local uchar* p, uchar16 data )If cl_intel_subgroups_short is supported, add variants of the ushort subgroup block read and write functions that support loading from and storing to pointers to the __local address space:
ushort intel_sub_group_block_read_us( const __local ushort* p )
ushort2 intel_sub_group_block_read_us2( const __local ushort* p )
ushort4 intel_sub_group_block_read_us4( const __local ushort* p )
ushort8 intel_sub_group_block_read_us8( const __local ushort* p )
void intel_sub_group_block_write_us( __local ushort* p, ushort data )
void intel_sub_group_block_write_us2( __local ushort* p, ushort2 data )
void intel_sub_group_block_write_us4( __local ushort* p, ushort4 data )
void intel_sub_group_block_write_us8( __local ushort* p, ushort8 data )If cl_intel_subgroups_long is supported, add variants of the ulong subgroup block read and write functions that support loading from and storing to pointers to the __local address space:
ulong intel_sub_group_block_read_ul( const __local ulong* p )
ulong2 intel_sub_group_block_read_ul2( const __local ulong* p )
ulong4 intel_sub_group_block_read_ul4( const __local ulong* p )
ulong8 intel_sub_group_block_read_ul8( const __local ulong* p )
void intel_sub_group_block_write_ul( __local ulong* p, ulong data )
void intel_sub_group_block_write_ul2( __local ulong* p, ulong2 data )
void intel_sub_group_block_write_ul4( __local ulong* p, ulong4 data )
void intel_sub_group_block_write_ul8( __local ulong* p, ulong8 data )Modifications to the OpenCL C Specification
Modifications to Section 6.13.X "Sub Group Read and Write Functions"
This section was added by the cl_intel_subgroups extension.
Add versions of the 32-bit block read and write functions that support loading from and storing to pointers to the __local address space:
| Function | Description |
|---|---|
|
Reads 1, 2, 4, or 8 uints of data for each work item in the subgroup from the specified pointer as a block operation… |
|
Writes 1, 2, 4, or 8 uints of data for each work item in the subgroup to the specified pointer as a block operation… |
If cl_intel_subgroups_char is supported, add versions of the 8-bit block read and write functions that support loading from and storing to pointers to the __local address space:
| Function | Description |
|---|---|
|
Reads 1, 2, 4, 8, or 16 uchars of data for each work item in the subgroup from the specified pointer as a block operation… |
|
Writes 1, 2, 4, 8, or 16 uchars of data for each work item in the subgroup to the specified pointer as a block operation… |
If cl_intel_subgroups_short is supported, add versions of the 16-bit block read and write functions that support loading from and storing to pointers to the __local address space:
| Function | Description |
|---|---|
|
Reads 1, 2, 4, or 8 ushorts of data for each work item in the subgroup from the specified pointer as a block operation… |
|
Writes 1, 2, 4, or 8 ushorts of data for each work item in the subgroup to the specified pointer as a block operation… |
If cl_intel_subgroups_long is supported, add versions of the 64-bit block read and write functions that support loading from and storing to pointers to the __local address space:
| Function | Description |
|---|---|
|
Reads 1, 2, 4, or 8 ulongs of data for each work item in the subgroup from the specified pointer as a block operation… |
|
Writes 1, 2, 4, or 8 ulongs of data for each work item in the subgroup to the specified pointer as a block operation… |
Modifications to Section 6.13.X.1 "Restrictions"
This section was added by the cl_intel_subgroups extension.
Change the description of the first section to: The following restrictions apply to the subgroup buffer block read and write functions that accept pointers to __global memory…
Insert a section between the restrictions on subgroup buffer block read and write functions that accept pointers to __global memory and the restrictions on subgroup image block read and write functions:
The following restrictions apply to the subgroup buffer block read and write functions that accept pointers to __local memory:
-
The pointer
pmust be 128-bit (16-byte) aligned for both reads and writes.
Modifications to the OpenCL SPIR-V Environment Specification
Modifications to Section 7.1.X.2 "Block IO Instructions"
This section was added by the cl_intel_spirv_subgroups extension.
Add to the validation rules for Ptr:
Additionally, if the OpenCL environment supports the extension cl_intel_subgroup_local_block_io, for Ptr valid Storage Classes are:
-
Workgroup (equivalent to the
localaddress space)
Modifications to Section 7.1.X.3 "Notes and Restrictions"
This section was added by the cl_intel_spirv_subgroups extension.
Change the description of the restrictions on SubgroupBufferBlockIOINTEL instructions to: The following restrictions apply to the SubgroupBufferBlockIOINTEL instructions when the pointer operand Ptr is a pointer to the CrossWorkgroup Storage Class…
Insert a section between the restrictions on SubgroupBufferBlockIOINTEL instructions when the pointer operand Ptr is a pointer to the CrossWorkGroup Storage Class and restrictions on SubgroupImageBlockIOINTEL instructions:
The following restrictions apply to the SubgroupBufferBlockIOINTEL instructions when the pointer operand Ptr is a pointer to the Workgroup Storage Class:
-
The pointer Ptr must be 128-bit (16-byte) aligned for both reads and writes.
Issues
-
What should this extension be called?
RESOLVED:
cl_intel_subgroup_local_block_io -
Do we need un-suffixed aliases of the 32-bit subgroup block read and write functions?
RESOLVED: Yes, this extension describes both suffixed functions and their un-suffixed aliases.
As background:
The 32-bit subgroup block read and write functions were originally un-suffixed in
cl_intel_subgroups.When we extended the subgroup block read and write functions for other types in
cl_intel_subgroups_short(and, eventually,cl_intel_subgroups_charandcl_intel_subgroups_long), we added suffixed aliases for consistency with the suffixed functions added to support the other types.For consistency with
cl_intel_subgroupswe should include both the un-suffixed and suffixed versions of the 32-bit functions.