cl_intel_subgroups

Name Strings

cl_intel_subgroups_char

Contact

Ben Ashbaugh, Intel (ben 'dot' ashbaugh 'at' intel 'dot' com)

Contributors

Ben Ashbaugh, Intel
Fangwen Fu, Intel
Sabareesh Ganapathy, Intel
Junjie Gu, Intel
Konrad Trifunovic, Intel

Notice

Status

Final Draft

Version

Built On: 2023-06-12
Revision: 1

Dependencies

OpenCL 1.2 and support for cl_intel_subgroups is required. This extension is written against the OpenCL API Specification Version 2.2 (revision v2.2-7), against the OpenCL C Language Specification Version 2.0 (revision v2.2-7), and against version 4 of the cl_intel_subgroups specification.

This extension requires OpenCL support for SPIR-V, either via OpenCL 2.1 or via the cl_khr_il_program extension.

This extension interacts with the cl_intel_spirv_subgroups extension.

Overview

The goal of this extension is to allow programmers to improve the performance of applications operating on 8-bit data types by extending the sub-group functions described in the cl_intel_subgroups extension to support 8-bit integer data types (chars and uchars). Specifically, the extension:

Extends the sub-group broadcast function to allow 8-bit integer values to be broadcast from one work item to all other work items in the sub-group.
Extends the sub-group scan and reduction functions to operate on 8-bit integer data types.
Extends the Intel sub-group shuffle functions to allow arbitrarily exchanging 8-bit integer values among work items in the sub-group.
Extends the Intel sub-group block read and write functions to allow reading and writing 8-bit integer data from images and buffers.

New API Functions

None.

New API Enums

None.

New OpenCL C Functions

Add char and uchar to the list of supported data types for the sub-group broadcast, scan, and reduction functions:

char    intel_sub_group_broadcast( char x, uint sub_group_local_id )
uchar   intel_sub_group_broadcast( uchar x, uint sub_group_local_id )

char    intel_sub_group_reduce_add( char x )
uchar   intel_sub_group_reduce_add( uchar x )
char    intel_sub_group_reduce_min( char x )
uchar   intel_sub_group_reduce_min( uchar x )
char    intel_sub_group_reduce_max( char x )
uchar   intel_sub_group_reduce_max( uchar x )

char    intel_sub_group_scan_exclusive_add( char x )
uchar   intel_sub_group_scan_exclusive_add( uchar x )
char    intel_sub_group_scan_exclusive_min( char x )
uchar   intel_sub_group_scan_exclusive_min( uchar x )
char    intel_sub_group_scan_exclusive_max( char x )
uchar   intel_sub_group_scan_exclusive_max( uchar x )

char    intel_sub_group_scan_inclusive_add( char x )
uchar   intel_sub_group_scan_inclusive_add( uchar x )
char    intel_sub_group_scan_inclusive_min( char x )
uchar   intel_sub_group_scan_inclusive_min( uchar x )
char    intel_sub_group_scan_inclusive_max( char x )
uchar   intel_sub_group_scan_inclusive_max( uchar x )

Add char, char2, char4, char8, char16, uchar, uchar2, uchar4, uchar8, and uchar16 to the list of gentype data types supported by the sub_group_shuffle, sub_group_shuffle_down, sub_group_shuffle_up, and sub_group_shuffle_xor functions:

gentype intel_sub_group_shuffle( gentype data, uint c )
gentype intel_sub_group_shuffle_down(
                gentype current, gentype next, uint delta )
gentype intel_sub_group_shuffle_up(
                gentype previous, gentype current, uint delta )
gentype intel_sub_group_shuffle_xor( gentype data, uint value )

Add uchar variants of the sub-group block read and write functions:

uchar   intel_sub_group_block_read_uc( const __global uchar* p )
uchar2  intel_sub_group_block_read_uc2( const __global uchar* p )
uchar4  intel_sub_group_block_read_uc4( const __global uchar* p )
uchar8  intel_sub_group_block_read_uc8( const __global uchar* p )
uchar16 intel_sub_group_block_read_uc16( const __global uchar* p )
uchar   intel_sub_group_block_read_uc( image2d_t image, int2 byte_coord )
uchar2  intel_sub_group_block_read_uc2( image2d_t image, int2 byte_coord )
uchar4  intel_sub_group_block_read_uc4( image2d_t image, int2 byte_coord )
uchar8  intel_sub_group_block_read_uc8( image2d_t image, int2 byte_coord )
uchar16 intel_sub_group_block_read_uc16( image1d_t image, int2 byte_coord )

void  intel_sub_group_block_write_uc( __global uchar* p, uchar data )
void  intel_sub_group_block_write_uc2( __global uchar* p, uchar2 data )
void  intel_sub_group_block_write_uc4( __global uchar* p, uchar4 data )
void  intel_sub_group_block_write_uc8( __global uchar* p, uchar8 data )
void  intel_sub_group_block_write_uc16( __global uchar* p, uchar16 data )
void  intel_sub_group_block_write_uc( image2d_t image, int2 byte_coord, uchar data )
void  intel_sub_group_block_write_uc2( image2d_t image, int2 byte_coord, uchar2 data )
void  intel_sub_group_block_write_uc4( image2d_t image, int2 byte_coord, uchar4 data )
void  intel_sub_group_block_write_uc8( image2d_t image, int2 byte_coord, uchar8 data )
void  intel_sub_group_block_write_uc16( image2d_t image, int2 byte_coord, uchar16 data )

For naming consistency, also add suffixed aliases of the uint sub-group block read and write functions described in the cl_intel_subgroups extension:

uint  intel_sub_group_block_read_ui( const __global uint* p )
uint2 intel_sub_group_block_read_ui2( const __global uint* p )
uint4 intel_sub_group_block_read_ui4( const __global uint* p )
uint8 intel_sub_group_block_read_ui8( const __global uint* p )
uint  intel_sub_group_block_read_ui( image2d_t image, int2 byte_coord )
uint2 intel_sub_group_block_read_ui2( image2d_t image, int2 byte_coord )
uint4 intel_sub_group_block_read_ui4( image2d_t image, int2 byte_coord )
uint8 intel_sub_group_block_read_ui8( image2d_t image, int2 byte_coord )

void  intel_sub_group_block_write_ui( __global uint* p, uint data )
void  intel_sub_group_block_write_ui2( __global uint* p, uint2 data )
void  intel_sub_group_block_write_ui4( __global uint* p, uint4 data )
void  intel_sub_group_block_write_ui8( __global uint* p, uint8 data )
void  intel_sub_group_block_write_ui( image2d_t image, int2 byte_coord, uint data )
void  intel_sub_group_block_write_ui2( image2d_t image, int2 byte_coord, uint2 data )
void  intel_sub_group_block_write_ui4( image2d_t image, int2 byte_coord, uint4 data )
void  intel_sub_group_block_write_ui8( image2d_t image, int2 byte_coord, uint8 data )

Modifications to the OpenCL C Specification

Additions to Section 6.13.15 - "Work-group Functions"

Add char and uchar to the list of supported data types for the sub-group broadcast, scan, and reduction functions:

Function Description

Function	Description
`gentype sub_group_broadcast( gentype x, uint sub_group_local_id ) char intel_sub_group_broadcast( char x, uint sub_group_local_id ) uchar intel_sub_group_broadcast( uchar x, uint sub_group_local_id )`	Broadcasts the value of x for work item identified by sub_group_local_id (value returned by get_sub_group_local_id) to all work items in the sub-group. sub_group_local_id must be the same value for all work items in the sub-group.
`gentype sub_group_reduce_add( gentype x ) gentype sub_group_reduce_min( gentype x ) gentype sub_group_reduce_max( gentype x ) char intel_sub_group_reduce_add( char x ) uchar intel_sub_group_reduce_add( uchar x ) char intel_sub_group_reduce_min( char x ) uchar intel_sub_group_reduce_min( uchar x ) char intel_sub_group_reduce_max( char x ) uchar intel_sub_group_reduce_max( uchar x )`	Returns the result of the specified reduction operation for all values of x specified by work items in a sub-group.
`gentype sub_group_scan_exclusive_add( gentype x ) gentype sub_group_scan_exclusive_min( gentype x ) gentype sub_group_scan_exclusive_max( gentype x ) char intel_sub_group_scan_exclusive_add( char x ) uchar intel_sub_group_scan_exclusive_add( uchar x ) char intel_sub_group_scan_exclusive_min( char x ) uchar intel_sub_group_scan_exclusive_min( uchar x ) char intel_sub_group_scan_exclusive_max( char x ) uchar intel_sub_group_scan_exclusive_max( uchar x )`	Performs the specified exclusive scan operation of all values x specified by work items in a sub-group. The scan results are returned for each work item. The scan order is defined by increasing sub-group local ID within the sub-group.
`gentype sub_group_scan_inclusive_add( gentype x) gentype sub_group_scan_inclusive_min( gentype x) gentype sub_group_scan_inclusive_max( gentype x) char intel_sub_group_scan_inclusive_add( char x ) uchar intel_sub_group_scan_inclusive_add( uchar x ) char intel_sub_group_scan_inclusive_min( char x ) uchar intel_sub_group_scan_inclusive_min( uchar x ) char intel_sub_group_scan_inclusive_max( char x ) uchar intel_sub_group_scan_inclusive_max( uchar x )`	Performs the specified inclusive scan operation of all values x specified by work items in a sub-group. The scan results are returned for each work item. The scan order is defined by increasing sub-group local ID within the sub-group.

gentype sub_group_broadcast(
          gentype x,
          uint sub_group_local_id )

char    intel_sub_group_broadcast(
          char x,
          uint sub_group_local_id )
uchar   intel_sub_group_broadcast(
          uchar x,
          uint sub_group_local_id )

Broadcasts the value of x for work item identified by sub_group_local_id (value returned by get_sub_group_local_id) to all work items in the sub-group. sub_group_local_id must be the same value for all work items in the sub-group.

gentype sub_group_reduce_add( gentype x )
gentype sub_group_reduce_min( gentype x )
gentype sub_group_reduce_max( gentype x )

char    intel_sub_group_reduce_add( char x )
uchar   intel_sub_group_reduce_add( uchar x )
char    intel_sub_group_reduce_min( char x )
uchar   intel_sub_group_reduce_min( uchar x )
char    intel_sub_group_reduce_max( char x )
uchar   intel_sub_group_reduce_max( uchar x )

Returns the result of the specified reduction operation for all values of x specified by work items in a sub-group.

gentype sub_group_scan_exclusive_add( gentype x )
gentype sub_group_scan_exclusive_min( gentype x )
gentype sub_group_scan_exclusive_max( gentype x )

char    intel_sub_group_scan_exclusive_add( char x )
uchar   intel_sub_group_scan_exclusive_add( uchar x )
char    intel_sub_group_scan_exclusive_min( char x )
uchar   intel_sub_group_scan_exclusive_min( uchar x )
char    intel_sub_group_scan_exclusive_max( char x )
uchar   intel_sub_group_scan_exclusive_max( uchar x )

Performs the specified exclusive scan operation of all values x specified by work items in a sub-group. The scan results are returned for each work item.

The scan order is defined by increasing sub-group local ID within the sub-group.

gentype sub_group_scan_inclusive_add( gentype x)
gentype sub_group_scan_inclusive_min( gentype x)
gentype sub_group_scan_inclusive_max( gentype x)

char    intel_sub_group_scan_inclusive_add( char x )
uchar   intel_sub_group_scan_inclusive_add( uchar x )
char    intel_sub_group_scan_inclusive_min( char x )
uchar   intel_sub_group_scan_inclusive_min( uchar x )
char    intel_sub_group_scan_inclusive_max( char x )
uchar   intel_sub_group_scan_inclusive_max( uchar x )

Performs the specified inclusive scan operation of all values x specified by work items in a sub-group. The scan results are returned for each work item.

The scan order is defined by increasing sub-group local ID within the sub-group.

Additions to Section 6.13.X - "Sub-group Shuffle Functions"

This section was added by the cl_intel_subgroups extension.

Add char, char2, char4, char8, char16, uchar, uchar2, uchar4, uchar8, and uchar16 to the list of data types supported by the sub_group_shuffle, sub_group_shuffle_down, sub_group_shuffle_up, and sub_group_shuffle_xor functions:: The OpenCL C programming language implements the following built-in functions to allow data to be exchanged among work items in a sub-group. These built-in functions need not be encountered by all work items in a sub-group executing the kernel, however, data may only be shuffled among work items encountering the sub-group shuffle function. Shuffling data from a work item that does not encounter the sub-group shuffle function will produce undefined results. For these functions, gentype is float, float2, float4, float8, float16, char, char2, char4, char8, char16, uchar, uchar2, uchar4, uchar8, uchar16, int, int2, int4, int8, int16, uint, uint2, uint4, uint8, uint16, long, or ulong.

If cl_khr_fp16 is supported, gentype also includes half.

If cl_khr_fp64 or doubles are supported, gentype also includes double.

Modifications to Section 6.13.X "Sub-group Read and Write Functions"

This section was added by the cl_intel_subgroups extension.

Add suffixed aliases of the previously un-suffixed 32-bit block read and write functions. There is no change to the description or behavior of these functions:

Function Description

Function	Description
`uint intel_sub_group_block_read( const __global uint* p ) uint2 intel_sub_group_block_read2( const __global uint* p ) uint4 intel_sub_group_block_read4( const __global uint* p ) uint8 intel_sub_group_block_read8( const __global uint* p ) uint intel_sub_group_block_read_ui( const __global uint* p ) uint2 intel_sub_group_block_read_ui2( const __global uint* p ) uint4 intel_sub_group_block_read_ui4( const __global uint* p ) uint8 intel_sub_group_block_read_ui8( const __global uint* p )`	Reads 1, 2, 4, or 8 uints of data for each work item in the sub-group from the specified pointer as a block operation…
uint intel_sub_group_block_read( image2d_t image, int2 byte_coord ) uint2 intel_sub_group_block_read2( image2d_t image, int2 byte_coord ) uint4 intel_sub_group_block_read4( image2d_t image, int2 byte_coord ) uint8 intel_sub_group_block_read8( image2d_t image, int2 byte_coord ) uint intel_sub_group_block_read_ui( image2d_t image, int2 byte_coord ) uint2 intel_sub_group_block_read_ui2( image2d_t image, int2 byte_coord ) uint4 intel_sub_group_block_read_ui4( image2d_t image, int2 byte_coord ) uint8 intel_sub_group_block_read_ui8( image2d_t image, int2 byte_coord )	Reads 1, 2, 4, or 8 uints of data for each work item in the sub-group from the specified image at the specified coordinate as a block operation…
void intel_sub_group_block_write( __global uint* p, uint data ) void intel_sub_group_block_write2( __global uint* p, uint2 data ) void intel_sub_group_block_write4( __global uint* p, uint4 data ) void intel_sub_group_block_write8( __global uint* p, uint8 data ) void intel_sub_group_block_write_ui( __global uint* p, uint data ) void intel_sub_group_block_write_ui2( __global uint* p, uint2 data ) void intel_sub_group_block_write_ui4( __global uint* p, uint4 data ) void intel_sub_group_block_write_ui8( __global uint* p, uint8 data )	Writes 1, 2, 4, or 8 uints of data for each work item in the sub-group to the specified pointer as a block operation…
void intel_sub_group_block_write( image2d_t image, int2 byte_coord, uint data ) void intel_sub_group_block_write2( image2d_t image, int2 byte_coord, uint2 data ) void intel_sub_group_block_write4( image2d_t image, int2 byte_coord, uint4 data ) void intel_sub_group_block_write8( image2d_t image, int2 byte_coord, uint8 data ) void intel_sub_group_block_write_ui( image2d_t image, int2 byte_coord, uint data ) void intel_sub_group_block_write_ui2( image2d_t image, int2 byte_coord, uint2 data ) void intel_sub_group_block_write_ui4( image2d_t image, int2 byte_coord, uint4 data ) void intel_sub_group_block_write_ui8( image2d_t image, int2 byte_coord, uint8 data )	Writes 1, 2, 4, or 8 uints of data for each work item in the sub-group to the specified image at the specified coordinate as a block operation…

uint  intel_sub_group_block_read(
        const __global uint* p )
uint2 intel_sub_group_block_read2(
        const __global uint* p )
uint4 intel_sub_group_block_read4(
        const __global uint* p )
uint8 intel_sub_group_block_read8(
        const __global uint* p )

uint  intel_sub_group_block_read_ui(
        const __global uint* p )
uint2 intel_sub_group_block_read_ui2(
        const __global uint* p )
uint4 intel_sub_group_block_read_ui4(
        const __global uint* p )
uint8 intel_sub_group_block_read_ui8(
        const __global uint* p )

Reads 1, 2, 4, or 8 uints of data for each work item in the sub-group from the specified pointer as a block operation…

uint  intel_sub_group_block_read(
        image2d_t image,
        int2 byte_coord )
uint2 intel_sub_group_block_read2(
        image2d_t image,
        int2 byte_coord )
uint4 intel_sub_group_block_read4(
        image2d_t image,
        int2 byte_coord )
uint8 intel_sub_group_block_read8(
        image2d_t image,
        int2 byte_coord )

uint  intel_sub_group_block_read_ui(
        image2d_t image,
        int2 byte_coord )
uint2 intel_sub_group_block_read_ui2(
        image2d_t image,
        int2 byte_coord )
uint4 intel_sub_group_block_read_ui4(
        image2d_t image,
        int2 byte_coord )
uint8 intel_sub_group_block_read_ui8(
        image2d_t image,
        int2 byte_coord )

Reads 1, 2, 4, or 8 uints of data for each work item in the sub-group from the specified image at the specified coordinate as a block operation…

void  intel_sub_group_block_write(
        __global uint* p, uint data )
void  intel_sub_group_block_write2(
        __global uint* p, uint2 data )
void  intel_sub_group_block_write4(
        __global uint* p, uint4 data )
void  intel_sub_group_block_write8(
        __global uint* p, uint8 data )

void  intel_sub_group_block_write_ui(
        __global uint* p, uint data )
void  intel_sub_group_block_write_ui2(
        __global uint* p, uint2 data )
void  intel_sub_group_block_write_ui4(
        __global uint* p, uint4 data )
void  intel_sub_group_block_write_ui8(
        __global uint* p, uint8 data )

Writes 1, 2, 4, or 8 uints of data for each work item in the sub-group to the specified pointer as a block operation…

void  intel_sub_group_block_write(
        image2d_t image,
        int2 byte_coord, uint data )
void  intel_sub_group_block_write2(
        image2d_t image,
        int2 byte_coord, uint2 data )
void  intel_sub_group_block_write4(
        image2d_t image,
        int2 byte_coord, uint4 data )
void  intel_sub_group_block_write8(
        image2d_t image,
        int2 byte_coord, uint8 data )

void  intel_sub_group_block_write_ui(
        image2d_t image,
        int2 byte_coord, uint data )
void  intel_sub_group_block_write_ui2(
        image2d_t image,
        int2 byte_coord, uint2 data )
void  intel_sub_group_block_write_ui4(
        image2d_t image,
        int2 byte_coord, uint4 data )
void  intel_sub_group_block_write_ui8(
        image2d_t image,
        int2 byte_coord, uint8 data )

Writes 1, 2, 4, or 8 uints of data for each work item in the sub-group to the specified image at the specified coordinate as a block operation…

Also, add uchar variants of the block read and write functions. In the descriptions of these functions, the "note below describing out-of-bounds behavior" is in the cl_intel_subgroups extension specification:

Function Description

Function	Description
`uchar intel_sub_group_block_read_uc( const __global uchar* p ) uchar2 intel_sub_group_block_read_uc2( const __global uchar* p ) uchar4 intel_sub_group_block_read_uc4( const __global uchar* p ) uchar8 intel_sub_group_block_read_uc8( const __global uchar* p ) uchar16 intel_sub_group_block_read_uc16( const __global uchar* p )`	Reads 1, 2, 4, 8, or 16 uchars of data for each work item in the sub-group from the specified pointer as a block operation. The data is read strided, so the first value read is: `p[ sub_group_local_id ]` and the second value read is: `p[ sub_group_local_id + max_sub_group_size ]` etc. p must be aligned to a 32-bit (4-byte) boundary. There is no defined out-of-range behavior for these functions.
`uchar intel_sub_group_block_read_uc( image2d_t image, int2 byte_coord ) uchar2 intel_sub_group_block_read_uc2( image2d_t image, int2 byte_coord ) uchar4 intel_sub_group_block_read_uc4( image2d_t image, int2 byte_coord ) uchar8 intel_sub_group_block_read_uc8( image2d_t image, int2 byte_coord ) uchar16 intel_sub_group_block_read_uc16( image2d_t image, int2 byte_coord )`	Reads 1, 2, 4, 8, or 16 uchars of data for each work item in the sub-group from the specified image at the specified coordinate as a block operation. Note that the coordinate is a byte coordinate, not an image element coordinate. Also note that the image data is read without format conversion, so each work item may read multiple image elements (for images with element size smaller than 8-bits). The data is read row-by-row, so the first value read is from the row specified in the y-component of the provided byte_coord, the second value is read from the y-component of the provided byte_coord plus one, etc. Please see the note below describing out-of-bounds behavior for these functions.
`void intel_sub_group_block_write_uc( __global uchar* p, uchar data ) void intel_sub_group_block_write_uc2( __global uchar* p, uchar2 data ) void intel_sub_group_block_write_uc4( __global uchar* p, uchar4 data ) void intel_sub_group_block_write_uc8( __global uchar* p, uchar8 data ) void intel_sub_group_block_write_uc16( __global uchar* p, uchar16 data )`	Writes 1, 2, 4, 8, or 16 uchars of data for each work item in the sub-group to the specified pointer as a block operation. The data is written strided, so the first value is written to: `p[ sub_group_local_id ]` and the second value is written to: `p[ sub_group_local_id + max_sub_group_size ]` etc. p must be aligned to a 128-bit (16-byte) boundary. There is no defined out-of-range behavior for these functions.
`void intel_sub_group_block_write_uc( image2d_t image, int2 byte_coord, uchar data ) void intel_sub_group_block_write_uc2( image2d_t image, int2 byte_coord, uchar2 data ) void intel_sub_group_block_write_uc4( image2d_t image, int2 byte_coord, uchar4 data ) void intel_sub_group_block_write_uc8( image2d_t image, int2 byte_coord, uchar8 data ) void intel_sub_group_block_write_uc16( image2d_t image, int2 byte_coord, uchar16 data )`	Writes 1, 2, 4, 8, or 16 uchars of data for each work item in the sub-group to the specified image at the specified coordinate as a block operation. Note that the coordinate is a byte coordinate, not an image element coordinate. Unlike the image block read function, which may read from any arbitrary byte offset, the x-component of the byte coordinate for the image block write functions must be a multiple of four; in other words, the write must begin at 32-bit boundary. There is no restriction on the y-component of the coordinate. Also, note that the image data is written without format conversion, so each work item may write multiple image elements (for images with element size smaller than 8-bits). The data is written row-by-row, so the first value written is from the row specified by the y-component of the provided byte_coord, the second value is written from the y-component of the provided byte_coord plus one, etc. Please see the note below describing out-of-bounds behavior for these functions.

uchar   intel_sub_group_block_read_uc(
          const __global uchar* p )
uchar2  intel_sub_group_block_read_uc2(
          const __global uchar* p )
uchar4  intel_sub_group_block_read_uc4(
          const __global uchar* p )
uchar8  intel_sub_group_block_read_uc8(
          const __global uchar* p )
uchar16 intel_sub_group_block_read_uc16(
          const __global uchar* p )

Reads 1, 2, 4, 8, or 16 uchars of data for each work item in the sub-group from the specified pointer as a block operation. The data is read strided, so the first value read is:

p[ sub_group_local_id ]

and the second value read is:

p[ sub_group_local_id + max_sub_group_size ]

etc.

p must be aligned to a 32-bit (4-byte) boundary.

There is no defined out-of-range behavior for these functions.

uchar   intel_sub_group_block_read_uc(
          image2d_t image,
          int2 byte_coord )
uchar2  intel_sub_group_block_read_uc2(
          image2d_t image,
          int2 byte_coord )
uchar4  intel_sub_group_block_read_uc4(
          image2d_t image,
          int2 byte_coord )
uchar8  intel_sub_group_block_read_uc8(
          image2d_t image,
          int2 byte_coord )
uchar16 intel_sub_group_block_read_uc16(
          image2d_t image,
          int2 byte_coord )

Reads 1, 2, 4, 8, or 16 uchars of data for each work item in the sub-group from the specified image at the specified coordinate as a block operation. Note that the coordinate is a byte coordinate, not an image element coordinate. Also note that the image data is read without format conversion, so each work item may read multiple image elements (for images with element size smaller than 8-bits).

The data is read row-by-row, so the first value read is from the row specified in the y-component of the provided byte_coord, the second value is read from the y-component of the provided byte_coord plus one, etc.

Please see the note below describing out-of-bounds behavior for these functions.

void  intel_sub_group_block_write_uc(
        __global uchar* p, uchar data )
void  intel_sub_group_block_write_uc2(
        __global uchar* p, uchar2 data )
void  intel_sub_group_block_write_uc4(
        __global uchar* p, uchar4 data )
void  intel_sub_group_block_write_uc8(
        __global uchar* p, uchar8 data )
void  intel_sub_group_block_write_uc16(
        __global uchar* p, uchar16 data )

Writes 1, 2, 4, 8, or 16 uchars of data for each work item in the sub-group to the specified pointer as a block operation. The data is written strided, so the first value is written to:

p[ sub_group_local_id ]

and the second value is written to:

p[ sub_group_local_id + max_sub_group_size ]

etc.

p must be aligned to a 128-bit (16-byte) boundary.

There is no defined out-of-range behavior for these functions.

void  intel_sub_group_block_write_uc(
        image2d_t image,
        int2 byte_coord, uchar data )
void  intel_sub_group_block_write_uc2(
        image2d_t image,
        int2 byte_coord, uchar2 data )
void  intel_sub_group_block_write_uc4(
        image2d_t image,
        int2 byte_coord, uchar4 data )
void  intel_sub_group_block_write_uc8(
        image2d_t image,
        int2 byte_coord, uchar8 data )
void  intel_sub_group_block_write_uc16(
        image2d_t image,
        int2 byte_coord, uchar16 data )

Writes 1, 2, 4, 8, or 16 uchars of data for each work item in the sub-group to the specified image at the specified coordinate as a block operation. Note that the coordinate is a byte coordinate, not an image element coordinate. Unlike the image block read function, which may read from any arbitrary byte offset, the x-component of the byte coordinate for the image block write functions must be a multiple of four; in other words, the write must begin at 32-bit boundary. There is no restriction on the y-component of the coordinate. Also, note that the image data is written without format conversion, so each work item may write multiple image elements (for images with element size smaller than 8-bits).

The data is written row-by-row, so the first value written is from the row specified by the y-component of the provided byte_coord, the second value is written from the y-component of the provided byte_coord plus one, etc.

Please see the note below describing out-of-bounds behavior for these functions.

Modifications to the OpenCL SPIR-V Environment Specification

The section numbers below refer to sections added by the cl_intel_spirv_subgroups extension.

Note that the restrictions described in Section 7.1.X.3 - Notes and Restrictions in the cl_intel_spirv_subgroups extension are unchanged and continue to apply for this extension.

Add to Section 7.1.X - `cl_intel_spirv_subgroups`

Add to the end of this section:

If the OpenCL environment supports the extension cl_intel_subgroups_char, then additional types are valid for the following Groups instructions with Scope for Execution equal to Subgroup:

OpGroupBroadcast
OpGroupIAdd
OpGroupSMin, OpGroupUMin
OpGroupSMax, OpGroupUMax

For these instructions, valid types for Value are:

Scalars of OpTypeInt with a Width of 8 bits and Signedness of 0 (equivalent to char and uchar)

Add to Section 7.1.X.1 - Shuffle Instruction

Add to the end of this section:

Additionally, if the OpenCL environment supports the extension cl_intel_subgroups_char:

Scalars and OpTypeVectors with 2, 3, 4, 8, or 16 Component Count components of the following Component Type types:
- OpTypeInt with a Width of 8 bits and Signedness of 0 (equivalent to char and uchar)

Add to Section 7.1.X.2 - Block IO Instructions

Add to the description of supported types in this section:

Additionally, if the OpenCL environment supports the extension cl_intel_subgroups_char:

Scalars and OpTypeVectors with 2, 4, 8, or 16 Component Count components of the following Component Type types:
- OpTypeInt with a Width of 8 bits and Signedness of 0 (equivalent to char and uchar)

Issues

None.

Revision History

Rev	Date	Author	Changes
1	2020-03-13	Ben Ashbaugh	First public revision.

Rev

Date

Author

Changes

2020-03-13

Ben Ashbaugh

First public revision.

cl_intel_subgroups_char

Name Strings

Contact

Contributors

Notice

Status

Version

Dependencies

Overview

New API Functions

New API Enums

New OpenCL C Functions

Modifications to the OpenCL C Specification

Additions to Section 6.13.15 - "Work-group Functions"

Additions to Section 6.13.X - "Sub-group Shuffle Functions"

Modifications to Section 6.13.X "Sub-group Read and Write Functions"

Modifications to the OpenCL SPIR-V Environment Specification

Add to Section 7.1.X - cl_intel_spirv_subgroups

Add to Section 7.1.X.1 - Shuffle Instruction

Add to Section 7.1.X.2 - Block IO Instructions

Issues

Revision History

Add to Section 7.1.X - `cl_intel_spirv_subgroups`