SPV_INTEL_subgroups
SPV_INTEL_subgroups
Table of Contents
Name Strings
Contact
Contributors
Notice
Status
Version
Dependencies
Overview
Extension Name
New Capabilities
New Instructions
Token Number Assignments
Modifications to the SPIR-V Specification, Version 1.2
Validation Rules
Issues
Revision History
Name Strings
SPV_INTEL_subgroups
Contact
To report problems with this extension, please open a new issue at:
Contributors
Ben Ashbaugh, Intel
Biju George, Intel
Michael Kinsner, Intel
Mariusz Merecki, Intel
Notice
Copyright (c) 2017-2018 Intel Corporation. All rights reserved.
Status
Final Draft
Version
Last Modified Date
2018-10-22
Revision
Dependencies
This extension is written against the SPIR-V Specification,
Version 1.2 Revision 1.
This extension requires SPIR-V 1.0.
Overview
The goal of this extension is to allow programmers to improve the performance of their applications by taking advantage of the fact that some work items in a work group execute together as a group (a "subgroup"), and that work items in a subgroup can use hardware features that are not available to all work items in a work group. Specifically, this extension is designed to allow work items in a subgroup to share data without the use of local memory and work group barriers, and to utilize specialized hardware to load and store blocks of data from images or buffers.
This extension builds upon "subgroups" functionality that is already in core SPIR-V, so this extension reuses many of the names, concepts, and instructions already described in SPIR-V. The key additions in this extension are:
Intel subgroups adds "shuffle" instructions to allow data interchange between work items within a subgroup without the use of local memory or barriers.
Intel subgroups adds "block read and write" instructions to take advantage of specialized hardware to read or write blocks of data from or to buffers or images.
This extension has a source language counterpart extension for the OpenCL-C kernel language,
cl_intel_subgroups
, which can be used for online compilation in an OpenCL environment.
Extension Name
To use this extension within a SPIR-V module, the appropriate
OpExtension
must be present in the module:
OpExtension "SPV_INTEL_subgroups"
New Capabilities
This extension introduces new capabilities:
SubgroupShuffleINTEL
SubgroupBufferBlockIOINTEL
SubgroupImageBlockIOINTEL
New Instructions
Instructions added under the
SubgroupShuffleINTEL
capability:
OpSubgroupShuffleINTEL
OpSubgroupShuffleDownINTEL
OpSubgroupShuffleUpINTEL
OpSubgroupShuffleXorINTEL
Instructions added under the
SubgroupBufferBlockIOINTEL
capability:
OpSubgroupBlockReadINTEL
OpSubgroupBlockWriteINTEL
Instructions added under the
SubgroupImageBlockIOINTEL
capability:
OpSubgroupImageBlockReadINTEL
OpSubgroupImageBlockWriteINTEL
Token Number Assignments
SubgroupShuffleINTEL
5568
SubgroupBufferBlockIOINTEL
5569
SubgroupImageBlockIOINTEL
5570
OpSubgroupShuffleINTEL
5571
OpSubgroupShuffleDownINTEL
5572
OpSubgroupShuffleUpINTEL
5573
OpSubgroupShuffleXorINTEL
5574
OpSubgroupBlockReadINTEL
5575
OpSubgroupBlockWriteINTEL
5576
OpSubgroupImageBlockReadINTEL
5577
OpSubgroupImageBlockWriteINTEL
5578
Modifications to the SPIR-V Specification, Version 1.2
Capabilities
Modify Section 3.31, Capability, adding rows to the Capability table:
Capability
Implicitly Declares
Enabled by Extension
5568
SubgroupShuffleINTEL
SPV_INTEL_subgroups
5569
SubgroupBufferBlockIOINTEL
SPV_INTEL_subgroups
5570
SubgroupImageBlockIOINTEL
SPV_INTEL_subgroups
Instructions
Modify Section 3.32.21, Group Instructions, adding to the end of the list of instructions:
OpSubgroupShuffleINTEL
Allows data to be arbitrarily transferred between invocations in a subgroup. The data that is returned for this invocation is the value of
Data
for the invocation identified by
InvocationId
InvocationId
need not be the same value for all invocations in the subgroup.
Result Type
may be a scalar or vector type.
The type of
Data
must be the same as
Result Type
InvocationId
must be a 32-bit
integer type
scalar.
Capability:
SubgroupShuffleINTEL
5571
Result Type
Result
Data
InvocationId
OpSubgroupShuffleDownINTEL
Allows data to be transferred from an invocation in the subgroup with a higher
SubgroupLocalInvocationId
down to a invocation in the subgroup with a lower
SubgroupLocalInvocationId
There are two data sources to this built-in function:
Current
and
Next
. To determine the result of this built-in function, first let the unsigned shuffle index be equivalent to the sum of this invocation’s
SubgroupLocalInvocationId
plus the specified
Delta
If the shuffle index is less than the
SubgroupMaxSize
, the result of this built-in function is the value of the
Current
data source for the invocation with
SubgroupLocalInvocationId
equal to the shuffle index.
If the shuffle index is greater than or equal to the
SubgroupMaxSize
but less than twice the
SubgroupMaxSize
, the result of this built-in function is the value of the
Next
data source for the invocation with
SubgroupLocalInvocationId
equal to the shuffle index minus the
SubgroupMaxSize
All other values of the shuffle index are considered to be out-of-range.
Delta
need not be the same value for all invocations in the subgroup.
Result Type
may be a scalar or vector type.
The type of
Current
and
Next
must be the same as
Result Type
Delta
must be a 32-bit
integer type
scalar.
Capability:
SubgroupShuffleINTEL
5572
Result Type
Result
Current
Next
Delta
OpSubgroupShuffleUpINTEL
Allows data to be transferred from an invocation in the subgroup with a lower
SubgroupLocalInvocationId
up to an invocation in the subgroup with a higher
SubgroupLocalInvocationId
There are two data sources to this built-in function:
Previous
and
Current
. To determine the result of this built-in function, first let the signed shuffle index be equivalent to this invocation’s
SubgroupLocalInvocationId
minus the specified
Delta
If the shuffle index is greater than or equal to zero and less than the
SubgroupMaxSize
, the result of this built-in function is the value of the
Current
data source for the invocation with
SubgroupLocalInvocationId
equal to the shuffle index.
If the shuffle index is less than zero but greater than or equal to the negative
SubgroupMaxSize
, the result of this built-in function is the value of the
Previous
data source for the invocation with
SubgroupLocalInvocationId
equal to the shuffle index plus the
SubgroupMaxSize
All other values of the shuffle index are considered to be out-of-range.
Delta
need not be the same value for all invocations in the subgroup.
Result Type
may be a scalar or vector type.
The type of
Previous
and
Current
must be the same as
Result Type
Delta
must be a 32-bit
integer type
scalar.
Capability:
SubgroupShuffleINTEL
5573
Result Type
Result
Previous
Current
Delta
OpSubgroupShuffleXorINTEL
Allows data to be transferred between invocations in a subgroup as a function of the invocation_s
SubgroupLocalInvocationId
. The data that is returned for this invocation is the value of
Data
for the invocation with
SubgroupLocalInvocationId
equal to this invocation’s
SubgroupLocalInvocationId
XOR_d with the specified
Value
. If the result of the XOR is greater than
SubgroupMaxSize
then it is considered out-of-range.
Value
need not be the same for all invocations in the subgroup.
Result Type
may be a scalar or vector type.
The type of
Data
must be the same as
Result Type
Value
must be a 32-bit
integer type
scalar.
Capability:
SubgroupShuffleINTEL
5574
Result Type
Result
Data
Value
OpSubgroupBlockReadINTEL
Reads one or more components of
Result
data for each invocation in the subgroup from the specified
Ptr
as a block operation.
The data is read strided, so the first value read is:
Ptr[
SubgroupLocalInvocationId
and the second value read is:
Ptr[
SubgroupLocalInvocationId
SubgroupMaxSize
etc.
Result Type
may be a scalar or vector type, and its component type must be equal to the type pointed to by
Ptr
The type of
Ptr
must be a
pointer type
, and must point to a
scalar type
Capability:
SubgroupBufferBlockIOINTEL
5575
Result Type
Result
Ptr
OpSubgroupBlockWriteINTEL
Writes one or more components of
Data
for each invocation in the subgroup from the specified
Ptr
as a block operation.
The data is written strided, so the first value is written to:
Ptr[
SubgroupLocalInvocationId
and the second value written is:
Ptr[
SubgroupLocalInvocationId
SubgroupMaxSize
etc.
The type of
Ptr
must be a
pointer type
, and must point to a
scalar type
The component type of
Data
must be equal to the type pointed to by
Ptr
Capability:
SubgroupBufferBlockIOINTEL
5576
Ptr
Data
OpSubgroupImageBlockReadINTEL
Reads one or more components of
Result
data for each invocation in the subgroup from the specified
Image
at the specified
Coordinate
as a block operation. Note that the
Coordinate
is a byte coordinate, not a texel coordinate. Also note that the image data is read without format conversion, so each invocation may read multiple image elements.
The data is read row-by-row, so the first value read is from the row specified by the y-component of the provided
Coordinate
, the second value is read from the row specified by the y-component of the provided
Coordinate
plus one, etc.
Result Type
may be a scalar or vector type.
Image
must be an object whose type is
OpTypeImage
with a
Sampled
operand of 0 or 2. If the
Sampled
operand is 2, then some dimensions require a capability.
Coordinate
is an integer scalar or vector. The x-component is a byte coordinate into rows of the image and remaining coordinates are non-normalized texel coordinates.
Capability:
SubgroupImageBlockIOINTEL
5577
Result Type
Result
Image
Coordinate
OpSubgroupImageBlockWriteINTEL
Writes one or more components of
Data
for each invocation in the subgroup to the specified
Image
at the specified
Coordinate
as a block operation. Note that the
Coordinate
is a byte coordinate, not a texel coordinate. Also note that the image data is read without format conversion, so each invocation may write multiple image elements.
The data is written row-by-row, so the first value is written to the row specified by the y-component of the provided
Coordinate
, the second value is written to the row specified by the y-component of the provided
Coordinate
plus one, etc.
Image
must be an object whose type is
OpTypeImage
with a
Sampled
operand of 0 or 2. If the
Sampled
operand is 2, then some dimensions require a capability.
Coordinate
is an integer scalar or vector. The x-component is a byte coordinate into rows of the image and remaining coordinates are non-normalized texel coordinates.
Result Type
may be a scalar or vector type.
Capability:
SubgroupImageBlockIOINTEL
5578
Image
Coordinate
Data
Validation Rules
None.
Issues
None.
Revision History
Rev
Date
Author
Changes
2017-09-29
Ben Ashbaugh
Initial revision
2018-10-22
Ben Ashbaugh
Minor formatting updates.
US