Vulkan-Docs/doc/specs/vulkan/appendices/VK_EXT_shader_subgroup_ball...

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include::meta/VK_EXT_shader_subgroup_ballot.txt[]
*Last Modified Date*::
2016-11-28
*IP Status*::
No known IP claims.
*Interactions and External Dependencies*::
- This extension requires the
https://www.khronos.org/registry/spir-v/extensions/KHR/SPV_KHR_shader_ballot.html[+SPV_KHR_shader_ballot+]
SPIR-V extension.
- This extension requires the
https://www.khronos.org/registry/OpenGL/extensions/ARB/ARB_shader_ballot.txt[+GL_ARB_shader_ballot+]
extension for GLSL source languages.
*Contributors*::
- Jeff Bolz, NVIDIA
- Neil Henning, Codeplay
- Daniel Koch, NVIDIA Corporation
This extension adds support for the following SPIR-V extension in Vulkan:
* +SPV_KHR_shader_ballot+
This extension provides the ability for a group of invocations, which
execute in parallel, to do limited forms of cross-invocation communication
via a group broadcast of a invocation value, or broadcast of a bitarray
representing a predicate value from each invocation in the group.
This extension provides access to a number of additional built-in shader
variables in Vulkan:
* code:SubgroupEqMaskKHR, which contains the subgroup mask of the current
subgroup invocation,
* code:SubgroupGeMaskKHR, which contains the subgroup mask of the
invocations greater than or equal to the current invocation,
* code:SubgroupGtMaskKHR, which contains the subgroup mask of the
invocations greater than the current invocation,
* code:SubgroupLeMaskKHR, which contains the subgroup mask of the
invocations less than or equal to the current invocation,
* code:SubgroupLtMaskKHR, which contains the subgroup mask of the
invocations less than the current invocation,
* code:SubgroupLocalInvocationId, which contains the index of an
invocation within a subgroup, and
* code:SubgroupSize, which contains the maximum number of invocations in a
subgroup.
Additionally, this extension provides access to the new SPIR-V instructions:
* code:OpSubgroupBallotKHR,
* code:OpSubgroupFirstInvocationKHR, and
* code:OpSubgroupReadInvocationKHR,
When using GLSL source-based shader languages, the following variables and
shader functions from GL_ARB_shader_ballot can map to these SPIR-V built-in
decorations and instructions:
* in uint64_t gl_SubGroupEqMaskARB; -> code:SubgroupEqMaskKHR,
* in uint64_t gl_SubGroupGeMaskARB; -> code:SubgroupGeMaskKHR,
* in uint64_t gl_SubGroupGtMaskARB; -> code:SubgroupGtMaskKHR,
* in uint64_t gl_SubGroupLeMaskARB; -> code:SubgroupLeMaskKHR,
* in uint64_t gl_SubGroupLtMaskARB; -> code:SubgroupLtMaskKHR,
* in uint gl_SubGroupInvocationARB; -> code:SubgroupLocalInvocationId,
* uniform uint gl_SubGroupSizeARB; -> code:SubgroupSize,
* ballotARB() -> code:OpSubgroupBallotKHR,
* readFirstInvocationARB() -> code:OpSubgroupFirstInvocationKHR, and
* readInvocationARB() -> code:OpSubgroupReadInvocationKHR.
=== New Object Types
None.
=== New Enum Constants
None.
=== New Enums
None.
=== New Structures
None.
=== New Functions
None.
=== New Built-In Variables
* <<interfaces-builtin-variables-sgeq,code:SubgroupEqMaskKHR>>
* <<interfaces-builtin-variables-sgge,code:SubgroupGeMaskKHR>>
* <<interfaces-builtin-variables-sggt,code:SubgroupGtMaskKHR>>
* <<interfaces-builtin-variables-sgle,code:SubgroupLeMaskKHR>>
* <<interfaces-builtin-variables-sglt,code:SubgroupLtMaskKHR>>
* <<interfaces-builtin-variables-sgli,code:SubgroupLocalInvocationId>>
* <<interfaces-builtin-variables-sgs,code:SubgroupSize>>
=== New SPIR-V Capabilities
* <<spirvenv-capabilities-table-subgroupballot,SubgroupBallotKHR>>
=== Issues
None.
=== Version History
* Revision 1, 2016-11-28 (Daniel Koch)
- Initial draft