1  include::meta/VK_EXT_shader_subgroup_ballot.txt[]
  2  
  3  *Last Modified Date*::
  4      2016-11-28
  5  *IP Status*::
  6      No known IP claims.
  7  *Interactions and External Dependencies*::
  8    - This extension requires the
  9      https://www.khronos.org/registry/spir-v/extensions/KHR/SPV_KHR_shader_ballot.html[`SPV_KHR_shader_ballot`]
 10      SPIR-V extension.
 11    - This extension requires the
 12      https://www.khronos.org/registry/OpenGL/extensions/ARB/ARB_shader_ballot.txt[`GL_ARB_shader_ballot`]
 13      extension for GLSL source languages.
 14  *Contributors*::
 15    - Jeff Bolz, NVIDIA
 16    - Neil Henning, Codeplay
 17    - Daniel Koch, NVIDIA Corporation
 18  
 19  This extension adds support for the following SPIR-V extension in Vulkan:
 20  
 21    * `SPV_KHR_shader_ballot`
 22  
 23  This extension provides the ability for a group of invocations, which
 24  execute in parallel, to do limited forms of cross-invocation communication
 25  via a group broadcast of a invocation value, or broadcast of a bitarray
 26  representing a predicate value from each invocation in the group.
 27  
 28  This extension provides access to a number of additional built-in shader
 29  variables in Vulkan:
 30  
 31    * code:SubgroupEqMaskKHR, which contains the subgroup mask of the current
 32      subgroup invocation,
 33    * code:SubgroupGeMaskKHR, which contains the subgroup mask of the
 34      invocations greater than or equal to the current invocation,
 35    * code:SubgroupGtMaskKHR, which contains the subgroup mask of the
 36      invocations greater than the current invocation,
 37    * code:SubgroupLeMaskKHR, which contains the subgroup mask of the
 38      invocations less than or equal to the current invocation,
 39    * code:SubgroupLtMaskKHR, which contains the subgroup mask of the
 40      invocations less than the current invocation,
 41    * code:SubgroupLocalInvocationId, which contains the index of an
 42      invocation within a subgroup, and
 43    * code:SubgroupSize, which contains the maximum number of invocations in a
 44      subgroup.
 45  
 46  Additionally, this extension provides access to the new SPIR-V instructions:
 47  
 48    * code:OpSubgroupBallotKHR,
 49    * code:OpSubgroupFirstInvocationKHR, and
 50    * code:OpSubgroupReadInvocationKHR,
 51  
 52  When using GLSL source-based shader languages, the following variables and
 53  shader functions from GL_ARB_shader_ballot can map to these SPIR-V built-in
 54  decorations and instructions:
 55  
 56    * `in uint64_t gl_SubGroupEqMaskARB;` -> code:SubgroupEqMaskKHR,
 57    * `in uint64_t gl_SubGroupGeMaskARB;` -> code:SubgroupGeMaskKHR,
 58    * `in uint64_t gl_SubGroupGtMaskARB;` -> code:SubgroupGtMaskKHR,
 59    * `in uint64_t gl_SubGroupLeMaskARB;` -> code:SubgroupLeMaskKHR,
 60    * `in uint64_t gl_SubGroupLtMaskARB;` -> code:SubgroupLtMaskKHR,
 61    * `in uint gl_SubGroupInvocationARB;` -> code:SubgroupLocalInvocationId,
 62    * `uniform uint gl_SubGroupSizeARB;` -> code:SubgroupSize,
 63    * code:ballotARB() -> code:OpSubgroupBallotKHR,
 64    * code:readFirstInvocationARB() -> code:OpSubgroupFirstInvocationKHR, and
 65    * code:readInvocationARB() -> code:OpSubgroupReadInvocationKHR.
 66  
 67  === New Object Types
 68  
 69  None.
 70  
 71  === New Enum Constants
 72  
 73  None.
 74  
 75  === New Enums
 76  
 77  None.
 78  
 79  === New Structures
 80  
 81  None.
 82  
 83  === New Functions
 84  
 85  None.
 86  
 87  === New Built-In Variables
 88  
 89    * <<interfaces-builtin-variables-sgeq,code:SubgroupEqMaskKHR>>
 90    * <<interfaces-builtin-variables-sgge,code:SubgroupGeMaskKHR>>
 91    * <<interfaces-builtin-variables-sggt,code:SubgroupGtMaskKHR>>
 92    * <<interfaces-builtin-variables-sgle,code:SubgroupLeMaskKHR>>
 93    * <<interfaces-builtin-variables-sglt,code:SubgroupLtMaskKHR>>
 94    * <<interfaces-builtin-variables-sgli,code:SubgroupLocalInvocationId>>
 95    * <<interfaces-builtin-variables-sgs,code:SubgroupSize>>
 96  
 97  === New SPIR-V Capabilities
 98  
 99    * <<spirvenv-capabilities-table-subgroupballot,SubgroupBallotKHR>>
100  
101  === Issues
102  
103  None.
104  
105  === Version History
106  
107    * Revision 1, 2016-11-28 (Daniel Koch)
108      - Initial draft