Vulkan-Docs/appendices/VK_EXT_shader_demote_to_helper_invocation.txt

include::meta/VK_EXT_shader_demote_to_helper_invocation.txt[]

*Last Modified Date*::
    2019-06-01
*IP Status*::
    No known IP claims.
*Contributors*::
  - Jeff Bolz, NVIDIA

This extension adds Vulkan support for the
`SPV_EXT_demote_to_helper_invocation` SPIR-V extension.
That SPIR-V extension provides a new instruction
code:OpDemoteToHelperInvocationEXT allowing shaders to "demote" a fragment
shader invocation to behave like a helper invocation for its duration.
The demoted invocation will have no further side effects and will not output
to the framebuffer, but remains active and can participate in computing
derivatives and in subgroup operations.
This is a better match for the "discard" instruction in HLSL.

=== New Object Types

None.

=== New Enum Constants

  * Extending elink:VkStructureType:
  ** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_SHADER_DEMOTE_TO_HELPER_INVOCATION_FEATURES_EXT

=== New Enums

None.

=== New Structures

  * slink:VkPhysicalDeviceShaderDemoteToHelperInvocationFeaturesEXT

=== New Functions

None.

=== New SPIR-V Capability

  * <<spirvenv-capabilities-table-demote,DemoteToHelperInvocationEXT>>

=== Issues

None.

=== Examples

None.

=== Version History

 * Revision 1, 2019-06-01 (Jeff Bolz)
   - Initial draft
Change log for June 30, 2019 Vulkan 1.1.113 spec update: * Update release number to 113. Github Issues: * Fix typo in `<<VK_EXT_global_priority>>` appendix (public issue 979). Internal Issues: * Expand the explanation of slink:VkSamplerYcbcrConversionImageFormatPropertiesKHR::pname:combinedImageSamplerDescriptorCount, and explain how it interacts with slink:VkWriteDescriptorSet, slink:VkDescriptorSetLayoutBinding::pname:descriptorCount, and slink:VkDescriptorPoolSize::pname:descriptorCount (internal issue 1643). * Clarify restrictions on components for code:OpImageGather in the <<spirvenv-module-validation, Validation Rules within a Module>> section (internal issue 1707). * Clarify the descriptions of <<limits-computeUnitsPerShaderArray, pname:computeUnitsPerShaderArray>> and <<limits-wavefrontSize, pname:wavefrontSize>> fields in slink:VkPhysicalDeviceShaderCorePropertiesAMD. New Extensions: * `<<VK_EXT_texel_buffer_alignment>>` * `<<VK_EXT_shader_demote_to_helper_invocation>>` 2019-06-29 23:14:02 -07:00			`include::meta/VK_EXT_shader_demote_to_helper_invocation.txt[]`

			`Last Modified Date::`
			`2019-06-01`
			`IP Status::`
			`No known IP claims.`
			`Contributors::`
			`- Jeff Bolz, NVIDIA`

			`This extension adds Vulkan support for the`
			`SPV_EXT_demote_to_helper_invocation` SPIR-V extension.
			`That SPIR-V extension provides a new instruction`
			`code:OpDemoteToHelperInvocationEXT allowing shaders to "demote" a fragment`
			`shader invocation to behave like a helper invocation for its duration.`
			`The demoted invocation will have no further side effects and will not output`
			`to the framebuffer, but remains active and can participate in computing`
			`derivatives and in subgroup operations.`
			`This is a better match for the "discard" instruction in HLSL.`

			`=== New Object Types`

			`None.`

			`=== New Enum Constants`

			`* Extending elink:VkStructureType:`
			`** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_SHADER_DEMOTE_TO_HELPER_INVOCATION_FEATURES_EXT`

			`=== New Enums`

			`None.`

			`=== New Structures`

			`* slink:VkPhysicalDeviceShaderDemoteToHelperInvocationFeaturesEXT`

			`=== New Functions`

			`None.`

			`=== New SPIR-V Capability`

			`* <<spirvenv-capabilities-table-demote,DemoteToHelperInvocationEXT>>`

			`=== Issues`

			`None.`

			`=== Examples`

			`None.`

			`=== Version History`

			`* Revision 1, 2019-06-01 (Jeff Bolz)`
			`- Initial draft`