VK_KHR_variable_pointers(3)

# VK_KHR_variable_pointers(3) Manual Page

## Name

VK_KHR_variable_pointers - device extension

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## Registered Extension Number

121

## Revision

1

## Ratification Status

Ratified

## Extension and Version Dependencies

VK_KHR_get_physical_device_properties2
and
VK_KHR_storage_buffer_storage_class

## SPIR-V Dependencies

- SPV_KHR_variable_pointers

## Deprecation State

- Promoted to Vulkan 1.1

## Contact

- Jesse Hall critsec

## Other Extension Metadata

Last Modified Date

  2017-09-05

IP Status

  No known IP claims.

Contributors

  - John Kessenich, Google

  - Neil Henning, Codeplay

  - David Neto, Google

  - Daniel Koch, Nvidia

  - Graeme Leese, Broadcom

  - Weifeng Zhang, Qualcomm

  - Stephen Clarke, Imagination Technologies

  - Faith Ekstrand, Intel

  - Jesse Hall, Google

## Description

The `VK_KHR_variable_pointers` extension allows implementations to indicate their level of support for the `SPV_KHR_variable_pointers` SPIR-V extension. The SPIR-V extension allows shader modules to use invocation-private pointers into uniform and/or storage buffers, where the pointer values can be dynamic and non-uniform.

The `SPV_KHR_variable_pointers` extension introduces two capabilities. The first, `VariablePointersStorageBuffer`, must be supported by all implementations of this extension. The second, `VariablePointers`, is optional.

## Promotion to Vulkan 1.1

All functionality in this extension is included in core Vulkan 1.1, with the KHR suffix omitted, however support for the `variablePointersStorageBuffer` feature is made optional. The original type, enum and command names are still available as aliases of the core functionality.

## New Structures

- Extending VkPhysicalDeviceFeatures2, VkDeviceCreateInfo:

  - VkPhysicalDeviceVariablePointerFeaturesKHR

  - VkPhysicalDeviceVariablePointersFeaturesKHR

## New Enum Constants

- `VK_KHR_VARIABLE_POINTERS_EXTENSION_NAME`

- `VK_KHR_VARIABLE_POINTERS_SPEC_VERSION`

- Extending VkStructureType:

  - `VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VARIABLE_POINTERS_FEATURES_KHR`

  - `VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VARIABLE_POINTER_FEATURES_KHR`

## New SPIR-V Capabilities

- `VariablePointers`

- `VariablePointersStorageBuffer`

## Issues

1) Do we need an optional property for the SPIR-V `VariablePointersStorageBuffer` capability or should it be mandatory when this extension is advertised?

RESOLVED: Add it as a distinct feature, but make support mandatory. Adding it as a feature makes the extension easier to include in a future core API version. In the extension, the feature is mandatory, so that presence of the extension guarantees some functionality. When included in a core API version, the feature would be optional.

2) Can support for these capabilities vary between shader stages?

RESOLVED: No, if the capability is supported in any stage it must be supported in all stages.

3) Should the capabilities be features or limits?

RESOLVED: Features, primarily for consistency with other similar extensions.

## Version History

- Revision 1, 2017-03-14 (Jesse Hall and John Kessenich)

  - Internal revisions

## See Also

VkPhysicalDeviceVariablePointerFeaturesKHR, VkPhysicalDeviceVariablePointersFeaturesKHR

## Document Notes

For more information, see the Vulkan Specification

This page is a generated document. Fixes and changes should be made to the generator scripts, not directly.

## Copyright

Copyright 2014-2023 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0