Promoted to Vulkan 1.2
Jesse Hall critsec
- Last Modified Date
- IP Status
No known IP claims.
- Interactions and External Dependencies
Requires SPIR-V 1.4.
Promoted to Vulkan 1.2 Core
Alexander Galazin, Arm
David Neto, Google
Jesse Hall, Google
John Kessenich, Google
Neil Henning, AMD
Tom Olson, Arm
This extension allows the use of SPIR-V 1.4 shader modules. SPIR-V 1.4’s new features primarily make it an easier target for compilers from high-level languages, rather than exposing new hardware functionality.
SPIR-V 1.4 incorporates features that are also available separately as
SPIR-V 1.4 shader modules do not need to enable those extensions with the
OpExtension opcode, since they are integral parts of SPIR-V 1.4.
SPIR-V 1.4 introduces new floating point execution mode capabilities, also
Implementations are not required to support all of these new capabilities;
support can be queried using
VkPhysicalDeviceFloatControlsPropertiesKHR from the
All functionality in this extension is included in core Vulkan 1.2, with the KHR suffix omitted. The original type, enum and command names are still available as aliases of the core functionality.
1. Should we have an extension specific to this SPIR-V version, or add a version-generic query for SPIR-V version? SPIR-V 1.4 does not need any other API changes.
RESOLVED: Just expose SPIR-V 1.4.
Most new SPIR-V versions introduce optionally-required capabilities or have implementation-defined limits, and would need more API and specification changes specific to that version to make them available in Vulkan. For example, to support the subgroup capabilities added in SPIR-V 1.3 required introducing VkPhysicalDeviceSubgroupProperties to allow querying the supported group operation categories, maximum supported subgroup size, etc. While we could expose the parts of a new SPIR-V version that do not need accompanying changes generically, we will still end up writing extensions specific to each version for the remaining parts. Thus the generic mechanism will not reduce future spec-writing effort. In addition, making it clear which parts of a future version are supported by the generic mechanism and which cannot be used without specific support would be difficult to get right ahead of time.
2. Can different stages of the same pipeline use shaders with different SPIR-V versions?
Mixing SPIR-V versions 1.0-1.3 in the same pipeline has not been disallowed, so it would be inconsistent to disallow mixing 1.4 with previous versions. SPIR-V 1.4 does not introduce anything that should cause new difficulties here.
3. Must Vulkan extensions corresponding to SPIR-V extensions that were promoted to core in 1.4 be enabled in order to use that functionality in a SPIR-V 1.4 module?
RESOLVED: No, with caveats.
The SPIR-V 1.4 module does not need to declare the SPIR-V extensions, since the functionality is now part of core, so there is no need to enable the Vulkan extension that allows SPIR-V modules to declare the SPIR-V extension. However, when the functionality that is now core in SPIR-V 1.4 is optionally supported, the query for support is provided by a Vulkan extension, and that query can only be used if the extension is enabled.
This applies to any SPIR-V version; specifically for SPIR-V 1.4 this only
applies to the functionality from
SPV_KHR_float_controls, which was made
available in Vulkan by
Even though the extension was promoted in SPIR-V 1.4, the capabilities are
still optional in implementations that support
A SPIR-V 1.4 module does not need to enable
order to use the capabilities, so if the application has a priori
knowledge that the implementation supports the capabilities, it does not
need to enable
However, if it does not have this knowledge and has to query for support at
runtime, it must enable
VK_KHR_shader_float_controls in order to
For more information, see the Vulkan Specification
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