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22a5a1459f
* Update release number to 124.
Github Issues:
* Fix Makefile SPECREMARK macro to work when not building in a git tree
(public issue 992).
* Ignore pname:aspectMask for unused attachments in
slink:VkSubpassDescription2KHR valid usage statements (public pull
request 1028).
* Minor markup / spelling fixes (public pull requests 1035, 1045).
Internal Issues:
* Fix markup in Valid Usage statement for slink:VkCreateFramebuffer
(internal issue 1823).
* Add a new <<synchronization-signal-operation-order, _signal operation
order_>> section to the synchronization chapter which describes in
detail the ordering guarantees provided by the API between fence and
semaphore signal operations (internal merge request 3368).
* Move generated `appendix/meta/` files into the Makefile GENERATED
directory (internal merge request 3381).
New Extensions
* `<<VK_KHR_shader_clock>>`
* `<<VK_KHR_timeline_semaphore>>`
136 lines
4.9 KiB
Plaintext
136 lines
4.9 KiB
Plaintext
// Copyright (c) 2014-2019 Khronos Group. This work is licensed under a
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// Creative Commons Attribution 4.0 International License; see
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// http://creativecommons.org/licenses/by/4.0/
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include::{generated}/meta/VK_KHR_shader_float_controls.txt[]
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*Last Modified Date*::
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2018-09-11
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*IP Status*::
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No known IP claims.
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*Interactions and External Dependencies*::
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- This extension requires
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{spirv}/KHR/SPV_KHR_float_controls.html[`SPV_KHR_float_controls`]
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*Contributors*::
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- Alexander Galazin, Arm
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- Jan-Harald Fredriksen, Arm
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- Jeff Bolz, NVIDIA
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- Graeme Leese, Broadcom
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- Daniel Rakos, AMD
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=== Description
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The `VK_KHR_shader_float_controls` extension enables efficient use of
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floating-point computations through the ability to query and override the
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implementation's default behavior for rounding modes, denormals, signed
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zero, and infinity.
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=== New Enum Constants
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* Extending elink:VkStructureType:
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** ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_FLOAT_CONTROLS_PROPERTIES_KHR
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=== New Enums
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* None
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=== New Structures
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* slink:VkPhysicalDeviceFloatControlsPropertiesKHR
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=== New Functions
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* None
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=== New SPIR-V Capabilities
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* <<spirvenv-capabilities-table-shaderfloatcontrols,code:DenormPreserve>>
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* <<spirvenv-capabilities-table-shaderfloatcontrols,code:DenormFlushToZero>>
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* <<spirvenv-capabilities-table-shaderfloatcontrols,code:SignedZeroInfNanPreserve>>
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* <<spirvenv-capabilities-table-shaderfloatcontrols,code:RoundingModeRTE>>
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* <<spirvenv-capabilities-table-shaderfloatcontrols,code:RoundingModeRTZ>>
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=== Issues
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1) Which instructions must flush denorms?
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*RESOLVED*: Only floating-point conversion, floating-point arithmetic,
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floating-point relational (except code:OpIsNaN, code:OpIsInf), and
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floating-point GLSL.std.450 extended instructions must flush denormals.
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2) What is the denorm behavior for intermediate results?
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*RESOLVED*: When a SPIR-V instruction is implemented as a sequence of other
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instructions:
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- in the code:DenormFlushToZero execution mode the intermediate
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instructions may flush denormals, the final result of the sequence must:
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not be denormal.
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- in the code:DenormPreserve execution mode denormals must be preserved
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throughout the whole sequence.
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3) Do denorm and rounding mode controls apply to code:OpSpecConstantOp?
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*RESOLVED*: Yes, except when the opcode is code:OpQuantizeToF16.
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4) The SPIR-V specification says that code:OpConvertFToU and
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code:OpConvertFToS unconditionally round towards zero.
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Do the rounding mode controls specified through the execution modes apply to
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them?
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*RESOLVED*: No, these instructions unconditionally round towards zero.
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5) Do any of the "Pack" GLSL.std.450 instructions count as conversion
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instructions and have the rounding mode apply?
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*RESOLVED*: No, only instructions listed in the section "3.32.11.
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Conversion Instructions" of the SPIR-V specification count as conversion
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instructions.
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6) When using inf/nan-ignore mode, what is expected of code:OpIsNan and
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code:OpIsInf?
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*RESOLVED*: These instructions must always accurately detect inf/nan if it
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is passed to them.
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[[VK_KHR_shader_controls_v4_incompatibility]]
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=== Version 4 API incompatiblity
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The original versions of VK_KHR_shader_controls shipped with booleans named
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"separateDenormSettings" and "separateRoundingModeSettings", which at first
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glance could've indicated "they can all independently set, or not".
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However the spec language as written indicated that the 32-bit value could
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always be set independently, and only the 16- and 64-bit controls needed to
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be the same if these values were VK_FALSE.
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As a result of this slight disparity, and lack of test coverage for this
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facet of the extension, we ended up with two different behaviors in the
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wild, where some implementations worked as written, and others worked based
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on the naming.
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As these are hard limits in hardware with reasons for exposure as written,
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it was not possible to standardise on a single way to make this work within
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the existing API.
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No known users of this part of the extension exist in the wild, and as such
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the Vulkan WG took the unusual step of retroactively changing the once
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boolean value into a tri-state enum, breaking source compatibility.
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This was however done in such a way as to retain ABI compatibility, in case
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any code using this did exist; with the numerical values 0 and 1 retaining
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their original specified meaning, and a new value signifying the additional
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"all need to be set together" state.
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If any applications exist today, compiled binaries will continue to work as
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written in most cases, but will need changes before the code can be
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recompiled.
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=== Version History
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* Revision 4, 2019-06-18 (Tobias Hector)
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- Modified settings restrictions, see
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<<VK_KHR_shader_controls_v4_incompatibility>>
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* Revision 3, 2018-09-11 (Alexander Galazin)
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- Minor restructuring
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* Revision 2, 2018-04-17 (Alexander Galazin)
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- Added issues and resolutions
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* Revision 1, 2018-04-11 (Alexander Galazin)
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- Initial draft
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