2019-01-05 19:40:12 -08:00
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// Copyright (c) 2014-2019 Khronos Group. This work is licensed under a
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2018-12-03 02:41:34 -08:00
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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::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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Change log for August 17, 2019 Vulkan 1.1.120 spec update:
* Update release number to 120.
Github Issues:
* Add slink:VkAccelerationStructureTypeNV explicitly to extension XML for
`<<VK_NV_ray_tracing>>` (public issue 848).
* Add missing valid usage statements for feature flags in
slink:VkCommandBufferInheritanceInfo (public pull request 1017).
Internal Issues:
* Clarify behavior of non-premultiplied destination colors for
`<<VK_EXT_blend_operation_advanced>>` prior to the definition of
slink:VkBlendOverlapEXT (internal issue 1766).
* Fix the confusing phrasing "`no other queue must: be (doing something)`"
for flink:vkQueuePresentKHR, flink:vkQueueSubmit, and
flink:vkQueueBindSparse (internal issue 1774).
* Add `<<VK_EXT_validation_features>>` flag to enable best practices
checks, which will soon be available in the validation layer (internal
issue 1779).
* Specify allowed characters for VUID tag name components in the style
guide (internal issue 1788).
* Update links to SPIR-V extension specifications, and parameterize their
markup in case the URLs change in the future (internal issue 1797).
* Fix an off-by-one error in the valid usage statement for
slink:VkPipelineExecutableInfoKHR (internal merge request 3303).
* Clean up markup indentation not matching the style guide (internal merge
request 3314).
* Minor script updates to allow refpage aliases, generate a dynamic TOC
for refpages, generate Apache rewrite rules for aliases, open external
links from refpages in a new window, and synchronize with the OpenCL
scripts. This will shortly enable a paned navigation setup for refpages,
similar to the OpenCL 2.2 refpages (internal merge request 3322).
* Script updates to add tests to the checker, refactor and reformat code,
generate better text for some valid usage statements, use more Pythonic
idioms, and synchronize with the OpenXR scripts (internal merge request
3239).
* Script updates and minor fixes in spec language to not raise checker
errors for refpage markup of pages not existing in the API, such as
VKAPI_NO_STDINT_H. Remove corresponding suppression of some
check_spec_links.py tests from .gitlab-ci.yml and 'allchecks' target
(internal merge request 3315).
2019-08-17 15:33:21 -07:00
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{spirv}/KHR/SPV_KHR_float_controls.html[`SPV_KHR_float_controls`]
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2018-12-03 02:41:34 -08:00
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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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2019-07-28 21:22:36 -07:00
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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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2018-12-03 02:41:34 -08:00
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=== Version History
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2019-07-28 21:22:36 -07:00
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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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2018-12-03 02:41:34 -08:00
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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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