<div dir="ltr"><div class="gmail_quote"><div dir="ltr">On Tue, Nov 6, 2018 at 9:43 PM Roland Scheidegger <<a href="mailto:sroland@vmware.com">sroland@vmware.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Am 06.11.18 um 22:48 schrieb Jason Ekstrand: > This came to the top of my list recently due to a difference between > OpenGL and Vulkan discard operations and D3D's discard operation. The > OpenGL and Vulkan discard is defined to be control flow and derivatives > are undefined after discard. With D3D, derivatives are considered > well-defined after discard. > > In order to work around this, DXVK (and I would assume VKD3D though I'm > not sure), simply sets a global boolean instead of doing the discard and > then emits `if (do_discard) discard;` at the end of the shader. For > complex shadaers, this leads to the shader doing way more work than > needed and poor performance. Is that really all they do? This will not work in presence of UAVs (shader images / ssbos), since after a discard writes must have no effect. </blockquote><div> </div><div>I'm not sure off-hand how UAVs are handled in the presence of discards. I would guess something like if (!discard) writeUAV(); </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> > If, on the other hand, they knew that > derivative groups are just subgroup quads, they could do something > better: > > bool want_discard; > > void d3d_discard() > { > want_discard = true; > if (subgroupClusteredAnd(want_discard, 4)) > discard; > } > > void main() > { > want_discard = false; > > // stuff > > if (some_condition) > d3d_discard(); > > // Exepensive stuff Expensive > > if (want_discard) > discard; If the expensive stuff includes buffer / image writes, that still wouldn't work as far as I can tell (although it could be fixed, just like without the extension, by wrapping the writes with if (!want_discard). </blockquote><div> </div><div>Correct. However, the common case is UBO pulls and textures.</div><div> </div><div>--Jason </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> Roland > } > --- > chapters/features.txt | 21 +++++++++++++++++++++ > chapters/shaders.txt | 12 ++++++++++++ > chapters/textures.txt | 8 ++++++++ > include/vulkan/vulkan_core.h | 15 +++++++++++++-- > xml/vk.xml | 13 ++++++++++--- > 5 files changed, 64 insertions(+), 5 deletions(-) > > diff --git a/chapters/features.txt b/chapters/features.txt > index 08c8d8420..3d22972ea 100644 > --- a/chapters/features.txt > +++ b/chapters/features.txt > @@ -2969,6 +2969,27 @@ more slink:VkSubgroupFeatureFlagBits. > > endif::VK_VERSION_1_1[] > > +ifdef::VK_EXT_derivative_group_quad[] > + > +[open,refpage='VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT',desc='Structure describing the relationship between derivative groups and subgroup quads for an implementation',type='structs'] > +-- > + > +The sname:VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT structure is > +defined as: > + > +include::../api/structs/VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT.txt[] > + > +The members of the sname:VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT > +structure describe the following implementation-dependent limits: > + > + * pname:derivativeGroupsAreSubgroupQuads is a boolean that specifies that > + derivative groups in fragment shaders correspond to subgroup quads. > +-- > + > +include::../validity/structs/VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT.txt[] > + > +endif::VK_EXT_derivative_group_quad[] > + > ifdef::VK_EXT_blend_operation_advanced[] > > [open,refpage='VkPhysicalDeviceBlendOperationAdvancedPropertiesEXT',desc='Structure describing advanced blending limits that can be supported by an implementation',type='structs'] > diff --git a/chapters/shaders.txt b/chapters/shaders.txt > index 5cb3edb35..11d3ea9db 100644 > --- a/chapters/shaders.txt > +++ b/chapters/shaders.txt > @@ -808,6 +808,11 @@ A _derivative group_ (see the subsection "`Control Flow`" of section 2 of > the SPIR-V 1.00 Revision 4 specification) for a fragment shader is the set > of invocations generated by a single primitive (point, line, or triangle), > including any helper invocations generated by that primitive. > +ifdef::VK_EXT_derivative_group_quad[] > +If the fname:derivativeGroupsAreSubgroupQuads field of > +slink:VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT is ename:VK_TRUE, a > +derivative group for a fragment shader is a single subgroup quad. > +endif::VK_EXT_derivative_group_quad[] > ifdef::VK_NV_compute_shader_derivatives[] > A derivative group for a compute shader is a single local workgroup. > endif::VK_NV_compute_shader_derivatives[] > @@ -920,6 +925,13 @@ The operations supported are add, mul, min, max, and, or, xor. > > The quad subgroup operations allow clusters of 4 invocations (a quad), to > share data efficiently with each other. > +ifdef::VK_EXT_derivative_group_quad[] > +For fragment shaders, if the fname:derivativeGroupsAreSubgroupQuads field of > +slink:VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT is ename:VK_TRUE, > +each quad corresponds to one of the groups of four shader > +invocations used for > +<<texture-derivatives-compute,derivatives>>. > +endif::VK_EXT_derivative_group_quad[] > ifdef::VK_NV_compute_shader_derivatives[] > For compute shaders using the code:DerivativeGroupQuadsNV or > code:DerivativeGroupLinearNV execution modes, each quad corresponds to one > diff --git a/chapters/textures.txt b/chapters/textures.txt > index a7bfaedc3..46a292381 100644 > --- a/chapters/textures.txt > +++ b/chapters/textures.txt > @@ -1387,6 +1387,14 @@ Implementations must: make the same choice of either coarse or fine for both > code:OpDPdx and code:OpDPdy, and implementations should: make the choice > that is more efficient to compute. > > +ifdef::VK_EXT_derivative_group_quad[] > +If the fname:derivativeGroupsAreSubgroupQuads field of > +slink:VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT is ename:VK_TRUE, > +the 2x2 neighborhood of fragments corresponds exactly to a subgroup quad > +the invocations in each quad are ordered to have attribute values of > +P~i0,j0~, P~i1,j0~, P~i0,j1~, and P~i1,j1~, respectively. > +endif::VK_EXT_derivative_group_quad[] > + > ifdef::VK_NV_compute_shader_derivatives[] > [[texture-derivatives-compute]] > === Compute Shader Derivatives > diff --git a/include/vulkan/vulkan_core.h b/include/vulkan/vulkan_core.h > index 4cd8ed51d..7b304eafe 100644 > --- a/include/vulkan/vulkan_core.h > +++ b/include/vulkan/vulkan_core.h > @@ -451,6 +451,7 @@ typedef enum VkStructureType { > VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_EXCLUSIVE_SCISSOR_FEATURES_NV = 1000205002, > VK_STRUCTURE_TYPE_CHECKPOINT_DATA_NV = 1000206000, > VK_STRUCTURE_TYPE_QUEUE_FAMILY_CHECKPOINT_PROPERTIES_NV = 1000206001, > + VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_DERIVATIVE_GROUP_QUAD_PROPERTIES_EXT = 1000209000, > VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VULKAN_MEMORY_MODEL_FEATURES_KHR = 1000211000, > VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_PCI_BUS_INFO_PROPERTIES_EXT = 1000212000, > VK_STRUCTURE_TYPE_IMAGEPIPE_SURFACE_CREATE_INFO_FUCHSIA = 1000214000, > @@ -7791,8 +7792,6 @@ typedef struct VkPipelineCoverageModulationStateCreateInfoNV { > > > #define VK_EXT_image_drm_format_modifier 1 > -#define VK_EXT_EXTENSION_159_SPEC_VERSION 0 > -#define VK_EXT_EXTENSION_159_EXTENSION_NAME "VK_EXT_extension_159" > #define VK_EXT_IMAGE_DRM_FORMAT_MODIFIER_SPEC_VERSION 1 > #define VK_EXT_IMAGE_DRM_FORMAT_MODIFIER_EXTENSION_NAME "VK_EXT_image_drm_format_modifier" > > @@ -8791,6 +8790,18 @@ VKAPI_ATTR void VKAPI_CALL vkGetQueueCheckpointDataNV( > VkCheckpointDataNV* pCheckpointData); > #endif > > +#define VK_EXT_derivative_group_quad 1 > +#define VK_EXT_DERIVATIVE_GROUP_QUAD_SPEC_VERSION 1 > +#define VK_EXT_DERIVATIVE_GROUP_QUAD_EXTENSION_NAME "VK_EXT_derivative_group_quad" > + > +typedef struct VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT { > + VkStructureType sType; > + const void* pNext; > + VkBool32 derivativeGroupsAreSubgroupQuads; > +} VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT; > + > + > + > #define VK_EXT_pci_bus_info 1 > #define VK_EXT_PCI_BUS_INFO_SPEC_VERSION 1 > #define VK_EXT_PCI_BUS_INFO_EXTENSION_NAME "VK_EXT_pci_bus_info" > diff --git a/xml/vk.xml b/xml/vk.xml > index 24cc3ce78..93dc66159 100644 > --- a/xml/vk.xml > +++ b/xml/vk.xml > @@ -3590,6 +3590,11 @@ server. > <member>const <type>void</type>* <name>pNext</name></member> > <member><type>VkMemoryOverallocationBehaviorAMD</type> <name>overallocationBehavior</name></member> > </type> > + <type category="struct" name="VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT" structextends="VkPhysicalDeviceProperties2"> > + <member values="VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_DERIVATIVE_GROUP_QUAD_PROPERTIES_EXT"><type>VkStructureType</type> <name>sType</name></member> > + <member>const <type>void</type>* <name>pNext</name></member> > + <member><type>VkBool32</type> <name>derivativeGroupsAreSubgroupQuads</name></member> > + </type> > </types> > > <comment>Vulkan enumerant (token) definitions</comment> > @@ -9893,10 +9898,12 @@ server. > <enum value=""VK_KHR_extension_209"" name="VK_KHR_EXTENSION_209_EXTENSION_NAME"/> > </require> > </extension> > - <extension name="VK_INTEL_extension_210" number="210" type="device" author="INTEL" contact="Jason Ekstrand @jekstrand" supported="disabled"> > + <extension name="VK_EXT_derivative_group_quad" number="210" type="device" requiresCore="1.1" author="EXT" contact="Jason Ekstrand @jekstrand" supported="vulkan"> > <require> > - <enum value="0" name="VK_KHR_EXTENSION_210_SPEC_VERSION"/> > - <enum value=""VK_KHR_extension_210"" name="VK_KHR_EXTENSION_210_EXTENSION_NAME"/> > + <enum value="1" name="VK_EXT_DERIVATIVE_GROUP_QUAD_SPEC_VERSION"/> > + <enum value=""VK_EXT_derivative_group_quad"" name="VK_EXT_DERIVATIVE_GROUP_QUAD_EXTENSION_NAME"/> > + <enum offset="0" extends="VkStructureType" name="VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_DERIVATIVE_GROUP_QUAD_PROPERTIES_EXT"/> > + <type name="VkPhysicalDeviceDerivativeGroupQuadPropertiesEXT"/> > </require> > </extension> > <extension name="VK_INTEL_extension_211" number="211" type="device" author="INTEL" contact="Jason Ekstrand @jekstrand" supported="disabled"> > </blockquote></div></div>