[Doc][HLSL] Add documentation for root signature

clang/docs/HLSL/HLSLDocs.rst

@@ -17,3 +17,4 @@ HLSL Design and Implementation
    EntryFunctions
    FunctionCalls
    AvailabilityDiagnostics
+   RootSignature

clang/docs/HLSL/RootSignature.rst

@@ -0,0 +1,312 @@
+====================
+HLSL Root Signatures
+====================
+
+.. contents::
+   :local:
+
+Usage
+=====
+
+In HLSL, the `root signature
+<https://learn.microsoft.com/en-us/windows/win32/direct3d12/root-signatures>`_
+defines what types of resources are bound to the graphics pipeline.
+
+A root signature can be specified in HLSL as a `string
+<https://learn.microsoft.com/en-us/windows/win32/direct3d12/specifying-root-signatures-in-hlsl#an-example-hlsl-root-signature>`_.
+The string contains a collection of comma-separated clauses that describe root
+signature constituent components.
+
+There are three mechanisms to compile an HLSL root signature. First, it is
+possible to attach a root signature string to a particular shader via the
+RootSignature attribute (in the following example, using the main entry
+point):
+
+.. code-block::
+
+    #define RS "RootFlags( ALLOW_INPUT_ASSEMBLER_INPUT_LAYOUT | " \
+              "DENY_VERTEX_SHADER_ROOT_ACCESS), " \
+              "CBV(b0, space = 1, flags = DATA_STATIC), " \
+              "SRV(t0), " \
+              "UAV(u0), " \
+              "DescriptorTable( CBV(b1), " \
+              "                 SRV(t1, numDescriptors = 8, " \
+              "                     flags = DESCRIPTORS_VOLATILE), " \
+              "                 UAV(u1, numDescriptors = unbounded, " \
+              "                     flags = DESCRIPTORS_VOLATILE)), " \
+              "DescriptorTable(Sampler(s0, space=1, numDescriptors = 4)), " \
+              "RootConstants(num32BitConstants=3, b10), " \
+              "StaticSampler(s1)," \
+              "StaticSampler(s2, " \
+              "              addressU = TEXTURE_ADDRESS_CLAMP, " \
+              "              filter = FILTER_MIN_MAG_MIP_LINEAR )"
+
+    [RootSignature(RS)]
+    float4 main(float4 coord : COORD) : SV_Target
+    {
+    …
+    }
+
+The compiler will create and verify the root signature blob for the shader and
+embed it alongside the shader byte code into the shader blob.
+
+The second mechanism is using -rootsig-define option to specify macro define of
+the root signature string.
+
+.. code-block::
+
+    #define RS "…"
+
+    float4 main(float4 coord : COORD) : SV_Target
+    {
+    …
+    }
+
+Instead of adding the root signature attribute, the root signature macro define
+is passed to the compiler with -rootsign-define.
+
+.. code-block:: sh
+
+  dxc.exe -T ps_6_0 MyRS1.hlsl -rootsig-define RS -Fo MyRS1.fxo
+
+
+The third mechanism is to create a standalone root signature blob, perhaps to
+reuse it with a large set of shaders, saving space. The name of the define
+string is specified via the usual -E argument. For example:
+
+.. code-block:: sh
+
+  dxc.exe -T rootsig_1_1 MyRS1.hlsl -E MyRS1 -Fo MyRS1.fxo
+
+Note that the root signature string define can also be passed on the command
+line, e.g, -D MyRS1=”…”.
+
+Root signature could also used in form of StateObject like this:
+
+.. code-block::
+
+  GlobalRootSignature MyGlobalRootSignature =
+  {
+      "DescriptorTable(UAV(u0)),"                     // Output texture
+      "SRV(t0),"                                      // Acceleration structure
+      "CBV(b0),"                                      // Scene constants
+      "DescriptorTable(SRV(t1, numDescriptors = 2))"  // Static index and vertex buffers.
+  };
+
+  LocalRootSignature MyLocalRootSignature =
+  {
+      "RootConstants(num32BitConstants = 4, b1)"  // Cube constants
+  };
+
+
+
+GlobalRootSignature
+===================
+
+A GlobalRootSignature corresponds to a D3D12_GLOBAL_ROOT_SIGNATURE structure.
+
+The fields consist of some number of strings describing the parts of the root signature.
+The string should follow Root Signature Grammar.
+
+.. code-block::
+
+  GlobalRootSignature MyGlobalRootSignature =
+  {
+      "DescriptorTable(UAV(u0)),"                     // Output texture
+      "SRV(t0),"                                      // Acceleration structure
+      "CBV(b0),"                                      // Scene constants
+      "DescriptorTable(SRV(t1, numDescriptors = 2))"  // Static index and vertex buffers
+  };
+
+
+LocalRootSignature
+==================
+
+A LocalRootSignature corresponds to a D3D12_LOCAL_ROOT_SIGNATURE structure.
+
+Just like the global root signature subobject, the fields consist of some
+number of strings describing the parts of the root signature.
+The string should follow Root Signature Grammar.
+
+.. code-block::
+
+  LocalRootSignature MyLocalRootSignature =
+  {
+      "RootConstants(num32BitConstants = 4, b1)"  // Cube constants
+  };
+
+
+SubobjectToExportsAssociation
+=============================
+
+By default, a subobject merely declared in the same library as an export is
+able to apply to that export.
+However, applications have the ability to override that and get specific about
+what subobject goes with which export. In HLSL, this "explicit association" is
+done using SubobjectToExportsAssociation.
+
+A SubobjectToExportsAssociation corresponds to a
+D3D12_DXIL_SUBOBJECT_TO_EXPORTS_ASSOCIATION structure.
+
+This subobject is declared with the syntax
+.. code-block::
+
+  SubobjectToExportsAssociation Name =
+  {
+      SubobjectName,
+      Exports
+  };
+
+The local/global root signature in above example could be used like this:
+
+.. code-block::
+
+  SubobjectToExportsAssociation MyLocalRootSignatureAssociation =
+  {
+      "MyLocalRootSignature",    // Subobject name
+      "MyHitGroup;MyMissShader"  // Exports association
+  };
+  SubobjectToExportsAssociation MyGlobalRootSignatureAssociation =
+  {
+      "MyGlobalRootSignature",    // Subobject name
+      "MyHitGroup;MyMissShader"  // Exports association
+  };
+
+
+Root Signature Grammar
+======================
+
+.. code-block:: peg
+
+    RootSignature : (RootElement(,RootElement)?)?
+
+    RootElement : RootFlags | RootConstants | RootCBV | RootSRV | RootUAV |
+                  DescriptorTable | StaticSampler
+
+    RootFlags : 'RootFlags' '(' (RootFlag(|RootFlag)?)? ')'
+
+    RootFlag : 'ALLOW_INPUT_ASSEMBLER_INPUT_LAYOUT' |
+               'DENY_VERTEX_SHADER_ROOT_ACCESS'
+
+    RootConstants : 'RootConstants' '(' 'num32BitConstants' '=' NUMBER ','
+           bReg (',' 'space' '=' NUMBER)?
+           (',' 'visibility' '=' SHADER_VISIBILITY)? ')'
+
+    RootCBV : 'CBV' '(' bReg (',' 'space' '=' NUMBER)?
+          (',' 'visibility' '=' SHADER_VISIBILITY)?
+          (',' 'flags' '=' DATA_FLAGS)? ')'
+
+    RootSRV : 'SRV' '(' tReg (',' 'space' '=' NUMBER)?
+          (',' 'visibility' '=' SHADER_VISIBILITY)?
+          (',' 'flags' '=' DATA_FLAGS)? ')'
+
+    RootUAV : 'UAV' '(' uReg (',' 'space' '=' NUMBER)?
+          (',' 'visibility' '=' SHADER_VISIBILITY)?
+          (',' 'flags' '=' DATA_FLAGS)? ')'
+
+    DescriptorTable : 'DescriptorTable' '(' (DTClause(|DTClause)?)?
+          (',' 'visibility' '=' SHADER_VISIBILITY)? ')'
+
+    DTClause : CBV | SRV | UAV | Sampler
+
+    CBV : 'CBV' '(' bReg (',' 'numDescriptors' '=' NUMBER)?
+          (',' 'space' '=' NUMBER)?
+          (',' 'offset' '=' DESCRIPTOR_RANGE_OFFSET)?
+          (',' 'flags' '=' DATA_FLAGS)? ')'
+
+    SRV : 'SRV' '(' tReg (',' 'numDescriptors' '=' NUMBER)?
+    (',' 'space' '=' NUMBER)?
+          (',' 'offset' '=' DESCRIPTOR_RANGE_OFFSET)?
+          (',' 'flags' '=' DATA_FLAGS)? ')'
+
+    UAV : 'UAV' '(' uReg (',' 'numDescriptors' '=' NUMBER)?
+          (',' 'space' '=' NUMBER)?
+          (',' 'offset' '=' DESCRIPTOR_RANGE_OFFSET)?
+          (',' 'flags' '=' DATA_FLAGS)? ')'
+
+    Sampler : 'Sampler' '(' sReg (',' 'numDescriptors' '=' NUMBER)?
+          (',' 'space' '=' NUMBER)?
+          (',' 'offset' '=' DESCRIPTOR_RANGE_OFFSET)? (',' 'flags' '=' NUMBER)? ')'
+
+
+    SHADER_VISIBILITY : 'SHADER_VISIBILITY_ALL' | 'SHADER_VISIBILITY_VERTEX' |
+                        'SHADER_VISIBILITY_HULL' |
+                        'SHADER_VISIBILITY_DOMAIN' |
+                        'SHADER_VISIBILITY_GEOMETRY' |
+                        'SHADER_VISIBILITY_PIXEL' |
+                        'SHADER_VISIBILITY_AMPLIFICATION' |
+                        'SHADER_VISIBILITY_MESH'
+
+    DATA_FLAGS : 'DATA_STATIC_WHILE_SET_AT_EXECUTE' | 'DATA_VOLATILE'
+
+    DESCRIPTOR_RANGE_OFFSET : 'DESCRIPTOR_RANGE_OFFSET_APPEND' | NUMBER
+
+    StaticSampler : 'StaticSampler' '(' sReg (',' 'filter' '=' FILTER)?
+             (',' 'addressU' '=' TEXTURE_ADDRESS)?
+             (',' 'addressV' '=' TEXTURE_ADDRESS)?
+             (',' 'addressW' '=' TEXTURE_ADDRESS)?
+             (',' 'mipLODBias' '=' NUMBER)?
+             (',' 'maxAnisotropy' '=' NUMBER)?
+             (',' 'comparisonFunc' '=' COMPARISON_FUNC)?
+             (',' 'borderColor' '=' STATIC_BORDER_COLOR)?
+             (',' 'minLOD' '=' NUMBER)?
+             (',' 'maxLOD' '=' NUMBER)? (',' 'space' '=' NUMBER)?
+             (',' 'visibility' '=' SHADER_VISIBILITY)? ')'
+
+    bReg : 'b' NUMBER
+
+    tReg : 't' NUMBER
+
+    uReg : 'u' NUMBER
+
+    sReg : 's' NUMBER
+
+    FILTER : 'FILTER_MIN_MAG_MIP_POINT' |
+             'FILTER_MIN_MAG_POINT_MIP_LINEAR' |
+             'FILTER_MIN_POINT_MAG_LINEAR_MIP_POINT' |
+             'FILTER_MIN_POINT_MAG_MIP_LINEAR' |
+             'FILTER_MIN_LINEAR_MAG_MIP_POINT' |
+             'FILTER_MIN_LINEAR_MAG_POINT_MIP_LINEAR' |
+             'FILTER_MIN_MAG_LINEAR_MIP_POINT' |
+             'FILTER_MIN_MAG_MIP_LINEAR' |
+             'FILTER_ANISOTROPIC' |
+             'FILTER_COMPARISON_MIN_MAG_MIP_POINT' |
+             'FILTER_COMPARISON_MIN_MAG_POINT_MIP_LINEAR' |
+             'FILTER_COMPARISON_MIN_POINT_MAG_LINEAR_MIP_POINT' |
+             'FILTER_COMPARISON_MIN_POINT_MAG_MIP_LINEAR' |
+             'FILTER_COMPARISON_MIN_LINEAR_MAG_MIP_POINT' |
+             'FILTER_COMPARISON_MIN_LINEAR_MAG_POINT_MIP_LINEAR' |
+             'FILTER_COMPARISON_MIN_MAG_LINEAR_MIP_POINT' |
+             'FILTER_COMPARISON_MIN_MAG_MIP_LINEAR' |
+             'FILTER_COMPARISON_ANISOTROPIC' |
+             'FILTER_MINIMUM_MIN_MAG_MIP_POINT' |
+             'FILTER_MINIMUM_MIN_MAG_POINT_MIP_LINEAR' |
+             'FILTER_MINIMUM_MIN_POINT_MAG_LINEAR_MIP_POINT' |
+             'FILTER_MINIMUM_MIN_POINT_MAG_MIP_LINEAR' |
+             'FILTER_MINIMUM_MIN_LINEAR_MAG_MIP_POINT' |
+             'FILTER_MINIMUM_MIN_LINEAR_MAG_POINT_MIP_LINEAR' |
+             'FILTER_MINIMUM_MIN_MAG_LINEAR_MIP_POINT' |
+             'FILTER_MINIMUM_MIN_MAG_MIP_LINEAR' |
+             'FILTER_MINIMUM_ANISOTROPIC' |
+             'FILTER_MAXIMUM_MIN_MAG_MIP_POINT' |
+             'FILTER_MAXIMUM_MIN_MAG_POINT_MIP_LINEAR' |
+             'FILTER_MAXIMUM_MIN_POINT_MAG_LINEAR_MIP_POINT' |
+             'FILTER_MAXIMUM_MIN_POINT_MAG_MIP_LINEAR' |
+             'FILTER_MAXIMUM_MIN_LINEAR_MAG_MIP_POINT' |
+             'FILTER_MAXIMUM_MIN_LINEAR_MAG_POINT_MIP_LINEAR' |
+             'FILTER_MAXIMUM_MIN_MAG_LINEAR_MIP_POINT' |
+             'FILTER_MAXIMUM_MIN_MAG_MIP_LINEAR' |
+             'FILTER_MAXIMUM_ANISOTROPIC'
+
+    TEXTURE_ADDRESS : 'TEXTURE_ADDRESS_WRAP' |
+                      'TEXTURE_ADDRESS_MIRROR' | 'TEXTURE_ADDRESS_CLAMP' |
+                      'TEXTURE_ADDRESS_BORDER' | 'TEXTURE_ADDRESS_MIRROR_ONCE'
+
+    COMPARISON_FUNC : 'COMPARISON_NEVER' | 'COMPARISON_LESS' |
+                      'COMPARISON_EQUAL' | 'COMPARISON_LESS_EQUAL' |
+                      'COMPARISON_GREATER' | 'COMPARISON_NOT_EQUAL' |
+                      'COMPARISON_GREATER_EQUAL' | 'COMPARISON_ALWAYS'
+
+    STATIC_BORDER_COLOR : 'STATIC_BORDER_COLOR_TRANSPARENT_BLACK' |
+                          'STATIC_BORDER_COLOR_OPAQUE_BLACK' |
+                          'STATIC_BORDER_COLOR_OPAQUE_WHITE'