Map `SV_VertexID` to `gl_VertexIndex-gl_BaseVertex`, add `SV_Vulkan*ID` semantics (#7150)

* Map SV_VertexID to `gl_VertexIndex - gl_BaseVertex`, provide SV_Vulkan* SV semantics

* Fix docs

* Regenerate toc

* Fix affected pointer-2 test

* Add tests

---------

Co-authored-by: Yong He <yonghe@outlook.com>

15 files changed, 177 insertions, 19 deletions

diff --git a/docs/user-guide/a2-01-spirv-target-specific.md b/docs/user-guide/a2-01-spirv-target-specific.md
index 1ab143cb0..dee19cd28 100644
--- a/docs/user-guide/a2-01-spirv-target-specific.md
+++ b/docs/user-guide/a2-01-spirv-target-specific.md
@@ -72,7 +72,7 @@ The system-value semantics are translated to the following SPIR-V code.
 | `SV_GroupThreadID`            | `BuiltIn LocalInvocationId`       |
 | `SV_InnerCoverage`            | `BuiltIn FullyCoveredEXT`         |
 | `SV_InsideTessFactor`         | `BuiltIn TessLevelInner`          |
-| `SV_InstanceID`<sup>**</sup>  | `BuiltIn InstanceIndex`           |
+| `SV_InstanceID`<sup>**</sup>  | `BuiltIn InstanceIndex` - `Builtin BaseInstance`  |
 | `SV_IntersectionAttributes`   | *Not supported*                   |
 | `SV_IsFrontFace`              | `BuiltIn FrontFacing`             |
 | `SV_OutputControlPointID`     | `BuiltIn InvocationId`            |
@@ -88,20 +88,25 @@ The system-value semantics are translated to the following SPIR-V code.
 | `SV_StencilRef`               | `BuiltIn FragStencilRefEXT`       |
 | `SV_Target<N>`                | `Location`                        |
 | `SV_TessFactor`               | `BuiltIn TessLevelOuter`          |
-| `SV_VertexID`                 | `BuiltIn VertexIndex`             |
+| `SV_VertexID`<sup>**</sup>    | `BuiltIn VertexIndex` - `Builtin BaseVertex`    |
 | `SV_ViewID`                   | `BuiltIn ViewIndex`               |
 | `SV_ViewportArrayIndex`       | `BuiltIn ViewportIndex`           |
+| `SV_VulkanInstanceID`         | `BuiltIn InstanceIndex`           |
+| `SV_VulkanVertexID`           | `BuiltIn VertexIndex`             |
 
 *Note* that `SV_DrawIndex`, `SV_PointSize` and `SV_PointCoord` are Slang-specific semantics that are not defined in HLSL.
-Also *Note* that `SV_InstanceID` counts all instances in a draw call, unlike how `InstanceIndex` is relative to `BaseInstance`. See [Using SV_InstanceID with SPIR-V target](#using-sv_instanceid-with-spir-v-target)
+Also *Note* that `SV_InstanceID`/`SV_VertexID` counts all instances/vertices in a draw call, unlike how `InstanceIndex`/`VertexIndex` is relative to `BaseInstance`/`BaseVertex`.
+See [Using SV_InstanceID/SV_VertexID with SPIR-V target](#using-sv_instanceid-and-sv_vertexid-with-spir-v-target)
 
-Using SV_InstanceID with SPIR-V target
+Using SV_InstanceID and SV_VertexID with SPIR-V target
 --------------------------------------
 
-When using `SV_InstanceID` with SPIR-V target, it is equivalent to the difference between the `InstanceIndex` and `BaseInstance` builtins.
-This matches the behavior of D3D where `SV_InstanceID` starts from zero for each draw call, while in SPIR-V, `InstanceIndex` includes the base instance.
+When using `SV_InstanceID` and `SV_VertexID` with SPIR-V target, it is equivalent to the difference between the index and base builtins.
+This matches the behavior of D3D where `SV_InstanceID` and `SV_VertexID` starts from zero for each draw call, while in SPIR-V, 
+`InstanceIndex` and `VertexIndex` includes the base instance.
 
-If you need direct access to the `InstanceIndex` value, you can use parameters with `SV_InstanceID` and `SV_StartInstanceLocation` semantics:
+If you need direct access to `InstanceIndex` and `VertexIndex` values, use `SV_VulkanInstanceID` and `SV_VulkanVertexID` semantic names. These are supported for all targets except HLSL.
+Alternatively you can use parameters with `SV_InstanceID`(or `SV_VertexID`) and `SV_StartInstanceLocation`(or `SV_StartVertexLocation`) semantics:
 
 ```slang
 void myVertexShader(
diff --git a/docs/user-guide/a2-02-metal-target-specific.md b/docs/user-guide/a2-02-metal-target-specific.md
index 8d69a5975..c0360efda 100644
--- a/docs/user-guide/a2-02-metal-target-specific.md
+++ b/docs/user-guide/a2-02-metal-target-specific.md
@@ -44,6 +44,8 @@ The system-value semantics are translated to the following Metal attributes:
 | `SV_ViewportArrayIndex`     | `[[viewport_array_index]]`                           |
 | `SV_StartVertexLocation`    | `[[base_vertex]]`                                    |
 | `SV_StartInstanceLocation`  | `[[base_instance]]`                                  |
+| `SV_VulkanInstanceID`       | `[[instance_id]]`                                    |
+| `SV_VulkanVertexID`         | `[[vertex_id]]`                                      |
 
 Custom semantics are mapped to user attributes:
 
diff --git a/docs/user-guide/a2-03-wgsl-target-specific.md b/docs/user-guide/a2-03-wgsl-target-specific.md
index cf28d4b49..e8a918dc8 100644
--- a/docs/user-guide/a2-03-wgsl-target-specific.md
+++ b/docs/user-guide/a2-03-wgsl-target-specific.md
@@ -50,6 +50,8 @@ The system-value semantics are translated to the following WGSL code.
 | SV_VertexID | `@builtin(vertex_index)` |
 | SV_ViewID | *Not supported* |
 | SV_ViewportArrayIndex | *Not supported* |
+| SV_VulkanInstanceID | `@builtin(instance_index)` |
+| SV_VulkanVertexID | `@builtin(vertex_index)` |
 
 
 Supported HLSL features when targeting WGSL
@@ -179,4 +181,4 @@ Translates to:
 
 ```wgsl
 @id(7) override a : i32 = 2;
-```
\ No newline at end of file
+```
diff --git a/docs/user-guide/toc.html b/docs/user-guide/toc.html
index ace7da1d0..47e0c05ad 100644
--- a/docs/user-guide/toc.html
+++ b/docs/user-guide/toc.html
@@ -195,7 +195,7 @@
 <li data-link="spirv-target-specific#memory-model"><span>Memory model</span></li>
 <li data-link="spirv-target-specific#combined-texture-sampler"><span>Combined texture sampler</span></li>
 <li data-link="spirv-target-specific#system-value-semantics"><span>System-Value semantics</span></li>
-<li data-link="spirv-target-specific#using-sv_instanceid-with-spir-v-target"><span>Using SV_InstanceID with SPIR-V target</span></li>
+<li data-link="spirv-target-specific#using-sv_instanceid-and-sv_vertexid-with-spir-v-target"><span>Using SV_InstanceID and SV_VertexID with SPIR-V target</span></li>
 <li data-link="spirv-target-specific#behavior-of-discard-after-spir-v-16"><span>Behavior of `discard` after SPIR-V 1.6</span></li>
 <li data-link="spirv-target-specific#supported-hlsl-features-when-targeting-spir-v"><span>Supported HLSL features when targeting SPIR-V</span></li>
 <li data-link="spirv-target-specific#unsupported-glsl-keywords-when-targeting-spir-v"><span>Unsupported GLSL keywords when targeting SPIR-V</span></li>
diff --git a/source/slang/glsl.meta.slang b/source/slang/glsl.meta.slang
index 2d9078855..588396251 100644
--- a/source/slang/glsl.meta.slang
+++ b/source/slang/glsl.meta.slang
@@ -159,6 +159,9 @@ public property uint3 gl_WorkGroupSize
 public in int gl_InvocationID : SV_GSInstanceID;
 
 internal in int __sv_InstanceIndex : SV_InstanceID;
+internal in int __sv_VertexIndex : SV_VertexID;
+internal in int __sv_VulkanInstanceIndex : SV_VulkanInstanceID;
+internal in int __sv_VulkanVertexIndex : SV_VulkanVertexID;
 
 // SPIRV InstanceIndex builtin for vertex shader
 public property int gl_InstanceIndex
@@ -168,24 +171,42 @@ public property int gl_InstanceIndex
     {
         __target_switch
         {
+        case glsl:
+        case spirv:
+        case metal:
+        case wgsl:
+            return __sv_VulkanInstanceIndex;
         default:
             return __sv_InstanceIndex;
+        }
+    }
+}
+
+// SPIRV VertexIndex builtin for vertex shader
+public property int gl_VertexIndex
+{
+    [require(vertex)]
+    get
+    {
+        __target_switch
+        {
         case glsl:
-            __intrinsic_asm "gl_InstanceIndex";
         case spirv:
-            return spirv_asm {
-                result:$$int = OpLoad builtin(InstanceIndex:int);
-            };
+        case metal:
+        case wgsl:
+            return __sv_VulkanVertexIndex;
+        default:
+            return __sv_VertexIndex;
         }
     }
 }
+
 public in bool gl_FrontFacing : SV_IsFrontFace;
 
 // TODO: define overload for geometry stage.
 public in int gl_Layer : SV_RenderTargetArrayIndex;
 
 public in int gl_SampleID : SV_SampleIndex;
-public in int gl_VertexIndex : SV_VertexID;
 public in int gl_ViewIndex : SV_ViewID;
 public in int gl_ViewportIndex : SV_ViewportArrayIndex;
 public in int gl_BaseVertex : SV_StartVertexLocation;
diff --git a/source/slang/slang-emit-c-like.cpp b/source/slang/slang-emit-c-like.cpp
index b2dc9b014..26b964d6e 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -351,6 +351,10 @@ String CLikeSourceEmitter::getTargetBuiltinVarName(IRInst* inst, IRTargetBuiltin
         return "gl_InstanceIndex";
     case IRTargetBuiltinVarName::SpvBaseInstance:
         return "gl_BaseInstance";
+    case IRTargetBuiltinVarName::SpvVertexIndex:
+        return "gl_VertexIndex";
+    case IRTargetBuiltinVarName::SpvBaseVertex:
+        return "gl_BaseVertex";
     }
     if (auto linkage = inst->findDecoration<IRLinkageDecoration>())
         return linkage->getMangledName();
diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index 5c1ccaf36..5dfa1c76c 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -5856,6 +5856,11 @@ struct SPIRVEmitContext : public SourceEmitterBase, public SPIRVEmitSharedContex
             case IRTargetBuiltinVarName::SpvBaseInstance:
                 requireSPIRVCapability(SpvCapabilityDrawParameters);
                 return getBuiltinGlobalVar(inst->getFullType(), SpvBuiltInBaseInstance, inst);
+            case IRTargetBuiltinVarName::SpvVertexIndex:
+                return getBuiltinGlobalVar(inst->getFullType(), SpvBuiltInVertexIndex, inst);
+            case IRTargetBuiltinVarName::SpvBaseVertex:
+                requireSPIRVCapability(SpvCapabilityDrawParameters);
+                return getBuiltinGlobalVar(inst->getFullType(), SpvBuiltInBaseVertex, inst);
             }
         }
         if (auto layout = getVarLayout(inst))
@@ -5948,7 +5953,7 @@ struct SPIRVEmitContext : public SourceEmitterBase, public SPIRVEmitSharedContex
                 {
                     return getBuiltinGlobalVar(inst->getFullType(), SpvBuiltInInvocationId, inst);
                 }
-                else if (semanticName == "sv_instanceid")
+                else if (semanticName == "sv_vulkaninstanceid")
                 {
                     return getBuiltinGlobalVar(inst->getFullType(), SpvBuiltInInstanceIndex, inst);
                 }
@@ -6046,7 +6051,7 @@ struct SPIRVEmitContext : public SourceEmitterBase, public SPIRVEmitSharedContex
                     requireSPIRVCapability(SpvCapabilityTessellation);
                     return getBuiltinGlobalVar(inst->getFullType(), SpvBuiltInTessLevelInner, inst);
                 }
-                else if (semanticName == "sv_vertexid")
+                else if (semanticName == "sv_vulkanvertexid")
                 {
                     return getBuiltinGlobalVar(inst->getFullType(), SpvBuiltInVertexIndex, inst);
                 }
diff --git a/source/slang/slang-ir-glsl-legalize.cpp b/source/slang/slang-ir-glsl-legalize.cpp
index 1223ea91c..c9791880f 100644
--- a/source/slang/slang-ir-glsl-legalize.cpp
+++ b/source/slang/slang-ir-glsl-legalize.cpp
@@ -630,6 +630,13 @@ GLSLSystemValueInfo* getGLSLSystemValueInfo(
         context->requireGLSLVersion(ProfileVersion::GLSL_460);
         context->requireGLSLExtension(toSlice("GL_ARB_shader_draw_parameters"));
     }
+    else if (semanticName == "sv_vulkaninstanceid")
+    {
+        // https://docs.microsoft.com/en-us/windows/desktop/direct3d11/d3d10-graphics-programming-guide-input-assembler-stage-using#instanceid
+        // uint in hlsl, int in glsl
+        requiredType = builder->getBasicType(BaseType::Int);
+        name = "gl_InstanceIndex";
+    }
     else if (semanticName == "sv_isfrontface")
     {
         // bool in hlsl & glsl
@@ -778,6 +785,16 @@ GLSLSystemValueInfo* getGLSLSystemValueInfo(
         // uint in hlsl, int in glsl (https://www.khronos.org/opengl/wiki/Built-in_Variable_(GLSL))
         requiredType = builder->getBasicType(BaseType::Int);
         name = "gl_VertexIndex";
+        targetVarName = IRTargetBuiltinVarName::HlslVertexID;
+        context->requireSPIRVVersion(SemanticVersion(1, 3));
+        context->requireGLSLVersion(ProfileVersion::GLSL_460);
+        context->requireGLSLExtension(toSlice("GL_ARB_shader_draw_parameters"));
+    }
+    else if (semanticName == "sv_vulkanvertexid")
+    {
+        // uint in hlsl, int in glsl (https://www.khronos.org/opengl/wiki/Built-in_Variable_(GLSL))
+        requiredType = builder->getBasicType(BaseType::Int);
+        name = "gl_VertexIndex";
     }
     else if (semanticName == "sv_viewid")
     {
@@ -1251,6 +1268,12 @@ void invokePathConstantFuncInHullShader(
     fixUpFuncType(constantFunc);
 }
 
+static bool targetBuiltinRequiresLegalization(IRTargetBuiltinVarName builtinVarName)
+{
+    return (builtinVarName == IRTargetBuiltinVarName::HlslInstanceID) ||
+           (builtinVarName == IRTargetBuiltinVarName::HlslVertexID);
+}
+
 ScalarizedVal createSimpleGLSLGlobalVarying(
     GLSLLegalizationContext* context,
     CodeGenContext* codeGenContext,
@@ -1284,7 +1307,7 @@ ScalarizedVal createSimpleGLSLGlobalVarying(
         // Validate the system value, convert to a regular parameter if this is not a valid system
         // value for a given target.
         if (systemSemantic && systemValueInfo && isSPIRV(codeGenContext->getTargetFormat()) &&
-            systemValueInfo->targetVarName == IRTargetBuiltinVarName::HlslInstanceID &&
+            targetBuiltinRequiresLegalization(systemValueInfo->targetVarName) &&
             ((stage == Stage::Fragment) ||
              (stage == Stage::Vertex &&
               inVarLayout->usesResourceKind(LayoutResourceKind::VaryingOutput))))
@@ -3918,12 +3941,13 @@ ScalarizedVal legalizeEntryPointReturnValueForGLSL(
     return result;
 }
 
+
 void legalizeTargetBuiltinVar(GLSLLegalizationContext& context)
 {
     List<KeyValuePair<IRTargetBuiltinVarName, IRInst*>> workItems;
     for (auto [builtinVarName, varInst] : context.builtinVarMap)
     {
-        if (builtinVarName == IRTargetBuiltinVarName::HlslInstanceID)
+        if (targetBuiltinRequiresLegalization(builtinVarName))
         {
             workItems.add(KeyValuePair(builtinVarName, varInst));
         }
@@ -3970,6 +3994,32 @@ void legalizeTargetBuiltinVar(GLSLLegalizationContext& context)
                     }
                 });
         }
+        // Repalce SV_VertexID with gl_VertexIndex - gl_BaseVertex.
+        else if (builtinVarName == IRTargetBuiltinVarName::HlslVertexID)
+        {
+            auto vertexIndex = getOrCreateBuiltinVar(
+                IRTargetBuiltinVarName::SpvVertexIndex,
+                varInst->getDataType());
+            auto baseVertex = getOrCreateBuiltinVar(
+                IRTargetBuiltinVarName::SpvBaseVertex,
+                varInst->getDataType());
+            traverseUses(
+                varInst,
+                [&](IRUse* use)
+                {
+                    auto user = use->getUser();
+                    if (user->getOp() == kIROp_Load)
+                    {
+                        IRBuilder builder(use->getUser());
+                        builder.setInsertBefore(use->getUser());
+                        auto sub = builder.emitSub(
+                            tryGetPointedToType(&builder, varInst->getDataType()),
+                            builder.emitLoad(vertexIndex),
+                            builder.emitLoad(baseVertex));
+                        user->replaceUsesWith(sub);
+                    }
+                });
+        }
     }
 }
 
diff --git a/source/slang/slang-ir-insts.h b/source/slang/slang-ir-insts.h
index c188b1eff..2ab4db980 100644
--- a/source/slang/slang-ir-insts.h
+++ b/source/slang/slang-ir-insts.h
@@ -203,8 +203,11 @@ enum class IRTargetBuiltinVarName
 {
     Unknown,
     HlslInstanceID,
+    HlslVertexID,
     SpvInstanceIndex,
     SpvBaseInstance,
+    SpvVertexIndex,
+    SpvBaseVertex,
 };
 
 struct IRInterpolationModeDecoration : IRDecoration
diff --git a/source/slang/slang-ir-legalize-varying-params.cpp b/source/slang/slang-ir-legalize-varying-params.cpp
index 180d8eaa7..f8a9839d2 100644
--- a/source/slang/slang-ir-legalize-varying-params.cpp
+++ b/source/slang/slang-ir-legalize-varying-params.cpp
@@ -3189,6 +3189,7 @@ protected:
                 break;
             }
         case SystemValueSemanticName::InstanceID:
+        case SystemValueSemanticName::VulkanInstanceID:
             {
                 result.systemValueName = toSlice("instance_id");
                 result.permittedTypes.add(builder.getBasicType(BaseType::UInt));
@@ -3252,6 +3253,7 @@ protected:
                 break;
             }
         case SystemValueSemanticName::VertexID:
+        case SystemValueSemanticName::VulkanVertexID:
             {
                 result.systemValueName = toSlice("vertex_id");
                 result.permittedTypes.add(builder.getBasicType(BaseType::UInt));
@@ -3855,6 +3857,7 @@ protected:
             break;
 
         case SystemValueSemanticName::InstanceID:
+        case SystemValueSemanticName::VulkanInstanceID:
             {
                 result.systemValueName = toSlice("instance_index");
                 result.permittedTypes.add(builder.getUIntType());
@@ -3908,6 +3911,7 @@ protected:
             }
 
         case SystemValueSemanticName::VertexID:
+        case SystemValueSemanticName::VulkanVertexID:
             {
                 result.systemValueName = toSlice("vertex_index");
                 result.permittedTypes.add(builder.getUIntType());
diff --git a/source/slang/slang-ir-legalize-varying-params.h b/source/slang/slang-ir-legalize-varying-params.h
index 21674cd9e..233acaf94 100644
--- a/source/slang/slang-ir-legalize-varying-params.h
+++ b/source/slang/slang-ir-legalize-varying-params.h
@@ -72,6 +72,8 @@ void depointerizeInputParams(IRFunc* entryPoint);
     M(WaveLaneCount, SV_WaveLaneCount)                   \
     M(WaveLaneIndex, SV_WaveLaneIndex)                   \
     M(QuadLaneIndex, SV_QuadLaneIndex)                   \
+    M(VulkanVertexID, SV_VulkanVertexID)                 \
+    M(VulkanInstanceID, SV_VulkanInstanceID)             \
 /* end */
 
 /// A known system-value semantic name that can be applied to a parameter
diff --git a/source/slang/slang-ir-spirv-legalize.cpp b/source/slang/slang-ir-spirv-legalize.cpp
index 87a6cc4b9..20b7f795f 100644
--- a/source/slang/slang-ir-spirv-legalize.cpp
+++ b/source/slang/slang-ir-spirv-legalize.cpp
@@ -636,6 +636,8 @@ struct SPIRVLegalizationContext : public SourceEmitterBase
             {
             case IRTargetBuiltinVarName::SpvInstanceIndex:
             case IRTargetBuiltinVarName::SpvBaseInstance:
+            case IRTargetBuiltinVarName::SpvVertexIndex:
+            case IRTargetBuiltinVarName::SpvBaseVertex:
                 return AddressSpace::BuiltinInput;
             }
         }
diff --git a/tests/spirv/pointer-2.slang b/tests/spirv/pointer-2.slang
index 201d97001..1f2b2d0ea 100644
--- a/tests/spirv/pointer-2.slang
+++ b/tests/spirv/pointer-2.slang
@@ -44,7 +44,7 @@ ConstantBuffer<PushConstants> constantBuffer;
 // CHECK_SPV_VIA_GLSL: OpTypePointer PhysicalStorageBuffer
 
 [shader("vertex")]
-VSOutput vertexMain(int vertexIndex: SV_VertexID)
+VSOutput vertexMain(int vertexIndex: SV_VulkanVertexID)
 {
     //
     // Test field access chains.
diff --git a/tests/spirv/sv-vertex-id.slang b/tests/spirv/sv-vertex-id.slang
new file mode 100644
index 000000000..c92f0351e
--- /dev/null
+++ b/tests/spirv/sv-vertex-id.slang
@@ -0,0 +1,16 @@
+//TEST:SIMPLE(filecheck=GLSL): -target glsl -entry vertMain -stage vertex
+//TEST:SIMPLE(filecheck=CHECK): -target spirv
+//TEST:SIMPLE(filecheck=CHECK): -target spirv  -emit-spirv-via-glsl
+
+// CHECK-DAG: %[[BASE_VERTEX:[0-9]+|[a-zA-Z_][a-zA-Z0-9_]*]] = OpVariable {{.*}} BuiltIn BaseVertex
+// CHECK-DAG: %[[REG1:[0-9a-zA-Z_]+]] = OpLoad %int %[[BASE_VERTEX]]
+// CHECK-DAG: %[[REG2:[0-9a-zA-Z_]+]] = OpLoad %int %gl_VertexIndex
+// CHECK-DAG: OpISub %int %[[REG2]] %[[REG1]]
+
+// GLSL: gl_VertexIndex - gl_BaseVertex
+
+[shader("vertex")]
+float4 vertMain(int i : SV_VertexID) : SV_Position
+{
+    return i;
+}
diff --git a/tests/spirv/sv-vulkan-instance-vertex-id.slang b/tests/spirv/sv-vulkan-instance-vertex-id.slang
new file mode 100644
index 000000000..c8654c857
--- /dev/null
+++ b/tests/spirv/sv-vulkan-instance-vertex-id.slang
@@ -0,0 +1,42 @@
+//TEST:SIMPLE(filecheck=SPIRV): -entry main -stage vertex -target spirv -emit-spirv-directly
+//TEST:SIMPLE(filecheck=GLSL): -entry main -stage vertex -target glsl
+//TEST:SIMPLE(filecheck=METAL): -entry main -stage vertex -target metal
+//TEST:SIMPLE(filecheck=WGSL): -entry main -stage vertex -target wgsl
+
+struct VSInput
+{
+    uint vertexID : SV_VulkanVertexID;
+    uint instanceID : SV_VulkanInstanceID;
+};
+
+struct VSOutput
+{
+    float4 position : SV_POSITION;
+};
+
+[shader("vertex")]
+VSOutput main(VSInput input)
+{
+    VSOutput output;
+    output.position = float4(input.vertexID + input.instanceID);
+
+    // SPIRV-DAG: BuiltIn InstanceIndex
+    // SPIRV-DAG: BuiltIn VertexIndex
+    // SPIRV-NOT: BuiltIn BaseInstance
+    // SPIRV-NOT: BuiltIn BaseVertex
+
+    // GLSL-NOT: GL_ARB_shader_draw_parameters
+    // GLSL-DAG: gl_VertexIndex
+    // GLSL-NOT: gl_BaseVertex
+    // GLSL-DAG: gl_InstanceIndex
+    // GLSL-NOT: gl_BaseInstance
+
+    // METAL-DAG: vertex_id
+    // METAL-DAG: instance_id
+
+    // WGSL-DAG: vertex_index
+    // WGSL-DAG: instance_index
+
+    return output;
+}
+