SPIR-V SV_InstanceId support in pixel shader

source/slang/slang-ir-glsl-legalize.cpp

@@ -1285,6 +1285,25 @@ ScalarizedVal createSimpleGLSLGlobalVarying(
         declarator,
         &systemValueInfoStorage);
 
+    {
+        uint32_t index = 0;
+        IRSystemValueSemanticAttr* systemSemantic = nullptr;
+        for (; index < inVarLayout->operandCount; index++)
+        {
+            if (auto systemValueSemanticAttr = as<IRSystemValueSemanticAttr>(inVarLayout->getOperand(index)))
+            {    
+                systemSemantic = systemValueSemanticAttr;
+                break;
+            }
+        }
+        // Validate the system value, convert to a regular parameter if this is not a valid system value for a given target.
+        if (systemSemantic && isSPIRV(codeGenContext->getTargetFormat()) && systemSemantic->getName().caseInsensitiveEquals(UnownedStringSlice("sv_instanceid"))
+            && ((stage == Stage::Fragment) || (stage == Stage::Vertex && inVarLayout->usesResourceKind(LayoutResourceKind::VaryingOutput))))
+        {
+            inVarLayout->removeOperand(index);
+        }
+    }
+
     IRType* type = inType;
     IRType* peeledRequiredType = nullptr;
 
@@ -2570,9 +2589,7 @@ static void legalizeMeshOutputParam(
     //
 
     // First, collect the subset of outputs being used
-    const bool isSPIRV = codeGenContext->getTargetFormat() == CodeGenTarget::SPIRV
-        || codeGenContext->getTargetFormat() == CodeGenTarget::SPIRVAssembly;
-    if(!isSPIRV)
+    if(!isSPIRV(codeGenContext->getTargetFormat()))
     {
         auto isMeshOutputBuiltin = [](IRInst* g)
         {

source/slang/slang-ir-inst-defs.h

@@ -1129,7 +1129,7 @@ INST(CudaKernelLaunch, CudaKernelLaunch, 6, 0)
 INST(GetEquivalentStructuredBuffer,     getEquivalentStructuredBuffer, 1, 0)
 
 /* Layout */
-    INST(VarLayout, varLayout, 1, HOISTABLE)
+    INST(VarLayout, varLayout, 1, 0)
 
     /* TypeLayout */
         INST(TypeLayoutBase, typeLayout, 0, HOISTABLE)

source/slang/slang-ir-util.h

@@ -338,6 +338,13 @@ void verifyComputeDerivativeGroupModifiers(
     bool linearAttr,
     IRNumThreadsDecoration* numThreadsDecor);
 
+
+inline bool isSPIRV(CodeGenTarget codeGenTarget)
+{
+    return codeGenTarget == CodeGenTarget::SPIRV
+            || codeGenTarget == CodeGenTarget::SPIRVAssembly;
+}
+
 }
 
 #endif

source/slang/slang-parameter-binding.cpp

@@ -4,6 +4,7 @@
 #include "slang-lookup.h"
 #include "slang-compiler.h"
 #include "slang-type-layout.h"
+#include "slang-ir-util.h"
 
 #include "../compiler-core/slang-artifact-desc-util.h"
 
@@ -1640,6 +1641,20 @@ static RefPtr<TypeLayout> processSimpleEntryPointParameter(
                 type,
                 kEntryPointParameterDirection_Output);
         }
+        else if (isSPIRV(context->getTargetRequest()->getTarget())
+             && (
+                    (state.directionMask & kEntryPointParameterDirection_Input && state.stage == Stage::Fragment)
+                    || (state.directionMask & kEntryPointParameterDirection_Output && state.stage == Stage::Vertex)
+                )
+            && sn == "sv_instanceid"
+            )
+        {
+            // This fragment-shader-input/vertex-shader-output is effectively not a system semantic for SPIR-V,
+            typeLayout = getSimpleVaryingParameterTypeLayout(
+                context->layoutContext,
+                type,
+                state.directionMask);
+        }
         else
         {
             // For a system-value parameter (that didn't match the

tests/bugs/gh-3087-multi-entry-point.slang

@@ -0,0 +1,34 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -fvk-use-entrypoint-name -emit-spirv-directly
+
+// CHECK-DAG: OpEntryPoint Vertex
+// CHECK-DAG: OpEntryPoint Fragment
+
+// we should only have 1 'BuiltIn InstanceIndex' since the `Output` and `Input` semantic
+// for `InstanceIndex` should be converted to a non-builtin
+// CHECK: BuiltIn InstanceIndex
+// CHECK-NOT: BuiltIn InstanceIndex
+
+struct VIn
+{
+    uint instanceID : SV_InstanceID;
+}
+
+struct VSOutput
+{
+    uint instanceID : SV_InstanceID;
+	float4 color : COLOR;
+};
+
+[shader("vertex")]
+VSOutput vmain(VIn vin) {
+    VSOutput t;
+    t.instanceID = vin.instanceID;
+    t.color = float4(0, 0, 0, 0);
+    return t;
+}
+
+[shader("pixel")]
+float4 pmain(VSOutput input) : SV_TARGET
+{
+	return float4(float(input.instanceID), input.color.xyz);
+}

tests/bugs/gh-3087.slang

@@ -0,0 +1,24 @@
+//TEST:SIMPLE(filecheck=HLSL): -allow-glsl -entry main -target hlsl
+//TEST:SIMPLE(filecheck=GLSL): -allow-glsl -entry main -target glsl
+//TEST:SIMPLE(filecheck=SPIRV): -allow-glsl -entry main -target spirv
+
+// HLSL-DAG: main
+// HLSL-DAG: SV_InstanceID
+
+// GLSL-DAG: main
+// GLSL-DAG: gl_InstanceIndex
+
+// SPIRV: OpEntryPoint
+// SPIRV-NOT: BuiltIn InstanceIndex
+
+struct PSInput
+{
+    uint vInstance : SV_InstanceID;
+	float4 color : COLOR;
+};
+
+[shader("pixel")]
+float4 main(PSInput input) : SV_TARGET
+{
+	return input.color + float(input.vInstance).xxxx;
+}