SPIR-V SV_InstanceId support in pixel shader

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

@@ -1285,6 +1285,36 @@ ScalarizedVal createSimpleGLSLGlobalVarying(
         declarator,
         &systemValueInfoStorage);
 
+    {
+
+        auto systemSemantic = inVarLayout->findAttr<IRSystemValueSemanticAttr>();
+        // 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))))
+        {
+            ShortList<IRInst*> newOperands;
+            auto opCount = inVarLayout->getOperandCount();
+            newOperands.reserveOverflowBuffer(opCount);
+            for (UInt i = 0; i < opCount; ++i)
+            {
+                auto op = inVarLayout->getOperand(i);
+                if (op == systemSemantic)
+                    continue;
+                newOperands.add(op);
+            }
+
+            auto newVarLayout = builder->emitIntrinsicInst(
+                inVarLayout->getFullType(),
+                inVarLayout->getOp(),
+                newOperands.getCount(),
+                newOperands.getArrayView().getBuffer());
+
+            newVarLayout->sourceLoc = inVarLayout->sourceLoc;
+
+            inVarLayout->replaceUsesWith(newVarLayout);
+        }
+    }
+
     IRType* type = inType;
     IRType* peeledRequiredType = nullptr;
 
@@ -2570,9 +2600,7 @@ 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-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 +1,38 @@
+//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-DAG: BuiltIn InstanceIndex
+// CHECK-NOT: BuiltIn InstanceIndex
+
+// We require 1 `Flat` for the fragment input `uint`
+// SPIRV: Flat
+// SPIRV-NOT: Flat
+
+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 +1,28 @@
+//TEST:SIMPLE(filecheck=HLSL): -entry main -target hlsl
+//TEST:SIMPLE(filecheck=GLSL): -entry main -target glsl
+//TEST:SIMPLE(filecheck=SPIRV): -entry main -target spirv
+
+// HLSL-DAG: main
+// HLSL-DAG: SV_InstanceID
+
+// GLSL-DAG: main
+// GLSL-DAG: gl_InstanceIndex
+
+// SPIRV: OpEntryPoint
+// SPIRV-NOT: BuiltIn InstanceIndex
+// We require 1 `Flat` for the fragment input `uint`
+// SPIRV: Flat
+// SPIRV-NOT: Flat
+
+
+struct PSInput
+{
+    uint vInstance : SV_InstanceID;
+	float4 color : COLOR;
+};
+
+[shader("pixel")]
+float4 main(PSInput input) : SV_TARGET
+{
+	return input.color + float(input.vInstance).xxxx;
+}