3 files changed, 109 insertions, 0 deletions
diff --git a/source/slang/slang-ir-specialize-resources.cpp b/source/slang/slang-ir-specialize-resources.cpp
index 2aafaaf31..871ba2c24 100644
--- a/source/slang/slang-ir-specialize-resources.cpp
+++ b/source/slang/slang-ir-specialize-resources.cpp
@@ -1359,6 +1359,10 @@ bool isIllegalGLSLParameterType(IRType* type)
         return true;
     if (as<IRDynamicResourceType>(type))
         return true;
+    if (as<IRHLSLInputPatchType>(type))
+        return true;
+    if (as<IRHLSLOutputPatchType>(type))
+        return true;
     return false;
 }
 
diff --git a/source/slang/slang-ir.cpp b/source/slang/slang-ir.cpp
index 07e8b2742..cdabb1ac2 100644
--- a/source/slang/slang-ir.cpp
+++ b/source/slang/slang-ir.cpp
@@ -5259,6 +5259,11 @@ IRInst* IRBuilder::emitElementAddress(IRInst* basePtr, IRInst* index)
         SLANG_ASSERT(as<IRIntLit>(index));
         type = (IRType*)tupleType->getOperand(getIntVal(index));
     }
+    else if (auto hlslInputPatchType = as<IRHLSLInputPatchType>(valueType))
+    {
+        type = hlslInputPatchType->getElementType();
+    }
+
     SLANG_RELEASE_ASSERT(type);
     auto inst = createInst<IRGetElementPtr>(
         this,
diff --git a/tests/spirv/tessellation-patch-as-argument.slang b/tests/spirv/tessellation-patch-as-argument.slang
new file mode 100644
index 000000000..685a8d632
--- /dev/null
+++ b/tests/spirv/tessellation-patch-as-argument.slang
@@ -0,0 +1,100 @@
+//TEST:SIMPLE(filecheck=HULL):   -target spirv -stage hull   -entry hullMain
+//TEST:SIMPLE(filecheck=DOMAIN): -target spirv -stage domain -entry domainMain
+
+// Testing if `InputPatch` and `OutputPatch` can be used as function arguments.
+// `[ForceInline]` can be used to workaround but it should work without it.
+
+// HULL: OpEntryPoint TessellationControl %hullMain
+// HULL: = OpVariable %{{[a-zA-Z_0-9]*}} Input
+
+// DOMAIN: OpEntryPoint TessellationEvaluation %domainMain
+// DOMAIN: = OpVariable %{{[a-zA-Z_0-9]*}} Output
+
+struct VS_OUT
+{
+    float3 position : POSITION;
+};
+
+struct HS_OUT
+{
+    float3 position : POSITION;
+};
+
+struct HSC_OUT
+{
+    float EdgeTessFactor[4] : SV_TessFactor;
+    float InsideTessFactor[2] : SV_InsideTessFactor;
+};
+
+struct DS_OUT
+{
+    float4 position : SV_Position;
+};
+
+
+VS_OUT GetInputPatch(InputPatch<VS_OUT, 4> patch, int index)
+{
+    return patch[index];
+}
+
+// Hull Shader (HS)
+[domain("quad")]
+[partitioning("integer")]
+[outputtopology("triangle_cw")]
+[outputcontrolpoints(4)]
+[patchconstantfunc("constants")]
+HS_OUT hullMain(InputPatch<VS_OUT, 4> patch, uint i : SV_OutputControlPointID)
+{
+    HS_OUT o;
+    o.position = patch[i].position;
+    return o;
+}
+
+HSC_OUT constants(InputPatch<VS_OUT, 4> patch)
+{
+    float3 p0 = GetInputPatch(patch, 0).position;
+    float3 p1 = patch[1].position;
+    float3 p2 = patch[2].position;
+    float3 p3 = patch[3].position;
+
+    HSC_OUT o;
+    o.EdgeTessFactor[0] = dot(p0, p1);
+    o.EdgeTessFactor[1] = dot(p0, p3);
+    o.EdgeTessFactor[2] = dot(p2, p3);
+    o.EdgeTessFactor[3] = dot(p1, p2);
+    o.InsideTessFactor[0] = lerp(o.EdgeTessFactor[1], o.EdgeTessFactor[3], 0.5);
+    o.InsideTessFactor[1] = lerp(o.EdgeTessFactor[0], o.EdgeTessFactor[2], 0.5);
+    return o;
+}
+
+HS_OUT GetOutputPatch(const OutputPatch<HS_OUT, 4> patch, int index)
+{
+    return patch[index];
+}
+
+[domain("quad")]
+DS_OUT domainMain(
+    float2 uv : SV_DomainLocation,      // Tessellated coordinates (u, v)
+    const OutputPatch<HS_OUT, 4> patch, // Control points from the hull shader
+    const HSC_OUT patchConstants        // Patch constants calculated by the hull shader
+)
+{
+    DS_OUT o;
+
+    // Interpolate the position of the tessellated point within the patch
+    float3 p0 = GetOutputPatch(patch, 0).position;
+    float3 p1 = patch[1].position;
+    float3 p2 = patch[2].position;
+    float3 p3 = patch[3].position;
+
+    // Bilinear interpolation of the position in the quad
+    float3 interpolatedPosition =
+          p0 * (1 - uv.x) * (1 - uv.y)
+        + p1 * uv.x * (1 - uv.y)
+        + p3 * uv.x * uv.y
+        + p2 * (1 - uv.x) * uv.y;
+
+    // Output final position in clip space
+    o.position = float4(interpolatedPosition, 1.0);
+    return o;
+}