3 files changed, 146 insertions, 0 deletions

diff --git a/source/slang/ir-glsl-legalize.cpp b/source/slang/ir-glsl-legalize.cpp
index b659cf293..9c4210be0 100644
--- a/source/slang/ir-glsl-legalize.cpp
+++ b/source/slang/ir-glsl-legalize.cpp
@@ -1238,6 +1238,23 @@ void legalizeEntryPointParameterForGLSL(
                 }
             }
 
+            // We will still have references to the parameter coming
+            // from the `EmitVertex` calls, so we need to replace it
+            // with something. There isn't anything reasonable to
+            // replace it with that would have the right type, so
+            // we will replace it with an undefined value, knowing
+            // that the emitted code will not actually reference it.
+            //
+            // TODO: This approach to generating geometry shader code
+            // is not ideal, and we should strive to find a better
+            // approach that involes coding the `EmitVertex` operation
+            // directly in the stdlib, similar to how ray-tracing
+            // operations like `TraceRay` are handled.
+            //
+            builder->setInsertBefore(func->getFirstBlock()->getFirstOrdinaryInst());
+            auto undefinedVal = builder->emitUndefined(pp->getFullType());
+            pp->replaceUsesWith(undefinedVal);
+
             return;
         }
     }
diff --git a/tests/cross-compile/geometry-shader.slang b/tests/cross-compile/geometry-shader.slang
new file mode 100644
index 000000000..614d71db9
--- /dev/null
+++ b/tests/cross-compile/geometry-shader.slang
@@ -0,0 +1,33 @@
+// geometry-shader.slang
+
+//TEST:CROSS_COMPILE: -profile sm_5_0 -stage geometry -entry main -target spirv-assembly
+
+struct CoarseVertex
+{
+    float4 position     : POSITION;
+    float3 color        : COLOR;
+    uint   id           : ID;
+}
+
+struct RasterVertex
+{
+    float4 position : POSITION;
+    float3 color    : COLOR;
+    uint   id       : SV_RenderTargetArrayIndex;
+}
+
+[maxvertexcount(3)]
+void main(
+    triangle CoarseVertex coarseVertices[3],
+    inout TriangleStream<RasterVertex> outputStream)
+{
+    for(int ii = 0; ii < 3; ++ii)
+    {
+        CoarseVertex coarseVertex = coarseVertices[ii];
+        RasterVertex rasterVertex;
+        rasterVertex.position   = coarseVertex.position;
+        rasterVertex.color      = coarseVertex.color;
+        rasterVertex.id         = coarseVertex.id;
+        outputStream.Append(rasterVertex);
+    }
+}
diff --git a/tests/cross-compile/geometry-shader.slang.glsl b/tests/cross-compile/geometry-shader.slang.glsl
new file mode 100644
index 000000000..cdd0f94de
--- /dev/null
+++ b/tests/cross-compile/geometry-shader.slang.glsl
@@ -0,0 +1,96 @@
+#version 450
+// geometry-shader.slang.glsl
+//TEST_IGNORE_FILE:
+
+#define RasterVertex RasterVertex_0
+#define CoarseVertex CoarseVertex_0
+
+#define input_position  _S1
+#define input_color     _S2
+#define input_id        _S3
+#define output_position _S4
+#define output_color    _S5
+
+layout(row_major) uniform;
+layout(row_major) buffer;
+
+layout(location = 0)
+in vec4  input_position[3];
+
+layout(location = 1)
+in vec3  input_color[3];
+
+layout(location = 2)
+in uint  input_id[3];
+
+layout(location = 0)
+out vec4 output_position;
+
+layout(location = 1)
+out vec3 output_color;
+
+struct RasterVertex
+{
+    vec4 position_0;
+    vec3 color_0;
+    uint id_0;
+};
+
+struct CoarseVertex
+{
+    vec4 position_1;
+    vec3 color_1;
+    uint id_1;
+};
+
+
+layout(max_vertices = 3) out;
+layout(triangles) in;
+layout(triangle_strip) out;
+
+void main()
+{
+    int ii_0;
+
+    // TODO: Having to make this copy to transpose things is unfortunate.
+    //
+    // The front-end should be able to generate code using aggregate
+    // types for the input, and/or eliminate the redundant temporary
+    // by indexing directly into the sub-arrays.
+    //
+    CoarseVertex_0  _S6[3] = {
+        CoarseVertex_0(input_position[0], input_color[0], input_id[0]),
+        CoarseVertex_0(input_position[1], input_color[1], input_id[1]),
+        CoarseVertex_0(input_position[2], input_color[2], input_id[2])
+    };
+
+    ii_0 = 0;
+    for(;;)
+    {
+        if(ii_0 < 3)
+        {}
+        else
+        {
+            break;
+        }
+
+        CoarseVertex_0 coarseVertex_0 = _S6[ii_0];
+
+        RasterVertex_0 rasterVertex_0;
+        rasterVertex_0.position_0 = coarseVertex_0.position_1;
+        rasterVertex_0.color_0 = coarseVertex_0.color_1;
+        rasterVertex_0.id_0 = coarseVertex_0.id_1;
+
+        RasterVertex_0 _S7 = rasterVertex_0;
+
+        output_position = _S7.position_0;
+        output_color = _S7.color_0;
+        gl_Layer = int(_S7.id_0);
+
+        EmitVertex();
+
+        ii_0 = ii_0 + 1;
+    }
+
+    return;
+}