4 files changed, 133 insertions, 0 deletions

diff --git a/source/slang/emit.cpp b/source/slang/emit.cpp
index f6a87fcfa..22b503b59 100644
--- a/source/slang/emit.cpp
+++ b/source/slang/emit.cpp
@@ -4574,6 +4574,57 @@ struct EmitVisitor
         }
     }
 
+    void emitInterpolationModifiers(
+        EmitContext*    ctx,
+        VarDeclBase*    decl,
+        Type*           valueType)
+    {
+        bool isGLSL = (ctx->shared->target == CodeGenTarget::GLSL);
+        bool anyModifiers = false;
+
+        if(decl->FindModifier<HLSLNoInterpolationModifier>())
+        {
+            anyModifiers = true;
+            Emit(isGLSL ? "flat " : "nointerpolation ");
+        }
+        else if(decl->FindModifier<HLSLNoPerspectiveModifier>())
+        {
+            anyModifiers = true;
+            Emit("noperspective ");
+        }
+        else if(decl->FindModifier<HLSLLinearModifier>())
+        {
+            anyModifiers = true;
+            Emit(isGLSL ? "smooth " : "linear ");
+        }
+        else if(decl->FindModifier<HLSLSampleModifier>())
+        {
+            anyModifiers = true;
+            Emit("sample ");
+        }
+        else if(decl->FindModifier<HLSLCentroidModifier>())
+        {
+            anyModifiers = true;
+            Emit("centroid ");
+        }
+
+        // If the user didn't explicitly qualify a varying
+        // with integer type, then we need to explicitly
+        // add the `flat` modifier for GLSL.
+        if(!anyModifiers && isGLSL)
+        {
+            maybeEmitGLSLFlatModifier(ctx, valueType);
+        }
+    }
+
+    void emitInterpolationModifiers(
+        EmitContext*    ctx,
+        VarLayout*      layout,
+        Type*           valueType)
+    {
+        emitInterpolationModifiers(ctx, layout->varDecl, valueType);
+    }
+
     void emitIRVarModifiers(
         EmitContext*    ctx,
         VarLayout*      layout,
@@ -5280,6 +5331,7 @@ struct EmitVisitor
             if(fieldType->Equals(getSession()->getVoidType()))
                 continue;
 
+            emitInterpolationModifiers(ctx, ff.getDecl(), fieldType);
             emitIRType(ctx, fieldType, getIRName(ff));
 
             EmitSemantics(ff.getDecl());
diff --git a/source/slang/modifier-defs.h b/source/slang/modifier-defs.h
index fdbb05748..baa08a160 100644
--- a/source/slang/modifier-defs.h
+++ b/source/slang/modifier-defs.h
@@ -258,6 +258,9 @@ END_SYNTAX_CLASS()
 // HLSL `nointerpolation` modifier
 SIMPLE_SYNTAX_CLASS(HLSLNoInterpolationModifier, InterpolationModeModifier)
 
+// HLSL `noperspective` modifier
+SIMPLE_SYNTAX_CLASS(HLSLNoPerspectiveModifier, InterpolationModeModifier)
+
 // HLSL `linear` modifier
 SIMPLE_SYNTAX_CLASS(HLSLLinearModifier, InterpolationModeModifier)
 
diff --git a/source/slang/parser.cpp b/source/slang/parser.cpp
index a3afbe87a..ea8e567b4 100644
--- a/source/slang/parser.cpp
+++ b/source/slang/parser.cpp
@@ -4358,6 +4358,7 @@ namespace Slang
         MODIFIER(column_major,  HLSLColumnMajorLayoutModifier);
 
         MODIFIER(nointerpolation,   HLSLNoInterpolationModifier);
+        MODIFIER(noperspective,     HLSLNoPerspectiveModifier);
         MODIFIER(linear,            HLSLLinearModifier);
         MODIFIER(sample,            HLSLSampleModifier);
         MODIFIER(centroid,          HLSLCentroidModifier);
diff --git a/tests/render/nointerpolation.hlsl b/tests/render/nointerpolation.hlsl
new file mode 100644
index 000000000..11613b30e
--- /dev/null
+++ b/tests/render/nointerpolation.hlsl
@@ -0,0 +1,77 @@
+//TEST(smoke):COMPARE_HLSL_RENDER:
+
+// Confirm that the `nointerpolation` modifier
+// makes it through Slang codegen with the
+// same effect as for HLSL.
+
+cbuffer Uniforms
+{
+	float4x4 modelViewProjection;
+}
+
+struct AssembledVertex
+{
+	float3	position;
+	float3	color;
+};
+
+struct CoarseVertex
+{
+	nointerpolation float3	color;
+};
+
+struct Fragment
+{
+	float4 color;
+};
+
+
+// Vertex  Shader
+
+struct VertexStageInput
+{
+	AssembledVertex assembledVertex	: A;
+};
+
+struct VertexStageOutput
+{
+	CoarseVertex	coarseVertex	: CoarseVertex;
+	float4			sv_position		: SV_Position;
+};
+
+VertexStageOutput vertexMain(VertexStageInput input)
+{
+	VertexStageOutput output;
+
+	float3 position = input.assembledVertex.position;
+	float3 color	= input.assembledVertex.color;
+
+	output.coarseVertex.color = color;
+	output.sv_position = mul(modelViewProjection, float4(position, 1.0));
+
+	return output;
+}
+
+// Fragment Shader
+
+struct FragmentStageInput
+{
+	CoarseVertex	coarseVertex	: CoarseVertex;
+};
+
+struct FragmentStageOutput
+{
+	Fragment fragment	: SV_Target;
+};
+
+FragmentStageOutput fragmentMain(FragmentStageInput input)
+{
+	FragmentStageOutput output;
+
+	float3 color = input.coarseVertex.color;
+
+	output.fragment.color = float4(color, 1.0);
+
+	return output;
+}
+