Fixup handling of empty structs in function return types and parameters. (#796)

* Fixup handling of empty structs in function return types and parameters.

* Bug fix in legalizeFunc()

* More comprehensive empty struct test

* Fix `legalizeFieldExtract` for empty struct field.

* Add empty struct handling for construct inst

1 files changed, 52 insertions, 0 deletions

diff --git a/tests/compute/empty-struct2.slang b/tests/compute/empty-struct2.slang
new file mode 100644
index 000000000..17cbb6ab4
--- /dev/null
+++ b/tests/compute/empty-struct2.slang
@@ -0,0 +1,52 @@
+//TEST(smoke,compute):COMPARE_COMPUTE:
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):dxbinding(0),glbinding(0),out
+// This is a basic test for Slang compute shader.
+
+RWStructuredBuffer<uint> outputBuffer;
+
+interface IInterface
+{
+    associatedtype T;
+    T getT();
+    [mutating]
+    void setT(T val);
+}
+interface IEmptyS
+{
+    float emptyFunc();
+};
+struct EmptyS : IEmptyS
+{
+    float emptyFunc() {return 0.0;}    
+};
+
+struct Empty<TT : IEmptyS> : IInterface
+{
+    typedef TT T;
+    TT value;
+    float a;
+    TT getT()
+    {
+        return value;
+    }
+    [mutating]
+    void setT(TT val)
+    {
+        value = val;
+        a = value.emptyFunc();
+    }
+}
+
+void test<Obj : IInterface>(Obj obj)
+{
+    Obj.T v = obj.getT();
+    obj.setT(v);
+}
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    Empty<EmptyS> obj;
+    test(obj);
+    outputBuffer[dispatchThreadID.x] = dispatchThreadID.x;
+}
\ No newline at end of file