Fix cast from uniform struct to varying struct.

expr.cpp

@@ -6786,7 +6786,8 @@ lUniformValueToVarying(FunctionEmitContext *ctx, llvm::Value *value,
 
         for (int i = 0; i < collectionType->GetElementCount(); ++i) {
             llvm::Value *v = ctx->ExtractInst(value, i, "get_element");
-            v = lUniformValueToVarying(ctx, v, collectionType->GetElementType(i));
+            if (collectionType->GetElementType(i)->IsVaryingType())
+                v = lUniformValueToVarying(ctx, v, collectionType->GetElementType(i));
             retValue = ctx->InsertInst(retValue, v, i, "set_element");
         }
         return retValue;

tests/struct-test-126.ispc

@@ -0,0 +1,23 @@
+
+export uniform int width() { return programCount; }
+
+
+struct Foo {
+    uniform float x;
+    varying float y;
+};
+
+export void f_fu(uniform float RET[], uniform float aFOO[], uniform float b) {
+    float a = aFOO[programIndex];
+    uniform Foo struct_1;
+    struct_1.x = b;
+    struct_1.y = aFOO[programIndex];
+    varying Foo struct_2 = struct_1;
+    RET[programIndex] = struct_2.x + struct_2.y;
+}
+
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 5 + programIndex + 1;
+}
+