Return insertion for void functions without explicit return

example/passthrough_fragment.glsl

@@ -2,5 +2,4 @@ layout(location = 0) out vec4 outColor;
 
 void main() {
   outColor = vec4(1.0, 0.0, 0.0, 1.0);
-  return;
 }

lib/CodeGen/MLIRCodeGen.cpp

@@ -774,6 +774,19 @@ void MLIRCodeGen::visit(FunctionDeclaration *funcDecl) {
 
   funcDecl->getBody()->accept(this);
 
+  // Return insertion for void functions
+  if (funcDecl->getReturnType()->getKind() == TypeKind::Void) {
+    if (auto stmts = dynamic_cast<StatementList*>(funcDecl->getBody())) {
+      auto &lastStmt = stmts->getStatements().back();
+
+      if (!dynamic_cast<ReturnStatement*>(lastStmt.get())) {
+        builder.create<spirv::ReturnOp>(builder.getUnknownLoc());
+      }
+    } else if (dynamic_cast<Statement*>(funcDecl->getBody()) && !dynamic_cast<ReturnStatement*>(funcDecl->getBody())) {
+        builder.create<spirv::ReturnOp>(builder.getUnknownLoc());
+    }
+  }
+
   inGlobalScope = true;
 
   functionMap.insert({funcDecl->getName(), funcOp});

test/Analysis/vardecl.glsl

@@ -25,6 +25,4 @@ int myFunc() {
 
     // error: boolean expression expected
     e = d ? 1 : 2;
-
-    return;
 }

test/CodeGen/arrays.glsl

@@ -47,6 +47,4 @@ void main() {
     // CHECK-NEXT: %cst_f32_16 = spirv.Constant 1.000000e+00 : f32
     // CHECK-NEXT: spirv.Store "Function" %22, %cst_f32_16 : f32
     multiArr[0][1] = 1.0;
-
-    return;
 }

test/CodeGen/binary_expressions.glsl

@@ -10,6 +10,4 @@ void main() {
 
     // CHECK: %6 = spirv.FAdd %cst_f64, %cst_f64_1 : f64
     double d = 1.0lf + 2.0lf;
-
-    return;
 }

test/CodeGen/structs.glsl

@@ -28,6 +28,4 @@ void main() {
     // CHECK-NEXT: %13 = spirv.Variable : !spirv.ptr<i1, Function>
     // CHECK-NEXT: spirv.Store "Function" %13, %12 : i1
     bool d = myStruct.d;
-
-    return;
 }