Create empty SetOfLocations for don't care arguments passed as action…

… out args. (#4762)

Signed-off-by: Kyle Cripps <[email protected]>

frontends/p4/alias.h

@@ -240,6 +240,10 @@ class ReadsWrites : public Inspector {
         rw.emplace(expression, result);
     }
 
+    void postorder(const IR::DefaultExpression *expression) override {
+        rw.emplace(expression, new SetOfLocations());
+    }
+
     const SetOfLocations *get(const IR::Expression *expression) {
         expression->apply(*this);
         auto result = ::get(rw, expression);

testdata/p4_16_samples/issue4760_dontcare_action_out_arg.p4

@@ -0,0 +1,27 @@
+struct S {
+    bit<64> f;
+}
+
+control C(inout S s) {
+    action d(in bit<64> f, out bit<64> b) {
+        b = f + 4;
+    }
+
+    action foo() {
+        d(s.f, _);
+    }
+
+    table t {
+        actions = { foo; }
+        default_action = foo;
+    }
+
+    apply {
+        t.apply();
+    }
+}
+
+control proto(inout S s);
+package top(proto p);
+
+top(C()) main;

testdata/p4_16_samples_outputs/issue4760_dontcare_action_out_arg-first.p4

@@ -0,0 +1,25 @@
+struct S {
+    bit<64> f;
+}
+
+control C(inout S s) {
+    action d(in bit<64> f, out bit<64> b) {
+        b = f + 64w4;
+    }
+    action foo() {
+        d(s.f, _);
+    }
+    table t {
+        actions = {
+            foo();
+        }
+        default_action = foo();
+    }
+    apply {
+        t.apply();
+    }
+}
+
+control proto(inout S s);
+package top(proto p);
+top(C()) main;

testdata/p4_16_samples_outputs/issue4760_dontcare_action_out_arg-frontend.p4

@@ -0,0 +1,21 @@
+struct S {
+    bit<64> f;
+}
+
+control C(inout S s) {
+    @name("C.foo") action foo() {
+    }
+    @name("C.t") table t_0 {
+        actions = {
+            foo();
+        }
+        default_action = foo();
+    }
+    apply {
+        t_0.apply();
+    }
+}
+
+control proto(inout S s);
+package top(proto p);
+top(C()) main;

testdata/p4_16_samples_outputs/issue4760_dontcare_action_out_arg-midend.p4

@@ -0,0 +1,21 @@
+struct S {
+    bit<64> f;
+}
+
+control C(inout S s) {
+    @name("C.foo") action foo() {
+    }
+    @name("C.t") table t_0 {
+        actions = {
+            foo();
+        }
+        default_action = foo();
+    }
+    apply {
+        t_0.apply();
+    }
+}
+
+control proto(inout S s);
+package top(proto p);
+top(C()) main;

testdata/p4_16_samples_outputs/issue4760_dontcare_action_out_arg.p4

@@ -0,0 +1,25 @@
+struct S {
+    bit<64> f;
+}
+
+control C(inout S s) {
+    action d(in bit<64> f, out bit<64> b) {
+        b = f + 4;
+    }
+    action foo() {
+        d(s.f, _);
+    }
+    table t {
+        actions = {
+            foo;
+        }
+        default_action = foo;
+    }
+    apply {
+        t.apply();
+    }
+}
+
+control proto(inout S s);
+package top(proto p);
+top(C()) main;