[#4625] Prune MethodCallStatements if child MethodCallExpression …

…resolves to a compile-time constant. (#4627)

* Prune MethodCallStatements if child MethodCallExpression resolves to a compile-time constant.

* Apply clang formatting

* code cleanup

frontends/p4/typeChecking/typeChecker.cpp

@@ -3615,6 +3615,11 @@ bool TypeInference::onlyBitsOrBitStructs(const IR::Type *type) const {
     return false;
 }
 
+const IR::Node *TypeInference::postorder(IR::MethodCallStatement *mcs) {
+    // Remove mcs if child methodCall resolves to a compile-time constant.
+    return !mcs->methodCall ? nullptr : mcs;
+}
+
 const IR::Node *TypeInference::postorder(IR::MethodCallExpression *expression) {
     if (done()) return expression;
     LOG2("Solving method call " << dbp(expression));
@@ -3653,6 +3658,7 @@ const IR::Node *TypeInference::postorder(IR::MethodCallExpression *expression) {
                 LOG3("Folding " << mem << " to " << w);
                 if (w < 0) return expression;
                 if (mem->member.name.endsWith("Bytes")) w = ROUNDUP(w, 8);
+                if (getParent<IR::MethodCallStatement>()) return nullptr;
                 auto result = new IR::Constant(expression->srcInfo, w);
                 auto tt = new IR::Type_Type(result->type);
                 setType(result->type, tt);
@@ -3670,6 +3676,7 @@ const IR::Node *TypeInference::postorder(IR::MethodCallExpression *expression) {
                     lit = new IR::BoolLiteral(expression->srcInfo, true);
                 if (lit) {
                     LOG3("Folding " << mem << " to " << lit);
+                    if (getParent<IR::MethodCallStatement>()) return nullptr;
                     setType(lit, IR::Type_Boolean::get());
                     setCompileTimeConstant(lit);
                     return lit;

frontends/p4/typeChecking/typeChecker.h

@@ -318,6 +318,7 @@ class TypeInference : public Transform {
     const IR::Node *postorder(IR::P4ListExpression *expression) override;
     const IR::Node *postorder(IR::StructExpression *expression) override;
     const IR::Node *postorder(IR::HeaderStackExpression *expression) override;
+    const IR::Node *postorder(IR::MethodCallStatement *mcs) override;
     const IR::Node *postorder(IR::MethodCallExpression *expression) override;
     const IR::Node *postorder(IR::ConstructorCallExpression *expression) override;
     const IR::Node *postorder(IR::SelectExpression *expression) override;

testdata/p4_16_samples/issue4625_remove_compile_time_bool_methodcall_of_mcs.p4

@@ -0,0 +1,24 @@
+header h_t {
+    bit<8> f;
+}
+
+control C() {
+    action bar() {
+        h_t h = (h_t){#};
+        h.isValid();
+    }
+
+    table t {
+        actions = { bar; }
+        default_action = bar;
+    }
+
+    apply {
+        t.apply();
+    }
+}
+
+control proto();
+package top(proto p);
+
+top(C()) main;

testdata/p4_16_samples/issue4625_remove_compile_time_const_methodcall_of_mcs.p4

@@ -0,0 +1,24 @@
+header h_t {
+    bit<8> f;
+}
+
+control C() {
+    action bar() {
+        h_t h;
+        h.minSizeInBits();
+    }
+
+    table t {
+        actions = { bar; }
+        default_action = bar;
+    }
+
+    apply {
+        t.apply();
+    }
+}
+
+control proto();
+package top(proto p);
+
+top(C()) main;

testdata/p4_16_samples_outputs/issue4625_remove_compile_time_bool_methodcall_of_mcs-first.p4

@@ -0,0 +1,23 @@
+header h_t {
+    bit<8> f;
+}
+
+control C() {
+    action bar() {
+        h_t h = (h_t){#};
+        h.isValid();
+    }
+    table t {
+        actions = {
+            bar();
+        }
+        default_action = bar();
+    }
+    apply {
+        t.apply();
+    }
+}
+
+control proto();
+package top(proto p);
+top(C()) main;

testdata/p4_16_samples_outputs/issue4625_remove_compile_time_bool_methodcall_of_mcs-frontend.p4

@@ -0,0 +1,21 @@
+header h_t {
+    bit<8> f;
+}
+
+control C() {
+    @name("C.bar") action bar() {
+    }
+    @name("C.t") table t_0 {
+        actions = {
+            bar();
+        }
+        default_action = bar();
+    }
+    apply {
+        t_0.apply();
+    }
+}
+
+control proto();
+package top(proto p);
+top(C()) main;

testdata/p4_16_samples_outputs/issue4625_remove_compile_time_bool_methodcall_of_mcs-midend.p4

@@ -0,0 +1,21 @@
+header h_t {
+    bit<8> f;
+}
+
+control C() {
+    @name("C.bar") action bar() {
+    }
+    @name("C.t") table t_0 {
+        actions = {
+            bar();
+        }
+        default_action = bar();
+    }
+    apply {
+        t_0.apply();
+    }
+}
+
+control proto();
+package top(proto p);
+top(C()) main;

testdata/p4_16_samples_outputs/issue4625_remove_compile_time_bool_methodcall_of_mcs.p4

@@ -0,0 +1,23 @@
+header h_t {
+    bit<8> f;
+}
+
+control C() {
+    action bar() {
+        h_t h = (h_t){#};
+        h.isValid();
+    }
+    table t {
+        actions = {
+            bar;
+        }
+        default_action = bar;
+    }
+    apply {
+        t.apply();
+    }
+}
+
+control proto();
+package top(proto p);
+top(C()) main;

testdata/p4_16_samples_outputs/issue4625_remove_compile_time_const_methodcall_of_mcs-first.p4

@@ -0,0 +1,22 @@
+header h_t {
+    bit<8> f;
+}
+
+control C() {
+    action bar() {
+        h_t h;
+    }
+    table t {
+        actions = {
+            bar();
+        }
+        default_action = bar();
+    }
+    apply {
+        t.apply();
+    }
+}
+
+control proto();
+package top(proto p);
+top(C()) main;

testdata/p4_16_samples_outputs/issue4625_remove_compile_time_const_methodcall_of_mcs-frontend.p4

@@ -0,0 +1,21 @@
+header h_t {
+    bit<8> f;
+}
+
+control C() {
+    @name("C.bar") action bar() {
+    }
+    @name("C.t") table t_0 {
+        actions = {
+            bar();
+        }
+        default_action = bar();
+    }
+    apply {
+        t_0.apply();
+    }
+}
+
+control proto();
+package top(proto p);
+top(C()) main;

testdata/p4_16_samples_outputs/issue4625_remove_compile_time_const_methodcall_of_mcs-midend.p4

@@ -0,0 +1,21 @@
+header h_t {
+    bit<8> f;
+}
+
+control C() {
+    @name("C.bar") action bar() {
+    }
+    @name("C.t") table t_0 {
+        actions = {
+            bar();
+        }
+        default_action = bar();
+    }
+    apply {
+        t_0.apply();
+    }
+}
+
+control proto();
+package top(proto p);
+top(C()) main;

testdata/p4_16_samples_outputs/issue4625_remove_compile_time_const_methodcall_of_mcs.p4

@@ -0,0 +1,23 @@
+header h_t {
+    bit<8> f;
+}
+
+control C() {
+    action bar() {
+        h_t h;
+        h.minSizeInBits();
+    }
+    table t {
+        actions = {
+            bar;
+        }
+        default_action = bar;
+    }
+    apply {
+        t.apply();
+    }
+}
+
+control proto();
+package top(proto p);
+top(C()) main;