proposed fix for #1135

frontends/p4/fromv1.0/converters.cpp

@@ -590,23 +590,7 @@ class ComputeCallGraph : public Inspector {
  public:
     explicit ComputeCallGraph(ProgramStructure* structure) : structure(structure)
     { CHECK_NULL(structure); setName("ComputeCallGraph"); }
-    void postorder(const IR::Apply* apply) override {
-        LOG3("Scanning " << apply->name);
-        auto tbl = structure->tables.get(apply->name.name);
-        if (tbl == nullptr)
-            ::error("Could not find table %1%", apply->name);
-        auto parent = findContext<IR::V1Control>();
-        BUG_CHECK(parent != nullptr, "%1%: Apply not within a control block?", apply);
-        auto ctrl = get(structure->tableMapping, tbl);
-        if (ctrl != nullptr && ctrl != parent) {
-            auto previous = get(structure->tableInvocation, tbl);
-            ::error("Table %1% invoked from two different controls: %2% and %3%",
-                    tbl, apply, previous);
-        }
-        LOG3("Invoking " << tbl << " in " << parent->name);
-        structure->tableMapping.emplace(tbl, parent);
-        structure->tableInvocation.emplace(tbl, apply);
-    }
+
     void postorder(const IR::V1Parser* parser) override {
         LOG3("Scanning parser " << parser->name);
         structure->parsers.add(parser->name);
@@ -716,6 +700,43 @@ class ComputeCallGraph : public Inspector {
     }
 };
 
+/// Table call graph should be built after the control call graph is built.
+/// In the case that the program contains an unused control block, the
+/// table invocation in the unused control block should not be considered.
+class ComputeTableCallGraph : public Inspector {
+    ProgramStructure *structure;
+
+ public:
+    explicit ComputeTableCallGraph(ProgramStructure *structure) : structure(structure) {
+        CHECK_NULL(structure);
+        setName("ComputeCallGraph");
+    }
+
+    void postorder(const IR::Apply *apply) override {
+        LOG3("Scanning " << apply->name);
+        auto tbl = structure->tables.get(apply->name.name);
+        if (tbl == nullptr)
+            ::error("Could not find table %1%", apply->name);
+        auto parent = findContext<IR::V1Control>();
+        BUG_CHECK(parent != nullptr, "%1%: Apply not within a control block?", apply);
+
+        auto ctrl = get(structure->tableMapping, tbl);
+
+        // skip checking control block that is unused.
+        if (!structure->calledControls.isCallee(parent->name))
+            return;
+
+        if (ctrl != nullptr && ctrl != parent) {
+            auto previous = get(structure->tableInvocation, tbl);
+            ::error("Table %1% invoked from two different controls: %2% and %3%",
+                    tbl, apply, previous);
+        }
+        LOG3("Invoking " << tbl << " in " << parent->name);
+        structure->tableMapping.emplace(tbl, parent);
+        structure->tableInvocation.emplace(tbl, apply);
+    }
+};
+
 class Rewriter : public Transform {
     ProgramStructure* structure;
  public:
@@ -1059,6 +1080,7 @@ Converter::Converter() {
     // Convert
     passes.emplace_back(new DiscoverStructure(&structure));
     passes.emplace_back(new ComputeCallGraph(&structure));
+    passes.emplace_back(new ComputeTableCallGraph(&structure));
     passes.emplace_back(new Rewriter(&structure));
     passes.emplace_back(new FixExtracts(&structure));
     passes.emplace_back(new RemoveAnnotatedFields);

frontends/p4/fromv1.0/programStructure.cpp

@@ -1940,6 +1940,12 @@ void ProgramStructure::createControls() {
 
     for (auto c : controlsToDo) {
         auto ct = controls.get(c);
+        /// do not convert control block if it is not invoked
+        /// by other control block and it is not ingress or egress.
+        if (!calledControls.isCallee(c) &&
+            ct != controls.get(v1model.ingress.name) &&
+            ct != controls.get(v1model.egress.name))
+            continue;
         auto ctrl = convertControl(ct, controls.get(ct));
         if (ctrl == nullptr)
             return;

testdata/p4_14_samples/double_apply.p4

@@ -0,0 +1,45 @@
+/*
+Copyright 2013-present Barefoot Networks, Inc. 
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+header_type h {
+    fields {
+        b : 1;
+    }
+}
+
+metadata h m;
+
+parser start {
+    return ingress;
+}
+
+action x() {}
+
+table t {
+    actions { x; }
+}
+
+control c {
+    apply(t);
+}
+
+control e {
+    apply(t);
+}
+
+control ingress {
+    c();
+}

testdata/p4_14_samples_outputs/double_apply-first.p4

@@ -0,0 +1,65 @@
+#include <core.p4>
+#include <v1model.p4>
+
+struct h {
+    bit<1> b;
+}
+
+struct metadata {
+    @name(".m") 
+    h m;
+}
+
+struct headers {
+}
+
+parser ParserImpl(packet_in packet, out headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name(".start") state start {
+        transition accept;
+    }
+}
+
+control c(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name(".x") action x() {
+    }
+    @name(".t") table t {
+        actions = {
+            x();
+            @defaultonly NoAction();
+        }
+        default_action = NoAction();
+    }
+    apply {
+        t.apply();
+    }
+}
+
+control ingress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name(".c") c() c_0;
+    apply {
+        c_0.apply(hdr, meta, standard_metadata);
+    }
+}
+
+control egress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    apply {
+    }
+}
+
+control DeparserImpl(packet_out packet, in headers hdr) {
+    apply {
+    }
+}
+
+control verifyChecksum(inout headers hdr, inout metadata meta) {
+    apply {
+    }
+}
+
+control computeChecksum(inout headers hdr, inout metadata meta) {
+    apply {
+    }
+}
+
+V1Switch<headers, metadata>(ParserImpl(), verifyChecksum(), ingress(), egress(), computeChecksum(), DeparserImpl()) main;
+

testdata/p4_14_samples_outputs/double_apply-frontend.p4

@@ -0,0 +1,65 @@
+#include <core.p4>
+#include <v1model.p4>
+
+struct h {
+    bit<1> b;
+}
+
+struct metadata {
+    @name(".m") 
+    h m;
+}
+
+struct headers {
+}
+
+parser ParserImpl(packet_in packet, out headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name(".start") state start {
+        transition accept;
+    }
+}
+
+control c(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name(".x") action x_0() {
+    }
+    @name(".t") table t_0 {
+        actions = {
+            x_0();
+            @defaultonly NoAction();
+        }
+        default_action = NoAction();
+    }
+    apply {
+        t_0.apply();
+    }
+}
+
+control ingress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name(".c") c() c_1;
+    apply {
+        c_1.apply(hdr, meta, standard_metadata);
+    }
+}
+
+control egress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    apply {
+    }
+}
+
+control DeparserImpl(packet_out packet, in headers hdr) {
+    apply {
+    }
+}
+
+control verifyChecksum(inout headers hdr, inout metadata meta) {
+    apply {
+    }
+}
+
+control computeChecksum(inout headers hdr, inout metadata meta) {
+    apply {
+    }
+}
+
+V1Switch<headers, metadata>(ParserImpl(), verifyChecksum(), ingress(), egress(), computeChecksum(), DeparserImpl()) main;
+

testdata/p4_14_samples_outputs/double_apply-midend.p4

@@ -0,0 +1,60 @@
+#include <core.p4>
+#include <v1model.p4>
+
+struct h {
+    bit<1> b;
+}
+
+struct metadata {
+    @name(".m") 
+    h m;
+}
+
+struct headers {
+}
+
+parser ParserImpl(packet_in packet, out headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name(".start") state start {
+        transition accept;
+    }
+}
+
+control ingress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name("NoAction") action NoAction_0() {
+    }
+    @name(".x") action _x() {
+    }
+    @name(".t") table _t_0 {
+        actions = {
+            _x();
+            @defaultonly NoAction_0();
+        }
+        default_action = NoAction_0();
+    }
+    apply {
+        _t_0.apply();
+    }
+}
+
+control egress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    apply {
+    }
+}
+
+control DeparserImpl(packet_out packet, in headers hdr) {
+    apply {
+    }
+}
+
+control verifyChecksum(inout headers hdr, inout metadata meta) {
+    apply {
+    }
+}
+
+control computeChecksum(inout headers hdr, inout metadata meta) {
+    apply {
+    }
+}
+
+V1Switch<headers, metadata>(ParserImpl(), verifyChecksum(), ingress(), egress(), computeChecksum(), DeparserImpl()) main;
+

testdata/p4_14_samples_outputs/double_apply.p4

@@ -0,0 +1,63 @@
+#include <core.p4>
+#include <v1model.p4>
+
+struct h {
+    bit<1> b;
+}
+
+struct metadata {
+    @name(".m") 
+    h m;
+}
+
+struct headers {
+}
+
+parser ParserImpl(packet_in packet, out headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name(".start") state start {
+        transition accept;
+    }
+}
+
+control c(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name(".x") action x() {
+    }
+    @name(".t") table t {
+        actions = {
+            x;
+        }
+    }
+    apply {
+        t.apply();
+    }
+}
+
+control ingress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    @name(".c") c() c_0;
+    apply {
+        c_0.apply(hdr, meta, standard_metadata);
+    }
+}
+
+control egress(inout headers hdr, inout metadata meta, inout standard_metadata_t standard_metadata) {
+    apply {
+    }
+}
+
+control DeparserImpl(packet_out packet, in headers hdr) {
+    apply {
+    }
+}
+
+control verifyChecksum(inout headers hdr, inout metadata meta) {
+    apply {
+    }
+}
+
+control computeChecksum(inout headers hdr, inout metadata meta) {
+    apply {
+    }
+}
+
+V1Switch(ParserImpl(), verifyChecksum(), ingress(), egress(), computeChecksum(), DeparserImpl()) main;
+