Fix for issue #496 (#500)

p4lang · Apr 22, 2017 · a9beb5b · a9beb5b
1 parent f3f5b64
commit a9beb5b
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Showing 16 changed files with 338 additions and 149 deletions.
diff --git a/backends/p4test/midend.cpp b/backends/p4test/midend.cpp
@@ -82,7 +82,7 @@ MidEnd::MidEnd(CompilerOptions& options) {
         new P4::RemoveAllUnusedDeclarations(&refMap),
         new P4::ClearTypeMap(&typeMap),
         evaluator,
-            new VisitFunctor([v1controls, evaluator](const IR::Node *root) -> const IR::Node * {
+        new VisitFunctor([v1controls, evaluator](const IR::Node *root) -> const IR::Node * {
             auto toplevel = evaluator->getToplevelBlock();
             auto main = toplevel->getMain();
             if (main == nullptr)

diff --git a/frontends/p4/unusedDeclarations.cpp b/frontends/p4/unusedDeclarations.cpp
@@ -106,6 +106,16 @@ const IR::Node* RemoveUnusedDeclarations::preorder(IR::Declaration_Instance* dec
     if (!refMap->isUsed(getOriginal<IR::Declaration_Instance>())) {
         if (giveWarning(getOriginal()))
             ::warning("%1%: unused instance", decl);
+        // We won't delete extern instances; these may be useful even if not references.
+        auto type = decl->type;
+        if (type->is<IR::Type_Specialized>())
+            type = type->to<IR::Type_Specialized>()->baseType;
+        if (type->is<IR::Type_Name>())
+            type = refMap->getDeclaration(type->to<IR::Type_Name>()->path, true)->to<IR::Type>();
+        if (!type->is<IR::Type_Extern>())
+            return process(decl);
+        prune();
+        return decl;
     }
     // don't scan the initializer: we don't want to delete virtual methods
     prune();

diff --git a/frontends/p4/unusedDeclarations.h b/frontends/p4/unusedDeclarations.h
@@ -24,7 +24,7 @@ namespace P4 {
 
 class RemoveUnusedDeclarations : public Transform {
     const ReferenceMap* refMap;
-    // If non-null give warnings about unused declarations
+    /// If non-null give warnings about unused declarations
     std::set<const IR::Node*>* warned;
     const IR::Node* process(const IR::IDeclaration* decl);
 
@@ -38,8 +38,8 @@ class RemoveUnusedDeclarations : public Transform {
     using Transform::preorder;
     using Transform::init_apply;
 
-    // True if we should report a warning; the node is
-    // added to warned in this case
+    /// True if we should report a warning; the node is
+    /// added to warned in this case
     bool giveWarning(const IR::Node* node);
 
     Visitor::profile_t init_apply(const IR::Node *root) override;
@@ -52,7 +52,7 @@ class RemoveUnusedDeclarations : public Transform {
 
     const IR::Node* preorder(IR::Declaration_Instance* decl) override;
 
-    // Do not delete the following even if unused
+    // The following kinds of nodes are not deleted even if they are unreferenced
     const IR::Node* preorder(IR::Type_Error* type) override
     { prune(); return type; }
     const IR::Node* preorder(IR::Declaration_MatchKind* decl) override
@@ -63,14 +63,14 @@ class RemoveUnusedDeclarations : public Transform {
     { prune(); return type; }
     const IR::Node* preorder(IR::Type_Method* type) override
     { prune(); return type; }
+    const IR::Node* preorder(IR::Parameter* param) override { return param; }  // never dead
 
     const IR::Node* preorder(IR::Declaration_Variable* decl)  override;
-    const IR::Node* preorder(IR::Parameter* param) override { return param; }  // never dead
     const IR::Node* preorder(IR::Declaration* decl) override { return process(decl); }
     const IR::Node* preorder(IR::Type_Declaration* decl) override { return process(decl); }
 };
 
-// Iterates RemoveUnusedDeclarations until convergence.
+/// Iterates RemoveUnusedDeclarations until convergence.
 class RemoveAllUnusedDeclarations : public PassManager {
  public:
     explicit RemoveAllUnusedDeclarations(ReferenceMap* refMap, bool warn = false) {