1 files changed, 146 insertions, 0 deletions
diff --git a/compilerplugins/clang/oncevar.cxx b/compilerplugins/clang/oncevar.cxx
new file mode 100644
index 000000000000..6a348b4235b9
--- /dev/null
+++ b/compilerplugins/clang/oncevar.cxx
@@ -0,0 +1,146 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <string>
+#include <iostream>
+#include <map>
+
+#include "plugin.hxx"
+#include "compat.hxx"
+#include "clang/AST/CXXInheritance.h"
+
+// Idea from tml.
+// Check for OUString variables that are
+//   (1) initialised from a string literal
+//   (2) only used in one spot
+// In which case, we might as well inline it.
+
+namespace
+{
+
+class OnceVar:
+    public RecursiveASTVisitor<OnceVar>, public loplugin::Plugin
+{
+public:
+    explicit OnceVar(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool TraverseFunctionDecl( FunctionDecl* stmt );
+    bool VisitDeclRefExpr( const DeclRefExpr* );
+
+private:
+    bool mbChecking;
+    std::map<SourceLocation,int> maVarUsesMap;
+    std::map<SourceLocation,SourceRange> maVarDeclSourceRangeMap;
+    std::map<SourceLocation,SourceRange> maVarUseSourceRangeMap;
+    StringRef getFilename(SourceLocation loc);
+};
+
+StringRef OnceVar::getFilename(SourceLocation loc)
+{
+    SourceLocation spellingLocation = compiler.getSourceManager().getSpellingLoc(loc);
+    StringRef name { compiler.getSourceManager().getFilename(spellingLocation) };
+    return name;
+}
+
+bool OnceVar::TraverseFunctionDecl(FunctionDecl * decl)
+{
+    if (ignoreLocation(decl)) {
+        return true;
+    }
+    if (!decl->hasBody()) {
+        return true;
+    }
+    if ( decl != decl->getCanonicalDecl() ) {
+        return true;
+    }
+
+    // some places, it makes the code worse
+    StringRef aFileName = getFilename(decl->getLocStart());
+    if (aFileName.startswith(SRCDIR "/sal/qa/osl/module/osl_Module.cxx")) {
+        return true;
+    }
+
+    maVarUsesMap.clear();
+    maVarDeclSourceRangeMap.clear();
+    mbChecking = true;
+    TraverseStmt(decl->getBody());
+    mbChecking = false;
+    for (auto it = maVarUsesMap.cbegin(); it != maVarUsesMap.cend(); ++it)
+    {
+        if (it->second == 1)
+        {
+            report(DiagnosticsEngine::Warning,
+                    "OUString var used only once, should be inlined",
+                   it->first)
+                << maVarDeclSourceRangeMap[it->first];
+            report(DiagnosticsEngine::Note,
+                   "to this spot",
+                   maVarUseSourceRangeMap[it->first].getBegin())
+                << maVarUseSourceRangeMap[it->first];
+        }
+    }
+    return true;
+}
+
+bool OnceVar::VisitDeclRefExpr( const DeclRefExpr* declRefExpr )
+{
+    if (!mbChecking)
+        return true;
+    const Decl* decl = declRefExpr->getDecl();
+    if (!isa<VarDecl>(decl) || isa<ParmVarDecl>(decl)) {
+        return true;
+    }
+    const VarDecl * varDecl = dyn_cast<VarDecl>(decl)->getCanonicalDecl();
+    if (!varDecl->hasInit() || varDecl->hasGlobalStorage()) {
+        return true;
+    }
+    if (varDecl->getType().getUnqualifiedType().getAsString().find("OUString") == std::string::npos) {
+        return true;
+    }
+    const CXXConstructExpr* constructExpr = dyn_cast<CXXConstructExpr>(varDecl->getInit());
+    if (!constructExpr || constructExpr->getNumArgs() < 1) {
+        return true;
+    }
+    if (!isa<StringLiteral>(constructExpr->getArg(0))) {
+        return true;
+    }
+
+    SourceLocation loc = varDecl->getLocation();
+
+    // ignore cases like:
+    //     const OUString("xxx") xxx;
+    //     rtl_something(xxx.pData);
+    // and
+    //      foo(&xxx);
+    // where we cannot inline the declaration.
+    if (isa<MemberExpr>(parentStmt(declRefExpr))
+        || isa<UnaryOperator>(parentStmt(declRefExpr))) {
+        maVarUsesMap[loc] = 2;
+        return true;
+    }
+
+    if (maVarUsesMap.find(loc) == maVarUsesMap.end()) {
+        maVarUsesMap[loc] = 1;
+        maVarDeclSourceRangeMap[loc] = varDecl->getSourceRange();
+        maVarUseSourceRangeMap[loc] = declRefExpr->getSourceRange();
+    } else {
+        maVarUsesMap[loc]++;
+    }
+    return true;
+}
+
+loplugin::Plugin::Registration< OnceVar > X("oncevar");
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */