loplugin:moveopt

An attempt that did not find anything convincing enough to finish it up
and make it permanently active.
So just leave it in /store for now.

Change-Id: I1750e177655a4a510da100f880ba81bf762be277
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/114742
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

1 files changed, 161 insertions, 0 deletions

diff --git a/compilerplugins/clang/store/optmove.cxx b/compilerplugins/clang/store/optmove.cxx
new file mode 100644
index 000000000000..a4831179ed14
--- /dev/null
+++ b/compilerplugins/clang/store/optmove.cxx
@@ -0,0 +1,161 @@
+/* -*- 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 "plugin.hxx"
+#include "check.hxx"
+
+#include <string>
+#include <set>
+
+/**
+ * This plugin is unfinished, abandoned because it did not find anything interesting.
+ *
+ * Look for variables that are
+ * (a) copied from
+ * (b) never used after the copy
+ * (c) have move operators
+ *
+ * The intention being to find places where we can move data (e.g. in containers) instead of copying.
+*/
+
+namespace
+{
+class OptMove : public loplugin::FilteringPlugin<OptMove>
+{
+public:
+    explicit OptMove(loplugin::InstantiationData const& data)
+        : FilteringPlugin(data)
+    {
+    }
+
+    virtual void run() override
+    {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+
+        for (auto const& pair : m_Candidates)
+        {
+            //auto varDecl = pair.first;
+            auto candidate = pair.second;
+            if (!candidate.canUseExpr)
+                continue;
+            report(DiagnosticsEngine::Warning, "can std::move value instead of copy",
+                   candidate.canUseExpr->getSourceRange().getBegin())
+                << candidate.canUseExpr->getSourceRange();
+            //varDecl->dump();
+        }
+    }
+
+    bool VisitVarDecl(const VarDecl*);
+    bool VisitCXXOperatorCallExpr(const CXXOperatorCallExpr*);
+    bool VisitDeclRefExpr(const DeclRefExpr*);
+    bool VisitFunctionDecl(const FunctionDecl* f)
+    {
+        if (f->getIdentifier() && f->getName() == "foo")
+            f->dump();
+        return true;
+    }
+
+private:
+    struct Candidate
+    {
+        const DeclRefExpr* operatorArg1 = nullptr;
+        const Expr* canUseExpr = nullptr;
+    };
+    std::map<const VarDecl*, Candidate> m_Candidates;
+};
+
+bool OptMove::VisitVarDecl(const VarDecl* varDecl)
+{
+    if (ignoreLocation(varDecl))
+        return true;
+    if (varDecl->hasGlobalStorage())
+        return true;
+    if (varDecl->getLinkageAndVisibility().getLinkage() == ExternalLinkage)
+        return true;
+    if (!varDecl->getType()->isRecordType())
+        return true;
+
+    auto cxxRecord = dyn_cast<CXXRecordDecl>(varDecl->getType()->getAsRecordDecl());
+    if (!cxxRecord || !cxxRecord->hasDefinition() || !cxxRecord->hasMoveAssignment())
+        return true;
+    // ignore our simpler types for now, I'm after bigger game
+    auto typeName = cxxRecord->getName();
+    if (typeName.contains("Reference") || typeName.contains("Color") || typeName.contains("VclPtr")
+        || typeName.contains("OString") || typeName.contains("OUString")
+        || typeName.contains("Rectangle") || typeName.contains("Size")
+        || typeName.contains("Selection") || typeName.contains("Point")
+        || typeName.contains("strong_int"))
+        return true;
+    m_Candidates.emplace(varDecl, Candidate());
+
+    if (!varDecl->hasInit())
+        return true;
+    auto cons = dyn_cast<CXXConstructExpr>(varDecl->getInit());
+    if (!cons || !cons->getConstructor()->isCopyConstructor())
+        return true;
+    auto arg1 = dyn_cast<DeclRefExpr>(compat::IgnoreImplicit(cons->getArg(0)));
+    if (!arg1)
+        return true;
+    auto varDecl1 = dyn_cast<VarDecl>(arg1->getDecl());
+    if (!varDecl1)
+        return true;
+    auto it = m_Candidates.find(varDecl1);
+    if (it == m_Candidates.end())
+        return true;
+    it->second.operatorArg1 = arg1;
+    it->second.canUseExpr = cons;
+    return true;
+}
+
+bool OptMove::VisitCXXOperatorCallExpr(CXXOperatorCallExpr const* cxxOperatorCallExpr)
+{
+    if (ignoreLocation(cxxOperatorCallExpr))
+        return true;
+    auto op = cxxOperatorCallExpr->getOperator();
+    if (op != OO_Equal)
+        return true;
+    auto arg0 = dyn_cast<DeclRefExpr>(compat::IgnoreImplicit(cxxOperatorCallExpr->getArg(0)));
+    auto arg1 = dyn_cast<DeclRefExpr>(compat::IgnoreImplicit(cxxOperatorCallExpr->getArg(1)));
+    if (!arg0 || !arg1)
+        return true;
+    auto varDecl0 = dyn_cast<VarDecl>(arg0->getDecl());
+    auto varDecl1 = dyn_cast<VarDecl>(arg1->getDecl());
+    if (!varDecl0 || !varDecl1)
+        return true;
+    auto cxxMethodDecl = dyn_cast_or_null<CXXMethodDecl>(cxxOperatorCallExpr->getDirectCallee());
+    if (!cxxMethodDecl || !cxxMethodDecl->isCopyAssignmentOperator())
+        return true;
+    auto it = m_Candidates.find(varDecl1);
+    if (it == m_Candidates.end())
+        return true;
+    it->second.operatorArg1 = arg1;
+    it->second.canUseExpr = cxxOperatorCallExpr;
+    return true;
+}
+
+bool OptMove::VisitDeclRefExpr(const DeclRefExpr* declRefExpr)
+{
+    if (ignoreLocation(declRefExpr))
+        return true;
+    auto varDecl = dyn_cast<VarDecl>(declRefExpr->getDecl());
+    if (!varDecl)
+        return true;
+    auto it = m_Candidates.find(varDecl);
+    if (it == m_Candidates.end())
+        return true;
+    if (it->second.operatorArg1 == declRefExpr)
+        return true;
+    m_Candidates.erase(it);
+    return true;
+}
+
+loplugin::Plugin::Registration<OptMove> noexceptmove("optmove");
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */