1 files changed, 682 insertions, 0 deletions
diff --git a/compilerplugins/clang/flatten.cxx b/compilerplugins/clang/flatten.cxx
new file mode 100644
index 000000000..bac4ae8a4
--- /dev/null
+++ b/compilerplugins/clang/flatten.cxx
@@ -0,0 +1,682 @@
+/* -*- 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 <cassert>
+#include <string>
+#include <iostream>
+#include <fstream>
+#include <set>
+#include <stack>
+
+/**
+  Look for places where we can flatten the control flow in a method by returning early.
+ */
+namespace {
+
+class Flatten:
+    public loplugin::FilteringRewritePlugin<Flatten>
+{
+public:
+    explicit Flatten(loplugin::InstantiationData const & data):
+        FilteringRewritePlugin(data) {}
+
+    virtual void run() override
+    {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool TraverseIfStmt(IfStmt *);
+    bool TraverseCXXCatchStmt(CXXCatchStmt * );
+    bool TraverseCompoundStmt(CompoundStmt *);
+    bool TraverseFunctionDecl(FunctionDecl *);
+    bool TraverseCXXMethodDecl(CXXMethodDecl *);
+    bool TraverseCXXConstructorDecl(CXXConstructorDecl *);
+    bool TraverseCXXConversionDecl(CXXConversionDecl *);
+    bool TraverseCXXDestructorDecl(CXXDestructorDecl *);
+    bool VisitIfStmt(IfStmt const * );
+private:
+    bool rewrite1(IfStmt const * );
+    bool rewrite2(IfStmt const * );
+    bool rewriteLargeIf(IfStmt const * );
+    SourceRange ignoreMacroExpansions(SourceRange range);
+    SourceRange extendOverComments(SourceRange range);
+    std::string getSourceAsString(SourceRange range);
+    llvm::Optional<std::string> invertCondition(Expr const * condExpr, SourceRange conditionRange);
+    bool isLargeCompoundStmt(Stmt const *);
+
+    Stmt const * lastStmtInCompoundStmt = nullptr;
+    FunctionDecl const * functionDecl = nullptr;
+    CompoundStmt const * functionDeclBody = nullptr;
+    Stmt const * mElseBranch = nullptr;
+};
+
+static Stmt const * containsSingleThrowExpr(Stmt const * stmt)
+{
+    if (auto compoundStmt = dyn_cast<CompoundStmt>(stmt)) {
+        if (compoundStmt->size() != 1)
+            return nullptr;
+        stmt = *compoundStmt->body_begin();
+    }
+    if (auto exprWithCleanups = dyn_cast<ExprWithCleanups>(stmt)) {
+        stmt = exprWithCleanups->getSubExpr();
+    }
+    return dyn_cast<CXXThrowExpr>(stmt);
+}
+
+static bool containsVarDecl(Stmt const * stmt)
+{
+    if (auto compoundStmt = dyn_cast<CompoundStmt>(stmt)) {
+        for (auto i = compoundStmt->body_begin(); i != compoundStmt->body_end(); ++i) {
+            auto declStmt = dyn_cast<DeclStmt>(*i);
+            if (declStmt && isa<VarDecl>(*declStmt->decl_begin()))
+                return true;
+        }
+        return false;
+    }
+    auto declStmt = dyn_cast<DeclStmt>(stmt);
+    return declStmt && isa<VarDecl>(*declStmt->decl_begin());
+}
+
+bool Flatten::TraverseCXXCatchStmt(CXXCatchStmt* )
+{
+    // ignore stuff inside catch statements, where doing a "if...else..throw" is more natural
+    return true;
+}
+
+bool Flatten::TraverseIfStmt(IfStmt * ifStmt)
+{
+    if (!WalkUpFromIfStmt(ifStmt)) {
+        return false;
+    }
+    auto const saved = mElseBranch;
+    mElseBranch = ifStmt->getElse();
+    auto ret = true;
+    for (auto const sub: ifStmt->children()) {
+        if (!TraverseStmt(sub)) {
+            ret = false;
+            break;
+        }
+    }
+    mElseBranch = saved;
+    return ret;
+}
+
+bool Flatten::TraverseCompoundStmt(CompoundStmt * compoundStmt)
+{
+    auto copy = lastStmtInCompoundStmt;
+    if (compoundStmt->size() > 0)
+        lastStmtInCompoundStmt = compoundStmt->body_back();
+    else
+        lastStmtInCompoundStmt = nullptr;
+
+    bool rv = RecursiveASTVisitor<Flatten>::TraverseCompoundStmt(compoundStmt);
+
+    lastStmtInCompoundStmt = copy;
+    return rv;
+}
+
+bool Flatten::TraverseFunctionDecl(FunctionDecl * fd)
+{
+    auto copy1 = functionDeclBody;
+    auto copy2 = fd;
+    functionDeclBody = dyn_cast_or_null<CompoundStmt>(fd->getBody());
+    functionDecl = fd;
+    bool rv = RecursiveASTVisitor<Flatten>::TraverseFunctionDecl(fd);
+    functionDeclBody = copy1;
+    functionDecl = copy2;
+    return rv;
+}
+
+bool Flatten::TraverseCXXMethodDecl(CXXMethodDecl * fd)
+{
+    auto copy1 = functionDeclBody;
+    auto copy2 = fd;
+    functionDeclBody = dyn_cast_or_null<CompoundStmt>(fd->getBody());
+    functionDecl = fd;
+    bool rv = RecursiveASTVisitor<Flatten>::TraverseCXXMethodDecl(fd);
+    functionDeclBody = copy1;
+    functionDecl = copy2;
+    return rv;
+}
+
+bool Flatten::TraverseCXXConstructorDecl(CXXConstructorDecl * fd)
+{
+    auto copy1 = functionDeclBody;
+    auto copy2 = fd;
+    functionDeclBody = dyn_cast_or_null<CompoundStmt>(fd->getBody());
+    functionDecl = fd;
+    bool rv = RecursiveASTVisitor<Flatten>::TraverseCXXConstructorDecl(fd);
+    functionDeclBody = copy1;
+    functionDecl = copy2;
+    return rv;
+}
+
+bool Flatten::TraverseCXXConversionDecl(CXXConversionDecl * fd)
+{
+    auto copy1 = functionDeclBody;
+    auto copy2 = fd;
+    functionDeclBody = dyn_cast_or_null<CompoundStmt>(fd->getBody());
+    functionDecl = fd;
+    bool rv = RecursiveASTVisitor<Flatten>::TraverseCXXConversionDecl(fd);
+    functionDeclBody = copy1;
+    functionDecl = copy2;
+    return rv;
+}
+
+bool Flatten::TraverseCXXDestructorDecl(CXXDestructorDecl * fd)
+{
+    auto copy1 = functionDeclBody;
+    auto copy2 = fd;
+    functionDeclBody = dyn_cast_or_null<CompoundStmt>(fd->getBody());
+    functionDecl = fd;
+    bool rv = RecursiveASTVisitor<Flatten>::TraverseCXXDestructorDecl(fd);
+    functionDeclBody = copy1;
+    functionDecl = copy2;
+    return rv;
+}
+
+
+bool Flatten::VisitIfStmt(IfStmt const * ifStmt)
+{
+    if (ignoreLocation(ifStmt))
+        return true;
+
+    // ignore if we are part of an if/then/else/if chain
+    if (ifStmt == mElseBranch || (ifStmt->getElse() && isa<IfStmt>(ifStmt->getElse())))
+        return true;
+
+    // look for a large if(){} block at the end of a function
+    if (!ifStmt->getElse()
+        && (functionDecl->getReturnType().isNull() || functionDecl->getReturnType()->isVoidType())
+        && functionDeclBody && functionDeclBody->size()
+        && functionDeclBody->body_back() == ifStmt
+        && isLargeCompoundStmt(ifStmt->getThen()))
+    {
+        if (!rewriteLargeIf(ifStmt))
+        {
+            report(
+                DiagnosticsEngine::Warning,
+                "large if statement at end of function, rather invert the condition and exit early, and flatten the function",
+                compat::getBeginLoc(ifStmt))
+              << ifStmt->getSourceRange();
+        }
+        return true;
+    }
+
+    if (!ifStmt->getElse())
+        return true;
+
+    auto const thenThrowExpr = containsSingleThrowExpr(ifStmt->getThen());
+    auto const elseThrowExpr = containsSingleThrowExpr(ifStmt->getElse());
+    // If neither contains a throw, nothing to do; if both contain throws, no
+    // improvement:
+    if ((thenThrowExpr == nullptr) == (elseThrowExpr == nullptr)) {
+        return true;
+    }
+
+    if (containsPreprocessingConditionalInclusion(ifStmt->getSourceRange())) {
+        return true;
+    }
+
+    if (elseThrowExpr)
+    {
+        // if the "if" statement is not the last statement in its block, and it contains
+        // var decls in its then block, we cannot de-indent the then block without
+        // extending the lifetime of some variables, which may be problematic
+        if (ifStmt != lastStmtInCompoundStmt && containsVarDecl(ifStmt->getThen()))
+            return true;
+
+        if (!rewrite1(ifStmt))
+        {
+            report(
+                DiagnosticsEngine::Warning,
+                "unconditional throw in else branch, rather invert the condition, throw early, and flatten the normal case",
+                compat::getBeginLoc(elseThrowExpr))
+                << elseThrowExpr->getSourceRange();
+            report(
+                DiagnosticsEngine::Note,
+                "if condition here",
+                compat::getBeginLoc(ifStmt))
+                << ifStmt->getSourceRange();
+        }
+    }
+    if (thenThrowExpr)
+    {
+        // if the "if" statement is not the last statement in its block, and it contains
+        // var decls in its else block, we cannot de-indent the else block without
+        // extending the lifetime of some variables, which may be problematic
+        if (ifStmt != lastStmtInCompoundStmt && containsVarDecl(ifStmt->getElse()))
+            return true;
+
+        if (!rewrite2(ifStmt))
+        {
+            report(
+                DiagnosticsEngine::Warning,
+                "unconditional throw in then branch, just flatten the else",
+                compat::getBeginLoc(thenThrowExpr))
+                << thenThrowExpr->getSourceRange();
+        }
+    }
+    return true;
+}
+
+static std::string stripOpenAndCloseBrace(std::string s);
+static std::string stripTrailingEmptyLines(std::string s);
+static std::string deindent(std::string const & s);
+static std::vector<std::string> split(std::string s);
+static bool startswith(std::string const & rStr, char const * pSubStr);
+static int countLeadingSpaces(std::string const &);
+static std::string padSpace(int iNoSpaces);
+static bool replace(std::string & s, std::string const & from, std::string const & to);
+
+bool Flatten::rewrite1(IfStmt const * ifStmt)
+{
+    if (!rewriter)
+        return false;
+
+    auto conditionRange = ignoreMacroExpansions(ifStmt->getCond()->getSourceRange());
+    if (!conditionRange.isValid()) {
+        return false;
+    }
+    auto thenRange = ignoreMacroExpansions(ifStmt->getThen()->getSourceRange());
+    if (!thenRange.isValid()) {
+        return false;
+    }
+    auto elseRange = ignoreMacroExpansions(ifStmt->getElse()->getSourceRange());
+    if (!elseRange.isValid()) {
+        return false;
+    }
+    SourceRange elseKeywordRange = ifStmt->getElseLoc();
+
+    thenRange = extendOverComments(thenRange);
+    elseRange = extendOverComments(elseRange);
+    elseKeywordRange = extendOverComments(elseKeywordRange);
+
+    // in adjusting the formatting I assume that "{" starts on a new line
+
+    llvm::Optional<std::string> conditionString = invertCondition(ifStmt->getCond(), conditionRange);
+    if (!conditionString)
+        return false;
+
+    std::string thenString = getSourceAsString(thenRange);
+    if (auto compoundStmt = dyn_cast<CompoundStmt>(ifStmt->getThen())) {
+        if (compoundStmt->getLBracLoc().isValid()) {
+            thenString = stripOpenAndCloseBrace(thenString);
+        }
+    }
+    thenString = deindent(thenString);
+
+    std::string elseString = getSourceAsString(elseRange);
+
+    if (!replaceText(elseRange, thenString)) {
+        return false;
+    }
+    if (!removeText(elseKeywordRange)) {
+        return false;
+    }
+    if (!replaceText(thenRange, elseString)) {
+        return false;
+    }
+    if (!replaceText(conditionRange, *conditionString)) {
+        return false;
+    }
+
+    return true;
+}
+
+bool Flatten::rewrite2(IfStmt const * ifStmt)
+{
+    if (!rewriter)
+        return false;
+
+    auto conditionRange = ignoreMacroExpansions(ifStmt->getCond()->getSourceRange());
+    if (!conditionRange.isValid()) {
+        return false;
+    }
+    auto thenRange = ignoreMacroExpansions(ifStmt->getThen()->getSourceRange());
+    if (!thenRange.isValid()) {
+        return false;
+    }
+    auto elseRange = ignoreMacroExpansions(ifStmt->getElse()->getSourceRange());
+    if (!elseRange.isValid()) {
+        return false;
+    }
+    SourceRange elseKeywordRange = ifStmt->getElseLoc();
+
+    elseRange = extendOverComments(elseRange);
+    elseKeywordRange = extendOverComments(elseKeywordRange);
+
+    // in adjusting the formatting I assume that "{" starts on a new line
+
+    std::string elseString = getSourceAsString(elseRange);
+    if (auto compoundStmt = dyn_cast<CompoundStmt>(ifStmt->getElse())) {
+        if (compoundStmt->getLBracLoc().isValid()) {
+            elseString = stripOpenAndCloseBrace(elseString);
+        }
+    }
+    elseString = deindent(elseString);
+
+    if (!replaceText(elseRange, elseString)) {
+        return false;
+    }
+    if (!removeText(elseKeywordRange)) {
+        return false;
+    }
+
+    return true;
+}
+
+bool Flatten::rewriteLargeIf(IfStmt const * ifStmt)
+{
+    if (!rewriter)
+        return false;
+
+    auto conditionRange = ignoreMacroExpansions(ifStmt->getCond()->getSourceRange());
+    if (!conditionRange.isValid()) {
+        return false;
+    }
+    auto thenRange = ignoreMacroExpansions(ifStmt->getThen()->getSourceRange());
+    if (!thenRange.isValid()) {
+        return false;
+    }
+
+    thenRange = extendOverComments(thenRange);
+
+    // in adjusting the formatting I assume that "{" starts on a new line
+
+    llvm::Optional<std::string> conditionString = invertCondition(ifStmt->getCond(), conditionRange);
+    if (!conditionString)
+        return false;
+
+    std::string thenString = getSourceAsString(thenRange);
+    if (auto compoundStmt = dyn_cast<CompoundStmt>(ifStmt->getThen())) {
+        if (compoundStmt->getLBracLoc().isValid()) {
+            thenString = stripOpenAndCloseBrace(thenString);
+        }
+    }
+    int iNoSpaces = countLeadingSpaces(thenString);
+    thenString = padSpace(iNoSpaces) + "return;\n\n" + deindent(thenString);
+    thenString = stripTrailingEmptyLines(thenString);
+
+    if (!replaceText(thenRange, thenString)) {
+        return false;
+    }
+    if (!replaceText(conditionRange, *conditionString)) {
+        return false;
+    }
+
+    return true;
+}
+
+llvm::Optional<std::string> Flatten::invertCondition(Expr const * condExpr, SourceRange conditionRange)
+{
+    std::string s = getSourceAsString(conditionRange);
+
+    condExpr = condExpr->IgnoreImpCasts();
+
+    if (auto exprWithCleanups = dyn_cast<ExprWithCleanups>(condExpr))
+        condExpr = exprWithCleanups->getSubExpr()->IgnoreImpCasts();
+
+    // an if statement will automatically invoke a bool-conversion method
+    if (auto memberCallExpr = dyn_cast<CXXMemberCallExpr>(condExpr))
+    {
+        if (isa<CXXConversionDecl>(memberCallExpr->getMethodDecl()))
+            condExpr = memberCallExpr->getImplicitObjectArgument()->IgnoreImpCasts();
+    }
+
+    if (auto unaryOp = dyn_cast<UnaryOperator>(condExpr))
+    {
+        if (unaryOp->getOpcode() != UO_LNot)
+            return "!(" + s + ")";
+        auto i = s.find("!");
+        assert (i != std::string::npos);
+        s = s.substr(i+1);
+    }
+    else if (auto binaryOp = dyn_cast<BinaryOperator>(condExpr))
+    {
+        bool ok = true;
+        switch (binaryOp->getOpcode())
+        {
+            case BO_LT: ok = replace(s, "<", ">="); break;
+            case BO_GT: ok = replace(s, ">", "<="); break;
+            case BO_LE: ok = replace(s, "<=", ">"); break;
+            case BO_GE: ok = replace(s, ">=", "<"); break;
+            case BO_EQ: ok = replace(s, "==", "!="); break;
+            case BO_NE: ok = replace(s, "!=", "=="); break;
+            default:
+                s = "!(" + s + ")";
+        }
+        if (!ok)
+           return llvm::Optional<std::string>();
+    }
+    else if (auto opCallExpr = dyn_cast<CXXOperatorCallExpr>(condExpr))
+    {
+        bool ok = true;
+        switch (opCallExpr->getOperator())
+        {
+            case OO_Less: ok = replace(s, "<", ">="); break;
+            case OO_Greater: ok = replace(s, ">", "<="); break;
+            case OO_LessEqual: ok = replace(s, "<=", ">"); break;
+            case OO_GreaterEqual: ok = replace(s, ">=", "<"); break;
+            case OO_EqualEqual: ok = replace(s, "==", "!="); break;
+            case OO_ExclaimEqual: ok = replace(s, "!=", "=="); break;
+            default:
+                s = "!(" + s + ")";
+        }
+        if (!ok)
+            return llvm::Optional<std::string>();
+    }
+    else if (isa<DeclRefExpr>(condExpr) || isa<CallExpr>(condExpr) || isa<MemberExpr>(condExpr))
+        s = "!" + s;
+    else
+        s = "!(" + s + ")";
+    return s;
+}
+
+std::string stripOpenAndCloseBrace(std::string s)
+{
+    size_t i = s.find("{");
+    if (i == std::string::npos)
+    {
+        assert( !"did not find {" );
+        abort();
+    }
+
+    ++i;
+    // strip to line end
+    while (s[i] == ' ')
+        ++i;
+    if (s[i] == '\n')
+         ++i;
+    s = s.substr(i);
+
+    i = s.rfind("}");
+    if (i == std::string::npos)
+    {
+        assert( !"did not find }" );
+        abort();
+    }
+    --i;
+    while (s[i] == ' ')
+        --i;
+    s = s.substr(0,i);
+    return s;
+}
+
+std::string deindent(std::string const & s)
+{
+    std::vector<std::string> lines = split(s);
+    std::string rv;
+    for (auto s : lines) {
+        if (startswith(s, "    "))
+            rv += s.substr(4);
+        else
+            rv += s;
+        rv += "\n";
+    }
+    return rv;
+}
+
+std::vector<std::string> split(std::string s)
+{
+    if (s.back() == '\n')
+        s = s.substr(0, s.size()-1);
+    size_t next = -1;
+    std::vector<std::string> rv;
+    do
+    {
+        size_t current = next + 1;
+        next = s.find_first_of( "\n", current );
+        rv.push_back(s.substr( current, next - current ));
+    }
+    while (next != std::string::npos);
+    return rv;
+}
+
+bool startswith(std::string const & rStr, char const * pSubStr)
+{
+    return rStr.compare(0, strlen(pSubStr), pSubStr) == 0;
+}
+
+int countLeadingSpaces(std::string const & s)
+{
+    int i = 0;
+    while (i < (int)s.length() && s[i] == ' ')
+        i++;
+    return i;
+}
+
+std::string padSpace(int iNoSpaces)
+{
+    std::string s;
+    for (int i = 0; i < iNoSpaces; ++i)
+        s += " ";
+    return s;
+}
+
+std::string stripTrailingEmptyLines(std::string s)
+{
+    while (s.back() == '\n')
+        s.resize(s.length() - 1);
+    return s;
+}
+
+bool replace(std::string & s, std::string const & from, std::string const & to)
+{
+    auto i = s.find(from);
+    assert (i != std::string::npos);
+    s.replace(i, from.length(), to);
+    // just in case we have something really weird, like the operator token is also present in the rest of the condition somehow
+   return s.find(from) == std::string::npos;
+}
+
+SourceRange Flatten::ignoreMacroExpansions(SourceRange range) {
+    while (compiler.getSourceManager().isMacroArgExpansion(range.getBegin())) {
+        range.setBegin(
+            compiler.getSourceManager().getImmediateMacroCallerLoc(
+                range.getBegin()));
+    }
+    if (range.getBegin().isMacroID()) {
+        SourceLocation loc;
+        if (Lexer::isAtStartOfMacroExpansion(
+                range.getBegin(), compiler.getSourceManager(),
+                compiler.getLangOpts(), &loc))
+        {
+            range.setBegin(loc);
+        }
+    }
+    while (compiler.getSourceManager().isMacroArgExpansion(range.getEnd())) {
+        range.setEnd(
+            compiler.getSourceManager().getImmediateMacroCallerLoc(
+                range.getEnd()));
+    }
+    if (range.getEnd().isMacroID()) {
+        SourceLocation loc;
+        if (Lexer::isAtEndOfMacroExpansion(
+                range.getEnd(), compiler.getSourceManager(),
+                compiler.getLangOpts(), &loc))
+        {
+            range.setEnd(loc);
+        }
+    }
+    return range.getBegin().isMacroID() || range.getEnd().isMacroID()
+        ? SourceRange() : range;
+}
+
+/**
+ * Extend the SourceRange to include any leading and trailing whitespace, and any comments.
+ */
+SourceRange Flatten::extendOverComments(SourceRange range)
+{
+    SourceManager& SM = compiler.getSourceManager();
+    SourceLocation startLoc = range.getBegin();
+    SourceLocation endLoc = range.getEnd();
+    char const *p1 = SM.getCharacterData( startLoc );
+    char const *p2 = SM.getCharacterData( endLoc );
+
+    // scan backwards from the beginning to include any spaces on that line
+    while (*(p1-1) == ' ')
+        --p1;
+    startLoc = startLoc.getLocWithOffset(p1 - SM.getCharacterData( startLoc ));
+
+    // look for trailing ";"
+    while (*(p2+1) == ';')
+        ++p2;
+    // look for trailing " "
+    while (*(p2+1) == ' ')
+        ++p2;
+    // look for single line comments attached to the end of the statement
+    if (*(p2+1) == '/' && *(p2+2) == '/')
+    {
+        p2 += 2;
+        while (*(p2+1) && *(p2+1) != '\n')
+            ++p2;
+        if (*(p2+1) == '\n')
+            ++p2;
+    }
+    else
+    {
+        // make the source code we extract include any trailing "\n"
+        if (*(p2+1) == '\n')
+            ++p2;
+    }
+    endLoc = endLoc.getLocWithOffset(p2 - SM.getCharacterData( endLoc ));
+
+    return SourceRange(startLoc, endLoc);
+}
+
+std::string Flatten::getSourceAsString(SourceRange range)
+{
+    SourceManager& SM = compiler.getSourceManager();
+    SourceLocation startLoc = range.getBegin();
+    SourceLocation endLoc = range.getEnd();
+    char const *p1 = SM.getCharacterData( startLoc );
+    char const *p2 = SM.getCharacterData( endLoc );
+    p2 += Lexer::MeasureTokenLength( endLoc, SM, compiler.getLangOpts());
+    if (p2 < p1) {
+        // workaround clang weirdness, but don't return empty string
+        // in case it happens during code replacement
+        return "clang returned bad pointers";
+    }
+    return std::string( p1, p2 - p1);
+}
+
+bool Flatten::isLargeCompoundStmt(Stmt const * stmt)
+{
+    auto stmtRange = stmt->getSourceRange();
+    std::string s = getSourceAsString(stmtRange);
+    return std::count(s.begin(), s.end(), '\n') > 10;
+}
+
+loplugin::Plugin::Registration< Flatten > X("flatten", false);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */