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//===--- InefficientVectorOperationCheck.cpp - clang-tidy------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "InefficientVectorOperationCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Lexer.h"
#include "../utils/DeclRefExprUtils.h"
#include "../utils/OptionsUtils.h"
using namespace clang::ast_matchers;
namespace clang {
namespace tidy {
namespace performance {
namespace {
// Matcher names. Given the code:
//
// \code
// void f() {
// vector<T> v;
// for (int i = 0; i < 10 + 1; ++i) {
// v.push_back(i);
// }
// }
// \endcode
//
// The matcher names are bound to following parts of the AST:
// - LoopCounterName: The entire for loop (as ForStmt).
// - LoopParentName: The body of function f (as CompoundStmt).
// - VectorVarDeclName: 'v' in (as VarDecl).
// - VectorVarDeclStmatName: The entire 'std::vector<T> v;' statement (as
// DeclStmt).
// - PushBackOrEmplaceBackCallName: 'v.push_back(i)' (as cxxMemberCallExpr).
// - LoopInitVarName: 'i' (as VarDecl).
// - LoopEndExpr: '10+1' (as Expr).
static const char LoopCounterName[] = "for_loop_counter";
static const char LoopParentName[] = "loop_parent";
static const char VectorVarDeclName[] = "vector_var_decl";
static const char VectorVarDeclStmtName[] = "vector_var_decl_stmt";
static const char PushBackOrEmplaceBackCallName[] = "append_call";
static const char LoopInitVarName[] = "loop_init_var";
static const char LoopEndExprName[] = "loop_end_expr";
static const char RangeLoopName[] = "for_range_loop";
ast_matchers::internal::Matcher<Expr> supportedContainerTypesMatcher() {
return hasType(cxxRecordDecl(hasAnyName(
"::std::vector", "::std::set", "::std::unordered_set", "::std::map",
"::std::unordered_map", "::std::array", "::std::deque")));
}
} // namespace
InefficientVectorOperationCheck::InefficientVectorOperationCheck(
StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
VectorLikeClasses(utils::options::parseStringList(
Options.get("VectorLikeClasses", "::std::vector"))) {}
void InefficientVectorOperationCheck::storeOptions(
ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "VectorLikeClasses",
utils::options::serializeStringList(VectorLikeClasses));
}
void InefficientVectorOperationCheck::registerMatchers(MatchFinder *Finder) {
const auto VectorDecl = cxxRecordDecl(hasAnyName(SmallVector<StringRef, 5>(
VectorLikeClasses.begin(), VectorLikeClasses.end())));
const auto VectorDefaultConstructorCall = cxxConstructExpr(
hasType(VectorDecl),
hasDeclaration(cxxConstructorDecl(isDefaultConstructor())));
const auto VectorVarDecl =
varDecl(hasInitializer(VectorDefaultConstructorCall))
.bind(VectorVarDeclName);
const auto VectorAppendCallExpr =
cxxMemberCallExpr(
callee(cxxMethodDecl(hasAnyName("push_back", "emplace_back"))),
on(hasType(VectorDecl)),
onImplicitObjectArgument(declRefExpr(to(VectorVarDecl))))
.bind(PushBackOrEmplaceBackCallName);
const auto VectorAppendCall = expr(ignoringImplicit(VectorAppendCallExpr));
const auto VectorVarDefStmt =
declStmt(hasSingleDecl(equalsBoundNode(VectorVarDeclName)))
.bind(VectorVarDeclStmtName);
const auto LoopVarInit =
declStmt(hasSingleDecl(varDecl(hasInitializer(integerLiteral(equals(0))))
.bind(LoopInitVarName)));
const auto RefersToLoopVar = ignoringParenImpCasts(
declRefExpr(to(varDecl(equalsBoundNode(LoopInitVarName)))));
// Matchers for the loop whose body has only 1 push_back/emplace_back calling
// statement.
const auto HasInterestingLoopBody =
hasBody(anyOf(compoundStmt(statementCountIs(1), has(VectorAppendCall)),
VectorAppendCall));
const auto InInterestingCompoundStmt =
hasParent(compoundStmt(has(VectorVarDefStmt)).bind(LoopParentName));
// Match counter-based for loops:
// for (int i = 0; i < n; ++i) { v.push_back(...); }
//
// FIXME: Support more types of counter-based loops like decrement loops.
Finder->addMatcher(
forStmt(
hasLoopInit(LoopVarInit),
hasCondition(binaryOperator(
hasOperatorName("<"), hasLHS(RefersToLoopVar),
hasRHS(expr(unless(hasDescendant(expr(RefersToLoopVar))))
.bind(LoopEndExprName)))),
hasIncrement(unaryOperator(hasOperatorName("++"),
hasUnaryOperand(RefersToLoopVar))),
HasInterestingLoopBody, InInterestingCompoundStmt)
.bind(LoopCounterName),
this);
// Match for-range loops:
// for (const auto& E : data) { v.push_back(...); }
//
// FIXME: Support more complex range-expressions.
Finder->addMatcher(
cxxForRangeStmt(
hasRangeInit(declRefExpr(supportedContainerTypesMatcher())),
HasInterestingLoopBody, InInterestingCompoundStmt)
.bind(RangeLoopName),
this);
}
void InefficientVectorOperationCheck::check(
const MatchFinder::MatchResult &Result) {
auto* Context = Result.Context;
if (Context->getDiagnostics().hasUncompilableErrorOccurred())
return;
const SourceManager &SM = *Result.SourceManager;
const auto *VectorVarDecl =
Result.Nodes.getNodeAs<VarDecl>(VectorVarDeclName);
const auto *ForLoop = Result.Nodes.getNodeAs<ForStmt>(LoopCounterName);
const auto *RangeLoop =
Result.Nodes.getNodeAs<CXXForRangeStmt>(RangeLoopName);
const auto *VectorAppendCall =
Result.Nodes.getNodeAs<CXXMemberCallExpr>(PushBackOrEmplaceBackCallName);
const auto *LoopEndExpr = Result.Nodes.getNodeAs<Expr>(LoopEndExprName);
const auto *LoopParent = Result.Nodes.getNodeAs<CompoundStmt>(LoopParentName);
const Stmt *LoopStmt = ForLoop;
if (!LoopStmt)
LoopStmt = RangeLoop;
llvm::SmallPtrSet<const DeclRefExpr *, 16> AllVectorVarRefs =
utils::decl_ref_expr::allDeclRefExprs(*VectorVarDecl, *LoopParent,
*Context);
for (const auto *Ref : AllVectorVarRefs) {
// Skip cases where there are usages (defined as DeclRefExpr that refers to
// "v") of vector variable `v` before the for loop. We consider these usages
// are operations causing memory preallocation (e.g. "v.resize(n)",
// "v.reserve(n)").
//
// FIXME: make it more intelligent to identify the pre-allocating operations
// before the for loop.
if (SM.isBeforeInTranslationUnit(Ref->getLocation(),
LoopStmt->getBeginLoc())) {
return;
}
}
llvm::StringRef VectorVarName = Lexer::getSourceText(
CharSourceRange::getTokenRange(
VectorAppendCall->getImplicitObjectArgument()->getSourceRange()),
SM, Context->getLangOpts());
std::string ReserveStmt;
// Handle for-range loop cases.
if (RangeLoop) {
// Get the range-expression in a for-range statement represented as
// `for (range-declarator: range-expression)`.
StringRef RangeInitExpName = Lexer::getSourceText(
CharSourceRange::getTokenRange(
RangeLoop->getRangeInit()->getSourceRange()),
SM, Context->getLangOpts());
ReserveStmt =
(VectorVarName + ".reserve(" + RangeInitExpName + ".size()" + ");\n")
.str();
} else if (ForLoop) {
// Handle counter-based loop cases.
StringRef LoopEndSource = Lexer::getSourceText(
CharSourceRange::getTokenRange(LoopEndExpr->getSourceRange()), SM,
Context->getLangOpts());
ReserveStmt = (VectorVarName + ".reserve(" + LoopEndSource + ");\n").str();
}
auto Diag =
diag(VectorAppendCall->getBeginLoc(),
"%0 is called inside a loop; "
"consider pre-allocating the vector capacity before the loop")
<< VectorAppendCall->getMethodDecl()->getDeclName();
if (!ReserveStmt.empty())
Diag << FixItHint::CreateInsertion(LoopStmt->getBeginLoc(), ReserveStmt);
}
} // namespace performance
} // namespace tidy
} // namespace clang
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