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//===---------- ExprSequence.cpp - clang-tidy -----------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "ExprSequence.h"
#include "clang/AST/ParentMapContext.h"
#include <optional>
namespace clang::tidy::utils {
// Returns the Stmt nodes that are parents of 'S', skipping any potential
// intermediate non-Stmt nodes.
//
// In almost all cases, this function returns a single parent or no parents at
// all.
//
// The case that a Stmt has multiple parents is rare but does actually occur in
// the parts of the AST that we're interested in. Specifically, InitListExpr
// nodes cause ASTContext::getParent() to return multiple parents for certain
// nodes in their subtree because RecursiveASTVisitor visits both the syntactic
// and semantic forms of InitListExpr, and the parent-child relationships are
// different between the two forms.
static SmallVector<const Stmt *, 1> getParentStmts(const Stmt *S,
ASTContext *Context) {
SmallVector<const Stmt *, 1> Result;
TraversalKindScope RAII(*Context, TK_AsIs);
DynTypedNodeList Parents = Context->getParents(*S);
SmallVector<DynTypedNode, 1> NodesToProcess(Parents.begin(), Parents.end());
while (!NodesToProcess.empty()) {
DynTypedNode Node = NodesToProcess.back();
NodesToProcess.pop_back();
if (const auto *S = Node.get<Stmt>()) {
Result.push_back(S);
} else {
Parents = Context->getParents(Node);
NodesToProcess.append(Parents.begin(), Parents.end());
}
}
return Result;
}
namespace {
bool isDescendantOrEqual(const Stmt *Descendant, const Stmt *Ancestor,
ASTContext *Context) {
if (Descendant == Ancestor)
return true;
for (const Stmt *Parent : getParentStmts(Descendant, Context)) {
if (isDescendantOrEqual(Parent, Ancestor, Context))
return true;
}
return false;
}
} // namespace
ExprSequence::ExprSequence(const CFG *TheCFG, const Stmt *Root,
ASTContext *TheContext)
: Context(TheContext), Root(Root) {
for (const auto &SyntheticStmt : TheCFG->synthetic_stmts()) {
SyntheticStmtSourceMap[SyntheticStmt.first] = SyntheticStmt.second;
}
}
bool ExprSequence::inSequence(const Stmt *Before, const Stmt *After) const {
Before = resolveSyntheticStmt(Before);
After = resolveSyntheticStmt(After);
// If 'After' is in the subtree of the siblings that follow 'Before' in the
// chain of successors, we know that 'After' is sequenced after 'Before'.
for (const Stmt *Successor = getSequenceSuccessor(Before); Successor;
Successor = getSequenceSuccessor(Successor)) {
if (isDescendantOrEqual(After, Successor, Context))
return true;
}
// If 'After' is a parent of 'Before' or is sequenced after one of these
// parents, we know that it is sequenced after 'Before'.
for (const Stmt *Parent : getParentStmts(Before, Context)) {
if (Parent == After || inSequence(Parent, After))
return true;
}
return false;
}
bool ExprSequence::potentiallyAfter(const Stmt *After,
const Stmt *Before) const {
return !inSequence(After, Before);
}
const Stmt *ExprSequence::getSequenceSuccessor(const Stmt *S) const {
for (const Stmt *Parent : getParentStmts(S, Context)) {
// If a statement has multiple parents, make sure we're using the parent
// that lies within the sub-tree under Root.
if (!isDescendantOrEqual(Parent, Root, Context))
continue;
if (const auto *BO = dyn_cast<BinaryOperator>(Parent)) {
// Comma operator: Right-hand side is sequenced after the left-hand side.
if (BO->getLHS() == S && BO->getOpcode() == BO_Comma)
return BO->getRHS();
} else if (const auto *InitList = dyn_cast<InitListExpr>(Parent)) {
// Initializer list: Each initializer clause is sequenced after the
// clauses that precede it.
for (unsigned I = 1; I < InitList->getNumInits(); ++I) {
if (InitList->getInit(I - 1) == S)
return InitList->getInit(I);
}
} else if (const auto *Compound = dyn_cast<CompoundStmt>(Parent)) {
// Compound statement: Each sub-statement is sequenced after the
// statements that precede it.
const Stmt *Previous = nullptr;
for (const auto *Child : Compound->body()) {
if (Previous == S)
return Child;
Previous = Child;
}
} else if (const auto *TheDeclStmt = dyn_cast<DeclStmt>(Parent)) {
// Declaration: Every initializer expression is sequenced after the
// initializer expressions that precede it.
const Expr *PreviousInit = nullptr;
for (const Decl *TheDecl : TheDeclStmt->decls()) {
if (const auto *TheVarDecl = dyn_cast<VarDecl>(TheDecl)) {
if (const Expr *Init = TheVarDecl->getInit()) {
if (PreviousInit == S)
return Init;
PreviousInit = Init;
}
}
}
} else if (const auto *ForRange = dyn_cast<CXXForRangeStmt>(Parent)) {
// Range-based for: Loop variable declaration is sequenced before the
// body. (We need this rule because these get placed in the same
// CFGBlock.)
if (S == ForRange->getLoopVarStmt())
return ForRange->getBody();
} else if (const auto *TheIfStmt = dyn_cast<IfStmt>(Parent)) {
// If statement:
// - Sequence init statement before variable declaration, if present;
// before condition evaluation, otherwise.
// - Sequence variable declaration (along with the expression used to
// initialize it) before the evaluation of the condition.
if (S == TheIfStmt->getInit()) {
if (TheIfStmt->getConditionVariableDeclStmt() != nullptr)
return TheIfStmt->getConditionVariableDeclStmt();
return TheIfStmt->getCond();
}
if (S == TheIfStmt->getConditionVariableDeclStmt())
return TheIfStmt->getCond();
} else if (const auto *TheSwitchStmt = dyn_cast<SwitchStmt>(Parent)) {
// Ditto for switch statements.
if (S == TheSwitchStmt->getInit()) {
if (TheSwitchStmt->getConditionVariableDeclStmt() != nullptr)
return TheSwitchStmt->getConditionVariableDeclStmt();
return TheSwitchStmt->getCond();
}
if (S == TheSwitchStmt->getConditionVariableDeclStmt())
return TheSwitchStmt->getCond();
} else if (const auto *TheWhileStmt = dyn_cast<WhileStmt>(Parent)) {
// While statement: Sequence variable declaration (along with the
// expression used to initialize it) before the evaluation of the
// condition.
if (S == TheWhileStmt->getConditionVariableDeclStmt())
return TheWhileStmt->getCond();
}
}
return nullptr;
}
const Stmt *ExprSequence::resolveSyntheticStmt(const Stmt *S) const {
if (SyntheticStmtSourceMap.count(S))
return SyntheticStmtSourceMap.lookup(S);
return S;
}
StmtToBlockMap::StmtToBlockMap(const CFG *TheCFG, ASTContext *TheContext)
: Context(TheContext) {
for (const auto *B : *TheCFG) {
for (const auto &Elem : *B) {
if (std::optional<CFGStmt> S = Elem.getAs<CFGStmt>())
Map[S->getStmt()] = B;
}
}
}
const CFGBlock *StmtToBlockMap::blockContainingStmt(const Stmt *S) const {
while (!Map.count(S)) {
SmallVector<const Stmt *, 1> Parents = getParentStmts(S, Context);
if (Parents.empty())
return nullptr;
S = Parents[0];
}
return Map.lookup(S);
}
} // namespace clang::tidy::utils
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