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//===--- PPCaching.cpp - Handle caching lexed tokens ----------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements pieces of the Preprocessor interface that manage the
// caching of lexed tokens.
//
//===----------------------------------------------------------------------===//
#include "clang/Lex/Preprocessor.h"
using namespace clang;
// EnableBacktrackAtThisPos - From the point that this method is called, and
// until CommitBacktrackedTokens() or Backtrack() is called, the Preprocessor
// keeps track of the lexed tokens so that a subsequent Backtrack() call will
// make the Preprocessor re-lex the same tokens.
//
// Nested backtracks are allowed, meaning that EnableBacktrackAtThisPos can
// be called multiple times and CommitBacktrackedTokens/Backtrack calls will
// be combined with the EnableBacktrackAtThisPos calls in reverse order.
void Preprocessor::EnableBacktrackAtThisPos() {
assert(LexLevel == 0 && "cannot use lookahead while lexing");
BacktrackPositions.push_back(CachedLexPos);
EnterCachingLexMode();
}
// Disable the last EnableBacktrackAtThisPos call.
void Preprocessor::CommitBacktrackedTokens() {
assert(!BacktrackPositions.empty()
&& "EnableBacktrackAtThisPos was not called!");
BacktrackPositions.pop_back();
}
// Make Preprocessor re-lex the tokens that were lexed since
// EnableBacktrackAtThisPos() was previously called.
void Preprocessor::Backtrack() {
assert(!BacktrackPositions.empty()
&& "EnableBacktrackAtThisPos was not called!");
CachedLexPos = BacktrackPositions.back();
BacktrackPositions.pop_back();
recomputeCurLexerKind();
}
void Preprocessor::CachingLex(Token &Result) {
if (!InCachingLexMode())
return;
// The assert in EnterCachingLexMode should prevent this from happening.
assert(LexLevel == 1 &&
"should not use token caching within the preprocessor");
if (CachedLexPos < CachedTokens.size()) {
Result = CachedTokens[CachedLexPos++];
Result.setFlag(Token::IsReinjected);
return;
}
ExitCachingLexMode();
Lex(Result);
if (isBacktrackEnabled()) {
// Cache the lexed token.
EnterCachingLexModeUnchecked();
CachedTokens.push_back(Result);
++CachedLexPos;
return;
}
if (CachedLexPos < CachedTokens.size()) {
EnterCachingLexModeUnchecked();
} else {
// All cached tokens were consumed.
CachedTokens.clear();
CachedLexPos = 0;
}
}
void Preprocessor::EnterCachingLexMode() {
// The caching layer sits on top of all the other lexers, so it's incorrect
// to cache tokens while inside a nested lex action. The cached tokens would
// be retained after returning to the enclosing lex action and, at best,
// would appear at the wrong position in the token stream.
assert(LexLevel == 0 &&
"entered caching lex mode while lexing something else");
if (InCachingLexMode()) {
assert(CurLexerKind == CLK_CachingLexer && "Unexpected lexer kind");
return;
}
EnterCachingLexModeUnchecked();
}
void Preprocessor::EnterCachingLexModeUnchecked() {
assert(CurLexerKind != CLK_CachingLexer && "already in caching lex mode");
PushIncludeMacroStack();
CurLexerKind = CLK_CachingLexer;
}
const Token &Preprocessor::PeekAhead(unsigned N) {
assert(CachedLexPos + N > CachedTokens.size() && "Confused caching.");
ExitCachingLexMode();
for (size_t C = CachedLexPos + N - CachedTokens.size(); C > 0; --C) {
CachedTokens.push_back(Token());
Lex(CachedTokens.back());
}
EnterCachingLexMode();
return CachedTokens.back();
}
void Preprocessor::AnnotatePreviousCachedTokens(const Token &Tok) {
assert(Tok.isAnnotation() && "Expected annotation token");
assert(CachedLexPos != 0 && "Expected to have some cached tokens");
assert(CachedTokens[CachedLexPos-1].getLastLoc() == Tok.getAnnotationEndLoc()
&& "The annotation should be until the most recent cached token");
// Start from the end of the cached tokens list and look for the token
// that is the beginning of the annotation token.
for (CachedTokensTy::size_type i = CachedLexPos; i != 0; --i) {
CachedTokensTy::iterator AnnotBegin = CachedTokens.begin() + i-1;
if (AnnotBegin->getLocation() == Tok.getLocation()) {
assert((BacktrackPositions.empty() || BacktrackPositions.back() <= i) &&
"The backtrack pos points inside the annotated tokens!");
// Replace the cached tokens with the single annotation token.
if (i < CachedLexPos)
CachedTokens.erase(AnnotBegin + 1, CachedTokens.begin() + CachedLexPos);
*AnnotBegin = Tok;
CachedLexPos = i;
return;
}
}
}
bool Preprocessor::IsPreviousCachedToken(const Token &Tok) const {
// There's currently no cached token...
if (!CachedLexPos)
return false;
const Token LastCachedTok = CachedTokens[CachedLexPos - 1];
if (LastCachedTok.getKind() != Tok.getKind())
return false;
SourceLocation::IntTy RelOffset = 0;
if ((!getSourceManager().isInSameSLocAddrSpace(
Tok.getLocation(), getLastCachedTokenLocation(), &RelOffset)) ||
RelOffset)
return false;
return true;
}
void Preprocessor::ReplacePreviousCachedToken(ArrayRef<Token> NewToks) {
assert(CachedLexPos != 0 && "Expected to have some cached tokens");
CachedTokens.insert(CachedTokens.begin() + CachedLexPos - 1, NewToks.begin(),
NewToks.end());
CachedTokens.erase(CachedTokens.begin() + CachedLexPos - 1 + NewToks.size());
CachedLexPos += NewToks.size() - 1;
}
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