| //===- StringMatcher.cpp - Generate a matcher for input strings -----------===// |
| // |
| // 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 the StringMatcher class. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/TableGen/StringMatcher.h" |
| #include "llvm/ADT/StringRef.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include <cassert> |
| #include <map> |
| #include <string> |
| #include <utility> |
| #include <vector> |
| |
| using namespace llvm; |
| |
| /// FindFirstNonCommonLetter - Find the first character in the keys of the |
| /// string pairs that is not shared across the whole set of strings. All |
| /// strings are assumed to have the same length. |
| static unsigned |
| FindFirstNonCommonLetter(const std::vector<const |
| StringMatcher::StringPair*> &Matches) { |
| assert(!Matches.empty()); |
| for (unsigned i = 0, e = Matches[0]->first.size(); i != e; ++i) { |
| // Check to see if letter i is the same across the set. |
| char Letter = Matches[0]->first[i]; |
| |
| for (unsigned str = 0, e = Matches.size(); str != e; ++str) |
| if (Matches[str]->first[i] != Letter) |
| return i; |
| } |
| |
| return Matches[0]->first.size(); |
| } |
| |
| /// EmitStringMatcherForChar - Given a set of strings that are known to be the |
| /// same length and whose characters leading up to CharNo are the same, emit |
| /// code to verify that CharNo and later are the same. |
| /// |
| /// \return - True if control can leave the emitted code fragment. |
| bool StringMatcher::EmitStringMatcherForChar( |
| const std::vector<const StringPair *> &Matches, unsigned CharNo, |
| unsigned IndentCount, bool IgnoreDuplicates) const { |
| assert(!Matches.empty() && "Must have at least one string to match!"); |
| std::string Indent(IndentCount * 2 + 4, ' '); |
| |
| // If we have verified that the entire string matches, we're done: output the |
| // matching code. |
| if (CharNo == Matches[0]->first.size()) { |
| if (Matches.size() > 1 && !IgnoreDuplicates) |
| report_fatal_error("Had duplicate keys to match on"); |
| |
| // If the to-execute code has \n's in it, indent each subsequent line. |
| StringRef Code = Matches[0]->second; |
| |
| std::pair<StringRef, StringRef> Split = Code.split('\n'); |
| OS << Indent << Split.first << "\t // \"" << Matches[0]->first << "\"\n"; |
| |
| Code = Split.second; |
| while (!Code.empty()) { |
| Split = Code.split('\n'); |
| OS << Indent << Split.first << "\n"; |
| Code = Split.second; |
| } |
| return false; |
| } |
| |
| // Bucket the matches by the character we are comparing. |
| std::map<char, std::vector<const StringPair*>> MatchesByLetter; |
| |
| for (unsigned i = 0, e = Matches.size(); i != e; ++i) |
| MatchesByLetter[Matches[i]->first[CharNo]].push_back(Matches[i]); |
| |
| |
| // If we have exactly one bucket to match, see how many characters are common |
| // across the whole set and match all of them at once. |
| if (MatchesByLetter.size() == 1) { |
| unsigned FirstNonCommonLetter = FindFirstNonCommonLetter(Matches); |
| unsigned NumChars = FirstNonCommonLetter-CharNo; |
| |
| // Emit code to break out if the prefix doesn't match. |
| if (NumChars == 1) { |
| // Do the comparison with if (Str[1] != 'f') |
| // FIXME: Need to escape general characters. |
| OS << Indent << "if (" << StrVariableName << "[" << CharNo << "] != '" |
| << Matches[0]->first[CharNo] << "')\n"; |
| OS << Indent << " break;\n"; |
| } else { |
| // Do the comparison with if memcmp(Str.data()+1, "foo", 3). |
| // FIXME: Need to escape general strings. |
| OS << Indent << "if (memcmp(" << StrVariableName << ".data()+" << CharNo |
| << ", \"" << Matches[0]->first.substr(CharNo, NumChars) << "\", " |
| << NumChars << ") != 0)\n"; |
| OS << Indent << " break;\n"; |
| } |
| |
| return EmitStringMatcherForChar(Matches, FirstNonCommonLetter, IndentCount, |
| IgnoreDuplicates); |
| } |
| |
| // Otherwise, we have multiple possible things, emit a switch on the |
| // character. |
| OS << Indent << "switch (" << StrVariableName << "[" << CharNo << "]) {\n"; |
| OS << Indent << "default: break;\n"; |
| |
| for (const auto &LI : MatchesByLetter) { |
| // TODO: escape hard stuff (like \n) if we ever care about it. |
| OS << Indent << "case '" << LI.first << "':\t // " << LI.second.size() |
| << " string"; |
| if (LI.second.size() != 1) |
| OS << 's'; |
| OS << " to match.\n"; |
| if (EmitStringMatcherForChar(LI.second, CharNo + 1, IndentCount + 1, |
| IgnoreDuplicates)) |
| OS << Indent << " break;\n"; |
| } |
| |
| OS << Indent << "}\n"; |
| return true; |
| } |
| |
| /// Emit - Top level entry point. |
| /// |
| void StringMatcher::Emit(unsigned Indent, bool IgnoreDuplicates) const { |
| // If nothing to match, just fall through. |
| if (Matches.empty()) return; |
| |
| // First level categorization: group strings by length. |
| std::map<unsigned, std::vector<const StringPair*>> MatchesByLength; |
| |
| for (unsigned i = 0, e = Matches.size(); i != e; ++i) |
| MatchesByLength[Matches[i].first.size()].push_back(&Matches[i]); |
| |
| // Output a switch statement on length and categorize the elements within each |
| // bin. |
| OS.indent(Indent*2+2) << "switch (" << StrVariableName << ".size()) {\n"; |
| OS.indent(Indent*2+2) << "default: break;\n"; |
| |
| for (const auto &LI : MatchesByLength) { |
| OS.indent(Indent * 2 + 2) |
| << "case " << LI.first << ":\t // " << LI.second.size() << " string" |
| << (LI.second.size() == 1 ? "" : "s") << " to match.\n"; |
| if (EmitStringMatcherForChar(LI.second, 0, Indent, IgnoreDuplicates)) |
| OS.indent(Indent*2+4) << "break;\n"; |
| } |
| |
| OS.indent(Indent*2+2) << "}\n"; |
| } |