154 lines · cpp
1//===- StringMatcher.cpp - Generate a matcher for input strings -----------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file implements the StringMatcher class.10//11//===----------------------------------------------------------------------===//12 13#include "llvm/TableGen/StringMatcher.h"14#include "llvm/ADT/STLExtras.h"15#include "llvm/Support/ErrorHandling.h"16#include "llvm/Support/raw_ostream.h"17#include <cassert>18#include <map>19#include <string>20#include <utility>21#include <vector>22 23using namespace llvm;24 25/// FindFirstNonCommonLetter - Find the first character in the keys of the26/// string pairs that is not shared across the whole set of strings. All27/// strings are assumed to have the same length.28static unsigned29FindFirstNonCommonLetter(ArrayRef<const StringMatcher::StringPair *> Matches) {30 assert(!Matches.empty());31 for (auto [Idx, Letter] : enumerate(Matches[0]->first)) {32 // Check to see if `Letter` is the same across the set. Since the letter is33 // from `Matches[0]`, we can skip `Matches[0]` in the loop below.34 for (const StringMatcher::StringPair *Match : Matches.drop_front())35 if (Match->first[Idx] != Letter)36 return Idx;37 }38 39 return Matches[0]->first.size();40}41 42/// EmitStringMatcherForChar - Given a set of strings that are known to be the43/// same length and whose characters leading up to CharNo are the same, emit44/// code to verify that CharNo and later are the same.45///46/// \return - True if control can leave the emitted code fragment.47bool StringMatcher::EmitStringMatcherForChar(48 ArrayRef<const StringPair *> Matches, unsigned CharNo, unsigned IndentCount,49 bool IgnoreDuplicates) const {50 assert(!Matches.empty() && "Must have at least one string to match!");51 std::string Indent(IndentCount * 2 + 4, ' ');52 53 // If we have verified that the entire string matches, we're done: output the54 // matching code.55 if (CharNo == Matches[0]->first.size()) {56 if (Matches.size() > 1 && !IgnoreDuplicates)57 report_fatal_error("Had duplicate keys to match on");58 59 // If the to-execute code has \n's in it, indent each subsequent line.60 StringRef Code = Matches[0]->second;61 62 std::pair<StringRef, StringRef> Split = Code.split('\n');63 OS << Indent << Split.first << "\t // \"" << Matches[0]->first << "\"\n";64 65 Code = Split.second;66 while (!Code.empty()) {67 Split = Code.split('\n');68 OS << Indent << Split.first << "\n";69 Code = Split.second;70 }71 return false;72 }73 74 // Bucket the matches by the character we are comparing.75 std::map<char, std::vector<const StringPair*>> MatchesByLetter;76 77 for (const StringPair *Match : Matches)78 MatchesByLetter[Match->first[CharNo]].push_back(Match);79 80 // If we have exactly one bucket to match, see how many characters are common81 // across the whole set and match all of them at once.82 if (MatchesByLetter.size() == 1) {83 unsigned FirstNonCommonLetter = FindFirstNonCommonLetter(Matches);84 unsigned NumChars = FirstNonCommonLetter-CharNo;85 86 // Emit code to break out if the prefix doesn't match.87 if (NumChars == 1) {88 // Do the comparison with if (Str[1] != 'f')89 // FIXME: Need to escape general characters.90 OS << Indent << "if (" << StrVariableName << "[" << CharNo << "] != '"91 << Matches[0]->first[CharNo] << "')\n";92 OS << Indent << " break;\n";93 } else {94 // Do the comparison with if memcmp(Str.data()+1, "foo", 3).95 // FIXME: Need to escape general strings.96 OS << Indent << "if (memcmp(" << StrVariableName << ".data()+" << CharNo97 << ", \"" << Matches[0]->first.substr(CharNo, NumChars) << "\", "98 << NumChars << ") != 0)\n";99 OS << Indent << " break;\n";100 }101 102 return EmitStringMatcherForChar(Matches, FirstNonCommonLetter, IndentCount,103 IgnoreDuplicates);104 }105 106 // Otherwise, we have multiple possible things, emit a switch on the107 // character.108 OS << Indent << "switch (" << StrVariableName << "[" << CharNo << "]) {\n";109 OS << Indent << "default: break;\n";110 111 for (const auto &[Letter, Matches] : MatchesByLetter) {112 // TODO: escape hard stuff (like \n) if we ever care about it.113 OS << Indent << "case '" << Letter << "':\t // " << Matches.size()114 << " string";115 if (Matches.size() != 1)116 OS << 's';117 OS << " to match.\n";118 if (EmitStringMatcherForChar(Matches, CharNo + 1, IndentCount + 1,119 IgnoreDuplicates))120 OS << Indent << " break;\n";121 }122 123 OS << Indent << "}\n";124 return true;125}126 127/// Emit - Top level entry point.128///129void StringMatcher::Emit(unsigned Indent, bool IgnoreDuplicates) const {130 // If nothing to match, just fall through.131 if (Matches.empty()) return;132 133 // First level categorization: group strings by length.134 std::map<unsigned, std::vector<const StringPair*>> MatchesByLength;135 136 for (const StringPair &Match : Matches)137 MatchesByLength[Match.first.size()].push_back(&Match);138 139 // Output a switch statement on length and categorize the elements within each140 // bin.141 OS.indent(Indent*2+2) << "switch (" << StrVariableName << ".size()) {\n";142 OS.indent(Indent*2+2) << "default: break;\n";143 144 for (const auto &[Length, Matches] : MatchesByLength) {145 OS.indent(Indent * 2 + 2)146 << "case " << Length << ":\t // " << Matches.size() << " string"147 << (Matches.size() == 1 ? "" : "s") << " to match.\n";148 if (EmitStringMatcherForChar(Matches, 0, Indent, IgnoreDuplicates))149 OS.indent(Indent*2+4) << "break;\n";150 }151 152 OS.indent(Indent*2+2) << "}\n";153}154