1 //===- StringMatcher.cpp - Generate a matcher for input strings -----------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements the StringMatcher class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/ADT/StringRef.h" 15 #include "llvm/Support/raw_ostream.h" 16 #include "llvm/TableGen/StringMatcher.h" 17 #include <cassert> 18 #include <map> 19 #include <string> 20 #include <utility> 21 #include <vector> 22 23 using namespace llvm; 24 25 /// FindFirstNonCommonLetter - Find the first character in the keys of the 26 /// string pairs that is not shared across the whole set of strings. All 27 /// strings are assumed to have the same length. 28 static unsigned 29 FindFirstNonCommonLetter(const std::vector<const 30 StringMatcher::StringPair*> &Matches) { 31 assert(!Matches.empty()); 32 for (unsigned i = 0, e = Matches[0]->first.size(); i != e; ++i) { 33 // Check to see if letter i is the same across the set. 34 char Letter = Matches[0]->first[i]; 35 36 for (unsigned str = 0, e = Matches.size(); str != e; ++str) 37 if (Matches[str]->first[i] != Letter) 38 return i; 39 } 40 41 return Matches[0]->first.size(); 42 } 43 44 /// EmitStringMatcherForChar - Given a set of strings that are known to be the 45 /// same length and whose characters leading up to CharNo are the same, emit 46 /// code to verify that CharNo and later are the same. 47 /// 48 /// \return - True if control can leave the emitted code fragment. 49 bool StringMatcher:: 50 EmitStringMatcherForChar(const std::vector<const StringPair*> &Matches, 51 unsigned CharNo, unsigned IndentCount) const { 52 assert(!Matches.empty() && "Must have at least one string to match!"); 53 std::string Indent(IndentCount*2+4, ' '); 54 55 // If we have verified that the entire string matches, we're done: output the 56 // matching code. 57 if (CharNo == Matches[0]->first.size()) { 58 assert(Matches.size() == 1 && "Had duplicate keys to match on"); 59 60 // If the to-execute code has \n's in it, indent each subsequent line. 61 StringRef Code = Matches[0]->second; 62 63 std::pair<StringRef, StringRef> Split = Code.split('\n'); 64 OS << Indent << Split.first << "\t // \"" << Matches[0]->first << "\"\n"; 65 66 Code = Split.second; 67 while (!Code.empty()) { 68 Split = Code.split('\n'); 69 OS << Indent << Split.first << "\n"; 70 Code = Split.second; 71 } 72 return false; 73 } 74 75 // Bucket the matches by the character we are comparing. 76 std::map<char, std::vector<const StringPair*>> MatchesByLetter; 77 78 for (unsigned i = 0, e = Matches.size(); i != e; ++i) 79 MatchesByLetter[Matches[i]->first[CharNo]].push_back(Matches[i]); 80 81 82 // If we have exactly one bucket to match, see how many characters are common 83 // across the whole set and match all of them at once. 84 if (MatchesByLetter.size() == 1) { 85 unsigned FirstNonCommonLetter = FindFirstNonCommonLetter(Matches); 86 unsigned NumChars = FirstNonCommonLetter-CharNo; 87 88 // Emit code to break out if the prefix doesn't match. 89 if (NumChars == 1) { 90 // Do the comparison with if (Str[1] != 'f') 91 // FIXME: Need to escape general characters. 92 OS << Indent << "if (" << StrVariableName << "[" << CharNo << "] != '" 93 << Matches[0]->first[CharNo] << "')\n"; 94 OS << Indent << " break;\n"; 95 } else { 96 // Do the comparison with if memcmp(Str.data()+1, "foo", 3). 97 // FIXME: Need to escape general strings. 98 OS << Indent << "if (memcmp(" << StrVariableName << ".data()+" << CharNo 99 << ", \"" << Matches[0]->first.substr(CharNo, NumChars) << "\", " 100 << NumChars << ") != 0)\n"; 101 OS << Indent << " break;\n"; 102 } 103 104 return EmitStringMatcherForChar(Matches, FirstNonCommonLetter, IndentCount); 105 } 106 107 // Otherwise, we have multiple possible things, emit a switch on the 108 // character. 109 OS << Indent << "switch (" << StrVariableName << "[" << CharNo << "]) {\n"; 110 OS << Indent << "default: break;\n"; 111 112 for (std::map<char, std::vector<const StringPair*>>::iterator LI = 113 MatchesByLetter.begin(), E = MatchesByLetter.end(); LI != E; ++LI) { 114 // TODO: escape hard stuff (like \n) if we ever care about it. 115 OS << Indent << "case '" << LI->first << "':\t // " 116 << LI->second.size() << " string"; 117 if (LI->second.size() != 1) OS << 's'; 118 OS << " to match.\n"; 119 if (EmitStringMatcherForChar(LI->second, CharNo+1, IndentCount+1)) 120 OS << Indent << " break;\n"; 121 } 122 123 OS << Indent << "}\n"; 124 return true; 125 } 126 127 /// Emit - Top level entry point. 128 /// 129 void StringMatcher::Emit(unsigned Indent) 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 (unsigned i = 0, e = Matches.size(); i != e; ++i) 137 MatchesByLength[Matches[i].first.size()].push_back(&Matches[i]); 138 139 // Output a switch statement on length and categorize the elements within each 140 // bin. 141 OS.indent(Indent*2+2) << "switch (" << StrVariableName << ".size()) {\n"; 142 OS.indent(Indent*2+2) << "default: break;\n"; 143 144 for (std::map<unsigned, std::vector<const StringPair*>>::iterator LI = 145 MatchesByLength.begin(), E = MatchesByLength.end(); LI != E; ++LI) { 146 OS.indent(Indent*2+2) << "case " << LI->first << ":\t // " 147 << LI->second.size() 148 << " string" << (LI->second.size() == 1 ? "" : "s") << " to match.\n"; 149 if (EmitStringMatcherForChar(LI->second, 0, Indent)) 150 OS.indent(Indent*2+4) << "break;\n"; 151 } 152 153 OS.indent(Indent*2+2) << "}\n"; 154 } 155