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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/TableGen/StringMatcher.h" | |
15 | #include "llvm/Support/raw_ostream.h" | |
16 | #include <map> | |
17 | using namespace llvm; | |
18 | ||
19 | /// FindFirstNonCommonLetter - Find the first character in the keys of the | |
20 | /// string pairs that is not shared across the whole set of strings. All | |
21 | /// strings are assumed to have the same length. | |
22 | static unsigned | |
23 | FindFirstNonCommonLetter(const std::vector<const | |
24 | StringMatcher::StringPair*> &Matches) { | |
25 | assert(!Matches.empty()); | |
26 | for (unsigned i = 0, e = Matches[0]->first.size(); i != e; ++i) { | |
27 | // Check to see if letter i is the same across the set. | |
28 | char Letter = Matches[0]->first[i]; | |
29 | ||
30 | for (unsigned str = 0, e = Matches.size(); str != e; ++str) | |
31 | if (Matches[str]->first[i] != Letter) | |
32 | return i; | |
33 | } | |
34 | ||
35 | return Matches[0]->first.size(); | |
36 | } | |
37 | ||
38 | /// EmitStringMatcherForChar - Given a set of strings that are known to be the | |
39 | /// same length and whose characters leading up to CharNo are the same, emit | |
40 | /// code to verify that CharNo and later are the same. | |
41 | /// | |
42 | /// \return - True if control can leave the emitted code fragment. | |
43 | bool StringMatcher:: | |
44 | EmitStringMatcherForChar(const std::vector<const StringPair*> &Matches, | |
45 | unsigned CharNo, unsigned IndentCount) const { | |
46 | assert(!Matches.empty() && "Must have at least one string to match!"); | |
47 | std::string Indent(IndentCount*2+4, ' '); | |
48 | ||
49 | // If we have verified that the entire string matches, we're done: output the | |
50 | // matching code. | |
51 | if (CharNo == Matches[0]->first.size()) { | |
52 | assert(Matches.size() == 1 && "Had duplicate keys to match on"); | |
53 | ||
54 | // If the to-execute code has \n's in it, indent each subsequent line. | |
55 | StringRef Code = Matches[0]->second; | |
56 | ||
57 | std::pair<StringRef, StringRef> Split = Code.split('\n'); | |
58 | OS << Indent << Split.first << "\t // \"" << Matches[0]->first << "\"\n"; | |
59 | ||
60 | Code = Split.second; | |
61 | while (!Code.empty()) { | |
62 | Split = Code.split('\n'); | |
63 | OS << Indent << Split.first << "\n"; | |
64 | Code = Split.second; | |
65 | } | |
66 | return false; | |
67 | } | |
68 | ||
69 | // Bucket the matches by the character we are comparing. | |
70 | std::map<char, std::vector<const StringPair*> > MatchesByLetter; | |
71 | ||
72 | for (unsigned i = 0, e = Matches.size(); i != e; ++i) | |
73 | MatchesByLetter[Matches[i]->first[CharNo]].push_back(Matches[i]); | |
74 | ||
75 | ||
76 | // If we have exactly one bucket to match, see how many characters are common | |
77 | // across the whole set and match all of them at once. | |
78 | if (MatchesByLetter.size() == 1) { | |
79 | unsigned FirstNonCommonLetter = FindFirstNonCommonLetter(Matches); | |
80 | unsigned NumChars = FirstNonCommonLetter-CharNo; | |
81 | ||
82 | // Emit code to break out if the prefix doesn't match. | |
83 | if (NumChars == 1) { | |
84 | // Do the comparison with if (Str[1] != 'f') | |
85 | // FIXME: Need to escape general characters. | |
86 | OS << Indent << "if (" << StrVariableName << "[" << CharNo << "] != '" | |
87 | << Matches[0]->first[CharNo] << "')\n"; | |
88 | OS << Indent << " break;\n"; | |
89 | } else { | |
90 | // Do the comparison with if memcmp(Str.data()+1, "foo", 3). | |
91 | // FIXME: Need to escape general strings. | |
92 | OS << Indent << "if (memcmp(" << StrVariableName << ".data()+" << CharNo | |
93 | << ", \"" << Matches[0]->first.substr(CharNo, NumChars) << "\", " | |
94 | << NumChars << "))\n"; | |
95 | OS << Indent << " break;\n"; | |
96 | } | |
97 | ||
98 | return EmitStringMatcherForChar(Matches, FirstNonCommonLetter, IndentCount); | |
99 | } | |
100 | ||
101 | // Otherwise, we have multiple possible things, emit a switch on the | |
102 | // character. | |
103 | OS << Indent << "switch (" << StrVariableName << "[" << CharNo << "]) {\n"; | |
104 | OS << Indent << "default: break;\n"; | |
105 | ||
106 | for (std::map<char, std::vector<const StringPair*> >::iterator LI = | |
107 | MatchesByLetter.begin(), E = MatchesByLetter.end(); LI != E; ++LI) { | |
108 | // TODO: escape hard stuff (like \n) if we ever care about it. | |
109 | OS << Indent << "case '" << LI->first << "':\t // " | |
110 | << LI->second.size() << " string"; | |
111 | if (LI->second.size() != 1) OS << 's'; | |
112 | OS << " to match.\n"; | |
113 | if (EmitStringMatcherForChar(LI->second, CharNo+1, IndentCount+1)) | |
114 | OS << Indent << " break;\n"; | |
115 | } | |
116 | ||
117 | OS << Indent << "}\n"; | |
118 | return true; | |
119 | } | |
120 | ||
121 | ||
122 | /// Emit - Top level entry point. | |
123 | /// | |
124 | void StringMatcher::Emit(unsigned Indent) const { | |
125 | // If nothing to match, just fall through. | |
126 | if (Matches.empty()) return; | |
127 | ||
128 | // First level categorization: group strings by length. | |
129 | std::map<unsigned, std::vector<const StringPair*> > MatchesByLength; | |
130 | ||
131 | for (unsigned i = 0, e = Matches.size(); i != e; ++i) | |
132 | MatchesByLength[Matches[i].first.size()].push_back(&Matches[i]); | |
133 | ||
134 | // Output a switch statement on length and categorize the elements within each | |
135 | // bin. | |
136 | OS.indent(Indent*2+2) << "switch (" << StrVariableName << ".size()) {\n"; | |
137 | OS.indent(Indent*2+2) << "default: break;\n"; | |
138 | ||
139 | for (std::map<unsigned, std::vector<const StringPair*> >::iterator LI = | |
140 | MatchesByLength.begin(), E = MatchesByLength.end(); LI != E; ++LI) { | |
141 | OS.indent(Indent*2+2) << "case " << LI->first << ":\t // " | |
142 | << LI->second.size() | |
143 | << " string" << (LI->second.size() == 1 ? "" : "s") << " to match.\n"; | |
144 | if (EmitStringMatcherForChar(LI->second, 0, Indent)) | |
145 | OS.indent(Indent*2+4) << "break;\n"; | |
146 | } | |
147 | ||
148 | OS.indent(Indent*2+2) << "}\n"; | |
149 | } |