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Diffstat (limited to 'contrib/llvm-project/llvm/lib/TableGen/StringMatcher.cpp')
| -rw-r--r-- | contrib/llvm-project/llvm/lib/TableGen/StringMatcher.cpp | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/TableGen/StringMatcher.cpp b/contrib/llvm-project/llvm/lib/TableGen/StringMatcher.cpp new file mode 100644 index 000000000000..c169b4e0a362 --- /dev/null +++ b/contrib/llvm-project/llvm/lib/TableGen/StringMatcher.cpp @@ -0,0 +1,155 @@ +//===- 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/ErrorHandling.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 (const StringMatcher::StringPair *Match : Matches) + if (Match->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 (const StringPair *Match : Matches) + MatchesByLetter[Match->first[CharNo]].push_back(Match); + + // 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 (const StringPair &Match : Matches) + MatchesByLength[Match.first.size()].push_back(&Match); + + // 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"; +} |