llvm/lib/Support/OptionStrCmp.cpp

   1 //===- OptionStrCmp.cpp - Option String Comparison --------------*- C++ -*-===//
   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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/Support/OptionStrCmp.h"
  10 #include "llvm/ADT/STLExtras.h"
  11
  12 using namespace llvm;
  13
  14 // Comparison function for Option strings (option names & prefixes).
  15 // The ordering is *almost* case-insensitive lexicographic, with an exception.
  16 // '\0' comes at the end of the alphabet instead of the beginning (thus options
  17 // precede any other options which prefix them). Additionally, if two options
  18 // are identical ignoring case, they are ordered according to case sensitive
  19 // ordering if `FallbackCaseSensitive` is true.
  20 int llvm::StrCmpOptionName(StringRef A, StringRef B,
  21                            bool FallbackCaseSensitive) {
  22   size_t MinSize = std::min(A.size(), B.size());
  23   if (int Res = A.substr(0, MinSize).compare_insensitive(B.substr(0, MinSize)))
  24     return Res;
  25
  26   // If they are identical ignoring case, use case sensitive ordering.
  27   if (A.size() == B.size())
  28     return FallbackCaseSensitive ? A.compare(B) : 0;
  29
  30   return (A.size() == MinSize) ? 1 /* A is a prefix of B. */
  31                                : -1 /* B is a prefix of A */;
  32 }
  33
  34 // Comparison function for Option prefixes.
  35 int llvm::StrCmpOptionPrefixes(ArrayRef<StringRef> APrefixes,
  36                                ArrayRef<StringRef> BPrefixes) {
  37   for (const auto &[APre, BPre] : zip(APrefixes, BPrefixes)) {
  38     if (int Cmp = StrCmpOptionName(APre, BPre))
  39       return Cmp;
  40   }
  41   // Both prefixes are identical.
  42   return 0;
  43 }