[demangler][NFC] Small cleanups and sync

[urnathan]

Summary

Some precursor work to adding module demangling.

• some mismatched comment and code in the demangler

• a const fn was not marked thusly

• we use std::islower. A direct range check is smaller code (no function call), and we know we're in ASCII-land and later in that same function make the same assumption about upper-case contiguity. Heck, maybe just drop the switch's precondition and rely on the optimizer to do its thing?

• the directory is cloned in two places, which had gotten out of sync. AFAICT there is no need for the different header protection macros. Perhaps, now this is a monorepo we can elide the need for a copy. Symlinks would be simplest to achieve that, but I don't think they're available on all file systems being built on?

[aaron.ballman]

LGTM!

Symlinks would be simplest to achieve that, but I don't think they're available on all file systems being built on?

I don't know how well that solution will work on Windows.

libcxxabi/src/demangle/ItaniumDemangle.h

public:
   virtual const Node *getSyntaxNode(OutputBuffer &) const { return this; }
 
   void print(OutputBuffer &OB) const {
     printLeft(OB);
     if (RHSComponentCache != Cache::No)
       printRight(OB);
   }
 
-  // Print the "left" side of this Node into OutputString.
+  // Print the "left" side of this Node into OutputBuffer.
   virtual void printLeft(OutputBuffer &) const = 0;
 
   // Print the "right". This distinction is necessary to represent C++ types
   // that appear on the RHS of their subtype, such as arrays or functions.
   // Since most types don't have such a component, provide a default
   // implementation.
   virtual void printRight(OutputBuffer &) const {}
 

 ///
 /// This node is created when some <template-args> are found that apply to an
 /// <encoding>, and is stored in the TemplateParams table. In order for this to
 /// appear in the final AST, it has to referenced via a <template-param> (ie,
 /// T_).
 class ParameterPack final : public Node {
   NodeArray Data;
 
-  // Setup OutputString for a pack expansion unless we're already expanding one.
+  // Setup OutputBuffer for a pack expansion, unless we're already expanding
+  // one.
   void initializePackExpansion(OutputBuffer &OB) const {
     if (OB.CurrentPackMax == std::numeric_limits<unsigned>::max()) {
       OB.CurrentPackMax = static_cast<unsigned>(Data.size());
       OB.CurrentPackIndex = 0;
     }
   }
 
 public:
if (First != Last && *First == C) {
       ++First;
       return true;
     }
     return false;
   }
 
   char consume() { return First != Last ? *First++ : '\0'; }
 
-  char look(unsigned Lookahead = 0) {
+  char look(unsigned Lookahead = 0) const {
     if (static_cast<size_t>(Last - First) <= Lookahead)
       return '\0';
     return First[Lookahead];
   }
 
   size_t numLeft() const { return static_cast<size_t>(Last - First); }
 
   StringView parseNumber(bool AllowNegative = false);

 // <substitution> ::= Si # ::std::basic_istream<char,  std::char_traits<char> >
 // <substitution> ::= So # ::std::basic_ostream<char,  std::char_traits<char> >
 // <substitution> ::= Sd # ::std::basic_iostream<char, std::char_traits<char> >
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseSubstitution() {
   if (!consumeIf('S'))
     return nullptr;
 
-  if (std::islower(look())) {
+  if (look() >= 'a' && look() <= 'z') {
     Node *SpecialSub;
     switch (look()) {
     case 'a':
       ++First;
       SpecialSub = make<SpecialSubstitution>(SpecialSubKind::allocator);
       break;
     case 'b':
       ++First;

llvm/include/llvm/Demangle/ItaniumDemangle.h

 //===------------------------- ItaniumDemangle.h ----------------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // Generic itanium demangler library. This file has two byte-per-byte identical
 // copies in the source tree, one in libcxxabi, and the other in llvm.
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_DEMANGLE_ITANIUMDEMANGLE_H
-#define LLVM_DEMANGLE_ITANIUMDEMANGLE_H
+#ifndef DEMANGLE_ITANIUMDEMANGLE_H
+#define DEMANGLE_ITANIUMDEMANGLE_H
 
 // FIXME: (possibly) incomplete list of features that clang mangles that this
 // file does not yet support:
 //   - C++ modules TS
 
 #include "DemangleConfig.h"
 #include "StringView.h"
 #include "Utility.h"

 ///
 /// This node is created when some <template-args> are found that apply to an
 /// <encoding>, and is stored in the TemplateParams table. In order for this to
 /// appear in the final AST, it has to referenced via a <template-param> (ie,
 /// T_).
 class ParameterPack final : public Node {
   NodeArray Data;
 
-  // Setup OutputBuffer for a pack expansion unless we're already expanding one.
+  // Setup OutputBuffer for a pack expansion, unless we're already expanding
+  // one.
   void initializePackExpansion(OutputBuffer &OB) const {
     if (OB.CurrentPackMax == std::numeric_limits<unsigned>::max()) {
       OB.CurrentPackMax = static_cast<unsigned>(Data.size());
       OB.CurrentPackIndex = 0;
     }
   }
 
 public:
if (First != Last && *First == C) {
       ++First;
       return true;
     }
     return false;
   }
 
   char consume() { return First != Last ? *First++ : '\0'; }
 
-  char look(unsigned Lookahead = 0) {
+  char look(unsigned Lookahead = 0) const {
     if (static_cast<size_t>(Last - First) <= Lookahead)
       return '\0';
     return First[Lookahead];
   }
 
   size_t numLeft() const { return static_cast<size_t>(Last - First); }
 
   StringView parseNumber(bool AllowNegative = false);

 // <substitution> ::= Si # ::std::basic_istream<char,  std::char_traits<char> >
 // <substitution> ::= So # ::std::basic_ostream<char,  std::char_traits<char> >
 // <substitution> ::= Sd # ::std::basic_iostream<char, std::char_traits<char> >
 template <typename Derived, typename Alloc>
 Node *AbstractManglingParser<Derived, Alloc>::parseSubstitution() {
   if (!consumeIf('S'))
     return nullptr;
 
-  if (std::islower(look())) {
+  if (look() >= 'a' && look() <= 'z') {
     Node *SpecialSub;
     switch (look()) {
     case 'a':
       ++First;
       SpecialSub = make<SpecialSubstitution>(SpecialSubKind::allocator);
       break;
     case 'b':
       ++First;

 template <typename Alloc>
 struct ManglingParser : AbstractManglingParser<ManglingParser<Alloc>, Alloc> {
   using AbstractManglingParser<ManglingParser<Alloc>,
                                Alloc>::AbstractManglingParser;
 };
 
 DEMANGLE_NAMESPACE_END
 
-#endif // LLVM_DEMANGLE_ITANIUMDEMANGLE_H
+#endif // DEMANGLE_ITANIUMDEMANGLE_H

llvm/include/llvm/Demangle/StringView.h

 //===--- StringView.h -------------------------------------------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // FIXME: Use std::string_view instead when we support C++17.
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_DEMANGLE_STRINGVIEW_H
-#define LLVM_DEMANGLE_STRINGVIEW_H
+#ifndef DEMANGLE_STRINGVIEW_H
+#define DEMANGLE_STRINGVIEW_H
 
 #include "DemangleConfig.h"
 #include <algorithm>
 #include <cassert>
 #include <cstring>
 
 DEMANGLE_NAMESPACE_BEGIN
 

llvm/include/llvm/Demangle/Utility.h

 //===--- Utility.h ----------------------------------------------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 //
 // Provide some utility classes for use in the demangler(s).
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_DEMANGLE_UTILITY_H
-#define LLVM_DEMANGLE_UTILITY_H
+#ifndef DEMANGLE_UTILITY_H
+#define DEMANGLE_UTILITY_H
 
 #include "StringView.h"
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
 #include <iterator>
 #include <limits>