PP: Replace some uses of unsigned with size_t

[erikjv]

Summary

All values are returned by a method as size_t, and subsequently passed
to functions taking a size_t, or used where a size_t is also valid.
Better still, two loops (which had an unsigned), can be replaced by
a range-based for loop.

[bkramer]

lib/Lex/PPDirectives.cpp

804

While there you could turn this into a for-range loop

for (IncludeStackInfo &ISEntry : llvm::reverse(IncludeMacroStack))

868

Looks like another candidate for for-range.

[bkramer]

lg

lib/Lex/PPDirectives.cpp

while (true) {
     // that we can't use Tok.getIdentifierInfo() because its lookup is disabled
     // when skipping.
     char DirectiveBuf[20];
     StringRef Directive;
     if (!Tok.needsCleaning() && RI.size() < 20) {
       Directive = RI;
     } else {
       std::string DirectiveStr = getSpelling(Tok);
-      unsigned IdLen = DirectiveStr.size();
+      size_t IdLen = DirectiveStr.size();
       if (IdLen >= 20) {
         CurPPLexer->ParsingPreprocessorDirective = false;
         // Restore comment saving mode.
         if (CurLexer) CurLexer->resetExtendedTokenMode();
         continue;
       }
       memcpy(DirectiveBuf, &DirectiveStr[0], IdLen);
       Directive = StringRef(DirectiveBuf, IdLen);
if (!FromDir && !FromFile) {
     } else {
       Includers.push_back(std::make_pair(FileEnt, FileEnt->getDir()));
     }
 
     // MSVC searches the current include stack from top to bottom for
     // headers included by quoted include directives.
     // See: http://msdn.microsoft.com/en-us/library/36k2cdd4.aspx
     if (LangOpts.MSVCCompat && !isAngled) {
-      for (unsigned i = 0, e = IncludeMacroStack.size(); i != e; ++i) {
-        IncludeStackInfo &ISEntry = IncludeMacroStack[e - i - 1];
+      for (IncludeStackInfo &ISEntry : llvm::reverse(IncludeMacroStack)) {
         if (IsFileLexer(ISEntry))
           if ((FileEnt = ISEntry.ThePPLexer->getFileEntry()))
             Includers.push_back(std::make_pair(FileEnt, FileEnt->getDir()));
       }
     }
   }
 
   CurDir = CurDirLookup;
if ((CurFileEnt = CurPPLexer->getFileEntry())) {
           HeaderInfo.getModuleMap().diagnoseHeaderInclusion(
               RequestingModule, RequestingModuleIsModuleInterface, FilenameLoc,
               Filename, FE);
         return FE;
       }
     }
   }
 
-  for (unsigned i = 0, e = IncludeMacroStack.size(); i != e; ++i) {
-    IncludeStackInfo &ISEntry = IncludeMacroStack[e-i-1];
+  for (IncludeStackInfo &ISEntry : llvm::reverse(IncludeMacroStack)) {
     if (IsFileLexer(ISEntry)) {
       if ((CurFileEnt = ISEntry.ThePPLexer->getFileEntry())) {
         if ((FE = HeaderInfo.LookupSubframeworkHeader(
                 Filename, CurFileEnt, SearchPath, RelativePath,
                 RequestingModule, SuggestedModule))) {
           if (SuggestedModule && !LangOpts.AsmPreprocessor)
             HeaderInfo.getModuleMap().diagnoseHeaderInclusion(
                 RequestingModule, RequestingModuleIsModuleInterface,
while (CurTok.isNot(tok::eod)) {
     }
 
     // Append the spelling of this token to the buffer. If there was a space
     // before it, add it now.
     if (CurTok.hasLeadingSpace())
       FilenameBuffer.push_back(' ');
 
     // Get the spelling of the token, directly into FilenameBuffer if possible.
-    unsigned PreAppendSize = FilenameBuffer.size();
+    size_t PreAppendSize = FilenameBuffer.size();
     FilenameBuffer.resize(PreAppendSize+CurTok.getLength());
 
     const char *BufPtr = &FilenameBuffer[PreAppendSize];
     unsigned ActualLen = getSpelling(CurTok, BufPtr);
 
     // If the token was spelled somewhere else, copy it into FilenameBuffer.
     if (BufPtr != &FilenameBuffer[PreAppendSize])
       memcpy(&FilenameBuffer[PreAppendSize], BufPtr, ActualLen);

 /// was implicitly treated as a module import.
 static void diagnoseAutoModuleImport(
     Preprocessor &PP, SourceLocation HashLoc, Token &IncludeTok,
     ArrayRef<std::pair<IdentifierInfo *, SourceLocation>> Path,
     SourceLocation PathEnd) {
   assert(PP.getLangOpts().ObjC2 && "no import syntax available");
 
   SmallString<128> PathString;
-  for (unsigned I = 0, N = Path.size(); I != N; ++I) {
+  for (size_t I = 0, N = Path.size(); I != N; ++I) {
     if (I)
       PathString += '.';
     PathString += Path[I].first->getName();
   }
   int IncludeKind = 0;
 
   switch (IncludeTok.getIdentifierInfo()->getPPKeywordID()) {
   case tok::pp_include: