[NFC] Optimize file kind determination (#139492)

There are checks in clang codebase that determine the type of source
file, associated with a given location - specifically, if it is an
ordonary file or comes from sources like command-line options or a
built-in definitions. These checks often rely on calls to
`getPresumedLoc`, which is relatively expensive. In certain cases, these
checks are combined, leading to repeated calculations of the costly
function negatively affecting compile time.

This change tries to optimize such checks. It must fix compile time
regression introduced in
#137306.

---------

Co-authored-by: cor3ntin <[email protected]>

Author: spavloff

clang/include/clang/Basic/SourceManager.h

@@ -1529,6 +1529,15 @@ class SourceManager : public RefCountedBase<SourceManager> {
     return Filename == "<scratch space>";
   }
 
+  /// Returns whether \p Loc is located in a built-in or command line source.
+  bool isInPredefinedFile(SourceLocation Loc) const {
+    PresumedLoc Presumed = getPresumedLoc(Loc);
+    if (Presumed.isInvalid())
+      return false;
+    StringRef Filename(Presumed.getFilename());
+    return Filename == "<built-in>" || Filename == "<command line>";
+  }
+
   /// Returns if a SourceLocation is in a system header.
   bool isInSystemHeader(SourceLocation Loc) const {
     if (Loc.isInvalid())

clang/lib/ExtractAPI/ExtractAPIConsumer.cpp

@@ -305,8 +305,7 @@ class MacroCallback : public PPCallbacks {
 
       auto DefLoc = MI->getDefinitionLoc();
 
-      if (SM.isWrittenInBuiltinFile(DefLoc) ||
-          SM.isWrittenInCommandLineFile(DefLoc))
+      if (SM.isInPredefinedFile(DefLoc))
         continue;
 
       auto AssociatedModuleMacros = MD.getModuleMacros();

clang/lib/Frontend/PrintPreprocessedOutput.cpp

@@ -569,8 +569,7 @@ void PrintPPOutputPPCallbacks::MacroDefined(const Token &MacroNameTok,
   SourceLocation DefLoc = MI->getDefinitionLoc();
   if (DirectivesOnly && !MI->isUsed()) {
     SourceManager &SM = PP.getSourceManager();
-    if (SM.isWrittenInBuiltinFile(DefLoc) ||
-        SM.isWrittenInCommandLineFile(DefLoc))
+    if (SM.isInPredefinedFile(DefLoc))
       return;
   }
   MoveToLine(DefLoc, /*RequireStartOfLine=*/true);

clang/lib/Lex/PPDirectives.cpp

@@ -374,9 +374,8 @@ bool Preprocessor::CheckMacroName(Token &MacroNameTok, MacroUse isDefineUndef,
   // Macro names with reserved identifiers are accepted if built-in or passed
   // through the command line (the later may be present if -dD was used to
   // generate the preprocessed file).
-  bool IsBuiltinOrCmd = SourceMgr.isWrittenInBuiltinFile(MacroNameLoc) ||
-                        SourceMgr.isWrittenInCommandLineFile(MacroNameLoc);
-  if (!IsBuiltinOrCmd && !SourceMgr.isInSystemHeader(MacroNameLoc)) {
+  if (!SourceMgr.isInPredefinedFile(MacroNameLoc) &&
+      !SourceMgr.isInSystemHeader(MacroNameLoc)) {
     MacroDiag D = MD_NoWarn;
     if (isDefineUndef == MU_Define) {
       D = shouldWarnOnMacroDef(*this, II);
@@ -1706,8 +1705,7 @@ void Preprocessor::HandleDigitDirective(Token &DigitTok) {
     // If a filename was present, read any flags that are present.
     if (ReadLineMarkerFlags(IsFileEntry, IsFileExit, FileKind, *this))
       return;
-    if (!SourceMgr.isWrittenInBuiltinFile(DigitTok.getLocation()) &&
-        !SourceMgr.isWrittenInCommandLineFile(DigitTok.getLocation()))
+    if (!SourceMgr.isInPredefinedFile(DigitTok.getLocation()))
       Diag(StrTok, diag::ext_pp_gnu_line_directive);
 
     // Exiting to an empty string means pop to the including file, so leave