[Serialization] Remove getMacroID (llvm#127413)

The last use was removed in:

  commit ee97793
  Author: Richard Smith <[email protected]>
  Date:   Fri May 1 21:22:17 2015 +0000

Author: kazutakahirata

clang/include/clang/Serialization/ASTWriter.h

@@ -751,9 +751,6 @@ class ASTWriter : public ASTDeserializationListener,
   /// Get the unique number used to refer to the given macro.
   serialization::MacroID getMacroRef(MacroInfo *MI, const IdentifierInfo *Name);
 
-  /// Determine the ID of an already-emitted macro.
-  serialization::MacroID getMacroID(MacroInfo *MI);
-
   uint32_t getMacroDirectivesOffset(const IdentifierInfo *Name);
 
   /// Emit a reference to a type.

clang/lib/Serialization/ASTWriter.cpp

@@ -6666,14 +6666,6 @@ MacroID ASTWriter::getMacroRef(MacroInfo *MI, const IdentifierInfo *Name) {
   return ID;
 }
 
-MacroID ASTWriter::getMacroID(MacroInfo *MI) {
-  if (!MI || MI->isBuiltinMacro())
-    return 0;
-
-  assert(MacroIDs.contains(MI) && "Macro not emitted!");
-  return MacroIDs[MI];
-}
-
 uint32_t ASTWriter::getMacroDirectivesOffset(const IdentifierInfo *Name) {
   return IdentMacroDirectivesOffsetMap.lookup(Name);
 }