Auto-sandboxing: Switch to automatic scratch register invalidation

lib/MC/MCParser/NaClAsmParser.cpp

 //===- NaClAsmParser.cpp - NaCl Assembly Parser ---------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCParser/MCAsmParserExtension.h"
@@ skipping 14 matching lines @@
 
     getParser().addDirectiveHandler(Directive, Handler);
   }
 
  public:
   NaClAsmParser(MCNaClExpander *Exp) : Expander(Exp) {}
   void Initialize(MCAsmParser &Parser) override {
     // Call the base implementation.
     MCAsmParserExtension::Initialize(Parser);
     addDirectiveHandler<&NaClAsmParser::ParseScratch>(".scratch");
-    addDirectiveHandler<&NaClAsmParser::ParseUnscratch>(".unscratch");
+    addDirectiveHandler<&NaClAsmParser::ParseUnscratch>(".scratch_clear");
   }
 
   /// ::= {.scratch} reg
   bool ParseScratch(StringRef Directive, SMLoc Loc) {
     getParser().checkForValidSection();
     unsigned RegNo;
     const char *kInvalidOptionError =
         "expected register name after '.scratch' directive";
 
     if (getLexer().isNot(AsmToken::EndOfStatement)) {
       if (getParser().getTargetParser().ParseRegister(RegNo, Loc, Loc))
         return Error(Loc, kInvalidOptionError);
 
       else if (getLexer().isNot(AsmToken::EndOfStatement))
         return Error(Loc, kInvalidOptionError);
     }
     else {
       return Error(Loc, kInvalidOptionError);
     }
     Lex();
 
-    Expander->pushScratchReg(RegNo);
+    if(Expander->addScratchReg(RegNo))
+      return Error(Loc, "Register can't be used as a scratch register");
     return false;
   }
 
   /// ::= {.unscratch}
   bool ParseUnscratch(StringRef Directive, SMLoc Loc) {
     getParser().checkForValidSection();
     if (getLexer().isNot(AsmToken::EndOfStatement))
-      return TokError("unexpected token in '.unscratch' directive");
+      return TokError("unexpected token in '.scratch_clear' directive");
     Lex();
 
-    if (Expander->numScratchRegs() == 0)
-      return Error(Loc, "No scratch registers specified");
-    Expander->popScratchReg();
+    Expander->clearScratchRegs();
 
     return false;
   }
 };
 
 namespace llvm {
 MCAsmParserExtension *createNaClAsmParser(MCNaClExpander *Exp) {
   return new NaClAsmParser(Exp);
 }
 }