Fix bug in x64 RegExp detecting start of string.

src/x64/regexp-macro-assembler-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 175 matching lines @@
 
 void RegExpMacroAssemblerX64::CheckCharacterGT(uc16 limit, Label* on_greater) {
   __ cmpl(current_character(), Immediate(limit));
   BranchOrBacktrack(greater, on_greater);
 }
 
 
 void RegExpMacroAssemblerX64::CheckAtStart(Label* on_at_start) {
   Label not_at_start;
   // Did we start the match at the start of the string at all?
-  __ cmpb(Operand(rbp, kStartIndex), Immediate(0));
+  __ cmpl(Operand(rbp, kStartIndex), Immediate(0));
   BranchOrBacktrack(not_equal, &not_at_start);
   // If we did, are we still at the start of the input?
   __ lea(rax, Operand(rsi, rdi, times_1, 0));
   __ cmpq(rax, Operand(rbp, kInputStart));
   BranchOrBacktrack(equal, on_at_start);
   __ bind(&not_at_start);
 }
 
 
 void RegExpMacroAssemblerX64::CheckNotAtStart(Label* on_not_at_start) {
   // Did we start the match at the start of the string at all?
-  __ cmpb(Operand(rbp, kStartIndex), Immediate(0));
+  __ cmpl(Operand(rbp, kStartIndex), Immediate(0));
   BranchOrBacktrack(not_equal, on_not_at_start);
   // If we did, are we still at the start of the input?
   __ lea(rax, Operand(rsi, rdi, times_1, 0));
   __ cmpq(rax, Operand(rbp, kInputStart));
   BranchOrBacktrack(not_equal, on_not_at_start);
 }
 
 
 void RegExpMacroAssemblerX64::CheckCharacterLT(uc16 limit, Label* on_less) {
   __ cmpl(current_character(), Immediate(limit));
@@ skipping 1192 matching lines @@
   }
 }
 
 #undef __
 
 #endif  // V8_INTERPRETED_REGEXP
 
 }}  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64