Use finite-length end-anchored regexps to reduce part of regexp that is searched.

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

 // Copyright 2009 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 127 matching lines @@
 }
 
 
 int RegExpMacroAssemblerX64::stack_limit_slack()  {
   return RegExpStack::kStackLimitSlack;
 }
 
 
 void RegExpMacroAssemblerX64::AdvanceCurrentPosition(int by) {
   if (by != 0) {
-    Label inside_string;
     __ addq(rdi, Immediate(by * char_size()));
   }
 }
 
 
 void RegExpMacroAssemblerX64::AdvanceRegister(int reg, int by) {
   ASSERT(reg >= 0);
   ASSERT(reg < num_registers_);
   if (by != 0) {
     __ addq(register_location(reg), Immediate(by));
@@ skipping 887 matching lines @@
   __ movq(rdi, register_location(reg));
 }
 
 
 void RegExpMacroAssemblerX64::ReadStackPointerFromRegister(int reg) {
   __ movq(backtrack_stackpointer(), register_location(reg));
   __ addq(backtrack_stackpointer(), Operand(rbp, kStackHighEnd));
 }
 
 
+void RegExpMacroAssemblerX64::SetCurrentPositionFromEnd(int by) {
+  NearLabel after_position;
+  __ cmpq(rdi, Immediate(-by * char_size()));
+  __ j(above_equal, &after_position);
+  __ movq(rdi, Immediate(-by * char_size()));
+  // On RegExp code entry (where this operation is used), the character before
+  // the current position is expected to be already loaded.
+  // We have advenced the position, so it's safe to read backwards.
+  LoadCurrentCharacterUnchecked(-1, 1);
+  __ bind(&after_position);
+}
+
+
 void RegExpMacroAssemblerX64::SetRegister(int register_index, int to) {
   ASSERT(register_index >= num_saved_registers_);  // Reserved for positions!
   __ movq(register_location(register_index), Immediate(to));
 }
 
 
 void RegExpMacroAssemblerX64::Succeed() {
   __ jmp(&success_label_);
 }
 
@@ skipping 297 matching lines @@
   }
 }
 
 #undef __
 
 #endif  // V8_INTERPRETED_REGEXP
 
 }}  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64