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

src/ia32/regexp-macro-assembler-ia32.cc

Index: src/ia32/regexp-macro-assembler-ia32.cc
diff --git a/src/ia32/regexp-macro-assembler-ia32.cc b/src/ia32/regexp-macro-assembler-ia32.cc
index 2aab7a8d943194c01d613a159446f8f59bf480a9..3d43a8b521ea56540f891480cbf9e3e14ee5785b 100644
--- a/src/ia32/regexp-macro-assembler-ia32.cc
+++ b/src/ia32/regexp-macro-assembler-ia32.cc
@@ -133,7 +133,6 @@ int RegExpMacroAssemblerIA32::stack_limit_slack()  {
 
 void RegExpMacroAssemblerIA32::AdvanceCurrentPosition(int by) {
   if (by != 0) {
-    Label inside_string;
     __ add(Operand(edi), Immediate(by * char_size()));
   }
 }
@@ -964,6 +963,17 @@ void RegExpMacroAssemblerIA32::ReadStackPointerFromRegister(int reg) {
   __ add(backtrack_stackpointer(), Operand(ebp, kStackHighEnd));
 }
 
+void RegExpMacroAssemblerIA32::SetCurrentPositionFromEnd(int by)  {
+  NearLabel after_position;
+  __ cmp(edi, -by * char_size());
+  __ j(above_equal, &after_position);
+  __ mov(edi, -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 RegExpMacroAssemblerIA32::SetRegister(int register_index, int to) {
   ASSERT(register_index >= num_saved_registers_);  // Reserved for positions!