Limit end-anchored regexps to testing end of string where possible.

src/jsregexp.cc

 // Copyright 2006-2009 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 5162 matching lines @@
   if ((data->capture_count + 1) * 2 - 1 > RegExpMacroAssembler::kMaxRegister) {
     return IrregexpRegExpTooBig();
   }
   RegExpCompiler compiler(data->capture_count, ignore_case, is_ascii);
   // Wrap the body of the regexp in capture #0.
   RegExpNode* captured_body = RegExpCapture::ToNode(data->tree,
                                                     0,
                                                     &compiler,
                                                     compiler.accept());
   RegExpNode* node = captured_body;
-  if (!data->tree->IsAnchored()) {
+  bool is_end_anchored = data->tree->IsAnchoredAtEnd();
+  bool is_start_anchored = data->tree->IsAnchoredAtStart();
+  int max_length = data->tree->max_match();
+  if (!is_start_anchored) {
     // Add a .*? at the beginning, outside the body capture, unless
     // this expression is anchored at the beginning.
     RegExpNode* loop_node =
         RegExpQuantifier::ToNode(0,
                                  RegExpTree::kInfinity,
                                  false,
                                  new RegExpCharacterClass('*'),
                                  &compiler,
                                  captured_body,
                                  data->contains_anchor);
@@ skipping 35 matching lines @@
 #elif V8_TARGET_ARCH_ARM
   RegExpMacroAssemblerARM macro_assembler(mode, (data->capture_count + 1) * 2);
 #endif
 
 #else  // V8_INTERPRETED_REGEXP
   // Interpreted regexp implementation.
   EmbeddedVector<byte, 1024> codes;
   RegExpMacroAssemblerIrregexp macro_assembler(codes);
 #endif  // V8_INTERPRETED_REGEXP
 
+  // Inserted here, instead of in Assembler, because it depends on information
+  // in the AST that isn't replicated in the Node structure.
+  static const int kMaxBacksearchLimit = 1024;
+  if (is_end_anchored &&
+      !is_start_anchored &&
+      max_length < kMaxBacksearchLimit) {
+    macro_assembler.SetCurrentPositionFromEnd(max_length);
+  }
+
   return compiler.Assemble(&macro_assembler,
                            node,
                            data->capture_count,
                            pattern);
 }
 
 
 int OffsetsVector::static_offsets_vector_[
     OffsetsVector::kStaticOffsetsVectorSize];
 
 }}  // namespace v8::internal