Significantly improve performance of code coverage tool by precomputing a map token_pos->line numbe…

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 37119)
+++ runtime/vm/object.cc	(working copy)
@@ -7927,6 +7927,16 @@
 }
 
 
+void Script::set_token_pos_to_line_nr(const TypedData& value) const {
+  StorePointer(&raw_ptr()->token_pos_to_line_nr_, value.raw());
+}
+
+
+RawTypedData* Script::token_pos_to_line_nr() const {
+  return raw_ptr()->token_pos_to_line_nr_;
+}
+
+
 void Script::Tokenize(const String& private_key) const {
   Isolate* isolate = Isolate::Current();
   const TokenStream& tkns = TokenStream::Handle(isolate, tokens());
@@ -7961,8 +7971,13 @@
                               intptr_t* line,
                               intptr_t* column) const {
   ASSERT(line != NULL);
-  const TokenStream& tkns = TokenStream::Handle(tokens());
   if (column == NULL) {
+    if (token_pos_to_line_nr() != TypedData::null()) {
+      const TypedData& array = TypedData::Handle(token_pos_to_line_nr());
+      *line = array.GetInt32(token_pos * array.ElementSizeInBytes());
+      return;
+    }
+    const TokenStream& tkns = TokenStream::Handle(tokens());
     TokenStream::Iterator tkit(tkns, 0, TokenStream::Iterator::kAllTokens);
     intptr_t cur_line = line_offset() + 1;
     while (tkit.CurrentPosition() < token_pos &&
@@ -7974,6 +7989,7 @@
     }
     *line = cur_line;
   } else {
+    const TokenStream& tkns = TokenStream::Handle(tokens());
     const String& src = String::Handle(Source());
     intptr_t src_pos = tkns.ComputeSourcePosition(token_pos);
     Scanner scanner(src, Symbols::Empty());
@@ -7989,6 +8005,32 @@
 }
 
 
+void Script::ComputeTokenPosToLineNumberArray() const {
+  if (token_pos_to_line_nr() != TypedData::null()) {
+    // Already computed.
+    return;
+  }
+
+  const TokenStream& tkns = TokenStream::Handle(tokens());
+  const intptr_t len = ExternalTypedData::Handle(tkns.GetStream()).Length();
+  const TypedData& array =
+      TypedData::Handle(TypedData::New(kTypedDataInt32ArrayCid, len));
+  const intptr_t elem_size_in_bytes = array.ElementSizeInBytes();
+  set_token_pos_to_line_nr(array);
+  TokenStream::Iterator tkit(tkns, 0, TokenStream::Iterator::kAllTokens);
+  intptr_t array_offset_in_bytes = 0;
+  intptr_t cur_line = line_offset() + 1;
+  while (tkit.CurrentTokenKind() != Token::kEOS) {
+    array.SetInt32(tkit.CurrentPosition() * elem_size_in_bytes, cur_line);
+    array_offset_in_bytes += elem_size_in_bytes;
+    if (tkit.CurrentTokenKind() == Token::kNEWLINE) {
+      cur_line++;
+    }
+    tkit.Advance();
+  }
+}
+
+
 void Script::TokenRangeAtLine(intptr_t line_number,
                               intptr_t* first_token_index,
                               intptr_t* last_token_index) const {
@@ -18263,6 +18305,7 @@
   if (len < 0 || len > TypedData::MaxElements(class_id)) {
     FATAL1("Fatal error in TypedData::New: invalid len %" Pd "\n", len);
   }
+  ASSERT(RawObject::IsTypedDataClassId(class_id));
   TypedData& result = TypedData::Handle();
   {
     intptr_t lengthInBytes = len * ElementSizeInBytes(class_id);