RFR: 8260198: TypeInstPtr::dump2() emits multiple lines if Verbose is set [v4]

[Evgeny Astigeevich]

On Wed, 17 Feb 2021 12:04:56 GMT, Evgeny Astigeevich <github.com+42899633+eastig at openjdk.org> wrote:

>> Xin Liu has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:
>> 
>>  - 8260198: TypeInstPtr::dump2() emits multiple lines if Verbose is set
>>    
>>    reimplement this feature. withdraw my intrusive change in outputStream.
>>    use stringStream only for the constant OopPtr. after oop->print_on(st),
>>    delete all appearances of '\n'
>>  - Merge branch 'master' into JDK-8260198
>>  - 8260198: TypeInstPtr::dump2() emits multiple lines if Verbose is set
>>    
>>    fix merge conflict.
>>  - Merge branch 'master' into JDK-8260198
>>  - 8260198: TypeInstPtr::dump2() emits multiple lines if Verbose is set
>>    
>>    Add a flag _suppress_cr to outputStream. outstream objects won't emit any CR if it's set.
>>    Correct TypeInstPtr::dump2 to make sure it only emits klass name once.
>>    Remove the comment because Klass::oop_print_on() has emitted the address of oop.
>>    
>>    Before:
>>    689  ConP  ===  0  [[ 821 ]]   Oop:java/lang/Stringjava.lang.String
>>    {0x000000010159d7c8} - klass: public final synchronized 'java/lang/String'
>>     - string: "a"
>>     :Constant:exact *
>>    
>>    After:
>>    689  ConP  ===  0  [[ 821 ]]   Oop:java.lang.String {0x000000010159d7c8} - klass: public final synchronized 'java/lang/String' - string: "a":Constant:exact *
>
> src/hotspot/share/opto/type.cpp line 4049:
> 
>> 4047:       ss.print(" ");
>> 4048:       const_oop()->print_oop(&ss);
>> 4049:       ss.tr_delete('\n');
> 
> `tr_delete` is expensive. Also deleting something in a stream does not fit into a concept of streams.
> I see that the content of `ss` is traversed many times.
> What about this code:
> for (const char *str = ss.base(); *str; ) {
>   size_t i = 0;
>   while (str[i] && str[i] != '\n' ) {
>        ++i;
>   }
>   st->print_raw(str, i);
>   str += i;
>   while (*str == '\n') {
>     ++str;
>   }
> }

Another option:
class filterStringStream: public stringStream {
private:
  char ch;
public:
  filterStringStream(char ch_to_filter, size_t initial_bufsize = 256) : stringStream(initial_bufsize), ch(ch_to_filter) {}

  virtual void write(const char* c, size_t len) override {
    const char* e = c + len;
    while (c != e) {
      size_t i = 0;
      while ((c+i) != e && c[i] != ch ) {
        ++i;
      }
      stringStream::write(c, i);
      c += i;
      while (c != e && *ch == ch) {
        ++c;
      }
    }     
  }
};

Your code will be:
filterStringStream ss('\n');
ss.print(" ");
const_oop->print_oop(&ss);
st->print_raw(ss.base(), ss,size());

-------------

PR: https://git.openjdk.java.net/jdk/pull/2178