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

[Evgeny Astigeevich]

On Sun, 14 Feb 2021 05:44:51 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> 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 *
>
> 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 *

Changes requested by eastig at github.com (no known OpenJDK username).

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;
  }
}

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

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