RFR: JDK-8301074: Replace NULL with nullptr in share/opto/

[Johan Sjölen]

On Fri, 17 Feb 2023 13:37:02 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Hi, this PR changes all occurrences of NULL to nullptr for the subdirectory share/opto/. Unfortunately the script that does the change isn't perfect, and so we
>> need to comb through these manually to make sure nothing has gone wrong. I also review these changes but things slip past my eyes sometimes.
>> 
>> Here are some typical things to look out for:
>> 
>>     No changes but copyright header changed (probably because I reverted some changes but forgot the copyright).
>>     Macros having their NULL changed to nullptr, these are added to the script when I find them. They should be NULL.
>>     nullptr in comments and logs. We try to use lower case "null" in these cases as it reads better. An exception is made when code expressions are in a comment.
>> 
>> An example of this:
>> 
>> 
>> // This function returns null
>> void* ret_null();
>> // This function returns true if *x == nullptr
>> bool is_nullptr(void** x);
>> 
>> 
>> Note how nullptr participates in a code expression here, we really are talking about the specific value nullptr.
>> 
>> Thanks!
>
> src/hotspot/share/opto/escape.cpp line 2344:
> 
>> 2342: }
>> 2343: 
>> 2344: // Returns unique pointed java object or null.
> 
> Use nullptr explicitly here?

No, not necessary.

> src/hotspot/share/opto/gcm.cpp line 1212:
> 
>> 1210:       // Bailout without retry
>> 1211:       assert(false, "graph should be schedulable");
>> 1212:       C->record_method_not_compilable("late schedule failed: LCA == null");
> 
> nullptr

is

> src/hotspot/share/opto/runtime.cpp line 1550:
> 
>> 1548:   SharedRuntime::_rethrow_ctr++;               // count rethrows
>> 1549: #endif
>> 1550:   assert (exception != nullptr, "should have thrown a nullPointerException");
> 
> Weird looking from the start, surely NullPointerException is the correct one?

I changed it to NullPointerException, avoiding resolving for now.

> src/hotspot/share/opto/stringopts.cpp line 130:
> 
>> 128:     // Look for a diamond shaped Null check of toString() result
>> 129:     // (could be code from String.valueOf()):
>> 130:     // (Proj == null) ? "null":"CastPP(Proj)#Notnull
> 
> nullptr

Also has a missing ". Should it be `CastPP(proj)#NotNull`?

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PR: https://git.openjdk.org/jdk/pull/12187