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

[Vladimir Kozlov]

On Fri, 17 Feb 2023 13:35:44 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 59:
> 
>> 57:   add_java_object(C->top(), PointsToNode::GlobalEscape);
>> 58:   phantom_obj = ptnode_adr(C->top()->_idx)->as_JavaObject();
>> 59:   // Add ConP(#null) and ConN(#null) nodes.
> 
> What does `#NULL` mean?

It means these nodes represent null pointer constant oop in IR graph.
I suggest `// Add ConP and ConN null oop nodes`.

> src/hotspot/share/opto/graphKit.cpp line 1610:
> 
>> 1608:                                 BasicType bt,
>> 1609:                                 DecoratorSet decorators) {
>> 1610:   // Transformation of a value which could be null pointer (CastPP #null)
> 
> `#NULL` pattern

okay `#null`.

> src/hotspot/share/opto/graphKit.cpp line 2406:
> 
>> 2404: // [foo] indicates that 'foo' is a parameter
>> 2405: //
>> 2406: //              [in]     null
> 
> null OK here?

OK

> src/hotspot/share/opto/graphKit.cpp line 2744:
> 
>> 2742:   // hierarchy and we have to scan the secondary superclass list the hard way.
>> 2743:   // Worst-case type is a little odd: null is allowed as a result (usually
>> 2744:   // klass loads can never produce a null).
> 
> nullptr or null?

Keep `null`

> src/hotspot/share/opto/matcher.cpp line 328:
> 
>> 326:   C->print_method(PHASE_BEFORE_MATCHING, 1);
>> 327: 
>> 328:   // Create new ideal node ConP #null even if it does exist in old space
> 
> `#null` pattern

keep it.

> src/hotspot/share/opto/matcher.cpp line 376:
> 
>> 374:       }
>> 375: 
>> 376:       // Generate new mach node for ConP #null
> 
> `#null`

keep it.

> src/hotspot/share/opto/matcher.hpp line 173:
> 
>> 171: #endif
>> 172: 
>> 173:   // Mach node for ConP #null
> 
> `#null`

keep it.

> src/hotspot/share/opto/node.cpp line 2076:
> 
>> 2074:   tty->print("    else: shortest path or all paths between this/start and target\n");
>> 2075:   tty->print("  options:\n");
>> 2076:   tty->print("    if null: same as \"cdmox at B\"\n");
> 
> null better here imho

yes

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