RFR: 8278479: RunThese test failure with +UseHeavyMonitors and +VerifyHeavyMonitors

[Coleen Phillimore]

On Fri, 1 Jul 2022 20:16:06 GMT, Dean Long <dlong at openjdk.org> wrote:

>> This change adds a null check before calling into Runtime1::monitorenter when -XX:+UseHeavyMonitors is set. There's a null check in the C2 and interpreter code before calling the runtime function but not C1.
>> 
>> Tested with tier1-7 (a little of 8) and built on most non-oracle platforms as well.
>
> src/hotspot/cpu/aarch64/c1_LIRAssembler_aarch64.cpp line 2563:
> 
>> 2561:     if (op->info() != NULL) {
>> 2562:       int null_check_offset = __ offset();
>> 2563:       __ null_check(obj, -1);
> 
> Suggestion:
> 
>       __ null_check(obj);

Yes, that would be better but it leads to a compilation error on macosx-aarch64 that null_check is ambiguous:

src/hotspot/cpu/aarch64/c1_LIRAssembler_aarch64.cpp:2563:10: error: call to member function 'null_check' is ambiguous
[2022-06-30T00:09:19,094Z]       __ null_check(obj);
[2022-06-30T00:09:19,094Z]       ~~~^~~~~~~~~~
src/hotspot/cpu/aarch64/macroAssembler_aarch64.hpp:602:16: note: candidate function
[2022-06-30T00:09:19,094Z]   virtual void null_check(Register reg, int offset = -1);
[2022-06-30T00:09:19,094Z]                ^
src/hotspot/cpu/aarch64/c1_MacroAssembler_aarch64.hpp:109:8: note: candidate function
[2022-06-30T00:09:19,094Z]   void null_check(Register r, Label *Lnull = NULL) { MacroAssembler::null_check(r); }
[2022-06-30T00:09:19,094Z]        ^

> src/hotspot/cpu/arm/c1_LIRAssembler_arm.cpp line 2438:
> 
>> 2436:       int null_check_offset = __ offset();
>> 2437:       __ null_check(obj);
>> 2438:       add_debug_info_for_null_check(null_check_offset, op->info());
> 
> Is this equivalent to the following?
> 
> add_debug_info_for_null_check_here(op->info());
> __ null_check(obj);

I don't know.  Is it better and preferable?

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

PR: https://git.openjdk.org/jdk/pull/9339