RFR: 8255615: Zero: demote ZeroStack::abi_stack_available guarantee to assert

[Aleksey Shipilev]

On Tue, 3 Nov 2020 11:01:27 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> It is currently `guarantee`, which slows down release bits unnecessarily. The affected method is private, and so what that `assert` really does is checks that no internal Zero code calls it with a wrong `thread` -- something that should be caught by `fastdebug` builds.
>> 
>> inline int ZeroStack::abi_stack_available(Thread *thread) const {
>>   guarantee(Thread::current() == thread, "should run in the same thread");
>> 
>> On my TR 3970X, changing that `guarantee` to `assert` improves:
>>  - Zero x86_64 release "make images" times from ~9.5 minutes to ~7.5 minutes
>>  - Zero x86_64 release "make bootcycle-images" times from ~49 minutes to ~44 minutes
>> 
>> Attention @jerboaa and @gnu-andrew, who have to suffer through the Zero build times occasionally.
>
> LGTM

Thanks @jerboaa! Thanks @AlphaHot (even though you are not the official reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/943