RFR: 8255900: x86: Reduce impact when VerifyOops is disabled

[Yumin Qi]

On Wed, 4 Nov 2020 14:49:41 GMT, Claes Redestad <redestad at openjdk.org> wrote:

> - Don't generate stub _verify_oop_subroutine_entry on startup if -VerifyOops
> - Make VerifyOops check in calls to MacroAssembler::verify_oop inlineable. (VerifyOops is a develop flag, so this allows more aggressive code elimination in a few place)
> - (trivial pile-on) remove unused set_word_if_not_zero
> 
> Slightly improves static footprint, gets rid of a stub and reduce jitter during jitting in product builds.

Then looks good to me.

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Marked as reviewed by minqi (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1058