RFR: JDK-8213199: GC abstraction for Assembler::needs_explicit_null_check()

Andrew Dinn adinn at redhat.com
Wed Nov 7 10:46:18 UTC 2018


On 07/11/18 10:37, Erik Österlund wrote:
> Thanks for digging that up.

No problem. The funny thing is that I knew about this ad file function
and -- roughly -- what it would achieve in terms of the graph reshape
and subsequent code generation. However, I never put 2 + 2 together and
followed through with the conclusion that this would cause loads of oops
stored as zero to potentially be modelled by and dereferenced at address
heap_base.

It's all very devious!

Do you think a small explanatory comment in uses_implicit_null_check
pointing readers at gen_narrow_oop_implicit_null_checks might be worth
including?

regards,


Andrew Dinn
-----------
Senior Principal Software Engineer
Red Hat UK Ltd
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