8369946: Bytecode rewriting causes Java heap corruption on PPC

[TheRealMDoerr]

Like the aarch64 fix (#27748).
PPC64 has additional requirements:

• It implements fast_invokevfinal which uses ResolvedMethodEntry.
• Speculative loads need to get prevented by memory barrier instructions (even on control dependent paths).

I've refactored load_field_entry and load_method_entry into a common function and added support for rewritten "fast" Bytecodes. I'm using isync instructions because we already have a control dependency (via Bytecode dispatch).

The isync instruction is relatively cheap in comparison to other memory barriers, but still introduces some performance loss. SPEC jvm98 with -Xint shows about 5% regression in compress sub-benchmark. The other sub-benchmarks are not significantly impacted. However, switching off RewriteBytecodes would cause a much higher performance loss.

Note: I had also ported the verify_field_offset check and used it in the fastdebug and product build for testing, but couldn't catch any issue. Not included in this PR. I'm not planning to contribute it.

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Issue

• JDK-8369946: Bytecode rewriting causes Java heap corruption on PPC (Bug - P2)

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[mlbridge]

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[reinrich]

Hi Martin,
nasty bug this is. Thanks for doing the fixing on ppc. And great work by Justin finding it!
I see that we've missed porting previous fixes to ppc that prevent reordering of the bytecode load with loads from ResolvedFieldEntry and -MethodEntry (JDK-8248219 and JDK-8327647). Now this is done in load_field_or_method_entry().
The change is good. The comment could be improved a little bit.
Thanks, Richard.