Re: RVC by default?

[Xiaolin Zheng]

Hi Vladimir,
Thank you for the newly-added hs_err and further tests. I guess it might have some relationship with the discussed [misaligned issue](https://mail.openjdk.org/pipermail/riscv-port-dev/2022-July/000559.html <https://mail.openjdk.org/pipermail/riscv-port-dev/2022-July/000559.html >) here. But just guessing. I have noticed one interesting thing that the crashed hs_err files are often like:
```
...
 0x0000003f7cc2f91e: mv a0,s7
 0x0000003f7cc2f922: auipc t0,0x10494
 0x0000003f7cc2f926: jalr 664(t0) # 0x0000003f8d0c3bba = AdapterHandlerEntry::print_adapter_on(outputStream*) const+470 <--- ??? Misaligned address: 0x0000003f7cc2f926
 0x0000003f7cc2f92a: sd zero,704(s7)
 0x0000003f7cc2f92e: sd zero,712(s7)
...
```
With RVC, it is certainly legal to locate at a 2-byte aligned address. But, this location is relocatable, which means it will be patched.
So, I might doubt something weird happened when performing the patching behavior. The patching logic, referencing the instruction segment, does not care about the alignment but only performs 4-byte memory load operations, such as Assembler::patch(). On machines having the misaligned address support, it would not go wrong of course; but it seems that our FPGA board discussed lacks this support. So I guess there might be an interesting chemical reaction happening here. I have written two patches to debug this issue and released one fastdebug build only for debugging purposes, and I put it at https://github.com/zhengxiaolinX/jdk/releases/tag/test-unaligned <https://github.com/zhengxiaolinX/jdk/releases/tag/test-unaligned >. The two patches fix most of the misaligned accesses to the instruction segment. I was wondering if you could have a simple test of it when you are available, to see whether this issue still exists?
I am just guessing the problem here, hope it can reveal something to us.
Thank you very much.
Best,
Xiaolin
------------------------------------------------------------------
From:Vladimir Kempik <vladimir.kempik at gmail.com>
Send Time:2022年9月15日(星期四) 23:25
To:郑孝林(云矅) <yunyao.zxl at alibaba-inc.com>
Cc:riscv-port-dev <riscv-port-dev-retn at openjdk.org>; Aleksey Shipilev <shade at redhat.com>; riscv-port-dev at openjdk.org <riscv-port-dev at openjdk.org>
Subject:Re: RVC by default?
Hello
Looks pretty similar to me.
for me it was vanilla recent jdk19 
But later, when I backported next patches to my jdk19 branch, the issue became different ( Arena alloc issue I have reported earlier):
8290496: riscv: Fix build warnings-as-errors with GCC 11
8290280: riscv: Clean up stack and register handling in interpreter
8290137: riscv: small refactoring for add_memory_int32/64
8290164: compiler/runtime/TestConstantsInError.java fails on riscv
8291952: riscv: Remove PRAGMA_NONNULL_IGNORED
8291947: riscv: fail to build after JDK-8290840
8291893: riscv: remove fence.i used in user space Backport-of:...
8292713: Unsafe.allocateInstance should be intrinsified without UseUnalignedAccesses
8292867: RISC-V: Simplify weak CAS return value handling
8292407: Improve Weak CAS VarHandle/Unsafe tests resilience under spurious failures
8293100: RISC-V: Need to save and restore callee-saved FloatRegisters in...
8293050: RISC-V: Remove redundant non-null assertions about macro-assembler
8293474: RISC-V: Unify the way of moving function pointer
8293524: RISC-V: Use macro-assembler functions as appropriate
8293566: RISC-V: Clean up push and pop registers
I’m gonna bisect this list and find what changed the behaviour.
The workaround says - update to ubuntu 21.04, but its not clear - update runtime environment or build environment.
For me the runtime is ubuntu 22.04, but I build the jdk with sysroot of ubuntu 20.04 ( for better compatibility) and gcc 11.2
Regards, Vladimir
15 сент. 2022 г., в 18:17, Xiaolin Zheng <yunyao.zxl at alibaba-inc.com <mailto:yunyao.zxl at alibaba-inc.com >> написал(а):
Hi Vladimir,
The mailing list says my e-mail exceeds 40KB so I get rejected. But I want to send it out anyway before getting off today's work. So here is a work around:
Please check:
https://gist.github.com/zhengxiaolinX/25c32853690f7ac1c125d2fe1da19710 <https://gist.github.com/zhengxiaolinX/25c32853690f7ac1c125d2fe1da19710 >
Looking forward to your opinions.
Best,
Xiaolin
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