RFR: 8305895: Implement JEP 450: Compact Object Headers (Experimental) [v26]

[Roman Kennke]

On Tue, 8 Oct 2024 15:58:33 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

>> @rkennke @sviswa7 These changes trigger the following assertion failure:
>> 
>> 
>> #
>> # A fatal error has been detected by the Java Runtime Environment:
>> #
>> #  Internal Error (codeBuffer.cpp:1004), pid=96032, tid=29699
>> #  guarantee(sect->end() <= tend) failed: sanity
>> 
>> 
>> when running the following tests with compact object headers disabled (i.e. default JVM settings):
>> 
>> - `java/lang/StringBuffer/ECoreIndexOf.java`
>> - `java/lang/String/IndexOf.java`
>> 
>> on our test macosx-x64 machines. These machines are equipped with Intel Core i7-8700B processors with the following characteristics:
>> 
>> CPU: total 12 (initial active 12) (6 cores per cpu, 2 threads per core) family 6 model 158 stepping 10 microcode 0xf4, cx8, cmov, fxsr, ht, mmx, 3dnowpref, sse, sse2, sse3, ssse3, sse4.1, sse4.2, popcnt, lzcnt, tsc, tscinvbit, avx, avx2, aes, erms, clmul, bmi1, bmi2, rtm, adx, fma, vzeroupper, clflush, clflushopt, rdtscp, f16c
>> 
>> 
>> If you need more details to reproduce the issue, please let me know and I will try to help.
>
> Turns out I can also reproduce the issue on my linux-x64 machine (Intel Core i7-9850H), simply running:
> 
> `make run-test TEST="java/lang/String/IndexOf.java" CONF=linux-x64-debug`
> 
> In this case I get:
> 
> 
> #
> # A fatal error has been detected by the Java Runtime Environment:
> #
> #  Internal Error (codeBuffer.hpp:200), pid=51958, tid=51975
> #  assert(allocates2(pc)) failed: not in CodeBuffer memory: 0x00007c2778843560 <= 0x00007c27788543b3 <= 0x00007c27788543b0
> 
> 
> A few more details of my processor:
> 
> family 6 model 158 stepping 13
> flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb ssbd ibrs ibpb stibp ibrs_enhanced tpr_shadow flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp vnmi md_clear flush_l1d arch_capabilities

Oh! We need to increase the compiler stub size for the indexOf changes. Strange that it blows up like this, I was sure there was a better check for this somewhere. I changed it like this, let me know if you agree that this is the correct fix:
https://github.com/openjdk/jdk/pull/20677/commits/b289ef885816958d9806c76f473b10e34a39e247

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PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1792186244