RFR: 8357258: x86: Improve receiver type profiling reliability [v3]

[Aleksey Shipilev]

On Fri, 21 Nov 2025 19:48:21 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:
>> 
>>  - Merge branch 'master' into JDK-8357258-x86-c1-optimize-virt-calls
>>  - Merge branch 'master' into JDK-8357258-x86-c1-optimize-virt-calls
>>  - Drop atomic counters
>>  - Initial version
>
> src/hotspot/cpu/x86/macroAssembler_x86.cpp line 4807:
> 
>> 4805: 
>> 4806:   Register offset = rscratch1;
>> 4807:   assert_different_registers(mdp, recv, offset);
> 
> We also have `rscratch2` which we can use for registers shuffling in the following code.

Unfortunately not. I remember trying that and that did not work. I just added `rscratch2` here, and it immediately failed on this path:


Stack: [0x000078f046f00000,0x000078f047000000],  sp=0x000078f046ffd350,  free space=1012k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V  [libjvm.so+0x9697f9]  void assert_different_registers_impl<Register, Register, Register, Register>(char const*, int, Register, Register, Register, Register)+0xc9  (macroAssembler_x86.cpp:4799)
V  [libjvm.so+0x1676bbd]  MacroAssembler::type_profile(Register, Register, int)+0xad  (macroAssembler_x86.cpp:4799)
V  [libjvm.so+0x962da7]  LIR_Assembler::emit_opTypeCheck(LIR_OpTypeCheck*)+0x757  (c1_LIRAssembler_x86.cpp:1266)
V  [libjvm.so+0x941a8c]  LIR_OpTypeCheck::emit_code(LIR_Assembler*)+0x1c  (c1_LIR.cpp:1023)
V  [libjvm.so+0x95157e]  LIR_Assembler::emit_lir_list(LIR_List*)+0xde  (c1_LIRAssembler.cpp:301)
V  [libjvm.so+0x951e66]  LIR_Assembler::emit_code(BlockList*)+0xf6  (c1_LIRAssembler.cpp:266)
V  [libjvm.so+0x8faef9]  Compilation::emit_code_body()+0x189  (c1_Compilation.cpp:348)
V  [libjvm.so+0x8fb41d]  Compilation::compile_java_method()+0x3bd  (c1_Compilation.cpp:409)
V  [libjvm.so+0x8fbbee]  Compilation::compile_method()+0x25e  (c1_Compilation.cpp:471)
V  [libjvm.so+0x8fc31f]  Compilation::Compilation(AbstractCompiler*, ciEnv*, ciMethod*, int, BufferBlob*, bool, DirectiveSet*)+0x35f  (c1_Compilation.cpp:600)
V  [libjvm.so+0x8fdd7a]  Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x20a  (c1_Compiler.cpp:263)

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PR Review Comment: https://git.openjdk.org/jdk/pull/25305#discussion_r2564452657