[lworld] RFR: 8267791: [lworld][lw3] Support compiler blackholes for inline types [v2]

[Tobias Hartmann]

On Mon, 31 May 2021 09:45:11 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> JDK-8259316 added the support for compiler blackholes. We need to check and implement the support for inline type arguments for them. I am sure we would find more wrinkles with nano-benchmarks, but insofar sample benchmark work as they should:
>> 
>> 
>> public class PrimitiveClasses {
>>     static primitive class Value {
>>         long x;
>>         long y;
>>         public Value(long x, long y) {
>>             this.x = x;
>>             this.y = y;
>>         }
>>     }
>> 
>>     [volatile] Value v = Value.default;
>> 
>>     @Benchmark
>>     public Value test() {
>>         return v;
>>     }
>> }
>> 
>> 
>> Before: crash on assert, `assert(vt->fast_out(i)->is_InlineTypeBase(), "Unexpected inline type user");`
>> 
>> After, generated code in non-`volatile` case shows blackhole of individual components:
>> 
>> 
>> $ java -Djmh.blackhole.mode=COMPILER -jar target/benchmarks.jar PrimitiveClasses -prof perfasm
>> ...
>> ....[Hottest Region 1]..............................................................................
>> c2, level 4, org.openjdk.jmh_generated.PrimitiveClasses_test_jmhTest::test_avgt_jmhStub, version 641 (39 bytes) 
>> ...
>>          ↗  0x00007f67bcc8eee0:   mov    0x18(%r8),%r10        ; read and blackhole MyValue.x
>>   0.02%  │  0x00007f67bcc8eee4:   mov    0x10(%r8),%r11        ; read and blackhole MyValue.y
>>   0.10%  │  0x00007f67bcc8eee8:   movzbl 0x94(%r14),%r11d      ; read isDone
>>   0.10%  │  0x00007f67bcc8eef0:   mov    0x3b0(%r15),%r10      ; TL handshake
>>   2.79%  │  0x00007f67bcc8eef7:   add    $0x1,%rbp             ; ops++
>>          │  0x00007f67bcc8eefb:   test   %eax,(%r10)           ; TL handshake
>>  86.74%  │  0x00007f67bcc8eefe:   test   %r11d,%r11d           ; isDone?
>>   2.31%  ╰  0x00007f67bcc8ef01:   je     0x00007f67bcc8eee0    
>> 
>> 
>> And generated code in `volatile` case shows blackhole of the box (with the null-check):
>> 
>> 
>>           ↗   0x00007f3948c8db70:   shl    $0x3,%r10            ; unpack and blackhole MyValue
>>   0.02%   │↗  0x00007f3948c8db74:   movzbl 0x94(%r14),%r8d      ; read isDone
>>   0.68%   ││  0x00007f3948c8db7c:   mov    0x3b0(%r15),%r9      ; TL handshake
>>   0.72%   ││  0x00007f3948c8db83:   add    $0x1,%rbp            ; ops++
>>           ││  0x00007f3948c8db87:   test   %eax,(%r9)           ; TL handshake
>>  92.30%   ││  0x00007f3948c8db8a:   test   %r8d,%r8d            ; isDone?
>>          ╭││  0x00007f3948c8db8d:   jne    0x00007f3948c8dba4   
>>          │││  0x00007f3948c8db8f:   mov    0xc(%r11),%r10d      ; load "v" (MyValue box)
>>   0.35%  │││  0x00007f3948c8db93:   test   %r10d,%r10d          ; null check it
>>          │╰│  0x00007f3948c8db96:   jne    0x00007f3948c8db70
>
> Aleksey Shipilev has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Replace: box -> buffer
>  - Move the test

Marked as reviewed by thartmann (Committer).

-------------

PR: https://git.openjdk.java.net/valhalla/pull/429