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

Aleksey Shipilev shade at openjdk.java.net
Mon May 31 09:45:11 UTC 2021


> 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

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

Changes:
  - all: https://git.openjdk.java.net/valhalla/pull/429/files
  - new: https://git.openjdk.java.net/valhalla/pull/429/files/909d929a..20ecae3f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=valhalla&pr=429&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=valhalla&pr=429&range=00-01

  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/429.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/429/head:pull/429

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


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