-XX:Inline ignored for system classes?

[Peter Veentjer]

I'm doing some Assembly analysis to gain a deeper understanding in
devirtualization and I'm running into some unexpected behavior. What I'm
seeing is that even though inlining is disabled, the call to ArrayList.size
got inlined. Look for '0x000000010be7e539' and you will see the unexpected
behavior. Is this intentional behavior or am I missing something?

This is the class

public class Devirtualization_MonoMorphic {

    public static void main(String[] args) {
        ArrayList arrayList = new ArrayList();

        int result = 0;

        for (int k = 0; k < 100_000; k++) {
            result += sizePlusOne(arrayList);
        }

        System.out.println("result:" + result);
    }

    public static int sizePlusOne(Collection c) {
        return c.size() + 1;
    }
}

The arguments

-XX:+UnlockDiagnosticVMOptions
-XX:PrintAssemblyOptions=intel
-XX:-TieredCompilation
-XX:-Inline
-XX:-BackgroundCompilation
-XX:CompileCommand=print,*Devirtualization_MonoMorphic.sizePlusOne

The assembly:

CompilerOracle: print *Devirtualization_MonoMorphic.sizePlusOne
Compiled method (c2)     247    9
com.devirtualization.Devirtualization_MonoMorphic::sizePlusOne (9 bytes)
 total in heap  [0x000000010be7e3d0,0x000000010be7e678] = 680
 relocation     [0x000000010be7e4f0,0x000000010be7e508] = 24
 main code      [0x000000010be7e520,0x000000010be7e580] = 96
 stub code      [0x000000010be7e580,0x000000010be7e598] = 24
 oops           [0x000000010be7e598,0x000000010be7e5a0] = 8
 metadata       [0x000000010be7e5a0,0x000000010be7e5b0] = 16
 scopes data    [0x000000010be7e5b0,0x000000010be7e5e0] = 48
 scopes pcs     [0x000000010be7e5e0,0x000000010be7e660] = 128
 dependencies   [0x000000010be7e660,0x000000010be7e668] = 8
 nul chk table  [0x000000010be7e668,0x000000010be7e678] = 16
Loaded disassembler from
/Library/Java/JavaVirtualMachines/jdk1.8.0.jdk/Contents/Home/jre/lib/hsdis-amd64.dylib
Decoding compiled method 0x000000010be7e3d0:
Code:
[Disassembling for mach='i386:x86-64']
[Entry Point]
[Verified Entry Point]
[Constants]
  # {method} {0x000000011417a560} 'sizePlusOne' '(Ljava/util/Collection;)I'
in 'com/devirtualization/Devirtualization_MonoMorphic'
  # parm0:    rsi:rsi   = 'java/util/Collection'
  #           [sp+0x20]  (sp of caller)
  0x000000010be7e520: mov    DWORD PTR [rsp-0x14000],eax
  0x000000010be7e527: push   rbp
  0x000000010be7e528: sub    rsp,0x10           ;*synchronization entry
                                                ; -
com.devirtualization.Devirtualization_MonoMorphic::sizePlusOne at -1 (line 21)

  0x000000010be7e52c: mov    r11d,DWORD PTR [rsi+0x8]  ; implicit
exception: dispatches to 0x000000010be7e55d
  0x000000010be7e530: cmp    r11d,0xf8003231    ;
{metadata('java/util/ArrayList')}
  0x000000010be7e537: jne    0x000000010be7e54a  ;*invokeinterface size
                                                ; -
com.devirtualization.Devirtualization_MonoMorphic::sizePlusOne at 1 (line 21)

  0x000000010be7e539: mov    eax,DWORD PTR [rsi+0x10]
  0x000000010be7e53c: inc    eax                ;*iadd
                                                ; -
com.devirtualization.Devirtualization_MonoMorphic::sizePlusOne at 7 (line 21)

  0x000000010be7e53e: add    rsp,0x10
  0x000000010be7e542: pop    rbp
  0x000000010be7e543: test   DWORD PTR [rip+0xffffffffff6fdab7],eax
 # 0x000000010b57c000
                                                ;   {poll_return}
  0x000000010be7e549: ret
  0x000000010be7e54a: mov    rbp,rsi
  0x000000010be7e54d: mov    esi,0xffffffde
  0x000000010be7e552: nop
  0x000000010be7e553: call   0x000000010be47120  ; OopMap{rbp=Oop off=56}
                                                ;*invokeinterface size
                                                ; -
com.devirtualization.Devirtualization_MonoMorphic::sizePlusOne at 1 (line 21)
                                                ;   {runtime_call}
  0x000000010be7e558: call   0x000000010a9a2e44  ;   {runtime_call}
  0x000000010be7e55d: mov    esi,0xfffffff6
  0x000000010be7e562: nop
  0x000000010be7e563: call   0x000000010be47120  ; OopMap{off=72}
                                                ;*invokeinterface size
                                                ; -
com.devirtualization.Devirtualization_MonoMorphic::sizePlusOne at 1 (line 21)
                                                ;   {runtime_call}
  0x000000010be7e568: call   0x000000010a9a2e44  ;*invokeinterface size
                                                ; -
com.devirtualization.Devirtualization_MonoMorphic::sizePlusOne at 1 (line 21)
                                                ;   {runtime_call}
  0x000000010be7e56d: hlt
  0x000000010be7e56e: hlt
  0x000000010be7e56f: hlt
  0x000000010be7e570: hlt
  0x000000010be7e571: hlt
  0x000000010be7e572: hlt
  0x000000010be7e573: hlt
  0x000000010be7e574: hlt
  0x000000010be7e575: hlt
  0x000000010be7e576: hlt
  0x000000010be7e577: hlt
  0x000000010be7e578: hlt
  0x000000010be7e579: hlt
  0x000000010be7e57a: hlt
  0x000000010be7e57b: hlt
  0x000000010be7e57c: hlt
  0x000000010be7e57d: hlt
  0x000000010be7e57e: hlt
  0x000000010be7e57f: hlt
[Exception Handler]
[Stub Code]
  0x000000010be7e580: jmp    0x000000010be6bf60  ;   {no_reloc}
[Deopt Handler Code]
  0x000000010be7e585: call   0x000000010be7e58a
  0x000000010be7e58a: sub    QWORD PTR [rsp],0x5
  0x000000010be7e58f: jmp    0x000000010be46d00  ;   {runtime_call}
  0x000000010be7e594: hlt
  0x000000010be7e595: hlt
  0x000000010be7e596: hlt
  0x000000010be7e597: hlt
OopMapSet contains 2 OopMaps

#0
OopMap{rbp=Oop off=56}
#1
OopMap{off=72}
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