出于好奇,这里是由JIT生成的汇编代码。总之,主要的区别是:
incrementAndGet
mov r8d,eax
inc r8d ;*iadd
addAndGet
mov r9d,r8d
add r9d,eax ;*iadd
的代码的其余部分基本上是相同的。这证实:
- 方法是不是内与机罩
- 下不打电话给对方,唯一的区别是
INC
VS ADD 1
我不是在读取组件到足够好知道为什么这有所作为。这并不能真正回答我最初的问题。
全面上市(incrementAndGet):
# {method} 'incrementAndGet' '()I' in 'java/util/concurrent/atomic/AtomicInteger'
# [sp+0x20] (sp of caller)
0x00000000026804c0: mov r10d,DWORD PTR [rdx+0x8]
0x00000000026804c4: shl r10,0x3
0x00000000026804c8: cmp rax,r10
0x00000000026804cb: jne 0x0000000002657b60 ; {runtime_call}
0x00000000026804d1: data32 xchg ax,ax
0x00000000026804d4: nop DWORD PTR [rax+rax*1+0x0]
0x00000000026804dc: data32 data32 xchg ax,ax
[Verified Entry Point]
0x00000000026804e0: sub rsp,0x18
0x00000000026804e7: mov QWORD PTR [rsp+0x10],rbp ;*synchronization entry
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 204)
0x00000000026804ec: mov eax,DWORD PTR [rdx+0xc] ;*invokevirtual compareAndSwapInt
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 135)
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 206)
0x00000000026804ef: mov r8d,eax
0x00000000026804f2: inc r8d ;*iadd
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 205)
0x00000000026804f5: lock cmpxchg DWORD PTR [rdx+0xc],r8d
0x00000000026804fb: sete r11b
0x00000000026804ff: movzx r11d,r11b ;*invokevirtual compareAndSwapInt
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 135)
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 206)
0x0000000002680503: test r11d,r11d
0x0000000002680506: je 0x0000000002680520 ;*iload_2
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 207)
0x0000000002680508: mov eax,r8d
0x000000000268050b: add rsp,0x10
0x000000000268050f: pop rbp
0x0000000002680510: test DWORD PTR [rip+0xfffffffffdbafaea],eax # 0x0000000000230000
; {poll_return}
0x0000000002680516: ret
0x0000000002680517: nop WORD PTR [rax+rax*1+0x0] ; OopMap{rdx=Oop off=96}
;*goto
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 208)
0x0000000002680520: test DWORD PTR [rip+0xfffffffffdbafada],eax # 0x0000000000230000
;*goto
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 208)
; {poll}
0x0000000002680526: mov r11d,DWORD PTR [rdx+0xc] ;*invokevirtual compareAndSwapInt
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 135)
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 206)
0x000000000268052a: mov r8d,r11d
0x000000000268052d: inc r8d ;*iadd
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 205)
0x0000000002680530: mov eax,r11d
0x0000000002680533: lock cmpxchg DWORD PTR [rdx+0xc],r8d
0x0000000002680539: sete r11b
0x000000000268053d: movzx r11d,r11b ;*invokevirtual compareAndSwapInt
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 135)
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 206)
0x0000000002680541: test r11d,r11d
0x0000000002680544: je 0x0000000002680520 ;*ifeq
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 206)
0x0000000002680546: jmp 0x0000000002680508
全面上市(addAndGet):
# {method} 'addAndGet' '(I)I' in 'java/util/concurrent/atomic/AtomicInteger'
# this: rdx:rdx = 'java/util/concurrent/atomic/AtomicInteger'
# parm0: r8 = int
# [sp+0x20] (sp of caller)
0x0000000002680d00: mov r10d,DWORD PTR [rdx+0x8]
0x0000000002680d04: shl r10,0x3
0x0000000002680d08: cmp rax,r10
0x0000000002680d0b: jne 0x0000000002657b60 ; {runtime_call}
0x0000000002680d11: data32 xchg ax,ax
0x0000000002680d14: nop DWORD PTR [rax+rax*1+0x0]
0x0000000002680d1c: data32 data32 xchg ax,ax
[Verified Entry Point]
0x0000000002680d20: sub rsp,0x18
0x0000000002680d27: mov QWORD PTR [rsp+0x10],rbp ;*synchronization entry
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 233)
0x0000000002680d2c: mov eax,DWORD PTR [rdx+0xc] ;*invokevirtual compareAndSwapInt
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 135)
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 235)
0x0000000002680d2f: mov r9d,r8d
0x0000000002680d32: add r9d,eax ;*iadd
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 234)
0x0000000002680d35: lock cmpxchg DWORD PTR [rdx+0xc],r9d
0x0000000002680d3b: sete r11b
0x0000000002680d3f: movzx r11d,r11b ;*invokevirtual compareAndSwapInt
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 135)
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 235)
0x0000000002680d43: test r11d,r11d
0x0000000002680d46: je 0x0000000002680d60 ;*iload_3
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 236)
0x0000000002680d48: mov eax,r9d
0x0000000002680d4b: add rsp,0x10
0x0000000002680d4f: pop rbp
0x0000000002680d50: test DWORD PTR [rip+0xfffffffffdbaf2aa],eax # 0x0000000000230000
; {poll_return}
0x0000000002680d56: ret
0x0000000002680d57: nop WORD PTR [rax+rax*1+0x0] ; OopMap{rdx=Oop off=96}
;*goto
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 237)
0x0000000002680d60: test DWORD PTR [rip+0xfffffffffdbaf29a],eax # 0x0000000000230000
;*goto
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 237)
; {poll}
0x0000000002680d66: mov r11d,DWORD PTR [rdx+0xc] ;*invokevirtual compareAndSwapInt
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 135)
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 235)
0x0000000002680d6a: mov r9d,r11d
0x0000000002680d6d: add r9d,r8d ;*iadd
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 234)
0x0000000002680d70: mov eax,r11d
0x0000000002680d73: lock cmpxchg DWORD PTR [rdx+0xc],r9d
0x0000000002680d79: sete r11b
0x0000000002680d7d: movzx r11d,r11b ;*invokevirtual compareAndSwapInt
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 135)
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 235)
0x0000000002680d81: test r11d,r11d
0x0000000002680d84: je 0x0000000002680d60 ;*ifeq
; - java.util.concurrent.atomic.AtomicInteger::[email protected] (line 235)
0x0000000002680d86: jmp 0x0000000002680d48
+1对于'JVM热身':) – 2013-02-28 18:35:22
虽然我怀疑这实际上会揭示答案,但您可以反汇编这两个函数,并在这里显示反汇编的Java字节码。它*可能会揭示一些事情。 – 2013-02-28 18:50:12