Menu
I compiled a simple Java file to assembly using Java 8 on Mac OS X. This is Test.java:
public class Test {
static volatile int a = 1;
public static void main(String[] args) {
a++;
}
}
I output the assembly code using:
java -server -Xcomp -XX:+UnlockDiagnosticVMOptions -XX:-Inline -XX:CompileCommand=print,*Test.main Test>Test.asm
This is the Test.asm output:
CompilerOracle: print *Test.main
Compiled method (c1) 1733 1750 3 Test::main (9 bytes)
total in heap [0x0000000111848650,0x0000000111848970] = 800
relocation [0x0000000111848778,0x00000001118487a0] = 40
main code [0x00000001118487a0,0x0000000111848860] = 192
stub code [0x0000000111848860,0x00000001118488f0] = 144
oops [0x00000001118488f0,0x00000001118488f8] = 8
metadata [0x00000001118488f8,0x0000000111848900] = 8
scopes data [0x0000000111848900,0x0000000111848918] = 24
scopes pcs [0x0000000111848918,0x0000000111848968] = 80
dependencies [0x0000000111848968,0x0000000111848970] = 8
Loaded disassembler from /Library/Java/JavaVirtualMachines/jdk1.8.0_112.jdk/Contents/Home/jre/lib/hsdis-amd64.dylib
Decoding compiled method 0x0000000111848650:
Code:
[Disassembling for mach='i386:x86-64']
[Entry Point]
[Verified Entry Point]
[Constants]
# {method} {0x000000010e40e240} 'main' '([Ljava/lang/String;)V' in 'Test'
# parm0: rsi:rsi = '[Ljava/lang/String;'
# [sp+0x40] (sp of caller)
0x00000001118487a0: mov %eax,-0x14000(%rsp)
0x00000001118487a7: push %rbp
0x00000001118487a8: sub $0x30,%rsp
0x00000001118487ac: movabs $0x10e40e4d0,%rdi ; {metadata(method data for {method} {0x000000010e40e240} 'main' '([Ljava/lang/String;)V' in 'Test')}
0x00000001118487b6: mov 0xdc(%rdi),%ebx
0x00000001118487bc: add $0x8,%ebx
0x00000001118487bf: mov %ebx,0xdc(%rdi)
0x00000001118487c5: movabs $0x10e40e240,%rdi ; {metadata({method} {0x000000010e40e240} 'main' '([Ljava/lang/String;)V' in 'Test')}
0x00000001118487cf: and $0x0,%ebx
0x00000001118487d2: cmp $0x0,%ebx
0x00000001118487d5: je 0x00000001118487fe
0x00000001118487db: movabs $0x7955fd1e8,%rsi ; {oop(a 'java/lang/Class' = 'Test')}
0x00000001118487e5: mov 0x68(%rsi),%edi ;*getstatic a
; - Test::main@0 (line 6)
0x00000001118487e8: inc %edi
0x00000001118487ea: mov %edi,0x68(%rsi)
0x00000001118487ed: lock addl $0x0,(%rsp) ;*putstatic a
; - Test::main@5 (line 6)
0x00000001118487f2: add $0x30,%rsp
0x00000001118487f6: pop %rbp
0x00000001118487f7: test %eax,-0x5f7f6fd(%rip) # 0x000000010b8c9100
; {poll_return}
0x00000001118487fd: retq
0x00000001118487fe: mov %rdi,0x8(%rsp)
0x0000000111848803: movq $0xffffffffffffffff,(%rsp)
0x000000011184880b: callq 0x0000000111543f60 ; OopMap{rsi=Oop off=112}
;*synchronization entry
; - Test::main@-1 (line 6)
; {runtime_call}
0x0000000111848810: jmp 0x00000001118487db
0x0000000111848812: nop
0x0000000111848813: nop
0x0000000111848814: mov 0x2a8(%r15),%rax
0x000000011184881b: movabs $0x0,%r10
0x0000000111848825: mov %r10,0x2a8(%r15)
0x000000011184882c: movabs $0x0,%r10
0x0000000111848836: mov %r10,0x2b0(%r15)
0x000000011184883d: add $0x30,%rsp
0x0000000111848841: pop %rbp
0x0000000111848842: jmpq 0x00000001114b24a0 ; {runtime_call}
0x0000000111848847: hlt
0x0000000111848848: hlt
0x0000000111848849: hlt
0x000000011184884a: hlt
0x000000011184884b: hlt
0x000000011184884c: hlt
0x000000011184884d: hlt
0x000000011184884e: hlt
0x000000011184884f: hlt
0x0000000111848850: hlt
0x0000000111848851: hlt
0x0000000111848852: hlt
0x0000000111848853: hlt
0x0000000111848854: hlt
0x0000000111848855: hlt
0x0000000111848856: hlt
0x0000000111848857: hlt
0x0000000111848858: hlt
0x0000000111848859: hlt
0x000000011184885a: hlt
0x000000011184885b: hlt
0x000000011184885c: hlt
0x000000011184885d: hlt
0x000000011184885e: hlt
0x000000011184885f: hlt
[Exception Handler]
[Stub Code]
0x0000000111848860: callq 0x00000001115418e0 ; {no_reloc}
0x0000000111848865: mov %rsp,-0x28(%rsp)
0x000000011184886a: sub $0x80,%rsp
0x0000000111848871: mov %rax,0x78(%rsp)
0x0000000111848876: mov %rcx,0x70(%rsp)
0x000000011184887b: mov %rdx,0x68(%rsp)
0x0000000111848880: mov %rbx,0x60(%rsp)
0x0000000111848885: mov %rbp,0x50(%rsp)
0x000000011184888a: mov %rsi,0x48(%rsp)
0x000000011184888f: mov %rdi,0x40(%rsp)
0x0000000111848894: mov %r8,0x38(%rsp)
0x0000000111848899: mov %r9,0x30(%rsp)
0x000000011184889e: mov %r10,0x28(%rsp)
0x00000001118488a3: mov %r11,0x20(%rsp)
0x00000001118488a8: mov %r12,0x18(%rsp)
0x00000001118488ad: mov %r13,0x10(%rsp)
0x00000001118488b2: mov %r14,0x8(%rsp)
0x00000001118488b7: mov %r15,(%rsp)
0x00000001118488bb: movabs $0x10c7d8060,%rdi ; {external_word}
0x00000001118488c5: movabs $0x111848865,%rsi ; {internal_word}
0x00000001118488cf: mov %rsp,%rdx
0x00000001118488d2: and $0xfffffffffffffff0,%rsp
0x00000001118488d6: callq 0x000000010c60361a ; {runtime_call}
0x00000001118488db: hlt
[Deopt Handler Code]
0x00000001118488dc: movabs $0x1118488dc,%r10 ; {section_word}
0x00000001118488e6: push %r10
0x00000001118488e8: jmpq 0x000000011148d3c0 ; {runtime_call}
0x00000001118488ed: hlt
0x00000001118488ee: hlt
0x00000001118488ef: hlt
OopMapSet contains 1 OopMaps
#0
OopMap{rsi=Oop off=112}
Compiled method (c1) 1747 1751 1 Test::main (9 bytes)
total in heap [0x0000000111847250,0x0000000111847518] = 712
relocation [0x0000000111847378,0x00000001118473a0] = 40
main code [0x00000001118473a0,0x0000000111847420] = 128
stub code [0x0000000111847420,0x00000001118474b0] = 144
oops [0x00000001118474b0,0x00000001118474b8] = 8
metadata [0x00000001118474b8,0x00000001118474c0] = 8
scopes data [0x00000001118474c0,0x00000001118474d0] = 16
scopes pcs [0x00000001118474d0,0x0000000111847510] = 64
dependencies [0x0000000111847510,0x0000000111847518] = 8
Decoding compiled method 0x0000000111847250:
Code:
[Entry Point]
[Verified Entry Point]
[Constants]
# {method} {0x000000010e40e240} 'main' '([Ljava/lang/String;)V' in 'Test'
# parm0: rsi:rsi = '[Ljava/lang/String;'
# [sp+0x40] (sp of caller)
0x00000001118473a0: mov %eax,-0x14000(%rsp)
0x00000001118473a7: push %rbp
0x00000001118473a8: sub $0x30,%rsp
0x00000001118473ac: movabs $0x7955fd1e8,%rsi ; {oop(a 'java/lang/Class' = 'Test')}
0x00000001118473b6: mov 0x68(%rsi),%edi ;*getstatic a
; - Test::main@0 (line 6)
0x00000001118473b9: inc %edi
0x00000001118473bb: mov %edi,0x68(%rsi)
0x00000001118473be: lock addl $0x0,(%rsp) ;*putstatic a
; - Test::main@5 (line 6)
0x00000001118473c3: add $0x30,%rsp
0x00000001118473c7: pop %rbp
0x00000001118473c8: test %eax,-0x5f7e2ce(%rip) # 0x000000010b8c9100
; {poll_return}
0x00000001118473ce: retq
0x00000001118473cf: nop
0x00000001118473d0: nop
0x00000001118473d1: mov 0x2a8(%r15),%rax
0x00000001118473d8: movabs $0x0,%r10
0x00000001118473e2: mov %r10,0x2a8(%r15)
0x00000001118473e9: movabs $0x0,%r10
0x00000001118473f3: mov %r10,0x2b0(%r15)
0x00000001118473fa: add $0x30,%rsp
0x00000001118473fe: pop %rbp
0x00000001118473ff: jmpq 0x00000001114b24a0 ; {runtime_call}
0x0000000111847404: hlt
0x0000000111847405: hlt
0x0000000111847406: hlt
0x0000000111847407: hlt
0x0000000111847408: hlt
0x0000000111847409: hlt
0x000000011184740a: hlt
0x000000011184740b: hlt
0x000000011184740c: hlt
0x000000011184740d: hlt
0x000000011184740e: hlt
0x000000011184740f: hlt
0x0000000111847410: hlt
0x0000000111847411: hlt
0x0000000111847412: hlt
0x0000000111847413: hlt
0x0000000111847414: hlt
0x0000000111847415: hlt
0x0000000111847416: hlt
0x0000000111847417: hlt
0x0000000111847418: hlt
0x0000000111847419: hlt
0x000000011184741a: hlt
0x000000011184741b: hlt
0x000000011184741c: hlt
0x000000011184741d: hlt
0x000000011184741e: hlt
0x000000011184741f: hlt
[Exception Handler]
[Stub Code]
0x0000000111847420: callq 0x00000001115418e0 ; {no_reloc}
0x0000000111847425: mov %rsp,-0x28(%rsp)
0x000000011184742a: sub $0x80,%rsp
0x0000000111847431: mov %rax,0x78(%rsp)
0x0000000111847436: mov %rcx,0x70(%rsp)
0x000000011184743b: mov %rdx,0x68(%rsp)
0x0000000111847440: mov %rbx,0x60(%rsp)
0x0000000111847445: mov %rbp,0x50(%rsp)
0x000000011184744a: mov %rsi,0x48(%rsp)
0x000000011184744f: mov %rdi,0x40(%rsp)
0x0000000111847454: mov %r8,0x38(%rsp)
0x0000000111847459: mov %r9,0x30(%rsp)
0x000000011184745e: mov %r10,0x28(%rsp)
0x0000000111847463: mov %r11,0x20(%rsp)
0x0000000111847468: mov %r12,0x18(%rsp)
0x000000011184746d: mov %r13,0x10(%rsp)
0x0000000111847472: mov %r14,0x8(%rsp)
0x0000000111847477: mov %r15,(%rsp)
0x000000011184747b: movabs $0x10c7d8060,%rdi ; {external_word}
0x0000000111847485: movabs $0x111847425,%rsi ; {internal_word}
0x000000011184748f: mov %rsp,%rdx
0x0000000111847492: and $0xfffffffffffffff0,%rsp
0x0000000111847496: callq 0x000000010c60361a ; {runtime_call}
0x000000011184749b: hlt
[Deopt Handler Code]
0x000000011184749c: movabs $0x11184749c,%r10 ; {section_word}
0x00000001118474a6: push %r10
0x00000001118474a8: jmpq 0x000000011148d3c0 ; {runtime_call}
0x00000001118474ad: hlt
0x00000001118474ae: hlt
0x00000001118474af: hlt
OopMapSet contains 0 OopMaps
The question is: why does the generated assembly code have two main methods and how do I make it have only one?
705
Why does the generated assembly code have two main methods?
The Assembly contains the result of the work of the C1 compiler at different compilation levels:
C1 / Level 3
C1 / Level 1
The appropriate information is present in the Test.asm output:
Compiled method (c1) 1733 1750 3 Test::main (9 bytes)
Compiled method (c1) 1747 1751 1 Test::main (9 bytes)
In order to remove an extra compilation overhead, you can set -XX:TieredStopAtLevel=1 - check this answer for more details.
193
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
