compiled code in JVM?
有什么方法可以查看JVM在JVM中生成的本机代码?
Assuming you're using the Sun Hotspot JVM (ie the one provided on java.com by Oracle), you can add the flag
-XX:+PrintOptoAssembly
when running your code. This will print out the optimized code generated by the JIT compiler and leaves out the rest.
If you want see the entire bytecode, including the unoptimized parts, add
-XX:CompileThreshold=#
when you're running your code.
You can read more about this command and the functionality of JIT in general here.
General usage
As explained by other answers, you can run with the following JVM options:
-XX:+UnlockDiagnosticVMOptions -XX:+PrintAssembly
Filter on a specific method
You can also filter on a specific method with the following syntax:
-XX:+UnlockDiagnosticVMOptions -XX:CompileCommand=print,*MyClass.myMethod
Notes:
How to: Install the required libraries on Windows
If you are running Windows, this page has instructions on how to build and install hsdis-amd64.dll
and hsdis-i386.dll
which are required to make it work. We copy below and extend the content of that page* for reference:
Where to get prebuilt binaries
You can download prebuilt binaries for Windows from the fcml project
How to build hsdis-amd64.dll
and hsdis-i386.dll
on Windows
This version of the guide was prepared on Windows 8.1 64bit using 64-bit Cygwin and producing hsdis-amd64.dll
Install Cygwin. At the Select Packages
screen, add the following packages (by expanding the Devel
category, then clicking once on the Skip
label next to each package name):
make
mingw64-x86_64-gcc-core
(only needed for hsdis-amd64.dll
) mingw64-i686-gcc-core
(only needed for hsdis-i386.dll
) diffutils
(in Utils
category) Run the Cygwin Terminal. This can be done using the Desktop or Start Menu icon created by the installer, and will create your Cygwin home directory ( C:cygwinhome<username>
or C:cygwin64home<username>
by default).
binutils-2.25.tar.bz2
. This should result in a directory named binutils-2.25
(or whatever the latest version is) in your Cygwin home directory. srcsharetools
) to your Cygwin home directory. cd ~/hsdis
. To build hsdis-amd64.dll
, enter
make OS=Linux MINGW=x86_64-w64-mingw32 'AR=$(MINGW)-ar' BINUTILS=~/binutils-2.25
To build hsdis-i386.dll
, enter
make OS=Linux MINGW=i686-w64-mingw32 'AR=$(MINGW)-ar' BINUTILS=~/binutils-2.25
In either case, replace 2.25
with the binutils version you downloaded. OS=Linux
is necessary because, although Cygwin is a Linux-like environment, the hsdis makefile fails to recognize it as such.
./chew: No such file or directory
and gcc: command not found
. Edit <Cygwin home directory>hsdisbuildLinux-amd64bfdMakefile
in a text editor like Wordpad or Notepad++ to change SUBDIRS = doc po
(line 342, if using binutils 2.25) to SUBDIRS = po
. Re-run the previous command. The DLL can now be installed by copying it from hsdisbuildLinux-amd64
or hsdisbuildLinux-i586
to your JRE's binserver
or binclient
directory. You can find all such directories on your system by searching for java.dll
.
Bonus tip: if you prefer Intel ASM syntax to AT&T, specify -XX:PrintAssemblyOptions=intel
alongside any other PrintAssembly options you use.
*page license is Creative Commons
You need an hsdis plugin to use PrintAssembly
. A convenient choice is the hsdis plugin based on FCML library.
It can be compiled for UNIX-like systems and on Windows you can use pre-built libraries available in the FCML download section on Sourceforge:
To install in Windows:
java.dll
(use Windows search). On my system, I found it at two locations: C:Program FilesJavajre1.8.0_45binserver
C:Program FilesJavajdk1.8.0_45jrebinserver
To install in Linux:
cd <source code dir>
./configure && make && sudo make install
cd example/hsdis && make && sudo make install
sudo ln -s /usr/local/lib/libhsdis.so <JDK PATH>/lib/amd64/hsdis-amd64.so
sudo ln -s /usr/local/lib/libhsdis.so <JDK PATH>/jre/lib/amd64/hsdis-amd64.so
/usr/lib/jvm/java-8-oracle
How to run it:
java -XX:+UnlockDiagnosticVMOptions -XX:+PrintAssembly
-XX:+LogCompilation -XX:PrintAssemblyOptions=intel,mpad=10,cpad=10,code
-jar fcml-test.jar
Additional configuration parameters:
code Print machine code before the mnemonic.
intel Use the Intel syntax.
gas Use the AT&T assembler syntax (GNU assembler compatible).
dec Prints IMM and displacement as decimal values.
mpad=XX Padding for the mnemonic part of the instruction.
cpad=XX Padding for the machine code.
seg Shows the default segment registers.
zeros Show leading zeros in case of HEX literals.
The Intel syntax is a default one in case of Windows, whereas the AT&T one is a default for the GNU/Linux.
For more details see the FCML Library Reference Manual
链接地址: http://www.djcxy.com/p/15184.html上一篇: 在Java中创建泛型类型的实例?
下一篇: 在JVM中编译代码?