Tuesday, October 16, 2012

How to print disassembly from JIT code ?

In my previous post, I have shown you some disassembly from JIT native code. How to do the same at home ?

I found relevant informations in this wiki page.

First, you need to get the dissasembler named
Put this disassembler into the bin directory of your JRE: C:\Program Files\Java\jre6\bin
Or for your JDK: C:\Program Files\Java\jdk1.6.0_35\jre\bin

Then launch your java command with the following options:
```-XX:+UnlockDiagnosticVMOptions -XX:+PrintAssembly

```
Then you will get:
```"C:\Program Files (x86)\Java\jdk1.6.0_23\jre\bin\java" -server
-XX:+UnlockDiagnosticVMOptions -XX:+PrintAssembly com.bempel.sandbox.TestJIT
Java HotSpot(TM) Server VM warning: PrintAssembly is enabled; turning on
Decoding compiled method 0x02548708:
Code:
[Disassembling for mach='i386']
[Entry Point]
[Verified Entry Point]
# {method} 'run' '()V' in 'com/bempel/sandbox/TestJIT\$C'
[...]
```
Enjoy !

Updated : To get intel syntax over AT&T, use -XX:PrintAssemblyOptions=intel