Re: [rvm-research] Regarding Help in jikes RVM

Hi,

On 04.10.2012 18:09, abhishek gupta wrote:
>  1. I am not able to find out how to use the command line options of
>     jikes. If their is any tutorial that give us whole idea how to
>     generate the dumps after   the different compilation phase etc ?.
>     (user guide does not have sufficient information on these things).

You can use ./rvm -X:opt:help to print all the options for the 
optimizing compiler subsystem, but it seems that you already know this.

If you want to dump the IR after certain compilation phases, the 
following options might be interesting to you:

print_all_ir
print_high
print_final_hir
print_cfg
print_ir_level
method_to_print

For example, ff you want to dump the IR after every compiler phase but 
are only interested in method foo, you can use

rvm -X:opt:print_all_ir=true -X:method_to_print=foo [rest of arguments]


>  2. I am able to generate some dumps but I am not able to understand the
>     information generated by them. So where I can find out how to
>     understand different dump information.

Have you taken a look at the presentation "Jikes RVM Optimizing Compiler 
Intermediate Code Representation" by Shane Brewer that is linked from 
http://jikesrvm.org/Presentations? IIRC it contains explanations for the 
format of the IR dump output.

You can also take a look at the places in the codebase that are used 
when producing the debug output, e.g. CompilerPhase.dumpIR() and 
Instruction.toString().

>  3. I would also like to know how can i add new optimizing pass to
>     jikes. Is there is any tutorial which  that can help me to speed my
>     work.?

I don't know of any tutorial but here are some hints that might be 
useful to you:

a) Remember that Jikes RVM is metacircular, i.e. the compilers are used 
during the build process of the Jikes RVM (e.g. the opt compiler is used 
to build production and development images).

If you do not want a certain region of code to execute when building the 
VM, you can use VM.runningVM:

if (VM.runningVM) {
.. some debug output ..
}

b) Compiler passes are subclasses of CompilerPhase. To add a new 
compiler pass to the system, you just need to create a new subclass of 
CompilerPhase and add that class to the OptimizationPlanner.

For example, if you want to implement a new high-level optimization, you 
could create a new compiler phase called NewOptimization and add it to 
the HIROptimizations:

--- a/rvm/src/org/jikesrvm/compilers/opt/driver/OptimizationPlanner.java
+++ b/rvm/src/org/jikesrvm/compilers/opt/driver/OptimizationPlanner.java
@@ -273,6 +273,8 @@
      // Perform local common-subexpression elimination for a
      // factored basic block.
      addComponent(p, new LocalCSE(true));
+    // Your new compiler phase
+    addComponent(p, new NewOptimization());
      // Flow-insensitive field analysis
      addComponent(p, new FieldAnalysis());
      if (VM.BuildForAdaptiveSystem) {

To check that your compiler phase is called, just add some debug code 
into your implementation of the perform() method. A quick way is to use 
VM.sysFail(..) to forcefully terminate the VM.

You can override the shouldPerform() method to make sure the compiler 
phase is only called when you want (e.g. not during bootimage writing, 
only when an option is set, ...).

c) Try to make progress in small steps that are easily verifiable.

d) The OptTestHarness (see http://www.jikesrvm.org/OptTestHarness) can 
be useful for testing and debugging. You can also use the OptTestHarness 
from Java programs that run on the RVM, e.g. unit tests. It's cumbersome 
because you have to use the command line interface (i.e. main method and 
string arrays) but it works.

e) You should think about an approach to testing your changes. Testing 
is very important. That's even more true for compilers, which are 
notoriously buggy because of their complexity.

f) The prototype, prototype-opt and development builds do IR 
verification by default. You can enable more extensive and expensive 
verification by enabling paranoid IR verification in IR.java.


Please don't hesitate to ask if you have more questions.


Kind regards,

Erik Brangs