Turn off All Optimizations

[Krystal Mo]

Hi Xin,

So what you're looking for is some kind of baseline compiler, right?
How does your study relate to the ones on different threading techniques 
for implementing interpreters? e.g. context-threading / inline-threading?

Unfortunately neither C1 nor C2 has a magic switch to turn off all 
optimizations. Turning code into SSA-form and back is already 
"optimizing" in a lot of cases; both C1 and C2 use SSA-form intermediate 
representations, so it wouldn't be reasonable to have such a magic switch.

If you're using the client VM, then you'd be using C1;
If you're using the server VM, and if tiered compilation is not turned 
on (e.g. it's not turned on by default on JDK6 and JDK7 to date), then 
you'd be using C2;
With tiered compilation, you'd be using both C1 and C2. A method could 
be compiled multiple times by either compilers.

- Kris

On 2012/11/23 1:18, Xin Tong wrote:
> I want the compiler to compile the code at the same time. i.e. i want
> to study why the compiler is so much faster than the intepreter from a
> microarchitectural point of view. enabling optimizations complicates
> the problem.
>
> there are 2 compilers in the hotspot, the c1 and opto. which one is used ?
>
> Xin
>
> On Thu, Nov 22, 2012 at 12:06 PM, Aleksey Shipilev
> <aleksey.shipilev at oracle.com>  wrote:
>> On 11/22/2012 09:00 PM, Xin Tong wrote:
>>> Is there a way to turn off all the optimizations the hotpot compiler
>>> will do to the bytecode when JITting it.
>> Use plain old interpreter with "-Xint"?
>>
>> -Aleksey.
>>