RFR (S): 8003853: specify offset of IC load in java_to_interp stub [Was: Re: RFR (S): Specify offset of IC load in java_to_interp stub.]

[Lindenmaier, Goetz]

Hi Chris,

We put it into the ad file because it describes an offset into the stub that is
generated from the ad file by emit_java_to_interp(CodeBuffer& cbuf), 
used by ir  node CallStaticJavaDirect.  Maybe I should not call it stub, but it's 
generated into the stubs section of the code buffer.
If that stub generator is moved out of the ad file to shared compiler code, one should
move the field with it, but for the current implementation I think that's fine.

Does C1 generate the same stub? Or is the CompiledStaticCall a C2 feature?
If so, one could protect the whole thing by #ifdef COMPILER2.

Thanks for all the bugids!

Best regards,
  Goetz.

-----Original Message-----
From: Christian Thalinger [mailto:christian.thalinger at oracle.com] 
Sent: Mittwoch, 21. November 2012 19:53
To: Lindenmaier, Goetz
Cc: hotspot-compiler-dev at openjdk.java.net
Subject: RFR (S): 8003853: specify offset of IC load in java_to_interp stub [Was: Re: RFR (S): Specify offset of IC load in java_to_interp stub.]


On Nov 21, 2012, at 12:15 AM, "Lindenmaier, Goetz" <goetz.lindenmaier at sap.com> wrote:

> Hi Chris, 
> 
> yes, there is no C1 on ppc.  
> We do tiered compilation with a stripped C2.

Right.  But some other architecture (or in the future) might need this for C1 as well.  We should find a better place for the value than the ad file.  The obvious place would be compiledIC_<arch>.hpp but we don't have that file, yet.

I filed:

8003853: specify offset of IC load in java_to_interp stub

-- Chris

> 
> Best regards,
>  Goetz
> 
> -----Original Message-----
> From: Christian Thalinger [mailto:christian.thalinger at oracle.com] 
> Sent: Dienstag, 20. November 2012 22:19
> To: Lindenmaier, Goetz
> Cc: hotspot-compiler-dev at openjdk.java.net
> Subject: Re: RFR (S): Specify offset of IC load in java_to_interp stub.
> 
> 
> On Nov 20, 2012, at 3:08 AM, "Lindenmaier, Goetz" <goetz.lindenmaier at sap.com> wrote:
> 
>> Hi,
>> 
>> The class CompiledStaticCall must know the location of the IC load in the java_to_interp stub
>> to update the IC  with NativeMovConstReg.  The current implementation assumes that
>> the load is always the first instruction in the stub.  This is an artificial restriction. E.g.,
>> it might be useful to load the constant pool address (MachConstantBase) before the
>> IC load (as we do on PPC).
>> 
>> This change adds a constant specifying an offset from the beginning of the stub to
>> the  IC load. The offset is platform specific and 0 on sparc and x86.
>> 
>> You can find the change here:
>> http://cr.openjdk.java.net/~goetz/webrevs/webrev-IC_offset/
> 
> That should be fixed indeed.  
> 
> +#ifndef COMPILER2
> +const int CompiledStaticCall::comp_to_int_load_offset = 0;
> 
> There is no C1 for PPC (sorry, I didn't check)?
> 
> -- Chris
> 
>> 
>> or in our ppc port:
>> http://hg.openjdk.java.net/ppc-aix-port/jdk7u/hotspot/rev/c6f9c897ea33
>> 
>> Thank you and best regards,
>>  Goetz
>> 
>> 
>> 
>