review request for 7156729: PPC: R_PPC_REL24 relocation error related to some libraries built without -fPIC

[Dean Long]

I filed 7178842 for future cleanup.  Mikael, can I count you as a 
reviewer for the current webrev?

I also need a review from a Reviewer.

dl

On 6/19/2012 4:54 PM, Mikael Vidstedt wrote:
>
> Sounds like a great idea!
>
> Cheers,
> Mikael
>
> On 2012-06-19 16:43, Dean Long wrote:
>> How about I file a separate RFE for that?  I would like to minimize 
>> changes for an update release, and I'm worried I might accidentally 
>> break something that we aren't  building, like "zero".
>>
>> dl
>>
>> On 6/19/2012 3:29 PM, Mikael Vidstedt wrote:
>>>
>>> Dean,
>>>
>>> Can I suggest that you turn the logic around to instead list/test 
>>> for the platforms where we know we can use the nonpic optimization? 
>>> That way we'll avoid running into this type of problem again.
>>>
>>> Cheers,
>>> Mikael
>>>
>>> On 2012-06-18 00:07, Dean Long wrote:
>>>> http://cr.openjdk.java.net/~dlong/7156729/
>>>> Summary of changes:    8 lines changed: 7 ins; 0 del; 1 mod; 40 unchg
>>>>
>>>> Non-PIC objects have a limited range when calling external 
>>>> functions, so dynamic linking can fail if for example libc is too 
>>>> far away.  The solution is to build all powerpc objects with -fPIC, 
>>>> including the oops and gc directories that were previously 
>>>> excluded.  This causes calls to go through the PLT.  PIC_ARCH is a 
>>>> list that can be expanded later (ARM could be next).  I also tried 
>>>> using -mlongcall instead of -fPIC, but it doesn't have any 
>>>> performance advantage over -fPIC and it causes a 17% increase in 
>>>> static footprint vs. a 5% decrease for -fPIC.
>>>>
>>>> To measure the performance regression, I ran some refworkload 
>>>> benchmarks with different heap sizes.  As expected, the smaller the 
>>>> heap, the bigger the slowdown.  With a 32m heap, specjvm98 "javac" 
>>>> slows down by 2.5%.  The GC logs show about a 6% slowdown in pause 
>>>> times.
>>>>
>>>> There are some known issues with -fPIC overhead in the current 
>>>> toolchain, so we expect to gain much of the performance back in the 
>>>> future when we can move to a newer toolchain.  But since this is 
>>>> targeted for 7u6/hs23.2, there isn't much choice for now.
>>>>
>>>> dl
>>>
>