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

[Dean Long]

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
>