RFR: JDK-8148929: Suboptimal code generated when setting sysroot include with Solaris Studio

[Erik Joelsson]

Differences are extensive in most C++ object files. The problem with 
viewing dissassembly diffs is that any difference tend to change all 
addresses later in the file.

/Erik

On 2016-02-04 13:43, Erik Joelsson wrote:
> I will investigate and report back.
>
> /Erik
>
> On 2016-02-04 13:29, David Holmes wrote:
>> On 4/02/2016 9:27 PM, Magnus Ihse Bursie wrote:
>>> On 2016-02-03 14:33, Erik Joelsson wrote:
>>>>
>>>>
>>>> On 2016-02-03 13:59, David Holmes wrote:
>>>>> Hi Erik,
>>>>>
>>>>> On 3/02/2016 10:48 PM, Erik Joelsson wrote:
>>>>>> Hello,
>>>>>>
>>>>>> Please review this small fix for building on Solaris using a
>>>>>> devkit/sysroot. The Solaris Studio compiler does special inlining 
>>>>>> and
>>>>>> intrinsics with system calls, like memcpy. The problem is that it 
>>>>>> only
>>>>>> seems to do this if it finds the definition of the system call in a
>>>>>> header file in the /usr/include directory. See bug description and
>>>>>> comments for details.
>>>>>>
>>>>>> I have found a way to work around this. Internally, the compiler 
>>>>>> adds
>>>>>> the option -I-xbuiltin to mark the start of the system header 
>>>>>> includes
>>>>>> when calling a sub process. By adding this to our SYSROOT_CFLAGS, 
>>>>>> the
>>>>>> special inlining is re-enabled.
>>>>>
>>>>> We have no way of knowing whether that will mess with the compilers
>>>>> use of other header files. We seem to be on very thin ice here. We
>>>>> know it fixes this one problem, but we don't know what else it may 
>>>>> do!
>>>>>
>>>> That is true. But then, we don't really know what else this compiler
>>>> is doing anyway, as is evident by your latest discovery. The way we
>>>> live with this is testing. We use the setup we have until it proves
>>>> not to work, we fix and we test. I'm just trying to do the best I can
>>>> with what we have. I would much prefer to ditch SS for gcc/clang
>>>> (where we seem to have way less problems) if it was my choice. I'm not
>>>> ready to give up the convenience of devkits/portable sysroots just
>>>> because one of the compilers we (have to) use needs a bit of special
>>>> handling to behave properly.
>>>
>>> I agree that this is a situation that's not really comfortable. :( But,
>>> as with many other things with the solaris studio compiler, in the end
>>> it's a result of the limited functionality of that compiler (in this
>>> case, the lack of a properly functioning --sysroot alternative).
>>>
>>> So in light of that, and Erik's comment about testing as the only 
>>> way to
>>> be sure, I'd like to see Eriks fix get in.
>>
>> Do we have the means to do a binary comparison of the object files 
>> before/after the change to ascertain what kind of affect this is having?
>>
>> Thanks,
>> David
>>
>>> /Magnus
>>>
>>>
>>>>
>>>> /Erik
>>>
>