RFR(XS): 8015437: SPARC cbcond offset value out of range

[David Chase]

I think I'm confused.  If it's a ba,a (or the newer BPA,a,pt), there's no need for a NOP, since it is never executed.
We can save 4 whole bytes of code space/instruction cache.

David

On 2013-06-07, at 12:08 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:

> On 6/7/13 8:56 AM, David Chase wrote:
>> Wouldn't we want to call it ba_without_delay or something like that?
> 
> It could be misleading since it could be interpreted as without delay slot. Our case is nop in delay slot which we should not execute.
> We can use neutral name ba_long() as opposite to ba_short().
> 
> Vladimir
> 
>> 
>> David
>> 
>> On 2013-06-07, at 11:47 AM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
>> 
>>> David is right.
>>> 
>>> We have a lot of places in sparc code where we are sloppy with annulled bit for direct branch and nop() in delay slot. I count about 10 cases which br() instruction and 15 with ba() which is not really bad.
>>> 
>>> We need separate macroassembler instruction for such case.
>>> ba_with_nop()?
>>> 
>>> Good starter task :)
>>> 
>>> Thanks,
>>> Vladimir
>>> 
>>> On 6/7/13 4:59 AM, David Chase wrote:
>>>> Huh.  ba,a (annulled branch -- if I recall, the sense of the annulled bit is reversed for ba) ought to get the job done without the delay-slot nop.
>>>> 
>>>> David
>>>> 
>>>> On 2013-06-07, at 6:54 AM, Morris Meyer <morris.meyer at oracle.com> wrote:
>>>> 
>>>>> I needed to have the delayed()->nop() in there as ba() crashed for me.
>>>>> 
>>>>> 
>>>>>      --mm
>>>>> 
>>>>> 
>>>>> On Jun 7, 2013, at 12:35 AM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
>>>>> 
>>>>>> Morris,
>>>>>> 
>>>>>> Why you used br(always, false, pt, slow_case) instead of ba(slow_case)?
>>>>>> 
>>>>>> Which is the same but simpler and it was specially added to avoid messing with parameters of br() instruction.
>>>>>> 
>>>>>> Thanks,
>>>>>> Vladimir
>>>>>> 
>>>>>> On 6/6/13 9:22 PM, Morris Meyer wrote:
>>>>>>> Folks,
>>>>>>> 
>>>>>>> Could I get a review for this issue?  The problem exists that we
>>>>>>> optimistically assign forward branch labels and re-patch later. When we
>>>>>>> emit a cbcond instruction - we check if the Label out of bounds.  If it
>>>>>>> is already bound the check is fine - if not bound a zero offset is
>>>>>>> emitted and the label is patched later
>>>>>>> 
>>>>>>> With Vladimir Kozlov's urgings I put about 4,000 lines of changes to add
>>>>>>> __FILE__ and __LINE__ parameters to every assembler.bind() call and
>>>>>>> checked the return of every patched branch to find out the line and
>>>>>>> location of the offending bind.  The bind distance from
>>>>>>> NewInstanceStub::emit_code() in c1_CodeStubs_sparc.cpp was to far from
>>>>>>> __ allocate_object macro assembler call in LIRGenerator::new_instance
>>>>>>> which uses the short branch in MacroAssembler::eden_allocate()
>>>>>>> 
>>>>>>> This change has been through JPRT.
>>>>>>> 
>>>>>>>        --morris
>>>>>>> 
>>>>>>> WEBREV - http://cr.openjdk.java.net/~morris/JDK-8015437.01
>>>>>>> JBS - https://jbs.oracle.com/bugs/browse/JDK-8015437
>>>>>>> 
>>>>>>> 
>>>> 
>>