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

[Vladimir Kozlov]

Morris,

Sorry, when I suggested ba() I did not say that it HAS delay slot. All branches on sparc has delay slot. Only new cbcond 
instruction used for short branches does not. So the fix is:

-    ba_short(slow_case);
+    ba(slow_case);
+    delayed()->nop();

The ba() method is macroassembler method which use br() to encode branch instruction:

inline void MacroAssembler::ba( Label& L ) {
   br(always, false, pt, L);
}

So your fix is correct but we use macroassembler methods to simplify code.


Thanks,
Vladimir

On 6/7/13 3:54 AM, Morris Meyer 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
>>>
>>>