[12] RFR(S): 8215313: [AOT] java/lang/String/Split.java fails with AOTed java.base

[Vladimir Kozlov]

+1

Thanks,
Vladimir

On 1/14/19 12:14 PM, Tom Rodriguez wrote:
> Looks good.
> 
> tom
> 
> Doug Simon wrote on 1/12/19 4:57 AM:
>>
>>
>>> On 11 Jan 2019, at 10:02, Doug Simon <doug.simon at oracle.com <mailto:doug.simon at oracle.com>> wrote:
>>>
>>> Hi Josef,
>>>
>>>> On 10 Jan 2019, at 22:52, Josef Haider <josef.haider at khg.jku.at <mailto:josef.haider at khg.jku.at>> wrote:
>>>>
>>>> Agreed, cmpw/cmpb would make more sense here, i just wanted
>>>> to keep the changeset minimal, since the entire method may soon be
>>>> changed again, anyway.
>>>>
>>> Can you please say more about this? Would you recommend applying your current patch as is to fix the crash or will 
>>> you have the changes you mention ready soon?
>>
>> Josef has updated his fix to use cmpw/cmpb:
>>
>> http://cr.openjdk.java.net/~dnsimon/8215313/
>>
>> Previous webrev is now at http://cr.openjdk.java.net/~dnsimon/8215313.old/20190112_1342
>>
>> Dean, can you please re-review.
>>
>> -Doug
>>
>>>
>>> -Doug
>>>>> Taking another look, it seems like cmpl could be replaced with the
>>>>> size-appropriate cmpb, cmpw, or cmpl based on byteMode(kind) and
>>>>> findTwoCharPrefix, but I guess AMD64Assembler only supports cmpl and
>>>>> cmpq right now.
>>>>>
>>>>> dl
>>>>>
>>>>> On 1/10/19 10:04 AM,dean.long at oracle.com <https://mail.openjdk.java.net/mailman/listinfo/hotspot-compiler-dev>  
>>>>> wrote:
>>>>> >/Is it OK to modify the values of searchValue[i]?  If the search value />/is already sign-extended, how about 
>>>>> sign-extending cmpResult instead />/of zero-extending searchValue? />//>/dl />//>/On 1/10/19 7:09 AM, Doug Simon 
>>>>> wrote: />>/Please review this fix supplied by Josef Haider for an incorrect />>/compilation of String.split. 
>>>>> />>//>>/When the String.indexOf intrinsic on AMD64 reaches the end of a />>/string, it tries to vectorize the last 
>>>>> compare operations by reading />>/past the bounds of the character/byte array. This is not safe if the 
>>>>> />>/out-of-bounds read would cross a page boundary, so in that case />>/characters are compared one-by-one. This is 
>>>>> done with a />>/`cmpl`-instruction, which only works as long as the bytes/chars are />>/not sign extended. 
>>>>> />>//>>/The fix is to simply `and` the characters we are searching for with />>/`0xff`/`0xffff` in order to 
>>>>> eliminate any erroneous sign extensions. />>//>>/http://cr.openjdk.java.net/~dnsimon/8215313 
>>>>> />>/https://bugs.openjdk.java.net/browse/JDK-8215313 />>//>>/-Doug />//
>>>>>
>>>>
>>>>
>>>
>>