[10] RFR(XS): 8194494: SHA-512 stub uses AVX 2 instructions on non-supporting CPUs

[Vladimir Kozlov]

Good.

Thanks,
Vladimir

On 1/3/18 11:35 PM, Tobias Hartmann wrote:
> Hi Vladimir,
> 
> On 03.01.2018 20:44, Vladimir Kozlov wrote:
>> Even so sha512 is only implemented for 64-bit I think you should not restrict check with LP64_ONLY(). The only
>> implementation uses avx2.
> 
> Okay, that makes sense. Here's the new webrev:
> http://cr.openjdk.java.net/~thartmann/8194494/webrev.01/
> 
> Thanks,
> Tobias
> 
> 
>> On 1/3/18 8:49 AM, Tobias Hartmann wrote:
>>> Hi,
>>>
>>> please review the following patch:
>>> https://bugs.openjdk.java.net/browse/JDK-8194494
>>> http://cr.openjdk.java.net/~thartmann/8194494/webrev.00/
>>>
>>> The VM crashes with SIGILL on CPUs that have the SHA extension but no AVX 2 support because since JDK-8165381 the
>>> SHA-512 stub uses AVX 2 instructions (for example, 'vpblendd'). In addition to UseSHA, we need to check for
>>> supports_avx2() && supports_bmi2() on x86.
>>>
>>> I had no suitable machine available for testing but I was able to trigger the problem by enforcing
>>> UseSHA512Intrinsics=true on my machine and disabling AVX 2 support (see comments in the bug for details).
>>>
>>> This problem was reported by Csaba Mate [1].
>>>
>>> Thanks,
>>> Tobias
>>>
>>> [1] http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2018-January/028002.html
>>>