[15] RFR(S): 8244433: Remove saving of RSP in Assembler::pusha_uncached()

[Christian Hagedorn]

Forgot to adjust the rsp variable in print_state64() on line 912. I 
updated my webrev in place.

Best regards,
Christian

On 14.05.20 11:49, Christian Hagedorn wrote:
> Thank you Erik for your review!
> 
> Best regards,
> Christian
> 
> On 14.05.20 11:47, Erik Österlund wrote:
>> Hi Christian,
>>
>> Thanks for taking care of this. Looks good to me.
>>
>> Thanks,
>> /Erik
>>
>> On 2020-05-14 11:38, Christian Hagedorn wrote:
>>> Hi
>>>
>>> Please review the following enhancement for x86:
>>> https://bugs.openjdk.java.net/browse/JDK-8244433
>>> http://cr.openjdk.java.net/~chagedorn/8244433/webrev.00/
>>>
>>> This removes the move instruction for saving the actual value of RSP 
>>> in Assembler::pusha_uncached()/pusha(). The original value of RSP is 
>>> normally not used on the stack as the value of RSP will automatically 
>>> be restored after popa to the same value before doing pusha. There 
>>> are two locations, however, where we need to know the original value 
>>> of RSP in order to print it. But these places can also compute the 
>>> correct value of RSP by using the new value of RSP after pusha and 
>>> adding 16 * wordSize to it. I fixed those.
>>>
>>> We still keep the same alignment by subtracting 16 * wordSize from 
>>> RSP in pusha. Does anybody see any potential problems by not saving 
>>> the value of RSP on the stack with pusha?
>>>
>>> Either way, as Erik Ö. has pointed out, the Windows x64 ABI does not 
>>> specify a red zone of 128 bytes. If we are unlucky and get an 
>>> interrupt between saving RSP and decrementing RSP in the current 
>>> code, we could end up with a corrupt value for RSP on Windows. 
>>> Therefore, we do need to fix pusha_uncached() if we still want to 
>>> save the old value of RSP. For example, we could first subtract 16 * 
>>> wordSize and then calculate the correct value:
>>>
>>> subq(rsp, 16 * wordSize);
>>> movq(Address(rsp, 11 * wordSize), rsp);
>>> addq(Address(rsp, 11 * wordSize), 16 * wordSize);
>>>
>>> Thank you!
>>>
>>> Best regards,
>>> Christian
>>