Re: [PATCH] Record ARM THUMB2 PLD/PLI cache instructions

[Simon Marchi <simark@simark.ca>]

On 2018-10-01 18:05, Trent Piepho wrote:
>> In the manual, however, in table "Table A5-20 Load byte, memory 
>> hints", some encodings with
>> Rt == 0b1111 decode to "UNPREDICTABLE".  Should the record fail for 
>> those?  I think currently
>> with your patch we will accept them.  I am thinking it would be good 
>> to fail, because since
>> we can't know the side effects of such instruction, we risk showing 
>> some false information if
>> we just assume nothing has changed.
> 
> I'm not sure what document this is from, but in https://static.docs.arm
> .com/ddi0406/c/DDI0406C_C_arm_architecture_reference_manual.pdf
> 
> Table A6-20 is titled as above.
> 
> Rather than this, I used the thumb2 supplement I found here: http://her
> mes.wings.cs.wisc.edu/files/Thumb-2SupplementReferenceManual.pdf
> 
> Section 3.3.3 had the most useful table and exhaustive list of possible
> encodings for this type of thumb2 instruction.

Not sure which section 3.3.3 you are referring to.  But I must have been 
using an outdated version of the manual, in the version you linked there 
is indeed no unpredictable encodings.

> I see now that not every possible addressing mode is supported for
> PLD/PLI, and there are ways to encode a reserved addressing mode for
> all instructions of this type.
> 
> I've prepared a follow on patch that should provide an exhaustive check
> for PLD and PLI instructions.  It also enhances the check for other
> instructions of this general format, but I've not verified that the
> code is exhaustive there.  It is at least better than it was.
> 
>> If you are motivated, it would be nice to add a test for this 
>> instruction in arm_record_test,
>> but I won't require it, since the current state is that this test 
>> isn't meant to test all
>> possible instruction, and I don't want to impose that burden on you.
> 
> I might that be THAT motivated, since I've never even used that test
> feature.

Err I'm not sure if you you meant that you are that motivated, or you 
are _not_ that motivated.  In case you are, I'll be happy to provide any 
help you would need :).

Simon