[14] RFR (S): 8234394: C2: Dynamic register class support in ADLC

[Vladimir Ivanov]

Thanks, Tobias.

Best regards,
Vladimir Ivanov

On 21.11.2019 17:10, Tobias Hartmann wrote:
> Hi Vladimir,
> 
> looks good to me.
> 
> Best regards,
> Tobias
> 
> On 19.11.19 14:40, Vladimir Ivanov wrote:
>> http://cr.openjdk.java.net/~vlivanov/jbhateja/8234394/webrev.00/
>> https://bugs.openjdk.java.net/browse/JDK-8234394
>>
>> Introduce new "placeholder" register class which denotes that instructions which use operands of
>> such class should dynamically query register masks from the operand instance and not hard-code them
>> in the code.
>>
>> It is required for generic vectors in order to support generic vector operand (vec/legVec)
>> replacement with fixed-sized vector operands (vec[SDXYZ]/legVec[SDXYZ]) after matching is over.
>>
>> As an example of usage, generic vector operand is declared as:
>>
>> operand vec() %{
>>    constraint(ALLOC_IN_RC(dynamic));
>>    match(VecX);
>>    match(VecY);
>>    match(VecZ);
>>    match(VecS);
>>    match(VecD);
>> ...
>>
>> Then for an instruction which uses vec as DEF
>>
>> x86.ad:
>> instruct loadV4(vec dst, memory mem) %{
>>
>> =ADLC=>
>>
>> ad_x86_misc.cpp:
>> const RegMask &loadV4Node::out_RegMask() const {
>>    return (*_opnds[0]->in_RegMask(0));
>> }
>>
>> vs
>>
>> x86.ad:
>> instruct loadV4(vecS dst, memory mem) %{
>>
>> =ADLC=>
>>
>> ad_x86_misc.cpp:
>> const RegMask &loadV4Node::out_RegMask() const {
>>    return (VECTORS_REG_VLBWDQ_mask());
>> }
>>
>>
>> An operand with dynamic register class can't be used during code emission and should be replaced
>> with something different before register allocation:
>>
>> const RegMask *vecOper::in_RegMask(int index) const {
>>    return &RegMask::Empty;
>> }
>>
>> Contributed-by: Jatin Bhateja <jatin.bhateja at intel.com>
>> Reviewed-by: vlivanov, sviswanathan, ?
>>
>> Testing: tier1-4 (both with and without generic vector operands)
>>
>> Best regards,
>> Vladimir Ivanov