RFR(S): 8162338: AArch64: Intrinsify fused mac operations

[Roland Westrelin]

Vladimir,

Thanks for looking at this (and while I have your attention: I would
need your opinion on 8169697 as well).

> You said in FC extension request that only aarch64 code is affected but 
> you changed c1/c1_LIR.cpp.
>
> Can you do without this change? Otherwise RFE have to be rejected since 
> there is no time to go through internal review process.

It's a bug fix. In the current code there's no call to
do_input(op3->_opr3) which is how the register allocator knows that
there's a third input to the LIR operation. So the current code works by
accident at best. Do you want me to get this fixed separately?

Roland.