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Re: subreg against register allocation?

Thanks for explanation.

here are three more questions
1 , If I am talking the right thing, there are two insns like
           "*mulsi3_1" and "*smulsi3_highpart_insn",
     which set two parts of DImode pseudo regs of DImode mult.

    Since both parts pf result are used in the original example,
    I am not sure how to make split pattern to handle this case
    without generating two duplicate mult insns in parallel.

2 , If I could set the two parts of result in parallel insn, I also have to
    handle mips specific constraints in this case, i.e, constraints
    for HI/LO registers.
    Unfortunately, There is no "h" constraint now according to patch

    It is not possible to write hi reg without clobbering the lo reg now,
    How should I handle this?

3 , Since I am studying IRA right now, I am very curious about whether
    possible to solve this in IRA. e.g, by shrinking live ranges
    of multi-word pseudo regs?

PS, maybe I am talking gibberish, Sorry If not clear enough.
Best Regards.

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