RFR (M) 8222074: Enhance auto vectorization for x86

[B. Blaser]

Hi Sandhya and Vladimir K.,

On Wed, 10 Apr 2019 at 03:06, Viswanathan, Sandhya
<sandhya.viswanathan at intel.com> wrote:
>
> Hi Vladimir,
>
> Yes, I missed the question below:
> >> There are cases where we can use less `TEMP tmp` registers by using 'dst' register like in mul4B_reg(). Is it intentional to not use 'dst' there?
>
> No it is not intentional, we can use the dst register in those cases and reduced the tmps.

I guess we have to be careful using $dst instead of $tmp registers as
the allocator sometimes provides identical $src & $dst. Also, I'm not
sure this would be possible in the case of mul4B_reg():

7349   format %{"pmovsxbw  $tmp,$src1\n\t"
7350            "pmovsxbw  $tmp2,$src2\n\t"

I believe this couldn't work if you use $dst instead of $tmp and $dst
= $src2, what do you think?

Thanks,
Bernard