[PATCH] Move transforms from InstCombine to InstSimplify

[Duncan Sands]

Hi David,

>         +      } else {
>         +        // 'shl CI2, x' produces [CI2, CI2 << (Width-1)]
>         +        Lower = CI2Value;
>         +        Upper = CI2Value.shl(Width - 1) + 1;
>
>
>     this one seems wrong to me.  Consider for example CI2 (in binary) equal to
>        10001000
>     Then Lower=10001000, Upper=00000001, but a left-shift by 1 of CI2 is
>     00010000 which is not in the range Lower .. Upper.
>
>
> Thanks, I've updated the patch so that we will set Lower to zero and Upper to
> CI2 << CLZ(CI2) which is conservative but, AFAIK, correct.

are you sure?

10110000

Lower = 0, Upper = 10110000, but shifting left by two gives 11000000 which is
out of the range.

Ciao, Duncan.