[PATCH] D109883: [Analysis] Add support for vscale in computeKnownBitsFromOperator

[David Sherwood via Phabricator via llvm-commits]

david-arm added a comment.

In D109883#3005766 <https://reviews.llvm.org/D109883#3005766>, @sdesmalen wrote:

> In D109883#3004334 <https://reviews.llvm.org/D109883#3004334>, @dmgreen wrote:
>
>> Sounds good. I assume that unsetting low bits from the min value does not help much?
>
> I could see this being useful when min == max, which may help fold away code that checks if the vscale value is known even or a power of two.

OK fair points @dmgreen and @sdesmalen! I'll look into taking min vscale into account as well. :)



================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:1831
                            unsigned Depth, const Query &Q) {
   KnownBits Known(getBitWidth(V->getType(), Q.DL));
   computeKnownBits(V, DemandedElts, Known, Depth, Q);
----------------
dmgreen wrote:
> This appears to be where Known is calculated.
Oh right I see. Thanks for explaining - I'll update the patch!


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