[LLVMdev] Combining physical registers

[Krzysztof Parzyszek]

On 5/16/2013 11:17 AM, Jakob Stoklund Olesen wrote:
>
> Would this TRI function solve your problem?
>[...]
>    ///
>    ///   Covering = getCoveringLanes();
>    ///   MaskA = getSubRegIndexLaneMask(SubA);
>    ///   MaskB = getSubRegIndexLaneMask(SubB);
>    ///
>    /// If (MaskA & ~(MaskB & Covering)) == 0, then SubA is completely covered by
>    /// SubB.
>    unsigned getCoveringLanes() const { return CoveringLanes; }

Yes, this would solve my problem.  I'm assuming that if I have 
subregisters Sub0..SubN (where Sub0 could be 0, i.e. the register 
itself), and corresponding masks Mask0..MaskN, and
   Mask0 & ~((Mask1|Mask2|..|MaskN) & Covering) == 0,
this will imply that the subregisters Sub1..SubN cover Sub0.

Thanks,
-Krzysztof


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