[LLVMdev] Canonicalizing vector masking.

Chandler Carruth chandlerc at google.com
Wed Oct 8 10:51:25 PDT 2014


On Wed, Oct 8, 2014 at 10:45 AM, Nadav Rotem <nrotem at apple.com> wrote:

> I think that the pattern below should be canonicalized into a vector
> ’select’ instruction with a constant mask.  I think that we already have
> code for canonicalizing select-like shuffles into selects.


It should be canonicalized to select in the *IR* but absolutely do not
canonicalize to VSELECT in the SelectionDAG. The VSELECT node is
significantly harder to analyze in the backend than the VECTOR_SHUFFLE node.
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