[VPlan] Expand VPBlendRecipes to select instructions. NFC (#133993)

When looking at some EVL tail folded code in SPEC CPU 2017 I noticed we
sometimes have both VPBlendRecipes and select VPInstructions in the same
plan:

    EMIT vp<%active.lane.mask> = active lane mask vp<%5>, vp<%3>
    EMIT vp<%7> = icmp ...
    EMIT vp<%8> = logical-and vp<%active.lane.mask>, vp<%7>
    BLEND ir<%8> = ir<%n.015> ir<%foo>/vp<%8>
    EMIT vp<%9> = select vp<%active.lane.mask>, ir<%8>, ir<%n.015>

Since a blend will ultimately generate a chain of selects, we could fold
the blend into the select:

    EMIT vp<%active.lane.mask> = active lane mask vp<%5>, vp<%3>
    EMIT vp<%7> = icmp ...
    EMIT vp<%8> = logical-and vp<%active.lane.mask>, vp<%7>
    EMIT ir<%8> = select vp<%8>, ir<%foo>, ir<%n.015>

So as a first step, this patch expands blends to a series of select
instructions, which may allow them to be simplified further with other
select instructions.

0 files changed, 0 insertions, 0 deletions