Implement four more xfermodes with Sk4px.

HardLight, Overlay, Darken, and Lighten are all
~2x faster with SSE, ~25% faster with NEON.

This covers all previously-implemented NEON xfermodes.
3 previous SSE xfermodes remain.  Those need division
and sqrt, so I'm planning on using SkPMFloat for them.
It'll help the readability and NEON speed if I move that
into [0,1] space first.

The main new concept here is c.thenElse(t,e), which behaves like
(c ? t : e) except, of course, both t and e are evaluated.  This allows
us to emulate conditionals with vectors.

This also removes the concept of SkNb.  Instead of a standalone bool
vector, each SkNi or SkNf will just return their own types for
comparisons.  Turns out to be a lot more manageable this way.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/b9d4163bebab0f5639f9c5928bb5fc15f472dddc

CQ_EXTRA_TRYBOTS=client.skia.compile:Build-Ubuntu-GCC-Arm64-Debug-Android-Trybot

Review URL: https://codereview.chromium.org/1196713004

1 files changed, 2 insertions, 0 deletions

diff --git a/src/core/Sk4px.h b/src/core/Sk4px.h
index 26d4d0f865..e046e265fe 100644
--- a/src/core/Sk4px.h
+++ b/src/core/Sk4px.h
@@ -85,6 +85,8 @@ public:
     // These just keep the types as Sk4px so the user doesn't have to keep casting.
     Sk4px operator + (const Sk4px& o) const { return INHERITED::operator+(o); }
     Sk4px operator - (const Sk4px& o) const { return INHERITED::operator-(o); }
+    Sk4px operator < (const Sk4px& o) const { return INHERITED::operator<(o); }
+    Sk4px thenElse(const Sk4px& t, const Sk4px& e) const { return INHERITED::thenElse(t,e); }
 
     // Generally faster than (*this * o).div255().
     // May be incorrect by +-1, but is always exactly correct when *this or o is 0 or 255.