Revert of SoftLight with SkPMFloat (patchset #6 id:100001 of https://codereview.chromium.org/1221493002/)

Reason for revert:
xfermodes and xfermodes2 show major diffs on Nexus 5 and Daisy (both ARMv7 w/NEON).  Nexus 9 and SSE all look fine...

Original issue's description:
> SoftLight with SkPMFloat
>
> SSE speeds up about 4.5x over existing integer SSE,
> NEON speeds up about 3x over serial integer code.
>
> We expect 1-2 bit component diffs in the usual GMs.
>
> Still guarded by SK_SUPPORT_LEGACY_XFERMODES,
> which I'll now try to lift in Chrome.
>
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/3e47d49b46b3ab62071218ef3dd44642c9713e04

TBR=reed@google.com,mtklein@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1221683002

2 files changed, 3 insertions, 27 deletions

diff --git a/src/core/Sk4pxXfermode.h b/src/core/Sk4pxXfermode.h
index 28fd9f1e7b..b587183046 100644
--- a/src/core/Sk4pxXfermode.h
+++ b/src/core/Sk4pxXfermode.h
@@ -141,31 +141,6 @@ XFERMODE(ColorBurn) {
                                           otherwise));
     return srcover * SkPMFloat(1,0,0,0) + colors * SkPMFloat(0,1,1,1);
 }
-XFERMODE(SoftLight) {
-    auto sa = s.alphas(),
-         da = d.alphas(),
-         isa = Sk4f(1)-sa,
-         ida = Sk4f(1)-da;
-
-    // Some common terms.
-    auto m  = (da > Sk4f(0)).thenElse(d / da, Sk4f(0)),
-         s2 = Sk4f(2)*s,
-         m4 = Sk4f(4)*m;
-
-    // The logic forks three ways:
-    //    1. dark src?
-    //    2. light src, dark dst?
-    //    3. light src, light dst?
-    auto darkSrc = d*(sa + (s2 - sa)*(Sk4f(1) - m)),        // Used in case 1.
-         darkDst = (m4*m4 + m4)*(m - Sk4f(1)) + Sk4f(7)*m,  // Used in case 2.
-         liteDst = m.sqrt() - m,                            // Used in case 3.
-         liteSrc = d*sa + da*(s2-sa)*(Sk4f(4)*d < da).thenElse(darkDst, liteDst); // Case 2 or 3?
-
-    auto alpha  = s + d*isa;
-    auto colors = s*ida + d*isa + (s2 < sa).thenElse(darkSrc, liteSrc);           // Case 1 or 2/3?
-
-    return alpha * SkPMFloat(1,0,0,0) + colors * SkPMFloat(0,1,1,1);
-}
 #undef XFERMODE
 
 // A reasonable fallback mode for doing AA is to simply apply the transfermode first,
@@ -269,7 +244,6 @@ static SkProcCoeffXfermode* SkCreate4pxXfermode(const ProcCoeff& rec, SkXfermode
 
         case SkXfermode::kColorDodge_Mode: return SkTPMFloatXfermode<ColorDodge>::Create(rec);
         case SkXfermode::kColorBurn_Mode:  return SkTPMFloatXfermode<ColorBurn>::Create(rec);
-        case SkXfermode::kSoftLight_Mode:  return SkTPMFloatXfermode<SoftLight>::Create(rec);
 #endif
         default: break;
     }
diff --git a/src/opts/SkXfermode_opts_SSE2.cpp b/src/opts/SkXfermode_opts_SSE2.cpp
index 2024a175a8..ca26263727 100644
--- a/src/opts/SkXfermode_opts_SSE2.cpp
+++ b/src/opts/SkXfermode_opts_SSE2.cpp
@@ -516,13 +516,15 @@ SkProcCoeffXfermode* SkPlatformXfermodeFactory_impl_SSE2(const ProcCoeff& rec,
                                                          SkXfermode::Mode mode) {
     SkXfermodeProcSIMD proc = nullptr;
     switch (mode) {
-        // TODO(mtklein): Sk4pxXfermode has these now.  Clean up the whole file!
+        // TODO(mtklein): Sk4pxXfermode has these now.  Clean up.
         case SkProcCoeffXfermode::kOverlay_Mode:    proc =    overlay_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kDarken_Mode:     proc =     darken_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kLighten_Mode:    proc =    lighten_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kHardLight_Mode:  proc =  hardlight_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kColorDodge_Mode: proc = colordodge_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kColorBurn_Mode:  proc =  colorburn_modeproc_SSE2; break;
+
+        // TODO(mtklein): implement this with SkPMFloat.
         case SkProcCoeffXfermode::kSoftLight_Mode:  proc =  softlight_modeproc_SSE2; break;
         default: break;
     }