skrpb: evaluate color filters for constant shaders once.

src/opts/SkRasterPipeline_opts.h

Index: src/opts/SkRasterPipeline_opts.h
diff --git a/src/opts/SkRasterPipeline_opts.h b/src/opts/SkRasterPipeline_opts.h
index bd42632b4b0cfb6ac049e15a41a2f589041b8f3c..155558e776de5d08705dd39c08db82a81133ae44 100644
--- a/src/opts/SkRasterPipeline_opts.h
+++ b/src/opts/SkRasterPipeline_opts.h
@@ -23,9 +23,9 @@ namespace {
     static constexpr int N = 4;
 #endif
 
-using SkNf = SkNx<N, float>;
-using SkNi = SkNx<N, int>;
-using SkNh = SkNx<N, uint16_t>;
+    using SkNf = SkNx<N, float>;
+    using SkNi = SkNx<N, int>;
+    using SkNh = SkNx<N, uint16_t>;
 
     struct BodyStage;
     struct TailStage;
@@ -379,6 +379,24 @@ STAGE(store_f16, false) {
     }
 }
 
+STAGE(store_f32, false) {
+    auto ptr = *(SkPM4f**)ctx + x;
+
+    SkPM4f buf[8];
+    SkNf::Store4(kIsTail ? buf : ptr, r,g,b,a);
+    if (kIsTail) {
+        switch (tail & (N-1)) {
+            case 7: ptr[6] = buf[6];
+            case 6: ptr[5] = buf[5];
+            case 5: ptr[4] = buf[4];
+            case 4: ptr[3] = buf[3];
+            case 3: ptr[2] = buf[2];
+            case 2: ptr[1] = buf[1];
+        }
+        ptr[0] = buf[0];
+    }
+}
+
 
 // Load 8-bit SkPMColor-order sRGB.
 STAGE(load_d_srgb, true) {