4f linear gradient shader blitters

src/core/SkXfermodeU64.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkHalf.h"
 #include "SkPM4fPriv.h"
 #include "SkUtils.h"
 #include "SkXfermode.h"
 
-static void sk_memset64(uint64_t dst[], uint64_t value, int count) {
-    for (int i = 0; i < count; ++i) {
-        dst[i] = value;
-    }
-}
-
 enum DstType {
     kU16_Dst,
     kF16_Dst,
 };
 
 static Sk4f lerp_by_coverage(const Sk4f& src, const Sk4f& dst, uint8_t srcCoverage) {
     return dst + (src - dst) * Sk4f(srcCoverage * (1/255.0f));
 }
 
 template <DstType D> Sk4f unit_to_bias(const Sk4f& x4) {
@@ skipping 217 matching lines @@
     flags &= 7;
     
     Mode mode;
     return this->asMode(&mode) ? find_proc(mode, flags) : gProcs_General[flags];
 }
 
 SkXfermode::D64Proc SkXfermode::GetD64Proc(SkXfermode* xfer, uint32_t flags) {
     return xfer ? xfer->onGetD64Proc(flags) : find_proc(SkXfermode::kSrcOver_Mode, flags);
 }