Revert of SkNx miplevel building

src/core/SkMipMap.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkMipMap.h"
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
-#include "SkNx.h"
 
 //
 // ColorTypeFilter is the "Type" we pass to some downsample template functions.
 // It controls how we expand a pixel into a large type, with space between each component,
 // so we can then perform our simple filter (either box or triangle) and store the intermediates
 // in the expanded type.
 //
 
 struct ColorTypeFilter_8888 {
     typedef uint32_t Type;
-#if defined(SKNX_IS_FAST)
-    static Sk4h Expand(uint32_t x) {
-        return SkNx_cast<uint16_t>(Sk4b::Load((const uint8_t*)&x));
-    }
-    static uint32_t Compact(const Sk4h& x) {
-        uint32_t r;
-        SkNx_cast<uint8_t>(x).store((uint8_t*)&r);
-        return r;
-    }
-#else
     static uint64_t Expand(uint32_t x) {
         return (x & 0xFF00FF) | ((uint64_t)(x & 0xFF00FF00) << 24);
     }
     static uint32_t Compact(uint64_t x) {
         return (uint32_t)((x & 0xFF00FF) | ((x >> 24) & 0xFF00FF00));
     }
-#endif
 };
 
 struct ColorTypeFilter_565 {
     typedef uint16_t Type;
     static uint32_t Expand(uint16_t x) {
         return (x & ~SK_G16_MASK_IN_PLACE) | ((x & SK_G16_MASK_IN_PLACE) << 16);
     }
     static uint16_t Compact(uint32_t x) {
         return (x & ~SK_G16_MASK_IN_PLACE) | ((x >> 16) & SK_G16_MASK_IN_PLACE);
     }
@@ skipping 12 matching lines @@
 struct ColorTypeFilter_8 {
     typedef uint8_t Type;
     static unsigned Expand(unsigned x) {
         return x;
     }
     static uint8_t Compact(unsigned x) {
         return (uint8_t)x;
     }
 };
 
-template <typename T> T add_121(const T& a, const T& b, const T& c) {
+template <typename T> T add_121(T a, T b, T c) {
     return a + b + b + c;
 }
 
 //
 //  To produce each mip level, we need to filter down by 1/2 (e.g. 100x100 -> 50,50)
 //  If the starting dimension is odd, we floor the size of the lower level (e.g. 101 -> 50)
 //  In those (odd) cases, we use a triangle filter, with 1-pixel overlap between samplings,
 //  else for even cases, we just use a 2x box filter.
 //
 //  This produces 4 possible filters: 2x2 2x3 3x2 3x3 where WxH indicates the number of src pixels
@@ skipping 16 matching lines @@
         p0 += 2;
         p1 += 2;
     }
 }
 
 template <typename F> void downsample_3_2(void* dst, const void* src, size_t srcRB, int count) {
     SkASSERT(count > 0);
     auto p0 = static_cast<const typename F::Type*>(src);
     auto p1 = (const typename F::Type*)((const char*)p0 + srcRB);
     auto d = static_cast<typename F::Type*>(dst);
-
+    
     auto c02 = F::Expand(p0[0]);
     auto c12 = F::Expand(p1[0]);
     for (int i = 0; i < count; ++i) {
         auto c00 = c02;
         auto c01 = F::Expand(p0[1]);
              c02 = F::Expand(p0[2]);
         auto c10 = c12;
         auto c11 = F::Expand(p1[1]);
              c12 = F::Expand(p1[2]);
 
         auto c = add_121(c00, c01, c02) + add_121(c10, c11, c12);
         d[i] = F::Compact(c >> 3);
         p0 += 2;
         p1 += 2;
     }
 }
 
 template <typename F> void downsample_2_3(void* dst, const void* src, size_t srcRB, int count) {
     auto p0 = static_cast<const typename F::Type*>(src);
     auto p1 = (const typename F::Type*)((const char*)p0 + srcRB);
     auto p2 = (const typename F::Type*)((const char*)p1 + srcRB);
     auto d = static_cast<typename F::Type*>(dst);
-
+    
     for (int i = 0; i < count; ++i) {
         auto c00 = F::Expand(p0[0]);
         auto c01 = F::Expand(p0[1]);
         auto c10 = F::Expand(p1[0]);
         auto c11 = F::Expand(p1[1]);
         auto c20 = F::Expand(p2[0]);
         auto c21 = F::Expand(p2[1]);
 
         auto c = add_121(c00, c10, c20) + add_121(c01, c11, c21);
         d[i] = F::Compact(c >> 3);
@@ skipping 217 matching lines @@
         return nullptr;
     }
     const SkPixmap& srcPixmap = srcUnlocker.pixmap();
     // Try to catch where we might have returned nullptr for src crbug.com/492818
     if (nullptr == srcPixmap.addr()) {
         sk_throw();
     }
     return Build(srcPixmap, fact);
 }