Revert of SkHalfToFloat_01 / SkFloatToHalf_01

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"
@@ skipping 28 matching lines @@
     return SkNx_cast<float>(Sk4h::Load(&value));
 }
 
 // takes floats already biased by 65535
 static uint64_t store_to_u16(const Sk4f& x4) {
     uint64_t value;
     SkNx_cast<uint16_t>(x4 + Sk4f(0.5f)).store(&value);
     return value;
 }
 
+static Sk4f load_from_f16(uint64_t value) {
+    const uint16_t* u16 = reinterpret_cast<const uint16_t*>(&value);
+    float f4[4];
+    for (int i = 0; i < 4; ++i) {
+        f4[i] = SkHalfToFloat(u16[i]);
+    }
+    return Sk4f::Load(f4);
+}
+
+static uint64_t store_to_f16(const Sk4f& x4) {
+    uint64_t value;
+    uint16_t* u16 = reinterpret_cast<uint16_t*>(&value);
+
+    float f4[4];
+    x4.store(f4);
+    for (int i = 0; i < 4; ++i) {
+        u16[i] = SkFloatToHalf(f4[i]);
+    }
+    return value;
+}
+
 // Returns dst in its "natural" bias (either unit-float or 16bit int)
 //
 template <DstType D> Sk4f load_from_dst(uint64_t dst) {
-    return (D == kU16_Dst) ? load_from_u16(dst) : SkHalfToFloat_01(dst);
+    return (D == kU16_Dst) ? load_from_u16(dst) : load_from_f16(dst);
 }
 
 // Assumes x4 is already in the "natural" bias (either unit-float or 16bit int)
 template <DstType D> uint64_t store_to_dst(const Sk4f& x4) {
-    return (D == kU16_Dst) ? store_to_u16(x4) : SkFloatToHalf_01(x4);
+    return (D == kU16_Dst) ? store_to_u16(x4) : store_to_f16(x4);
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 template <DstType D> void src_1(const SkXfermode::U64State& state, uint64_t dst[],
                                 const SkPM4f& src, int count, const SkAlpha aa[]) {
     const Sk4f s4 = unit_to_dst_bias<D>(Sk4f::Load(src.fVec));
     if (aa) {
         for (int i = 0; i < count; ++i) {
             const Sk4f d4 = load_from_dst<D>(dst[i]);
@@ skipping 83 matching lines @@
     return { nullptr, nullptr };
 }
 
 SkXfermode::U64Proc1 SkXfermode::GetU64Proc1(Mode mode, uint32_t flags) {
     return find_procs(mode, flags).fP1;
 }
 
 SkXfermode::U64ProcN SkXfermode::GetU64ProcN(Mode mode, uint32_t flags) {
     return find_procs(mode, flags).fPN;
 }