Move float<->byte conversions into Sk4f.

src/opts/SkPMFloat_neon.h

-/*
- * Copyright 2015 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-namespace { // See SkPMFloat.h
-
-static_assert(SK_A32_SHIFT == 24, "This file assumes little-endian.");
-
-inline SkPMFloat::SkPMFloat(SkPMColor c) {
-    SkPMColorAssert(c);
-    uint8x8_t   fix8    = (uint8x8_t)vdup_n_u32(c);
-    uint16x8_t  fix8_16 = vmovl_u8(fix8);
-    uint32x4_t  fix8_32 = vmovl_u16(vget_low_u16(fix8_16));
-    fVec = vmulq_f32(vcvtq_f32_u32(fix8_32), vdupq_n_f32(1.0f/255));
-    SkASSERT(this->isValid());
-}
-
-inline SkPMColor SkPMFloat::round() const {
-    // vcvt_u32_f32 truncates, so we round manually by adding a half before converting.
-    float32x4_t rounded = vmlaq_f32(vdupq_n_f32(0.5f), fVec, vdupq_n_f32(255));
-    uint32x4_t  fix8_32 = vcvtq_u32_f32(rounded);
-    uint16x4_t  fix8_16 = vqmovn_u32(fix8_32);
-    uint8x8_t   fix8    = vqmovn_u16(vcombine_u16(fix8_16, vdup_n_u16(0)));
-    SkPMColor c = vget_lane_u32((uint32x2_t)fix8, 0);
-    SkPMColorAssert(c);
-    return c;
-}
-
-inline Sk4f SkPMFloat::alphas() const {
-    return vdupq_lane_f32(vget_high_f32(fVec), 1);  // Duplicate high lane of high half i.e. lane 3.
-}
-
-inline SkPMFloat SkPMFloat::FromOpaqueColor(SkColor c) {
-    SkASSERT(SkColorGetA(c) == 0xFF);
-    uint8x8_t fix8 = (uint8x8_t)vdup_n_u32(c);
-#if defined(SK_PMCOLOR_IS_RGBA)
-    fix8 = vtbl1_u8(fix8, vcreate_u8(0x0300010203000102ULL));  // 03 00 01 02, 2x, i.e. swap R&B.
-#endif
-    uint16x8_t fix8_16 = vmovl_u8(fix8);
-    uint32x4_t fix8_32 = vmovl_u16(vget_low_u16(fix8_16));
-
-    SkPMFloat pmf = Sk4f(vmulq_f32(vcvtq_f32_u32(fix8_32), vdupq_n_f32(1.0f/255)));
-    SkASSERT(pmf.isValid());
-    return pmf;
-}
-
-}  // namespace