Convert SkPMFloat to [0,1] range and prune its API.

src/opts/SkPMFloat_SSSE3.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
-
-// For SkPMFloat(SkPMColor), we widen our 8 bit components (fix8) to 8-bit components in 32 bits
-// (fix8_32), then convert those to floats.
-
-// round() does the opposite, working from floats to 8-bit-in-32-bits, then back to packed 8 bit.
-
-// roundClamp() is the same as _SSE2: floats to 8-in-32, to 8-in-16, to packed 8 bit, with
-// _mm_packus_epi16() both clamping and narrowing.
-
-inline SkPMFloat::SkPMFloat(SkPMColor c) {
-    SkPMColorAssert(c);
-    const int _ = 255;  // _ means to zero that byte.
-    __m128i fix8    = _mm_set_epi32(0,0,0,c),
-            fix8_32 = _mm_shuffle_epi8(fix8, _mm_set_epi8(_,_,_,3, _,_,_,2, _,_,_,1, _,_,_,0));
-    fVec = _mm_cvtepi32_ps(fix8_32);
-    SkASSERT(this->isValid());
-}
-
-inline SkPMColor SkPMFloat::trunc() const {
-    const int _ = 255;  // _ means to zero that byte.
-    __m128i fix8_32 = _mm_cvttps_epi32(fVec),
-            fix8    = _mm_shuffle_epi8(fix8_32, _mm_set_epi8(_,_,_,_, _,_,_,_, _,_,_,_, 12,8,4,0));
-    SkPMColor c = _mm_cvtsi128_si32(fix8);
-    SkPMColorAssert(c);
-    return c;
-}
-
-inline SkPMColor SkPMFloat::round() const {
-    return SkPMFloat(Sk4f(0.5f) + *this).trunc();
-}
-
-inline SkPMColor SkPMFloat::roundClamp() const {
-    // We don't use _mm_cvtps_epi32, because we want precise control over how 0.5 rounds (up).
-    __m128i fix8_32 = _mm_cvttps_epi32(_mm_add_ps(_mm_set1_ps(0.5f), fVec)),
-            fix8_16 = _mm_packus_epi16(fix8_32, fix8_32),
-            fix8    = _mm_packus_epi16(fix8_16, fix8_16);
-    SkPMColor c = _mm_cvtsi128_si32(fix8);
-    SkPMColorAssert(c);
-    return c;
-}
-
-inline void SkPMFloat::From4PMColors(const SkPMColor colors[4],
-                                     SkPMFloat* a, SkPMFloat* b, SkPMFloat* c, SkPMFloat* d) {
-    // Haven't beaten this yet.
-    *a = FromPMColor(colors[0]);
-    *b = FromPMColor(colors[1]);
-    *c = FromPMColor(colors[2]);
-    *d = FromPMColor(colors[3]);
-}
-
-inline void SkPMFloat::RoundTo4PMColors(
-        const SkPMFloat& a, const SkPMFloat& b, const SkPMFloat&c, const SkPMFloat& d,
-        SkPMColor colors[4]) {
-    // Haven't beaten this yet.  Still faster than RoundClampTo4PMColors?
-    colors[0] = a.round();
-    colors[1] = b.round();
-    colors[2] = c.round();
-    colors[3] = d.round();
-}
-
-inline void SkPMFloat::RoundClampTo4PMColors(
-        const SkPMFloat& a, const SkPMFloat& b, const SkPMFloat&c, const SkPMFloat& d,
-        SkPMColor colors[4]) {
-    // Same as _SSE2.h's.  We use 3 _mm_packus_epi16() where the naive loop uses 8.
-    // We don't use _mm_cvtps_epi32, because we want precise control over how 0.5 rounds (up).
-    __m128i c0 = _mm_cvttps_epi32(_mm_add_ps(_mm_set1_ps(0.5f), a.fVec)),
-            c1 = _mm_cvttps_epi32(_mm_add_ps(_mm_set1_ps(0.5f), b.fVec)),
-            c2 = _mm_cvttps_epi32(_mm_add_ps(_mm_set1_ps(0.5f), c.fVec)),
-            c3 = _mm_cvttps_epi32(_mm_add_ps(_mm_set1_ps(0.5f), d.fVec));
-    __m128i c3210 = _mm_packus_epi16(_mm_packus_epi16(c0, c1),
-                                     _mm_packus_epi16(c2, c3));
-    _mm_storeu_si128((__m128i*)colors, c3210);
-    SkPMColorAssert(colors[0]);
-    SkPMColorAssert(colors[1]);
-    SkPMColorAssert(colors[2]);
-    SkPMColorAssert(colors[3]);
-}
-
-}  // namespace