SkPx: new approach to fixed-point SIMD

src/opts/SkPx_none.h

Index: src/opts/SkPx_none.h
diff --git a/src/opts/SkPx_none.h b/src/opts/SkPx_none.h
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index 0000000000000000000000000000000000000000..bc4c6a32aa82360466577fe2a021c555cf49bc94
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+++ b/src/opts/SkPx_none.h
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+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkPx_none_DEFINED
+#define SkPx_none_DEFINED
+
+// Nothing fancy here.  We're the backup _none case after all.
+// Our declared sweet spot is simply a single pixel at a time.
+
+struct SkPx_none {
+    static const int N = 1;
+    uint8_t f8[4];
+
+    SkPx_none(uint32_t px) { memcpy(f8, &px, 4); }
+    SkPx_none(uint8_t x, uint8_t y, uint8_t z, uint8_t a) {
+        f8[0] = x; f8[1] = y; f8[2] = z; f8[3] = a;
+    }
+
+    static SkPx_none Dup(uint32_t px) { return px; }
+    static SkPx_none Load(const uint32_t* px) { return *px; }
+    static SkPx_none Load(const uint32_t* px, int n) {
+        SkASSERT(false);  // There are no 0<n<1.
+        return 0;
+    }
+
+    void store(uint32_t* px) const { memcpy(px, f8, 4); }
+    void store(uint32_t* px, int n) const {
+        SkASSERT(false);  // There are no 0<n<1.
+    }
+
+    struct Alpha {
+        uint8_t fA;
+        Alpha(uint8_t a) : fA(a) {}
+
+        static Alpha Dup(uint8_t a) { return a; }
+        static Alpha Load(const uint8_t* a) { return *a; }
+        static Alpha Load(const uint8_t* a, int n) {
+            SkASSERT(false);  // There are no 0<n<1.
+            return 0;
+        }
+        Alpha inv() const { return 255 - fA; }
+    };
+
+    struct Wide {
+        uint16_t f16[4];
+
+        Wide(uint16_t x, uint16_t y, uint16_t z, uint16_t a) {
+            f16[0] = x; f16[1] = y; f16[2] = z; f16[3] = a;
+        }
+
+        Wide operator+(const Wide& o) const {
+            return Wide(f16[0]+o.f16[0], f16[1]+o.f16[1], f16[2]+o.f16[2], f16[3]+o.f16[3]);
+        }
+        Wide operator-(const Wide& o) const {
+            return Wide(f16[0]-o.f16[0], f16[1]-o.f16[1], f16[2]-o.f16[2], f16[3]-o.f16[3]);
+        }
+        template <int bits> Wide shl() const {
+            return Wide(f16[0]<<bits, f16[1]<<bits, f16[2]<<bits, f16[3]<<bits);
+        }
+        template <int bits> Wide shr() const {
+            return Wide(f16[0]>>bits, f16[1]>>bits, f16[2]>>bits, f16[3]>>bits);
+        }
+
+        SkPx_none addNarrowHi(const SkPx_none& o) const {
+            Wide sum = (*this + o.widenLo()).shr<8>();
+            return SkPx_none(sum.f16[0], sum.f16[1], sum.f16[2], sum.f16[3]);
+        }
+    };
+
+    Alpha alpha() const { return f8[3]; }
+
+    Wide widenLo() const { return Wide(f8[0], f8[1], f8[2], f8[3]); }
+    Wide widenHi() const { return this->widenLo().shl<8>(); }
+    Wide widenLoHi() const { return this->widenLo() + this->widenHi(); }
+
+    SkPx_none operator+(const SkPx_none& o) const {
+        return SkPx_none(f8[0]+o.f8[0], f8[1]+o.f8[1], f8[2]+o.f8[2], f8[3]+o.f8[3]);
+    }
+    SkPx_none operator-(const SkPx_none& o) const {
+        return SkPx_none(f8[0]-o.f8[0], f8[1]-o.f8[1], f8[2]-o.f8[2], f8[3]-o.f8[3]);
+    }
+    SkPx_none saturatedAdd(const SkPx_none& o) const {
+        return SkPx_none(SkTMax(0, SkTMin(255, f8[0]+o.f8[0])),
+                         SkTMax(0, SkTMin(255, f8[1]+o.f8[1])),
+                         SkTMax(0, SkTMin(255, f8[2]+o.f8[2])),
+                         SkTMax(0, SkTMin(255, f8[3]+o.f8[3])));
+    }
+
+    Wide operator*(const Alpha& a) const {
+        return Wide(f8[0]*a.fA, f8[1]*a.fA, f8[2]*a.fA, f8[3]*a.fA);
+    }
+    SkPx_none approxMulDiv255(const Alpha& a) const {
+        return (*this * a).addNarrowHi(*this);
+    }
+
+    SkPx_none addAlpha(const Alpha& a) const {
+        return SkPx_none(f8[0], f8[1], f8[2], f8[3]+a.fA);
+    }
+};
+typedef SkPx_none SkPx;
+
+#endif//SkPx_none_DEFINED