sknx refactoring

src/core/SkNx.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.
  */
 
 #ifndef SkNx_DEFINED
 #define SkNx_DEFINED
 
-
 //#define SKNX_NO_SIMD
 
 #include "SkScalar.h"
 #include "SkTypes.h"
 #include <math.h>
-#define REQUIRE(x) static_assert(x, #x)
-
-// This file may be included multiple times by .cpp files with different flags, leading
-// to different definitions.  Usually that doesn't matter because it's all inlined, but
-// in Debug modes the compilers may not inline everything.  So wrap everything in an
-// anonymous namespace to give each includer their own silo of this code (or the linker
-// will probably pick one randomly for us, which is rarely correct).
-namespace {
 
 // The default implementations just fall back on a pair of size N/2.
 // These support the union of operations we might do to ints and floats, but
 // platform specializations might support fewer (e.g. no float <<, no int /).
 template <int N, typename T>
 class SkNx {
 public:
     SkNx() {}
-    SkNx(const SkNx<N/2, T>& lo, const SkNx<N/2, T>& hi) : fLo(lo), fHi(hi) {}
     SkNx(T val) : fLo(val), fHi(val) {}
+
+    typedef SkNx<N/2, T> Half;
+    SkNx(const Half& lo, const Half& hi) : fLo(lo), fHi(hi) {}
+
+    SkNx(T a, T b)                                : fLo(a),       fHi(b)       {}
+    SkNx(T a, T b, T c, T d)                      : fLo(a,b),     fHi(c,d)     {}
+    SkNx(T a, T b, T c, T d,  T e, T f, T g, T h) : fLo(a,b,c,d), fHi(e,f,g,h) {}
+    SkNx(T a, T b, T c, T d,  T e, T f, T g, T h,
+         T i, T j, T k, T l,  T m, T n, T o, T p) : fLo(a,b,c,d, e,f,g,h), fHi(i,j,k,l, m,n,o,p) {}
+
     static SkNx Load(const void* ptr) {
         auto vals = (const T*)ptr;
-        return SkNx(SkNx<N/2,T>::Load(vals), SkNx<N/2,T>::Load(vals+N/2));
+        return SkNx(Half::Load(vals), Half::Load(vals+N/2));
     }
 
-    SkNx(T a, T b)                                : fLo(a),       fHi(b)       { REQUIRE(N==2); }
-    SkNx(T a, T b, T c, T d)                      : fLo(a,b),     fHi(c,d)     { REQUIRE(N==4); }
-    SkNx(T a, T b, T c, T d,  T e, T f, T g, T h) : fLo(a,b,c,d), fHi(e,f,g,h) { REQUIRE(N==8); }
-    SkNx(T a, T b, T c, T d,  T e, T f, T g, T h,
-         T i, T j, T k, T l,  T m, T n, T o, T p)
-        : fLo(a,b,c,d, e,f,g,h), fHi(i,j,k,l, m,n,o,p) { REQUIRE(N==16); }
-
     void store(void* ptr) const {
         auto vals = (T*)ptr;
         fLo.store(vals);
         fHi.store(vals+N/2);
     }
 
-    SkNx saturatedAdd(const SkNx& o) const {
-        return SkNx(fLo.saturatedAdd(o.fLo), fHi.saturatedAdd(o.fHi));
-    }
+#define OP(op) SkNx operator op(const SkNx& o) const { return {fLo op o.fLo, fHi op o.fHi}; }
+    OP(+) OP(-) OP(*) OP(/)
+    OP(&) OP(|) OP(^)
+    OP(==) OP(!=) OP(<) OP(>) OP(<=) OP(>=)
+#undef OP
 
-    SkNx operator + (const SkNx& o) const { return SkNx(fLo + o.fLo, fHi + o.fHi); }
-    SkNx operator - (const SkNx& o) const { return SkNx(fLo - o.fLo, fHi - o.fHi); }
-    SkNx operator * (const SkNx& o) const { return SkNx(fLo * o.fLo, fHi * o.fHi); }
-    SkNx operator / (const SkNx& o) const { return SkNx(fLo / o.fLo, fHi / o.fHi); }
+#define OP(op) SkNx op() const { return {fLo.op(), fHi.op()}; }
+    OP(abs)
+    OP(sqrt) OP(rsqrt0) OP(rsqrt1) OP(rsqrt2)
+    OP(invert) OP(approxInvert)
+#undef OP
 
     SkNx operator << (int bits) const { return SkNx(fLo << bits, fHi << bits); }
     SkNx operator >> (int bits) const { return SkNx(fLo >> bits, fHi >> bits); }
 
-    SkNx operator == (const SkNx& o) const { return SkNx(fLo == o.fLo, fHi == o.fHi); }
-    SkNx operator != (const SkNx& o) const { return SkNx(fLo != o.fLo, fHi != o.fHi); }
-    SkNx operator  < (const SkNx& o) const { return SkNx(fLo  < o.fLo, fHi  < o.fHi); }
-    SkNx operator  > (const SkNx& o) const { return SkNx(fLo  > o.fLo, fHi  > o.fHi); }
-    SkNx operator <= (const SkNx& o) const { return SkNx(fLo <= o.fLo, fHi <= o.fHi); }
-    SkNx operator >= (const SkNx& o) const { return SkNx(fLo >= o.fLo, fHi >= o.fHi); }
+    SkNx saturatedAdd(const SkNx& o) const {
+        return {fLo.saturatedAdd(o.fLo), fHi.saturatedAdd(o.fHi)};
+    }
 
     static SkNx Min(const SkNx& a, const SkNx& b) {
-        return SkNx(SkNx<N/2, T>::Min(a.fLo, b.fLo), SkNx<N/2, T>::Min(a.fHi, b.fHi));
+        return {Half::Min(a.fLo, b.fLo), Half::Min(a.fHi, b.fHi)};
     }
     static SkNx Max(const SkNx& a, const SkNx& b) {
-        return SkNx(SkNx<N/2, T>::Max(a.fLo, b.fLo), SkNx<N/2, T>::Max(a.fHi, b.fHi));
+        return {Half::Max(a.fLo, b.fLo), Half::Max(a.fHi, b.fHi)};
     }
 
-    SkNx abs() const { return SkNx(fLo.abs(), fHi.abs()); }
+    T operator[](int k) const {
+        SkASSERT(0 <= k && k < N);
+        return k < N/2 ? fLo[k] : fHi[k-N/2];
+    }
 
-    SkNx sqrt() const { return SkNx(fLo.sqrt(), fHi.sqrt()); }
-    // Generally, increasing precision, increasing cost.
-    SkNx rsqrt0() const { return SkNx(fLo.rsqrt0(), fHi.rsqrt0()); }
-    SkNx rsqrt1() const { return SkNx(fLo.rsqrt1(), fHi.rsqrt1()); }
-    SkNx rsqrt2() const { return SkNx(fLo.rsqrt2(), fHi.rsqrt2()); }
-
-    SkNx       invert() const { return SkNx(fLo.      invert(), fHi.      invert()); }
-    SkNx approxInvert() const { return SkNx(fLo.approxInvert(), fHi.approxInvert()); }
-
-    template <int k> T kth() const {
-        SkASSERT(0 <= k && k < N);
-        return k < N/2 ? fLo.template kth<k>() : fHi.template kth<k-N/2>();
-    }
+    template <int k> T kth() const { return (*this)[k]; }
 
     bool allTrue() const { return fLo.allTrue() && fHi.allTrue(); }
     bool anyTrue() const { return fLo.anyTrue() || fHi.anyTrue(); }
     SkNx thenElse(const SkNx& t, const SkNx& e) const {
         return SkNx(fLo.thenElse(t.fLo, e.fLo), fHi.thenElse(t.fHi, e.fHi));
     }
 
 protected:
-    REQUIRE(0 == (N & (N-1)));
+    static_assert(0 == (N & (N-1)), "N must be a power of 2.");
 
-    SkNx<N/2, T> fLo, fHi;
+    Half fLo, fHi;
 };
 
 // Bottom out the default implementations with scalars when nothing's been specialized.
 template <typename T>
-class SkNx<1,T> {
+class SkNx<1, T> {
 public:
     SkNx() {}
     SkNx(T val) : fVal(val) {}
+
     static SkNx Load(const void* ptr) {
         auto vals = (const T*)ptr;
         return SkNx(vals[0]);
     }
 
     void store(void* ptr) const {
         auto vals = (T*) ptr;
         vals[0] = fVal;
     }
 
+#define OP(op) SkNx operator op(const SkNx& o) const { return fVal op o.fVal; }
+    OP(+) OP(-) OP(*) OP(/)
+    OP(&) OP(|) OP(^)
+    OP(==) OP(!=) OP(<) OP(>) OP(<=) OP(>=)
+#undef OP
+
+    SkNx operator << (int bits) const { return fVal << bits; }
+    SkNx operator >> (int bits) const { return fVal >> bits; }
+
     SkNx saturatedAdd(const SkNx& o) const {
-        SkASSERT((T)(~0) > 0); // TODO: support signed T
+        SkASSERT((T)(~0) > 0); // TODO: support signed T?
         T sum = fVal + o.fVal;
-        return SkNx(sum < fVal ? (T)(~0) : sum);
+        return sum < fVal ? (T)(~0) : sum;
     }
 
-    SkNx operator + (const SkNx& o) const { return SkNx(fVal + o.fVal); }
-    SkNx operator - (const SkNx& o) const { return SkNx(fVal - o.fVal); }
-    SkNx operator * (const SkNx& o) const { return SkNx(fVal * o.fVal); }
-    SkNx operator / (const SkNx& o) const { return SkNx(fVal / o.fVal); }
-
-    SkNx operator << (int bits) const { return SkNx(fVal << bits); }
-    SkNx operator >> (int bits) const { return SkNx(fVal >> bits); }
-
-    SkNx operator == (const SkNx& o) const { return SkNx(fVal == o.fVal); }
-    SkNx operator != (const SkNx& o) const { return SkNx(fVal != o.fVal); }
-    SkNx operator  < (const SkNx& o) const { return SkNx(fVal  < o.fVal); }
-    SkNx operator  > (const SkNx& o) const { return SkNx(fVal  > o.fVal); }
-    SkNx operator <= (const SkNx& o) const { return SkNx(fVal <= o.fVal); }
-    SkNx operator >= (const SkNx& o) const { return SkNx(fVal >= o.fVal); }
-
-    static SkNx Min(const SkNx& a, const SkNx& b) { return SkNx(SkTMin(a.fVal, b.fVal)); }
-    static SkNx Max(const SkNx& a, const SkNx& b) { return SkNx(SkTMax(a.fVal, b.fVal)); }
+    static SkNx Min(const SkNx& a, const SkNx& b) { return SkTMin(a.fVal, b.fVal); }
+    static SkNx Max(const SkNx& a, const SkNx& b) { return SkTMax(a.fVal, b.fVal); }
 
     SkNx abs() const { return SkTAbs(fVal); }
 
-    SkNx  sqrt () const { return SkNx(Sqrt(fVal)); }
-    SkNx rsqrt0() const { return this->sqrt().invert();  }
+    SkNx  sqrt () const { return Sqrt(fVal); }
+    SkNx rsqrt0() const { return this->sqrt().invert(); }
     SkNx rsqrt1() const { return this->rsqrt0(); }
     SkNx rsqrt2() const { return this->rsqrt1(); }
 
-    SkNx       invert() const { return SkNx(1) / SkNx(fVal); }
-    SkNx approxInvert() const { return this->invert();    }
+    SkNx       invert() const { return 1 / fVal; }
+    SkNx approxInvert() const { return this->invert(); }
 
-    template <int k> T kth() const {
+    T operator[](int k) const {
         SkASSERT(0 == k);
         return fVal;
     }
 
+    template <int k> T kth() const { return (*this)[k]; }
+
     bool allTrue() const { return fVal != 0; }
     bool anyTrue() const { return fVal != 0; }
     SkNx thenElse(const SkNx& t, const SkNx& e) const { return fVal != 0 ? t : e; }
 
 protected:
     static double Sqrt(double val) { return ::sqrt (val); }
     static float  Sqrt(float  val) { return ::sqrtf(val); }
 
     T fVal;
 };
 
-// This default implementation can be specialized by ../opts/SkNx_foo.h
-// if there's a better platform-specific shuffle strategy.
-template <typename Nx, int... Ix>
-inline Nx SkNx_shuffle_impl(const Nx& src) { return Nx( src.template kth<Ix>()... ); }
+// This generic shuffle can be called to create any valid SkNx<N,T>.
+//     Sk4f f(a,b,c,d);
+//     Sk2f t = SkNx_shuffle<2,1>(f);  // ~~~> Sk2f(c,b)
+//     f = SkNx_shuffle<0,1,1,0>(t);   // ~~~> Sk4f(c,b,b,c)
+template <int... Ix, int N, typename T>
+static inline SkNx<sizeof...(Ix), T> SkNx_shuffle(const SkNx<N,T>& src) { return { src[Ix]... }; }
 
-// This generic shuffle can be called with 1 or N indices:
-//     Sk4f f(a,b,c,d);
-//     SkNx_shuffle<3>(f);        // ~~~> Sk4f(d,d,d,d)
-//     SkNx_shuffle<2,1,0,3>(f);  // ~~~> Sk4f(c,b,a,d)
-template <int... Ix, typename Nx>
-inline Nx SkNx_shuffle(const Nx& src) { return SkNx_shuffle_impl<Nx, Ix...>(src); }
-
-// A reminder alias that shuffles can be used to duplicate a single index across a vector.
-template <int Ix, typename Nx>
-inline Nx SkNx_dup(const Nx& src) { return SkNx_shuffle<Ix>(src); }
-
-// This is a poor-man's std::make_index_sequence from C++14.
-// I'd implement it fully, but it hurts my head.
-template <int...> struct SkIntSequence {};
-template <int N> struct MakeSkIntSequence;
-template <> struct MakeSkIntSequence< 1> : SkIntSequence<0                                    >{};
-template <> struct MakeSkIntSequence< 2> : SkIntSequence<0,1                                  >{};
-template <> struct MakeSkIntSequence< 4> : SkIntSequence<0,1,2,3                              >{};
-template <> struct MakeSkIntSequence< 8> : SkIntSequence<0,1,2,3,4,5,6,7                      >{};
-template <> struct MakeSkIntSequence<16> : SkIntSequence<0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15>{};
-
-// This is the default/fallback implementation for SkNx_cast.  Best to specialize SkNx_cast!
-template <typename D, typename S, int N, int... Ix>
-SkNx<N,D> SkNx_cast_fallback(const SkNx<N,S>& src, SkIntSequence<Ix...>) {
-    return SkNx<N,D>( (D)src.template kth<Ix>()... );
+// This is a generic cast between two SkNx with the same number of elements N.  E.g.
+//   Sk4b bs = ...;                     // Load 4 bytes.
+//   Sk4f fs = SkNx_cast<float>(bs);    // Cast each byte to a float.
+//   Sk4h hs = SkNx_cast<uint16_t>(fs); // Cast each float to uint16_t.
+template <typename D, typename S>
+static inline SkNx<2,D> SkNx_cast(const SkNx<2,S>& src) {
+    return { (D)src[0], (D)src[1] };
 }
 
-// This is a generic cast between two SkNx with the same number of elements N.  E.g.
-//   Sk4b bs = ...;                    // Load 4 bytes.
-//   Sk4f fs = SkNx_cast<float>(bs);   // Cast each byte to a float.
-//   Sk4i is = SkNx_cast<int>(fs);     // Cast each float to int.
-// This can be specialized in ../opts/SkNx_foo.h if there's a better platform-specific cast.
-template <typename D, typename S, int N>
-SkNx<N,D> SkNx_cast(const SkNx<N,S>& src) {
-    return SkNx_cast_fallback<D,S,N>(src, MakeSkIntSequence<N>());
+template <typename D, typename S>
+static inline SkNx<4,D> SkNx_cast(const SkNx<4,S>& src) {
+    return { (D)src[0], (D)src[1], (D)src[2], (D)src[3] };
 }
 
-}  // namespace
+template <typename D, typename S>
+static inline SkNx<8,D> SkNx_cast(const SkNx<8,S>& src) {
+    return { (D)src[0], (D)src[1], (D)src[2], (D)src[3],
+             (D)src[4], (D)src[5], (D)src[6], (D)src[7] };
+}
 
-typedef SkNx<2, float> Sk2f;
-typedef SkNx<4, float> Sk4f;
-typedef SkNx<8, float> Sk8f;
+template <typename D, typename S>
+static inline SkNx<16,D> SkNx_cast(const SkNx<16,S>& src) {
+    return { (D)src[ 0], (D)src[ 1], (D)src[ 2], (D)src[ 3],
+             (D)src[ 4], (D)src[ 5], (D)src[ 6], (D)src[ 7],
+             (D)src[ 8], (D)src[ 9], (D)src[10], (D)src[11],
+             (D)src[12], (D)src[13], (D)src[14], (D)src[15] };
+}
 
-typedef SkNx<2, double> Sk2d;
-typedef SkNx<4, double> Sk4d;
-typedef SkNx<8, double> Sk8d;
+typedef SkNx<2,     float> Sk2f;
+typedef SkNx<4,     float> Sk4f;
+typedef SkNx<2,  SkScalar> Sk2s;
+typedef SkNx<4,  SkScalar> Sk4s;
 
-typedef SkNx<2, SkScalar> Sk2s;
-typedef SkNx<4, SkScalar> Sk4s;
-typedef SkNx<8, SkScalar> Sk8s;
-
-typedef SkNx< 4, uint16_t> Sk4h;
-typedef SkNx< 8, uint16_t> Sk8h;
+typedef SkNx<4,   uint8_t> Sk4b;
+typedef SkNx<16,  uint8_t> Sk16b;
+typedef SkNx<4,  uint16_t> Sk4h;
 typedef SkNx<16, uint16_t> Sk16h;
 
-typedef SkNx< 4, uint8_t>  Sk4b;
-typedef SkNx< 8, uint8_t>  Sk8b;
-typedef SkNx<16, uint8_t>  Sk16b;
-
-typedef SkNx<4, int> Sk4i;
-
 // Include platform specific specializations if available.
 #if !defined(SKNX_NO_SIMD) && SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
     #include "../opts/SkNx_sse.h"
 #elif !defined(SKNX_NO_SIMD) && defined(SK_ARM_HAS_NEON)
     #include "../opts/SkNx_neon.h"
 #else
     static inline
     void Sk4f_ToBytes(uint8_t p[16], const Sk4f& a, const Sk4f& b, const Sk4f& c, const Sk4f& d) {
         SkNx_cast<uint8_t>(a).store(p+ 0);
         SkNx_cast<uint8_t>(b).store(p+ 4);
         SkNx_cast<uint8_t>(c).store(p+ 8);
         SkNx_cast<uint8_t>(d).store(p+12);
     }
 #endif
 
-#undef REQUIRE
-
-
 #endif//SkNx_DEFINED