add Min to SkNi, specialized for u8 and u16 on SSE and NEON

tests/SkNxTest.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkNx.h"
+#include "SkRandom.h"
 #include "Test.h"
 
 template <int N, typename T>
 static void test_Nf(skiatest::Reporter* r) {
 
     auto assert_nearly_eq = [&](double eps, const SkNf<N,T>& v, T a, T b, T c, T d) {
         auto close = [=](T a, T b) { return fabs(a-b) <= eps; };
         T vals[4];
         v.store(vals);
         bool ok = close(vals[0], a) && close(vals[1], b)
@@ skipping 104 matching lines @@
 
 DEF_TEST(SkNi, r) {
     test_Ni<2, uint16_t>(r);
     test_Ni<4, uint16_t>(r);
     test_Ni<8, uint16_t>(r);
 
     test_Ni<2, int>(r);
     test_Ni<4, int>(r);
     test_Ni<8, int>(r);
 }
+
+DEF_TEST(SkNi_min, r) {
+    // Exhaustively check the 8x8 bit space.
+    for (int a = 0; a < (1<<8); a++) {
+    for (int b = 0; b < (1<<8); b++) {
+        REPORTER_ASSERT(r, Sk16b::Min(Sk16b(a), Sk16b(b)).kth<0>() == SkTMin(a, b));
+    }}
+
+    // Exhausting the 16x16 bit space is kind of slow, so only do that in release builds.
+#ifdef SK_DEBUG
+    SkRandom rand;
+    for (int i = 0; i < (1<<16); i++) {
+        uint16_t a = rand.nextU() >> 16,
+                 b = rand.nextU() >> 16;
+        REPORTER_ASSERT(r, Sk8h::Min(Sk8h(a), Sk8h(b)).kth<0>() == SkTMin(a, b));
+    }
+#else
+    for (int a = 0; a < (1<<16); a++) {
+    for (int b = 0; b < (1<<16); b++) {
+        REPORTER_ASSERT(r, Sk8h::Min(Sk8h(a), Sk8h(b)).kth<0>() == SkTMin(a, b));
+    }}
+#endif
+}