new version of SkHalfToFloat_01

tests/Float16Test.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Test.h"
 #include "SkColor.h"
 #include "SkHalf.h"
@@ skipping 48 matching lines @@
 
     uint16_t hscratch[7];
     SkOpts::float_to_half(hscratch, fs, 7);
     REPORTER_ASSERT(reporter, 0 == memcmp(hscratch, hs, sizeof(hs)));
 
     float fscratch[7];
     SkOpts::half_to_float(fscratch, hs, 7);
     REPORTER_ASSERT(reporter, 0 == memcmp(fscratch, fs, sizeof(fs)));
 }
 
+static uint32_t u(float f) {
+    uint32_t x;
+    memcpy(&x, &f, 4);
+    return x;
+}
+
 DEF_TEST(HalfToFloat_01, r) {
     for (uint16_t h = 0; h < 0x8000; h++) {
         float f = SkHalfToFloat(h);
         if (f >= 0 && f <= 1) {
+            float got = SkHalfToFloat_01(h)[0];
+            if (got != f) {
+                SkDebugf("0x%04x -> 0x%08x (%g), want 0x%08x (%g)\n",
+                        h,
+                        u(got), got,
+                        u(f), f);
+            }
             REPORTER_ASSERT(r, SkHalfToFloat_01(h)[0] == f);
             REPORTER_ASSERT(r, SkFloatToHalf_01(SkHalfToFloat_01(h)) == h);
         }
     }
 }
 
 DEF_TEST(FloatToHalf_01, r) {
 #if 0
     for (uint32_t bits = 0; bits < 0x80000000; bits++) {
 #else
     SkRandom rand;
     for (int i = 0; i < 1000000; i++) {
         uint32_t bits = rand.nextU();
 #endif
         float f;
         memcpy(&f, &bits, 4);
         if (f >= 0 && f <= 1) {
             uint16_t h1 = (uint16_t)SkFloatToHalf_01(Sk4f(f,0,0,0)),
                      h2 = SkFloatToHalf(f);
             bool ok = (h1 == h2 || h1 == h2-1);
             REPORTER_ASSERT(r, ok);
             if (!ok) {
                 SkDebugf("%08x (%d) -> %04x (%d), want %04x (%d)\n",
                          bits, bits>>23, h1, h1>>10, h2, h2>>10);
                 break;
             }
         }
     }
 }