f16<->f32 ftz is an optional thing for speed.

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 "SkAutoPixmapStorage.h"
 #include "SkColor.h"
@@ skipping 52 matching lines @@
     return (h & 0x7c00) != 0x7c00;
 }
 
 DEF_TEST(SkHalfToFloat_finite_ftz, r) {
     for (uint32_t h = 0; h <= 0xffff; h++) {
         if (!is_finite(h)) {
             // _finite_ftz() only works for values that can be represented as a finite half float.
             continue;
         }
 
-        // _finite_ftz() flushes denorms to zero.  0.0f will compare == with both +0.0f and -0.0f.
-        float expected = is_denorm(h) ? 0.0f : SkHalfToFloat(h);
+        // _finite_ftz() may flush denorms to zero.  0.0f will compare == with both +0.0f and -0.0f.
+        float expected  = SkHalfToFloat(h),
+              alternate = is_denorm(h) ? 0.0f : expected;
 
-        REPORTER_ASSERT(r, SkHalfToFloat_finite_ftz(h)[0] == expected);
+        float actual = SkHalfToFloat_finite_ftz(h)[0];
+
+        REPORTER_ASSERT(r, actual == expected || actual == alternate);
     }
 }
 
 DEF_TEST(SkFloatToHalf_finite_ftz, r) {
 #if 0
     for (uint64_t bits = 0; bits <= 0xffffffff; bits++) {
 #else
     SkRandom rand;
     for (int i = 0; i < 1000000; i++) {
         uint32_t bits = rand.nextU();
 #endif
         float f;
         memcpy(&f, &bits, 4);
 
         uint16_t expected = SkFloatToHalf(f);
         if (!is_finite(expected)) {
             // _finite_ftz() only works for values that can be represented as a finite half float.
             continue;
         }
 
+        uint16_t alternate = expected;
         if (is_denorm(expected)) {
-            // _finite_ftz() flushes denorms to zero, and happens to keep the sign bit.
-            expected = signbit(f) ? 0x8000 : 0x0000;
+            // _finite_ftz() may flush denorms to zero, and happens to keep the sign bit.
+            alternate = signbit(f) ? 0x8000 : 0x0000;
         }
 
         uint16_t actual = SkFloatToHalf_finite_ftz(Sk4f{f})[0];
-        // _finite_ftz() truncates instead of rounding, so it may be one too small.
-        REPORTER_ASSERT(r, actual == expected || actual == expected - 1);
+        // _finite_ftz() may truncate instead of rounding, so it may be one too small.
+        REPORTER_ASSERT(r, actual == expected  || actual == expected  - 1 ||
+                           actual == alternate || actual == alternate - 1);
     }
 }