1 /*
2 * Copyright 2016 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "src/base/SkHalf.h"
9 #include "src/base/SkRandom.h"
10 #include "src/base/SkVx.h"
11 #include "tests/Test.h"
12
13 #include <cmath>
14 #include <cstdint>
15 #include <cstring>
16
is_denorm(uint16_t h)17 static bool is_denorm(uint16_t h) {
18 return (h & 0x7fff) < 0x0400;
19 }
20
is_finite(uint16_t h)21 static bool is_finite(uint16_t h) {
22 return (h & 0x7c00) != 0x7c00;
23 }
24
DEF_TEST(SkHalfToFloat_finite_ftz,r)25 DEF_TEST(SkHalfToFloat_finite_ftz, r) {
26 for (uint32_t h = 0; h <= 0xffff; h++) {
27 if (!is_finite(h)) {
28 // _finite_ftz() only works for values that can be represented as a finite half float.
29 continue;
30 }
31
32 // _finite_ftz() may flush denorms to zero. 0.0f will compare == with both +0.0f and -0.0f.
33 float expected = SkHalfToFloat(h),
34 alternate = is_denorm(h) ? 0.0f : expected;
35
36 float actual = SkHalfToFloat_finite_ftz(h)[0];
37
38 REPORTER_ASSERT(r, actual == expected || actual == alternate);
39 }
40 }
41
DEF_TEST(SkFloatToHalf_finite_ftz,r)42 DEF_TEST(SkFloatToHalf_finite_ftz, r) {
43 #if 0
44 for (uint64_t bits = 0; bits <= 0xffffffff; bits++) {
45 #else
46 SkRandom rand;
47 for (int i = 0; i < 1000000; i++) {
48 uint32_t bits = rand.nextU();
49 #endif
50 float f;
51 memcpy(&f, &bits, 4);
52
53 uint16_t expected = SkFloatToHalf(f);
54 if (!is_finite(expected)) {
55 // _finite_ftz() only works for values that can be represented as a finite half float.
56 continue;
57 }
58
59 uint16_t alternate = expected;
60 if (is_denorm(expected)) {
61 // _finite_ftz() may flush denorms to zero, and happens to keep the sign bit.
62 alternate = std::signbit(f) ? 0x8000 : 0x0000;
63 }
64
65 uint16_t actual = SkFloatToHalf_finite_ftz(skvx::float4{f})[0];
66 // _finite_ftz() may truncate instead of rounding, so it may be one too small.
67 REPORTER_ASSERT(r, actual == expected || actual == expected - 1 ||
68 actual == alternate || actual == alternate - 1);
69 }
70 }
71