SkHalfToFloat_01 / SkFloatToHalf_01
These are basically inlined, 4-at-a-time versions of our existing functions,
but cut down to avoid any work that's only necessary outside [0,1].
Both f16 and f32 denorms should work fine modulo the usual ARMv7 NEON denorm==zero caveat.
In exchange for a little speed, f32->f16 does not round properly.
Instead it truncates, so it's never off by more than 1 bit.
Support for finite values >1 or <0 is straightforward to add back.
>1 might already work as-is.
Getting close to _u16 performance:
micros bench
261.13 xferu64_bw_1_opaque_u16
1833.51 xferu64_bw_1_alpha_u16
2762.32 ? xferu64_aa_1_opaque_u16
3334.29 xferu64_aa_1_alpha_u16
249.78 xferu64_bw_1_opaque_f16
3383.18 xferu64_bw_1_alpha_f16
4214.72 xferu64_aa_1_opaque_f16
4701.19 xferu64_aa_1_alpha_f16
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1685133005
Committed: https://skia.googlesource.com/skia/+/9ea11a4235b3e3521cc8bf914a27c2d0dc062db9
CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot
Review URL: https://codereview.chromium.org/1685133005
diff --git a/tests/Float16Test.cpp b/tests/Float16Test.cpp
index f437268..f96d904 100644
--- a/tests/Float16Test.cpp
+++ b/tests/Float16Test.cpp
@@ -10,6 +10,7 @@
#include "SkHalf.h"
#include "SkOpts.h"
#include "SkPixmap.h"
+#include "SkRandom.h"
static bool eq_within_half_float(float a, float b) {
const float kTolerance = 1.0f / (1 << (8 + 10));
@@ -64,3 +65,37 @@
SkOpts::half_to_float(fscratch, hs, 7);
REPORTER_ASSERT(reporter, 0 == memcmp(fscratch, fs, sizeof(fs)));
}
+
+DEF_TEST(HalfToFloat_01, r) {
+ for (uint16_t h = 0; h < 0x8000; h++) {
+ float f = SkHalfToFloat(h);
+ if (f >= 0 && f <= 1) {
+ 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;
+ }
+ }
+ }
+}