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authorMarek Olšák <[email protected]>2018-02-13 16:02:14 +0100
committerMarek Olšák <[email protected]>2018-07-31 18:09:57 -0400
commit38ab39f6501f78ea7048e8a16a97fdb075b9d8c7 (patch)
tree8c1166d4d47c30d4e2a1316f62fa33e971c69bb6 /src/util
parent5be352b4303a759c8ebbbd047365e94f66a098f0 (diff)
mesa: add ASTC 2D LDR decoder
Tested-by: Mike Lothian <[email protected]> Tested-By: Gert Wollny <[email protected]> Tested-by: Dieter Nützel <[email protected]>
Diffstat (limited to 'src/util')
-rw-r--r--src/util/half_float.c59
-rw-r--r--src/util/half_float.h5
2 files changed, 64 insertions, 0 deletions
diff --git a/src/util/half_float.c b/src/util/half_float.c
index 4df64c2ccf9..588f050d924 100644
--- a/src/util/half_float.c
+++ b/src/util/half_float.c
@@ -2,6 +2,8 @@
* Mesa 3-D graphics library
*
* Copyright (C) 1999-2007 Brian Paul All Rights Reserved.
+ * Copyright 2015 Philip Taylor <[email protected]>
+ * Copyright 2018 Advanced Micro Devices, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
@@ -175,3 +177,60 @@ _mesa_half_to_float(uint16_t val)
result = fi.f;
return result;
}
+
+/**
+ * Convert 0.0 to 0x00, 1.0 to 0xff.
+ * Values outside the range [0.0, 1.0] will give undefined results.
+ */
+uint8_t _mesa_half_to_unorm8(uint16_t val)
+{
+ const int m = val & 0x3ff;
+ const int e = (val >> 10) & 0x1f;
+ const int s = (val >> 15) & 0x1;
+
+ /* v = round_to_nearest(1.mmmmmmmmmm * 2^(e-15) * 255)
+ * = round_to_nearest((1.mmmmmmmmmm * 255) * 2^(e-15))
+ * = round_to_nearest((1mmmmmmmmmm * 255) * 2^(e-25))
+ * = round_to_zero((1mmmmmmmmmm * 255) * 2^(e-25) + 0.5)
+ * = round_to_zero(((1mmmmmmmmmm * 255) * 2^(e-24) + 1) / 2)
+ *
+ * This happens to give the correct answer for zero/subnormals too
+ */
+ assert(s == 0 && val <= FP16_ONE); /* check 0 <= this <= 1 */
+ /* (implies e <= 15, which means the bit-shifts below are safe) */
+
+ uint32_t v = ((1 << 10) | m) * 255;
+ v = ((v >> (24 - e)) + 1) >> 1;
+ return v;
+}
+
+/**
+ * Takes a uint16_t, divides by 65536, converts the infinite-precision
+ * result to fp16 with round-to-zero. Used by the ASTC decoder.
+ */
+uint16_t _mesa_uint16_div_64k_to_half(uint16_t v)
+{
+ /* Zero or subnormal. Set the mantissa to (v << 8) and return. */
+ if (v < 4)
+ return v << 8;
+
+ /* Count the leading 0s in the uint16_t */
+ int n = __builtin_clz(v) - (sizeof(unsigned int) - sizeof(uint16_t)) * 8;
+
+ /* Shift the mantissa up so bit 16 is the hidden 1 bit,
+ * mask it off, then shift back down to 10 bits
+ */
+ int m = ( ((uint32_t)v << (n + 1)) & 0xffff ) >> 6;
+
+ /* (0{n} 1 X{15-n}) * 2^-16
+ * = 1.X * 2^(15-n-16)
+ * = 1.X * 2^(14-n - 15)
+ * which is the FP16 form with e = 14 - n
+ */
+ int e = 14 - n;
+
+ assert(e >= 1 && e <= 30);
+ assert(m >= 0 && m < 0x400);
+
+ return (e << 10) | m;
+}
diff --git a/src/util/half_float.h b/src/util/half_float.h
index b3bc3f687ad..01557424735 100644
--- a/src/util/half_float.h
+++ b/src/util/half_float.h
@@ -32,8 +32,13 @@
extern "C" {
#endif
+#define FP16_ONE 0x3C00
+#define FP16_ZERO 0
+
uint16_t _mesa_float_to_half(float val);
float _mesa_half_to_float(uint16_t val);
+uint8_t _mesa_half_to_unorm8(uint16_t v);
+uint16_t _mesa_uint16_div_64k_to_half(uint16_t v);
static inline bool
_mesa_half_is_negative(uint16_t h)