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authormarha <marha@users.sourceforge.net>2012-07-02 08:47:42 +0200
committermarha <marha@users.sourceforge.net>2012-07-02 08:47:42 +0200
commitfdef5bff99e6079f64bc6b91c91b42195c85adeb (patch)
tree5d9c311d9f36cfa26850d02801388953ccc17b54 /mesalib/src/gallium/auxiliary/util/u_half.h
parentf6d1847eef027266daa0f75ee92ceb09698b2761 (diff)
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mesa pixman xserver git update 2 Jul 2012
Diffstat (limited to 'mesalib/src/gallium/auxiliary/util/u_half.h')
-rw-r--r--mesalib/src/gallium/auxiliary/util/u_half.h101
1 files changed, 67 insertions, 34 deletions
diff --git a/mesalib/src/gallium/auxiliary/util/u_half.h b/mesalib/src/gallium/auxiliary/util/u_half.h
index ad030e90c..f7009f548 100644
--- a/mesalib/src/gallium/auxiliary/util/u_half.h
+++ b/mesalib/src/gallium/auxiliary/util/u_half.h
@@ -35,51 +35,84 @@
extern "C" {
#endif
-extern const uint32_t util_half_to_float_mantissa_table[2048];
-extern const uint32_t util_half_to_float_exponent_table[64];
-extern const uint32_t util_half_to_float_offset_table[64];
-extern const uint16_t util_float_to_half_base_table[512];
-extern const uint8_t util_float_to_half_shift_table[512];
-
/*
- * Note that if the half float is a signaling NaN, the x87 FPU will turn
- * it into a quiet NaN immediately upon loading into a float.
- *
- * Additionally, denormals may be flushed to zero.
+ * References for float <-> half conversions
*
- * To avoid this, use the floatui functions instead of the float ones
- * when just doing conversion rather than computation on the resulting
- * floats.
+ * http://fgiesen.wordpress.com/2012/03/28/half-to-float-done-quic/
+ * https://gist.github.com/2156668
+ * https://gist.github.com/2144712
*/
-static INLINE uint32_t
-util_half_to_floatui(uint16_t h)
+static INLINE uint16_t
+util_float_to_half(float f)
{
- unsigned exp = h >> 10;
- return util_half_to_float_mantissa_table[util_half_to_float_offset_table[exp] + (h & 0x3ff)] + util_half_to_float_exponent_table[exp];
+ uint32_t sign_mask = 0x80000000;
+ uint32_t round_mask = ~0xfff;
+ uint32_t f32inf = 0xff << 23;
+ uint32_t f16inf = 0x1f << 23;
+ uint32_t sign;
+ union fi magic;
+ union fi f32;
+ uint16_t f16;
+
+ magic.ui = 0xf << 23;
+
+ f32.f = f;
+
+ /* Sign */
+ sign = f32.ui & sign_mask;
+ f32.ui ^= sign;
+
+ if (f32.ui == f32inf) {
+ /* Inf */
+ f16 = 0x7c00;
+ } else if (f32.ui > f32inf) {
+ /* NaN */
+ f16 = 0x7e00;
+ } else {
+ /* Number */
+ f32.ui &= round_mask;
+ f32.f *= magic.f;
+ f32.ui -= round_mask;
+
+ /* Clamp to infinity if overflowed */
+ if (f32.ui > f16inf)
+ f32.ui = f16inf;
+
+ f16 = f32.ui >> 13;
+ }
+
+ /* Sign */
+ f16 |= sign >> 16;
+
+ return f16;
}
static INLINE float
-util_half_to_float(uint16_t h)
+util_half_to_float(uint16_t f16)
{
- union fi r;
- r.ui = util_half_to_floatui(h);
- return r.f;
-}
+ union fi infnan;
+ union fi magic;
+ union fi f32;
-static INLINE uint16_t
-util_floatui_to_half(uint32_t v)
-{
- unsigned signexp = v >> 23;
- return util_float_to_half_base_table[signexp] + ((v & 0x007fffff) >> util_float_to_half_shift_table[signexp]);
-}
+ infnan.ui = 0x8f << 23;
+ infnan.f = 65536.0f;
+ magic.ui = 0xef << 23;
-static INLINE uint16_t
-util_float_to_half(float f)
-{
- union fi i;
- i.f = f;
- return util_floatui_to_half(i.ui);
+ /* Exponent / Mantissa */
+ f32.ui = (f16 & 0x7fff) << 13;
+
+ /* Adjust */
+ f32.f *= magic.f;
+
+ /* Inf / NaN */
+ if (f32.f >= infnan.f)
+ f32.ui |= 0xff << 23;
+
+ /* Sign */
+ f32.ui |= (f16 & 0x8000) << 16;
+
+ return f32.f;
}
#ifdef __cplusplus