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Cycles: Add utility function to convert float to half 

handles overflow and underflow, but not NaN/inf.
This commit is contained in:
Sergey Sharybin 2017-02-23 14:42:06 +01:00
parent 9eb647f1c8
commit 13e075600a
1 changed files with 22 additions and 0 deletions
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22
intern/cycles/util/util_half.h
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@ -110,6 +110,28 @@ ccl_device_inline float4 half4_to_float4(half4 h)
return f;
}
ccl_device_inline half float_to_half(float f)
{
const uint u = __float_as_uint(f);
/* Sign bit, shifted to it's position. */
uint sign_bit = u & 0x80000000;
sign_bit >>= 16;
/* Exponent. */
uint exponent_bits = u & 0x7f800000;
/* Non-sign bits. */
uint value_bits = u & 0x7fffffff;
value_bits >>= 13; /* Align mantissa on MSB. */
value_bits -= 0x1c000; /* Adjust bias. */
/* Flush-to-zero. */
value_bits = (exponent_bits < 0x38800000) ? 0 : value_bits;
/* Clamp-to-max. */
value_bits = (exponent_bits > 0x47000000) ? 0x7bff : value_bits;
/* Denormals-as-zero. */
value_bits = (exponent_bits == 0 ? 0 : value_bits);
/* Re-insert sign bit and return. */
return (value_bits | sign_bit);
}
#endif
#endif