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glsl: Add "built-in" functions to do fp64_to_uint(fp64)

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Signed-off-by: Elie Tournier <elie.tournier@collabora.com>
This commit is contained in:
Elie Tournier 2017-08-08 19:13:45 +01:00 • committed by Matt Turner
parent 4a93401546
commit a3551ee61f
1 changed files with 61 additions and 0 deletions
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61
src/compiler/glsl/float64.glsl
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@ -797,3 +797,64 @@ __fmul64(uint64_t a, uint64_t b)
}
return __roundAndPackFloat64(zSign, zExp, zFrac0, zFrac1, zFrac2);
}
/* Shifts the 64-bit value formed by concatenating `a0' and `a1' right by the
* number of bits given in `count'. Any bits shifted off are lost. The value
* of `count' can be arbitrarily large; in particular, if `count' is greater
* than 64, the result will be 0. The result is broken into two 32-bit pieces
* which are stored at the locations pointed to by `z0Ptr' and `z1Ptr'.
*/
void
__shift64Right(uint a0, uint a1,
int count,
out uint z0Ptr,
out uint z1Ptr)
{
uint z0;
uint z1;
int negCount = (-count) & 31;
z0 = 0u;
z0 = mix(z0, (a0 >> count), count < 32);
z0 = mix(z0, a0, count == 0);
z1 = mix(0u, (a0 >> (count & 31)), count < 64);
z1 = mix(z1, (a0<<negCount) | (a1>>count), count < 32);
z1 = mix(z1, a0, count == 0);
z1Ptr = z1;
z0Ptr = z0;
}
/* Returns the result of converting the double-precision floating-point value
* `a' to the unsigned integer format. The conversion is performed according
* to the IEEE Standard for Floating-Point Arithmetic.
*/
uint
__fp64_to_uint(uint64_t a)
{
uint aFracLo = __extractFloat64FracLo(a);
uint aFracHi = __extractFloat64FracHi(a);
int aExp = __extractFloat64Exp(a);
uint aSign = __extractFloat64Sign(a);
if ((aExp == 0x7FF) && ((aFracHi | aFracLo) != 0u))
return 0xFFFFFFFFu;
aFracHi |= mix(0u, 0x00100000u, aExp != 0);
int shiftDist = 0x427 - aExp;
if (0 < shiftDist)
__shift64RightJamming(aFracHi, aFracLo, shiftDist, aFracHi, aFracLo);
if ((aFracHi & 0xFFFFF000u) != 0u)
return mix(~0u, 0u, (aSign != 0u));
uint z = 0u;
uint zero = 0u;
__shift64Right(aFracHi, aFracLo, 12, zero, z);
uint expt = mix(~0u, 0u, (aSign != 0u));
return mix(z, expt, (aSign != 0u) && (z != 0u));
}