[Mesa-dev] [PATCH 7/8] i965/vec4: Allow constant propagation of VF immediates.

[Matt Turner]

On 12/22/14, Ian Romanick <idr at freedesktop.org> wrote:
> On 12/21/2014 03:24 PM, Matt Turner wrote:
>> +      } else if (value.type == BRW_REGISTER_TYPE_VF) {
>> +         value.fixed_hw_reg.dw1.ud &= ~0x80808080;
>
> What's the magic constant?  Sign bits of all the vector float values?

Yes. The 32-bit VF immediate consists of 4 8-bit restricted floats,
where each restricted float is 1 sign bit, 3 exponent bits, and 4
mantissa bits.