Decode the three VOP3 16-bit interpolation instructions (attribute, channel
and high-half select in the src0 field, the I/J VGPR in src1, P0 or the first
step's result in src2) and translate them with a new
GetInterpolationParameterF16 IR value. It reads the selected 16-bit half of
each vertex's parameter through VK_KHR_fragment_shader_barycentric, so P10 and
P20 are vertex differences rounded to f16; both steps are a multiply and an
add, as in the f32 forms.
An input in FP16_INTERP_MODE whose low half is defaulted is still declared at
its slot when its high half is read, and the high half takes its default from
USE_DEFAULT_ATTR1 and DEFAULT_VAL_ATTR1. Without barycentrics, on an input
without FP16_INTERP_MODE or on a pass-through input the instructions throw.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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