Desktop GPUs commonly have support for float64, and it's accessible in GLSL (how else would you use it?) and presumably HLSL. The data types are prefixed with

Desktop GPUs commonly have support for float64, and it's accessible in GLSL (how else would you use it?) and presumably HLSL. The data types are prefixed with "d", so you have vec4 for float[4], and dvec4 for double[4].