ispc

Is your feature request related to a problem? Please describe

Very often, with working with conformance view, I work with different versions of the same compiler, all options are the same. Or I work with different C++ standards, with the same compiler and the same options (exception for this one). Or...

Right now, to add a new compiler in the conformance view, I have to start from an empty

varying float<3> col = { 0, 0, 0 };
uniform float <3> reduce_col;
reduce_col.x = reduce_add( col.x );
reduce_col.y = reduce_add( col.y );
reduce_col.z = reduce_add( col.z );
reduce_col.w = reduce_add( col.w );

This currently does not produce an error. I expect attempting to access the w component of a three component type to be an error.