Potentially significant, since they add new types and control structures. The new types inform the optimizer if data is local to SIMD computations or not, can o

Potentially significant, since they add new types and control structures. The new types inform the optimizer if data is local to SIMD computations or not, can optimize memory layout for SIMD computations, and the control structures allow for converged control-flow at runtime where only one branch is taken by all threads. See the full paper I link to as a top-level comment for more details.