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An instruction that is "always uniform" is so even if it occurs in an irreducible cycle. The output produced by such an instruction may depend on the implementation defined cycle hierarchy, but that does not affect the uniformity of the output. In other words, an "always uniform" instruction is uniform even if it is not m-converged. Reviewed By: ruiling, ronlieb Differential Revision: https://reviews.llvm.org/D145572