32-bit ARM assembly language provided conditional execution for most instructions. This was dropped in the 64-bit instruction set. (https://en.wikipedia.org/wik

32-bit ARM assembly language provided conditional execution for most instructions. This was dropped in the 64-bit instruction set. (https://en.wikipedia.org/wiki/Predication_(computer_architecture) https://en.wikipedia.org/wiki/Predication_(computer_architec..., https://en.wikipedia.org/wiki/ARM_architecture#64-bit https://en.wikipedia.org/wiki/ARM_architecture#64-bit) I imagine the architects had a clear picture of the advantages and disadvantages, and made a very well-informed decision. I guess that part of the reason might have been that it's not clear when compilers should emit predicated code instead of branches. Also, you can get something very similar even for scalar code as long as your machine has a conditional move operation, which they all have: /* true path */ a = ... b = ... true_result = ... /* false path */ x = ... y = ... false_result = ... /* final result */ result = (condition ? true_result : false_result) This works if the two "branches" have no side effects (memory writes, function calls) and cannot raise exceptions. Again, it's very difficult to estimate for compilers (and humans) if it will pay off to run both computations rather than branch. The trade-offs for vectorization are different from scalar code since vectorizing a loop by a factor N gives a huge win, and even if you waste some time doing some redundant computations, you still have a reasonable chance of being faster than scalar.