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When the divisor is a constant value, we can emit more efficient code. For powers of two, we can use bit shifts. For other values, we can instead use a multiplication by magic constant method. - Example 1 - Division by 16 (power of two) Before: mov w24, #0x10 ; =16 udiv w27, w25, w24 After: lsr w27, w25, #4 - Example 2 - Division by 10 (fast) Before: mov w25, #0xa ; =10 udiv w27, w26, w25 After: mov w27, #0xcccd ; =52429 movk w27, #0xcccc, lsl #16 umull x27, w26, w27 lsr x27, x27, #35 - Example 3 - Division by 127 (slow) Before: mov w26, #0x7f ; =127 udiv w27, w27, w26 After: mov w26, #0x408 ; =1032 movk w26, #0x8102, lsl #16 umaddl x27, w27, w26, x26 lsr x27, x27, #38