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Real-time integer division in the ARM libraries

The division routine supplied with the ARM libraries provides good overall performance. However, the amount of time required to perform a division depends on the input values. For example, a division that generates a four-bit quotient might require only 12 cycles while a 32-bit quotient might require 96 cycles. Depending on your target, some applications require a faster worst-case cycle count at the expense of lower average performance. For this reason, the ARM library provides two divide routines.

The real-time routine:

  • always executes in fewer than 45 cycles

  • is faster than the standard division routine for larger quotients

  • is slower than the standard division routine for typical quotients

  • returns the same results

  • does not require any change in the surrounding code.

Note

  • Real-time division is not available in the libraries for Cortex-M1 or Cortex-M0.

  • The Cortex-R4 and Cortex-M3 processors support hardware floating-point divide, so they do not require the library divide routines.