[opt] Add simplification for division by a bounded set of constants.#4101
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[opt] Add simplification for division by a bounded set of constants.#4101copybara-service[bot] wants to merge 1 commit intomainfrom
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When a division's divisor is known to take values only from a small set of constants (or even a large set, if almost all of them are powers of two), we replace the expensive variable-divisor division with a select tree over constant divisions. This avoids expensive hardware dividers by allowing subsequent passes to reduce the constant divisions into multiplications or shifts. This provides a significant area and/or latency win for cases where the set of possible divisors is small - and gives us more opportunity to let users express division naturally without getting a full hardware divider. PiperOrigin-RevId: 896714610
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[opt] Add simplification for division by a bounded set of constants.
When a division's divisor is known to take values only from a small set of constants (or even a large set, if almost all of them are powers of two), we replace the expensive variable-divisor division with a select tree over constant divisions. This avoids expensive hardware dividers by allowing subsequent passes to reduce the constant divisions into multiplications or shifts.
This provides a significant area and/or latency win for cases where the set of possible divisors is small - and gives us more opportunity to let users express division naturally without getting a full hardware divider.