[ Upstream commit cbf164cd44e06c78938b4a4a4479d3541779c319 ] The original _bin2bcd() function used / 10 and % 10 operations for conversion. Although GCC optimizes these operations and does not generate division or modulus instructions, the new implementation reduces the number of mov instructions in the generated code for both x86-64 and ARM architectures.
This optimization calculates the tens digit using (val * 103) >> 10, which is accurate for values of 'val' in the range [0, 178]. Given that the valid input range is [0, 99], this method ensures correctness while simplifying the generated code. Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Kuan-Wei Chiu <[email protected]> Cc: Ching-Chun (Jim) Huang <[email protected]> Signed-off-by: Andrew Morton <[email protected]> [[email protected]: Adapt to bin2bcd() in include/bcd.h] Signed-off-by: Kuan-Wei Chiu <[email protected]> --- include/bcd.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/bcd.h b/include/bcd.h index 9ecd328284e..289810b99b7 100644 --- a/include/bcd.h +++ b/include/bcd.h @@ -17,7 +17,9 @@ static inline unsigned int bcd2bin(unsigned int val) static inline unsigned int bin2bcd(unsigned int val) { - return (((val / 10) << 4) | (val % 10)); + const unsigned int t = (val * 103) >> 10; + + return (t << 4) | (val - t * 10); } #endif /* _BCD_H */ -- 2.52.0.239.gd5f0c6e74e-goog
