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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/20240812170229.229380-1-visitorckw@gmail.com Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com> Cc: Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
18 lines
338 B
C
18 lines
338 B
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/bcd.h>
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#include <linux/export.h>
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unsigned _bcd2bin(unsigned char val)
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{
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return (val & 0x0f) + (val >> 4) * 10;
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}
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EXPORT_SYMBOL(_bcd2bin);
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unsigned char _bin2bcd(unsigned val)
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{
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const unsigned int t = (val * 103) >> 10;
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return (t << 4) | (val - t * 10);
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}
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EXPORT_SYMBOL(_bin2bcd);
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