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lib: vsprintf: optimize division by 10 for small integers
Shrink the reciprocal approximations used in put_dec_full4() based on the comments in put_dec_full9(). Signed-off-by: George Spelvin <linux@horizon.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Michal Nazarewicz <mina86@mina86.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -243,13 +243,14 @@ char *put_dec(char *buf, unsigned long long n)
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/* Second algorithm: valid only for 64-bit long longs */
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/* Second algorithm: valid only for 64-bit long longs */
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/* See comment in put_dec_full9 for choice of constants */
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static noinline_for_stack
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static noinline_for_stack
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char *put_dec_full4(char *buf, unsigned q)
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char *put_dec_full4(char *buf, unsigned q)
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{
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{
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unsigned r;
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unsigned r;
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r = (q * 0xcccd) >> 19;
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r = (q * 0xccd) >> 15;
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*buf++ = (q - 10 * r) + '0';
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*buf++ = (q - 10 * r) + '0';
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q = (r * 0x199a) >> 16;
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q = (r * 0xcd) >> 11;
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*buf++ = (r - 10 * q) + '0';
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*buf++ = (r - 10 * q) + '0';
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r = (q * 0xcd) >> 11;
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r = (q * 0xcd) >> 11;
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*buf++ = (q - 10 * r) + '0';
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*buf++ = (q - 10 * r) + '0';
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