Messages in this thread | | | From | <> | Subject | .../asm-i386/bitops.h performance improvements | Date | Wed, 15 Jun 2005 04:53:12 -0400 |
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In find_first_bit() there exists this the sequence:
shll $3,%%edi addl %%edi,%%eax
LEA knows how to multiply by small powers of 2 and add all in one shot very efficiently:
leal (%%eax,%%edi,8),%%eax
In find_first_zero_bit() the sequence:
shll $3,%%edi addl %%edi,%%edx
could similarly become:
leal (%%edx,%%edi,8),%%edx
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