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71 lines
1.9 KiB
C
71 lines
1.9 KiB
C
/* ffs -- find first set bit in a word, counted from least significant end.
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S/390 version.
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Copyright (C) 2000-2020 Free Software Foundation, Inc.
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Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <limits.h>
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#define ffsl __something_else
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#include <string.h>
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#undef ffs
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/* ffs: find first bit set. This is defined the same way as
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the libc and compiler builtin ffs routines, therefore
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differs in spirit from the above ffz (man ffs). */
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int
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__ffs (int x)
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{
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int r;
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if (x == 0)
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return 0;
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__asm__(" lr %%r1,%1\n"
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" sr %0,%0\n"
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" tml %%r1,0xFFFF\n"
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" jnz 0f\n"
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" ahi %0,16\n"
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" srl %%r1,16\n"
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"0: tml %%r1,0x00FF\n"
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" jnz 1f\n"
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" ahi %0,8\n"
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" srl %%r1,8\n"
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"1: tml %%r1,0x000F\n"
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" jnz 2f\n"
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" ahi %0,4\n"
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" srl %%r1,4\n"
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"2: tml %%r1,0x0003\n"
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" jnz 3f\n"
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" ahi %0,2\n"
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" srl %%r1,2\n"
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"3: tml %%r1,0x0001\n"
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" jnz 4f\n"
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" ahi %0,1\n"
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"4:"
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: "=&d" (r) : "d" (x) : "cc", "1" );
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return r+1;
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}
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weak_alias (__ffs, ffs)
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libc_hidden_def (__ffs)
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libc_hidden_builtin_def (ffs)
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#if ULONG_MAX == UINT_MAX
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#undef ffsl
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weak_alias (__ffs, ffsl)
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#endif
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