44 lines
1.5 KiB
C
44 lines
1.5 KiB
C
/* clang-format off */
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/* ===-- ctzdi2.c - Implement __ctzdi2 -------------------------------------===
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*
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* The LLVM Compiler Infrastructure
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*
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* This file is dual licensed under the MIT and the University of Illinois Open
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* Source Licenses. See LICENSE.TXT for details.
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*
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* ===----------------------------------------------------------------------===
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*
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* This file implements __ctzdi2 for the compiler_rt library.
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*
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* ===----------------------------------------------------------------------===
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*/
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STATIC_YOINK("huge_compiler_rt_license");
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#include "third_party/compiler_rt/int_lib.h"
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/* Returns: the number of trailing 0-bits */
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#if !defined(__clang__) && \
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((defined(__sparc__) && defined(__arch64__)) || \
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defined(__mips64) || \
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(defined(__riscv) && __SIZEOF_POINTER__ >= 8))
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/* On 64-bit architectures with neither a native clz instruction nor a native
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* ctz instruction, gcc resolves __builtin_ctz to __ctzdi2 rather than
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* __ctzsi2, leading to infinite recursion. */
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#define __builtin_ctz(a) __ctzsi2(a)
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extern si_int __ctzsi2(si_int);
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#endif
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/* Precondition: a != 0 */
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COMPILER_RT_ABI si_int
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__ctzdi2(di_int a)
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{
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dwords x;
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x.all = a;
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const si_int f = -(x.s.low == 0);
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return __builtin_ctz((x.s.high & f) | (x.s.low & ~f)) +
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(f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
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}
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