93 lines
2.2 KiB
C
93 lines
2.2 KiB
C
/* v2/ffs.h - ARCv2 public nanokernel find-first-set interface */
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/*
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* Copyright (c) 2014 Wind River Systems, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*
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* DESCRIPTION
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* ARC-specific nanokernel ffs interface. Included by ARC/arch.h.
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*/
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#ifndef _ARCH_ARC_V2_FFS_H_
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#define _ARCH_ARC_V2_FFS_H_
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#ifndef _ASMLANGUAGE
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#include <stdint.h>
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/**
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*
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* @brief find most significant bit set in a 32-bit word
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*
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* This routine finds the first bit set starting from the most significant bit
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* in the argument passed in and returns the index of that bit. Bits are
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* numbered starting at 1 from the least significant bit. A return value of
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* zero indicates that the value passed is zero.
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*
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* @return most significant bit set, 0 if @a op is 0
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*/
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#if defined(__GNUC__)
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static ALWAYS_INLINE unsigned int find_msb_set(uint32_t op)
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{
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unsigned int bit;
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__asm__ volatile(
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/* see explanation in ffs.S */
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"fls.f %0, %1;\n\t"
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"add.nz %0, %0, 1;\n\t"
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: "=r"(bit)
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: "r"(op));
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return bit;
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}
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#endif
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/**
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*
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* @brief find least significant bit set in a 32-bit word
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*
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* This routine finds the first bit set starting from the least significant bit
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* in the argument passed in and returns the index of that bit. Bits are
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* numbered starting at 1 from the least significant bit. A return value of
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* zero indicates that the value passed is zero.
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*
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* @return least significant bit set, 0 if @a op is 0
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*/
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#if defined(__GNUC__)
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static ALWAYS_INLINE unsigned int find_lsb_set(uint32_t op)
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{
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unsigned int bit;
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__asm__ volatile(
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/* see explanation in ffs.S */
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"ffs.f %0, %1;\n\t"
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"add.nz %0, %0, 1;\n\t"
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"mov.z %0, 0;\n\t"
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: "=&r"(bit)
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: "r"(op));
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return bit;
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}
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#endif
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#endif /* _ASMLANGUAGE */
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#endif /* _ARCH_ARC_V2_FFS_H_ */
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