mirror of https://github.com/torvalds/linux.git
123 lines
3.0 KiB
C
123 lines
3.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (c) 2024-2025, NVIDIA CORPORATION & AFFILIATES
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*
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* Helper macros for working with log2 values
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*
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*/
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#ifndef __GENERIC_PT_LOG2_H
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#define __GENERIC_PT_LOG2_H
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#include <linux/bitops.h>
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#include <linux/limits.h>
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/* Compute a */
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#define log2_to_int_t(type, a_lg2) ((type)(((type)1) << (a_lg2)))
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static_assert(log2_to_int_t(unsigned int, 0) == 1);
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/* Compute a - 1 (aka all low bits set) */
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#define log2_to_max_int_t(type, a_lg2) ((type)(log2_to_int_t(type, a_lg2) - 1))
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/* Compute a / b */
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#define log2_div_t(type, a, b_lg2) ((type)(((type)a) >> (b_lg2)))
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static_assert(log2_div_t(unsigned int, 4, 2) == 1);
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/*
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* Compute:
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* a / c == b / c
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* aka the high bits are equal
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*/
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#define log2_div_eq_t(type, a, b, c_lg2) \
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(log2_div_t(type, (a) ^ (b), c_lg2) == 0)
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static_assert(log2_div_eq_t(unsigned int, 1, 1, 2));
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/* Compute a % b */
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#define log2_mod_t(type, a, b_lg2) \
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((type)(((type)a) & log2_to_max_int_t(type, b_lg2)))
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static_assert(log2_mod_t(unsigned int, 1, 2) == 1);
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/*
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* Compute:
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* a % b == b - 1
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* aka the low bits are all 1s
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*/
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#define log2_mod_eq_max_t(type, a, b_lg2) \
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(log2_mod_t(type, a, b_lg2) == log2_to_max_int_t(type, b_lg2))
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static_assert(log2_mod_eq_max_t(unsigned int, 3, 2));
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/*
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* Return a value such that:
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* a / b == ret / b
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* ret % b == val
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* aka set the low bits to val. val must be < b
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*/
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#define log2_set_mod_t(type, a, val, b_lg2) \
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((((type)(a)) & (~log2_to_max_int_t(type, b_lg2))) | ((type)(val)))
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static_assert(log2_set_mod_t(unsigned int, 3, 1, 2) == 1);
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/* Return a value such that:
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* a / b == ret / b
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* ret % b == b - 1
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* aka set the low bits to all 1s
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*/
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#define log2_set_mod_max_t(type, a, b_lg2) \
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(((type)(a)) | log2_to_max_int_t(type, b_lg2))
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static_assert(log2_set_mod_max_t(unsigned int, 2, 2) == 3);
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/* Compute a * b */
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#define log2_mul_t(type, a, b_lg2) ((type)(((type)a) << (b_lg2)))
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static_assert(log2_mul_t(unsigned int, 2, 2) == 8);
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#define _dispatch_sz(type, fn, a) \
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(sizeof(type) == 4 ? fn##32((u32)a) : fn##64(a))
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/*
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* Return the highest value such that:
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* fls_t(u32, 0) == 0
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* fls_t(u3, 1) == 1
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* a >= log2_to_int(ret - 1)
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* aka find last set bit
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*/
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static inline unsigned int fls32(u32 a)
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{
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return fls(a);
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}
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#define fls_t(type, a) _dispatch_sz(type, fls, a)
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/*
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* Return the highest value such that:
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* ffs_t(u32, 0) == UNDEFINED
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* ffs_t(u32, 1) == 0
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* log_mod(a, ret) == 0
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* aka find first set bit
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*/
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static inline unsigned int __ffs32(u32 a)
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{
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return __ffs(a);
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}
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#define ffs_t(type, a) _dispatch_sz(type, __ffs, a)
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/*
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* Return the highest value such that:
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* ffz_t(u32, U32_MAX) == UNDEFINED
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* ffz_t(u32, 0) == 0
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* ffz_t(u32, 1) == 1
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* log_mod(a, ret) == log_to_max_int(ret)
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* aka find first zero bit
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*/
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static inline unsigned int ffz32(u32 a)
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{
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return ffz(a);
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}
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static inline unsigned int ffz64(u64 a)
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{
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if (sizeof(u64) == sizeof(unsigned long))
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return ffz(a);
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if ((u32)a == U32_MAX)
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return ffz32(a >> 32) + 32;
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return ffz32(a);
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}
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#define ffz_t(type, a) _dispatch_sz(type, ffz, a)
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#endif
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