| #ifndef _ASM_GENERIC_DIV64_H |
| #define _ASM_GENERIC_DIV64_H |
| /* |
| * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com> |
| * Based on former asm-ppc/div64.h and asm-m68knommu/div64.h |
| * |
| * Optimization for constant divisors on 32-bit machines: |
| * Copyright (C) 2006-2015 Nicolas Pitre |
| * |
| * The semantics of do_div() are: |
| * |
| * u32 do_div(u64 *n, u32 base) |
| * { |
| * u32 remainder = *n % base; |
| * *n = *n / base; |
| * return remainder; |
| * } |
| * |
| * NOTE: macro parameter n is evaluated multiple times, |
| * beware of side effects! |
| */ |
| |
| #include <linux/types.h> |
| #include <linux/compiler.h> |
| |
| #if BITS_PER_LONG == 64 |
| |
| # define do_div(n,base) ({ \ |
| u32 __base = (base); \ |
| u32 __rem; \ |
| __rem = ((u64)(n)) % __base; \ |
| (n) = ((u64)(n)) / __base; \ |
| __rem; \ |
| }) |
| |
| #elif BITS_PER_LONG == 32 |
| |
| #include <linux/log2.h> |
| |
| /* |
| * If the divisor happens to be constant, we determine the appropriate |
| * inverse at compile time to turn the division into a few inline |
| * multiplications which ought to be much faster. And yet only if compiling |
| * with a sufficiently recent gcc version to perform proper 64-bit constant |
| * propagation. |
| * |
| * (It is unfortunate that gcc doesn't perform all this internally.) |
| */ |
| |
| #ifndef __div64_const32_is_OK |
| #define __div64_const32_is_OK (__GNUC__ >= 4) |
| #endif |
| |
| #define __div64_const32(n, ___b) \ |
| ({ \ |
| /* \ |
| * Multiplication by reciprocal of b: n / b = n * (p / b) / p \ |
| * \ |
| * We rely on the fact that most of this code gets optimized \ |
| * away at compile time due to constant propagation and only \ |
| * a few multiplication instructions should remain. \ |
| * Hence this monstrous macro (static inline doesn't always \ |
| * do the trick here). \ |
| */ \ |
| u64 ___res, ___x, ___t, ___m, ___n = (n); \ |
| u32 ___p, ___bias; \ |
| \ |
| /* determine MSB of b */ \ |
| ___p = 1 << ilog2(___b); \ |
| \ |
| /* compute m = ((p << 64) + b - 1) / b */ \ |
| ___m = (~0ULL / ___b) * ___p; \ |
| ___m += (((~0ULL % ___b + 1) * ___p) + ___b - 1) / ___b; \ |
| \ |
| /* one less than the dividend with highest result */ \ |
| ___x = ~0ULL / ___b * ___b - 1; \ |
| \ |
| /* test our ___m with res = m * x / (p << 64) */ \ |
| ___res = ((___m & 0xffffffff) * (___x & 0xffffffff)) >> 32; \ |
| ___t = ___res += (___m & 0xffffffff) * (___x >> 32); \ |
| ___res += (___x & 0xffffffff) * (___m >> 32); \ |
| ___t = (___res < ___t) ? (1ULL << 32) : 0; \ |
| ___res = (___res >> 32) + ___t; \ |
| ___res += (___m >> 32) * (___x >> 32); \ |
| ___res /= ___p; \ |
| \ |
| /* Now sanitize and optimize what we've got. */ \ |
| if (~0ULL % (___b / (___b & -___b)) == 0) { \ |
| /* special case, can be simplified to ... */ \ |
| ___n /= (___b & -___b); \ |
| ___m = ~0ULL / (___b / (___b & -___b)); \ |
| ___p = 1; \ |
| ___bias = 1; \ |
| } else if (___res != ___x / ___b) { \ |
| /* \ |
| * We can't get away without a bias to compensate \ |
| * for bit truncation errors. To avoid it we'd need an \ |
| * additional bit to represent m which would overflow \ |
| * a 64-bit variable. \ |
| * \ |
| * Instead we do m = p / b and n / b = (n * m + m) / p. \ |
| */ \ |
| ___bias = 1; \ |
| /* Compute m = (p << 64) / b */ \ |
| ___m = (~0ULL / ___b) * ___p; \ |
| ___m += ((~0ULL % ___b + 1) * ___p) / ___b; \ |
| } else { \ |
| /* \ |
| * Reduce m / p, and try to clear bit 31 of m when \ |
| * possible, otherwise that'll need extra overflow \ |
| * handling later. \ |
| */ \ |
| u32 ___bits = -(___m & -___m); \ |
| ___bits |= ___m >> 32; \ |
| ___bits = (~___bits) << 1; \ |
| /* \ |
| * If ___bits == 0 then setting bit 31 is unavoidable. \ |
| * Simply apply the maximum possible reduction in that \ |
| * case. Otherwise the MSB of ___bits indicates the \ |
| * best reduction we should apply. \ |
| */ \ |
| if (!___bits) { \ |
| ___p /= (___m & -___m); \ |
| ___m /= (___m & -___m); \ |
| } else { \ |
| ___p >>= ilog2(___bits); \ |
| ___m >>= ilog2(___bits); \ |
| } \ |
| /* No bias needed. */ \ |
| ___bias = 0; \ |
| } \ |
| \ |
| /* \ |
| * Now we have a combination of 2 conditions: \ |
| * \ |
| * 1) whether or not we need to apply a bias, and \ |
| * \ |
| * 2) whether or not there might be an overflow in the cross \ |
| * product determined by (___m & ((1 << 63) | (1 << 31))). \ |
| * \ |
| * Select the best way to do (m_bias + m * n) / (1 << 64). \ |
| * From now on there will be actual runtime code generated. \ |
| */ \ |
| ___res = __arch_xprod_64(___m, ___n, ___bias); \ |
| \ |
| ___res /= ___p; \ |
| }) |
| |
| #ifndef __arch_xprod_64 |
| /* |
| * Default C implementation for __arch_xprod_64() |
| * |
| * Prototype: u64 __arch_xprod_64(const u64 m, u64 n, bool bias) |
| * Semantic: retval = ((bias ? m : 0) + m * n) >> 64 |
| * |
| * The product is a 128-bit value, scaled down to 64 bits. |
| * Assuming constant propagation to optimize away unused conditional code. |
| * Architectures may provide their own optimized assembly implementation. |
| */ |
| static inline u64 __arch_xprod_64(const u64 m, u64 n, bool bias) |
| { |
| u32 m_lo = m; |
| u32 m_hi = m >> 32; |
| u32 n_lo = n; |
| u32 n_hi = n >> 32; |
| u64 res, tmp; |
| |
| if (!bias) { |
| res = ((u64)m_lo * n_lo) >> 32; |
| } else if (!(m & ((1ULL << 63) | (1ULL << 31)))) { |
| /* there can't be any overflow here */ |
| res = (m + (u64)m_lo * n_lo) >> 32; |
| } else { |
| res = m + (u64)m_lo * n_lo; |
| tmp = (res < m) ? (1ULL << 32) : 0; |
| res = (res >> 32) + tmp; |
| } |
| |
| if (!(m & ((1ULL << 63) | (1ULL << 31)))) { |
| /* there can't be any overflow here */ |
| res += (u64)m_lo * n_hi; |
| res += (u64)m_hi * n_lo; |
| res >>= 32; |
| } else { |
| tmp = res += (u64)m_lo * n_hi; |
| res += (u64)m_hi * n_lo; |
| tmp = (res < tmp) ? (1ULL << 32) : 0; |
| res = (res >> 32) + tmp; |
| } |
| |
| res += (u64)m_hi * n_hi; |
| |
| return res; |
| } |
| #endif |
| |
| #ifndef __div64_32 |
| extern u32 __div64_32(u64 *dividend, u32 divisor); |
| #endif |
| |
| /* The unnecessary pointer compare is there |
| * to check for type safety (n must be 64bit) |
| */ |
| # define do_div(n,base) ({ \ |
| u32 __base = (base); \ |
| u32 __rem; \ |
| (void)(((typeof((n)) *)0) == ((u64 *)0)); \ |
| if (__builtin_constant_p(__base) && \ |
| is_power_of_2(__base)) { \ |
| __rem = (n) & (__base - 1); \ |
| (n) >>= ilog2(__base); \ |
| } else if (__div64_const32_is_OK && \ |
| __builtin_constant_p(__base) && \ |
| __base != 0) { \ |
| u32 __res_lo, __n_lo = (n); \ |
| (n) = __div64_const32(n, __base); \ |
| /* the remainder can be computed with 32-bit regs */ \ |
| __res_lo = (n); \ |
| __rem = __n_lo - __res_lo * __base; \ |
| } else if (likely(((n) >> 32) == 0)) { \ |
| __rem = (u32)(n) % __base; \ |
| (n) = (u32)(n) / __base; \ |
| } else \ |
| __rem = __div64_32(&(n), __base); \ |
| __rem; \ |
| }) |
| |
| #else /* BITS_PER_LONG == ?? */ |
| |
| # error do_div() does not yet support the C64 |
| |
| #endif /* BITS_PER_LONG */ |
| |
| /* Wrapper for do_div(). Doesn't modify dividend and returns |
| * the result, not remainder. |
| */ |
| static inline u64 lldiv(u64 dividend, u32 divisor) |
| { |
| u64 __res = dividend; |
| do_div(__res, divisor); |
| return(__res); |
| } |
| |
| #endif /* _ASM_GENERIC_DIV64_H */ |