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Diffstat (limited to 'arch/x86/include/asm/div64.h')
-rw-r--r-- | arch/x86/include/asm/div64.h | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/arch/x86/include/asm/div64.h b/arch/x86/include/asm/div64.h new file mode 100644 index 0000000000..9931e4c7d7 --- /dev/null +++ b/arch/x86/include/asm/div64.h @@ -0,0 +1,107 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_DIV64_H +#define _ASM_X86_DIV64_H + +#ifdef CONFIG_X86_32 + +#include <linux/types.h> +#include <linux/log2.h> + +/* + * do_div() is NOT a C function. It wants to return + * two values (the quotient and the remainder), but + * since that doesn't work very well in C, what it + * does is: + * + * - modifies the 64-bit dividend _in_place_ + * - returns the 32-bit remainder + * + * This ends up being the most efficient "calling + * convention" on x86. + */ +#define do_div(n, base) \ +({ \ + unsigned long __upper, __low, __high, __mod, __base; \ + __base = (base); \ + if (__builtin_constant_p(__base) && is_power_of_2(__base)) { \ + __mod = n & (__base - 1); \ + n >>= ilog2(__base); \ + } else { \ + asm("" : "=a" (__low), "=d" (__high) : "A" (n));\ + __upper = __high; \ + if (__high) { \ + __upper = __high % (__base); \ + __high = __high / (__base); \ + } \ + asm("divl %2" : "=a" (__low), "=d" (__mod) \ + : "rm" (__base), "0" (__low), "1" (__upper)); \ + asm("" : "=A" (n) : "a" (__low), "d" (__high)); \ + } \ + __mod; \ +}) + +static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder) +{ + union { + u64 v64; + u32 v32[2]; + } d = { dividend }; + u32 upper; + + upper = d.v32[1]; + d.v32[1] = 0; + if (upper >= divisor) { + d.v32[1] = upper / divisor; + upper %= divisor; + } + asm ("divl %2" : "=a" (d.v32[0]), "=d" (*remainder) : + "rm" (divisor), "0" (d.v32[0]), "1" (upper)); + return d.v64; +} +#define div_u64_rem div_u64_rem + +static inline u64 mul_u32_u32(u32 a, u32 b) +{ + u32 high, low; + + asm ("mull %[b]" : "=a" (low), "=d" (high) + : [a] "a" (a), [b] "rm" (b) ); + + return low | ((u64)high) << 32; +} +#define mul_u32_u32 mul_u32_u32 + +/* + * __div64_32() is never called on x86, so prevent the + * generic definition from getting built. + */ +#define __div64_32 + +#else +# include <asm-generic/div64.h> + +/* + * Will generate an #DE when the result doesn't fit u64, could fix with an + * __ex_table[] entry when it becomes an issue. + */ +static inline u64 mul_u64_u64_div_u64(u64 a, u64 mul, u64 div) +{ + u64 q; + + asm ("mulq %2; divq %3" : "=a" (q) + : "a" (a), "rm" (mul), "rm" (div) + : "rdx"); + + return q; +} +#define mul_u64_u64_div_u64 mul_u64_u64_div_u64 + +static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 div) +{ + return mul_u64_u64_div_u64(a, mul, div); +} +#define mul_u64_u32_div mul_u64_u32_div + +#endif /* CONFIG_X86_32 */ + +#endif /* _ASM_X86_DIV64_H */ |