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32 results

div64.h

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  • div64.h 2.01 KiB
    /* 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
    
    #else
    # include <asm-generic/div64.h>
    
    static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 div)
    {
    	u64 q;
    
    	asm ("mulq %2; divq %3" : "=a" (q)
    				: "a" (a), "rm" ((u64)mul), "rm" ((u64)div)
    				: "rdx");
    
    	return q;
    }
    #define mul_u64_u32_div	mul_u64_u32_div
    
    #endif /* CONFIG_X86_32 */
    
    #endif /* _ASM_X86_DIV64_H */