LXR linux/arch/arm/include/asm/div64.h

   1#ifndef __ASM_ARM_DIV64
   2#define __ASM_ARM_DIV64
   3
   4#include <linux/types.h>
   5#include <asm/compiler.h>
   6
   7/*
   8 * The semantics of __div64_32() are:
   9 *
  10 * uint32_t __div64_32(uint64_t *n, uint32_t base)
  11 * {
  12 *      uint32_t remainder = *n % base;
  13 *      *n = *n / base;
  14 *      return remainder;
  15 * }
  16 *
  17 * In other words, a 64-bit dividend with a 32-bit divisor producing
  18 * a 64-bit result and a 32-bit remainder.  To accomplish this optimally
  19 * we override the generic version in lib/div64.c to call our __do_div64
  20 * assembly implementation with completely non standard calling convention
  21 * for arguments and results (beware).
  22 */
  23
  24#ifdef __ARMEB__
  25#define __xh "r0"
  26#define __xl "r1"
  27#else
  28#define __xl "r0"
  29#define __xh "r1"
  30#endif
  31
  32static inline uint32_t __div64_32(uint64_t *n, uint32_t base)
  33{
  34        register unsigned int __base      asm("r4") = base;
  35        register unsigned long long __n   asm("r0") = *n;
  36        register unsigned long long __res asm("r2");
  37        register unsigned int __rem       asm(__xh);
  38        asm(    __asmeq("%0", __xh)
  39                __asmeq("%1", "r2")
  40                __asmeq("%2", "r0")
  41                __asmeq("%3", "r4")
  42                "bl     __do_div64"
  43                : "=r" (__rem), "=r" (__res)
  44                : "r" (__n), "r" (__base)
  45                : "ip", "lr", "cc");
  46        *n = __res;
  47        return __rem;
  48}
  49#define __div64_32 __div64_32
  50
  51#if !defined(CONFIG_AEABI)
  52
  53/*
  54 * In OABI configurations, some uses of the do_div function
  55 * cause gcc to run out of registers. To work around that,
  56 * we can force the use of the out-of-line version for
  57 * configurations that build a OABI kernel.
  58 */
  59#define do_div(n, base) __div64_32(&(n), base)
  60
  61#else
  62
  63/*
  64 * gcc versions earlier than 4.0 are simply too problematic for the
  65 * __div64_const32() code in asm-generic/div64.h. First there is
  66 * gcc PR 15089 that tend to trig on more complex constructs, spurious
  67 * .global __udivsi3 are inserted even if none of those symbols are
  68 * referenced in the generated code, and those gcc versions are not able
  69 * to do constant propagation on long long values anyway.
  70 */
  71
  72#define __div64_const32_is_OK (__GNUC__ >= 4)
  73
  74static inline uint64_t __arch_xprod_64(uint64_t m, uint64_t n, bool bias)
  75{
  76        unsigned long long res;
  77        register unsigned int tmp asm("ip") = 0;
  78
  79        if (!bias) {
  80                asm (   "umull  %Q0, %R0, %Q1, %Q2\n\t"
  81                        "mov    %Q0, #0"
  82                        : "=&r" (res)
  83                        : "r" (m), "r" (n)
  84                        : "cc");
  85        } else if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
  86                res = m;
  87                asm (   "umlal  %Q0, %R0, %Q1, %Q2\n\t"
  88                        "mov    %Q0, #0"
  89                        : "+&r" (res)
  90                        : "r" (m), "r" (n)
  91                        : "cc");
  92        } else {
  93                asm (   "umull  %Q0, %R0, %Q2, %Q3\n\t"
  94                        "cmn    %Q0, %Q2\n\t"
  95                        "adcs   %R0, %R0, %R2\n\t"
  96                        "adc    %Q0, %1, #0"
  97                        : "=&r" (res), "+&r" (tmp)
  98                        : "r" (m), "r" (n)
  99                        : "cc");
 100        }
 101
 102        if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
 103                asm (   "umlal  %R0, %Q0, %R1, %Q2\n\t"
 104                        "umlal  %R0, %Q0, %Q1, %R2\n\t"
 105                        "mov    %R0, #0\n\t"
 106                        "umlal  %Q0, %R0, %R1, %R2"
 107                        : "+&r" (res)
 108                        : "r" (m), "r" (n)
 109                        : "cc");
 110        } else {
 111                asm (   "umlal  %R0, %Q0, %R2, %Q3\n\t"
 112                        "umlal  %R0, %1, %Q2, %R3\n\t"
 113                        "mov    %R0, #0\n\t"
 114                        "adds   %Q0, %1, %Q0\n\t"
 115                        "adc    %R0, %R0, #0\n\t"
 116                        "umlal  %Q0, %R0, %R2, %R3"
 117                        : "+&r" (res), "+&r" (tmp)
 118                        : "r" (m), "r" (n)
 119                        : "cc");
 120        }
 121
 122        return res;
 123}
 124#define __arch_xprod_64 __arch_xprod_64
 125
 126#include <asm-generic/div64.h>
 127
 128#endif
 129
 130#endif
 131