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
  32 static 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
  74 static 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