arch/arm/include/asm/div64.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __ASM_ARM_DIV64
   3 #define __ASM_ARM_DIV64
   4
   5 #include <linux/types.h>
   6 #include <asm/compiler.h>
   7
   8 /*
   9  * The semantics of __div64_32() are:
  10  *
  11  * uint32_t __div64_32(uint64_t *n, uint32_t base)
  12  * {
  13  *      uint32_t remainder = *n % base;
  14  *      *n = *n / base;
  15  *      return remainder;
  16  * }
  17  *
  18  * In other words, a 64-bit dividend with a 32-bit divisor producing
  19  * a 64-bit result and a 32-bit remainder.  To accomplish this optimally
  20  * we override the generic version in lib/div64.c to call our __do_div64
  21  * assembly implementation with completely non standard calling convention
  22  * for arguments and results (beware).
  23  */
  24
  25 #ifdef __ARMEB__
  26 #define __xh "r0"
  27 #define __xl "r1"
  28 #else
  29 #define __xl "r0"
  30 #define __xh "r1"
  31 #endif
  32
  33 static inline uint32_t __div64_32(uint64_t *n, uint32_t base)
  34 {
  35         register unsigned int __base      asm("r4") = base;
  36         register unsigned long long __n   asm("r0") = *n;
  37         register unsigned long long __res asm("r2");
  38         register unsigned int __rem       asm(__xh);
  39         asm(    __asmeq("%0", __xh)
  40                 __asmeq("%1", "r2")
  41                 __asmeq("%2", "r0")
  42                 __asmeq("%3", "r4")
  43                 "bl     __do_div64"
  44                 : "=r" (__rem), "=r" (__res)
  45                 : "r" (__n), "r" (__base)
  46                 : "ip", "lr", "cc");
  47         *n = __res;
  48         return __rem;
  49 }
  50 #define __div64_32 __div64_32
  51
  52 #if !defined(CONFIG_AEABI)
  53
  54 /*
  55  * In OABI configurations, some uses of the do_div function
  56  * cause gcc to run out of registers. To work around that,
  57  * we can force the use of the out-of-line version for
  58  * configurations that build a OABI kernel.
  59  */
  60 #define do_div(n, base) __div64_32(&(n), base)
  61
  62 #else
  63
  64 /*
  65  * gcc versions earlier than 4.0 are simply too problematic for the
  66  * __div64_const32() code in asm-generic/div64.h. First there is
  67  * gcc PR 15089 that tend to trig on more complex constructs, spurious
  68  * .global __udivsi3 are inserted even if none of those symbols are
  69  * referenced in the generated code, and those gcc versions are not able
  70  * to do constant propagation on long long values anyway.
  71  */
  72
  73 #define __div64_const32_is_OK (__GNUC__ >= 4)
  74
  75 static inline uint64_t __arch_xprod_64(uint64_t m, uint64_t n, bool bias)
  76 {
  77         unsigned long long res;
  78         register unsigned int tmp asm("ip") = 0;
  79
  80         if (!bias) {
  81                 asm (   "umull  %Q0, %R0, %Q1, %Q2\n\t"
  82                         "mov    %Q0, #0"
  83                         : "=&r" (res)
  84                         : "r" (m), "r" (n)
  85                         : "cc");
  86         } else if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
  87                 res = m;
  88                 asm (   "umlal  %Q0, %R0, %Q1, %Q2\n\t"
  89                         "mov    %Q0, #0"
  90                         : "+&r" (res)
  91                         : "r" (m), "r" (n)
  92                         : "cc");
  93         } else {
  94                 asm (   "umull  %Q0, %R0, %Q2, %Q3\n\t"
  95                         "cmn    %Q0, %Q2\n\t"
  96                         "adcs   %R0, %R0, %R2\n\t"
  97                         "adc    %Q0, %1, #0"
  98                         : "=&r" (res), "+&r" (tmp)
  99                         : "r" (m), "r" (n)
 100                         : "cc");
 101         }
 102
 103         if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
 104                 asm (   "umlal  %R0, %Q0, %R1, %Q2\n\t"
 105                         "umlal  %R0, %Q0, %Q1, %R2\n\t"
 106                         "mov    %R0, #0\n\t"
 107                         "umlal  %Q0, %R0, %R1, %R2"
 108                         : "+&r" (res)
 109                         : "r" (m), "r" (n)
 110                         : "cc");
 111         } else {
 112                 asm (   "umlal  %R0, %Q0, %R2, %Q3\n\t"
 113                         "umlal  %R0, %1, %Q2, %R3\n\t"
 114                         "mov    %R0, #0\n\t"
 115                         "adds   %Q0, %1, %Q0\n\t"
 116                         "adc    %R0, %R0, #0\n\t"
 117                         "umlal  %Q0, %R0, %R2, %R3"
 118                         : "+&r" (res), "+&r" (tmp)
 119                         : "r" (m), "r" (n)
 120                         : "cc");
 121         }
 122
 123         return res;
 124 }
 125 #define __arch_xprod_64 __arch_xprod_64
 126
 127 #include <asm-generic/div64.h>
 128
 129 #endif
 130
 131 #endif