linux/arch/arm/include/asm/div64.h
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   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 */
  24static inline uint32_t __div64_32(uint64_t *n, uint32_t base)
  25{
  26        register unsigned int __base      asm("r4") = base;
  27        register unsigned long long __n   asm("r0") = *n;
  28        register unsigned long long __res asm("r2");
  29        unsigned int __rem;
  30        asm(    __asmeq("%0", "r0")
  31                __asmeq("%1", "r2")
  32                __asmeq("%2", "r4")
  33                "bl     __do_div64"
  34                : "+r" (__n), "=r" (__res)
  35                : "r" (__base)
  36                : "ip", "lr", "cc");
  37        __rem = __n >> 32;
  38        *n = __res;
  39        return __rem;
  40}
  41#define __div64_32 __div64_32
  42
  43#if !defined(CONFIG_AEABI)
  44
  45/*
  46 * In OABI configurations, some uses of the do_div function
  47 * cause gcc to run out of registers. To work around that,
  48 * we can force the use of the out-of-line version for
  49 * configurations that build a OABI kernel.
  50 */
  51#define do_div(n, base) __div64_32(&(n), base)
  52
  53#else
  54
  55/*
  56 * gcc versions earlier than 4.0 are simply too problematic for the
  57 * __div64_const32() code in asm-generic/div64.h. First there is
  58 * gcc PR 15089 that tend to trig on more complex constructs, spurious
  59 * .global __udivsi3 are inserted even if none of those symbols are
  60 * referenced in the generated code, and those gcc versions are not able
  61 * to do constant propagation on long long values anyway.
  62 */
  63
  64#define __div64_const32_is_OK (__GNUC__ >= 4)
  65
  66static inline uint64_t __arch_xprod_64(uint64_t m, uint64_t n, bool bias)
  67{
  68        unsigned long long res;
  69        register unsigned int tmp asm("ip") = 0;
  70
  71        if (!bias) {
  72                asm (   "umull  %Q0, %R0, %Q1, %Q2\n\t"
  73                        "mov    %Q0, #0"
  74                        : "=&r" (res)
  75                        : "r" (m), "r" (n)
  76                        : "cc");
  77        } else if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
  78                res = m;
  79                asm (   "umlal  %Q0, %R0, %Q1, %Q2\n\t"
  80                        "mov    %Q0, #0"
  81                        : "+&r" (res)
  82                        : "r" (m), "r" (n)
  83                        : "cc");
  84        } else {
  85                asm (   "umull  %Q0, %R0, %Q2, %Q3\n\t"
  86                        "cmn    %Q0, %Q2\n\t"
  87                        "adcs   %R0, %R0, %R2\n\t"
  88                        "adc    %Q0, %1, #0"
  89                        : "=&r" (res), "+&r" (tmp)
  90                        : "r" (m), "r" (n)
  91                        : "cc");
  92        }
  93
  94        if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
  95                asm (   "umlal  %R0, %Q0, %R1, %Q2\n\t"
  96                        "umlal  %R0, %Q0, %Q1, %R2\n\t"
  97                        "mov    %R0, #0\n\t"
  98                        "umlal  %Q0, %R0, %R1, %R2"
  99                        : "+&r" (res)
 100                        : "r" (m), "r" (n)
 101                        : "cc");
 102        } else {
 103                asm (   "umlal  %R0, %Q0, %R2, %Q3\n\t"
 104                        "umlal  %R0, %1, %Q2, %R3\n\t"
 105                        "mov    %R0, #0\n\t"
 106                        "adds   %Q0, %1, %Q0\n\t"
 107                        "adc    %R0, %R0, #0\n\t"
 108                        "umlal  %Q0, %R0, %R2, %R3"
 109                        : "+&r" (res), "+&r" (tmp)
 110                        : "r" (m), "r" (n)
 111                        : "cc");
 112        }
 113
 114        return res;
 115}
 116#define __arch_xprod_64 __arch_xprod_64
 117
 118#include <asm-generic/div64.h>
 119
 120#endif
 121
 122#endif
 123
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