LXR uboot/arch/x86/lib/div64.c

   1// SPDX-License-Identifier: BSD-3-Clause
   2/*
   3 * This file is copied from the coreboot repository as part of
   4 * the libpayload project:
   5 *
   6 * Copyright 2014 Google Inc.
   7 */
   8
   9#include <common.h>
  10
  11union overlay64 {
  12        u64 longw;
  13        struct {
  14                u32 lower;
  15                u32 higher;
  16        } words;
  17};
  18
  19u64 __ashldi3(u64 num, unsigned int shift)
  20{
  21        union overlay64 output;
  22
  23        output.longw = num;
  24        if (shift >= 32) {
  25                output.words.higher = output.words.lower << (shift - 32);
  26                output.words.lower = 0;
  27        } else {
  28                if (!shift)
  29                        return num;
  30                output.words.higher = (output.words.higher << shift) |
  31                        (output.words.lower >> (32 - shift));
  32                output.words.lower = output.words.lower << shift;
  33        }
  34        return output.longw;
  35}
  36
  37u64 __lshrdi3(u64 num, unsigned int shift)
  38{
  39        union overlay64 output;
  40
  41        output.longw = num;
  42        if (shift >= 32) {
  43                output.words.lower = output.words.higher >> (shift - 32);
  44                output.words.higher = 0;
  45        } else {
  46                if (!shift)
  47                        return num;
  48                output.words.lower = output.words.lower >> shift |
  49                        (output.words.higher << (32 - shift));
  50                output.words.higher = output.words.higher >> shift;
  51        }
  52        return output.longw;
  53}
  54
  55#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
  56
  57static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
  58{
  59        u64 result = 0;
  60
  61        /*
  62         * If divider is zero - let the rest of the system care about the
  63         * exception.
  64         */
  65        if (!divider)
  66                return 1 / (u32)divider;
  67
  68        /* As an optimization, let's not use 64 bit division unless we must. */
  69        if (dividend <= MAX_32BIT_UINT) {
  70                if (divider > MAX_32BIT_UINT) {
  71                        result = 0;
  72                        if (rem_p)
  73                                *rem_p = divider;
  74                } else {
  75                        result = (u32)dividend / (u32)divider;
  76                        if (rem_p)
  77                                *rem_p = (u32)dividend % (u32)divider;
  78                }
  79                return result;
  80        }
  81
  82        while (divider <= dividend) {
  83                u64 locald = divider;
  84                u64 limit = __lshrdi3(dividend, 1);
  85                int shifts = 0;
  86
  87                while (locald <= limit) {
  88                        shifts++;
  89                        locald = locald + locald;
  90                }
  91                result |= __ashldi3(1, shifts);
  92                dividend -= locald;
  93        }
  94
  95        if (rem_p)
  96                *rem_p = dividend;
  97
  98        return result;
  99}
 100
 101u64 __udivdi3(u64 num, u64 den)
 102{
 103        return _64bit_divide(num, den, NULL);
 104}
 105
 106u64 __umoddi3(u64 num, u64 den)
 107{
 108        u64 v = 0;
 109
 110        _64bit_divide(num, den, &v);
 111        return v;
 112}
 113