1 /* ===-- udivsi3.c - Implement __udivsi3 -----------------------------------=== 2 * 3 * The LLVM Compiler Infrastructure 4 * 5 * This file is distributed under the University of Illinois Open Source 6 * License. See LICENSE.TXT for details. 7 * 8 * ===----------------------------------------------------------------------=== 9 * 10 * This file implements __udivsi3 for the compiler_rt library. 11 * 12 * ===----------------------------------------------------------------------=== 13 */ 14 15 #include "int_lib.h" 16 17 /* Returns: a / b */ 18 19 /* Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide */ 20 21 su_int 22 __udivsi3(su_int n, su_int d) 23 { 24 const unsigned n_uword_bits = sizeof(su_int) * CHAR_BIT; 25 su_int q; 26 su_int r; 27 unsigned sr; 28 /* special cases */ 29 if (d == 0) 30 return 0; /* ?! */ 31 if (n == 0) 32 return 0; 33 sr = __builtin_clz(d) - __builtin_clz(n); 34 /* 0 <= sr <= n_uword_bits - 1 or sr large */ 35 if (sr > n_uword_bits - 1) /* d > r */ 36 return 0; 37 if (sr == n_uword_bits - 1) /* d == 1 */ 38 return n; 39 ++sr; 40 /* 1 <= sr <= n_uword_bits - 1 */ 41 /* Not a special case */ 42 q = n << (n_uword_bits - sr); 43 r = n >> sr; 44 su_int carry = 0; 45 for (; sr > 0; --sr) 46 { 47 /* r:q = ((r:q) << 1) | carry */ 48 r = (r << 1) | (q >> (n_uword_bits - 1)); 49 q = (q << 1) | carry; 50 /* carry = 0; 51 * if (r.all >= d.all) 52 * { 53 * r.all -= d.all; 54 * carry = 1; 55 * } 56 */ 57 const si_int s = (si_int)(d - r - 1) >> (n_uword_bits - 1); 58 carry = s & 1; 59 r -= d & s; 60 } 61 q = (q << 1) | carry; 62 return q; 63 } 64
