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Diffstat (limited to 'lib/udivsi3.c')
-rw-r--r-- | lib/udivsi3.c | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/lib/udivsi3.c b/lib/udivsi3.c new file mode 100644 index 000000000..16af22858 --- /dev/null +++ b/lib/udivsi3.c @@ -0,0 +1,61 @@ +//===-- udivsi3.c - Implement __udivsi3 -----------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements __udivsi3 for the compiler_rt library. +// +//===----------------------------------------------------------------------===// + +#include "int_lib.h" + +// Returns: a / b + +// Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide + +su_int +__udivsi3(su_int n, su_int d) +{ + const unsigned n_uword_bits = sizeof(su_int) * CHAR_BIT; + su_int q; + su_int r; + unsigned sr; + // special cases + if (d == 0) + return 0; // ?! + if (n == 0) + return 0; + sr = __builtin_clz(d) - __builtin_clz(n); + // 0 <= sr <= n_uword_bits - 1 or sr large + if (sr > n_uword_bits - 1) // d > r + return 0; + if (sr == n_uword_bits - 1) // d == 1 + return n; + ++sr; + // 1 <= sr <= n_uword_bits - 1 + // Not a special case + q = n << (n_uword_bits - sr); + r = n >> sr; + su_int carry = 0; + for (; sr > 0; --sr) + { + // r:q = ((r:q) << 1) | carry + r = (r << 1) | (q >> (n_uword_bits - 1)); + q = (q << 1) | carry; + // carry = 0; + // if (r.all >= d.all) + // { + // r.all -= d.all; + // carry = 1; + // } + const si_int s = (si_int)(d - r - 1) >> (n_uword_bits - 1); + carry = s & 1; + r -= d & s; + } + q = (q << 1) | carry; + return q; +} |