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Diffstat (limited to 'contrib/compiler-rt/lib/udivsi3.c')
-rw-r--r-- | contrib/compiler-rt/lib/udivsi3.c | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/contrib/compiler-rt/lib/udivsi3.c b/contrib/compiler-rt/lib/udivsi3.c new file mode 100644 index 0000000..70528b6 --- /dev/null +++ b/contrib/compiler-rt/lib/udivsi3.c @@ -0,0 +1,63 @@ +/* ===-- 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; +} |