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Diffstat (limited to 'lib/udivmodti4.c')
| -rw-r--r-- | lib/udivmodti4.c | 256 |
1 files changed, 256 insertions, 0 deletions
diff --git a/lib/udivmodti4.c b/lib/udivmodti4.c new file mode 100644 index 000000000000..53b407256e67 --- /dev/null +++ b/lib/udivmodti4.c @@ -0,0 +1,256 @@ +/* ===-- udivmodti4.c - Implement __udivmodti4 -----------------------------=== + * + * The LLVM Compiler Infrastructure + * + * This file is distributed under the University of Illinois Open Source + * License. See LICENSE.TXT for details. + * + * ===----------------------------------------------------------------------=== + * + * This file implements __udivmodti4 for the compiler_rt library. + * + * ===----------------------------------------------------------------------=== + */ + +#if __x86_64 + +#include "int_lib.h" + +/* Effects: if rem != 0, *rem = a % b + * Returns: a / b + */ + +/* Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide */ + +tu_int +__udivmodti4(tu_int a, tu_int b, tu_int* rem) +{ + const unsigned n_udword_bits = sizeof(du_int) * CHAR_BIT; + const unsigned n_utword_bits = sizeof(tu_int) * CHAR_BIT; + utwords n; + n.all = a; + utwords d; + d.all = b; + utwords q; + utwords r; + unsigned sr; + /* special cases, X is unknown, K != 0 */ + if (n.s.high == 0) + { + if (d.s.high == 0) + { + /* 0 X + * --- + * 0 X + */ + if (rem) + *rem = n.s.low % d.s.low; + return n.s.low / d.s.low; + } + /* 0 X + * --- + * K X + */ + if (rem) + *rem = n.s.low; + return 0; + } + /* n.s.high != 0 */ + if (d.s.low == 0) + { + if (d.s.high == 0) + { + /* K X + * --- + * 0 0 + */ + if (rem) + *rem = n.s.high % d.s.low; + return n.s.high / d.s.low; + } + /* d.s.high != 0 */ + if (n.s.low == 0) + { + /* K 0 + * --- + * K 0 + */ + if (rem) + { + r.s.high = n.s.high % d.s.high; + r.s.low = 0; + *rem = r.all; + } + return n.s.high / d.s.high; + } + /* K K + * --- + * K 0 + */ + if ((d.s.high & (d.s.high - 1)) == 0) /* if d is a power of 2 */ + { + if (rem) + { + r.s.low = n.s.low; + r.s.high = n.s.high & (d.s.high - 1); + *rem = r.all; + } + return n.s.high >> __builtin_ctzll(d.s.high); + } + /* K K + * --- + * K 0 + */ + sr = __builtin_clzll(d.s.high) - __builtin_clzll(n.s.high); + /* 0 <= sr <= n_udword_bits - 2 or sr large */ + if (sr > n_udword_bits - 2) + { + if (rem) + *rem = n.all; + return 0; + } + ++sr; + /* 1 <= sr <= n_udword_bits - 1 */ + /* q.all = n.all << (n_utword_bits - sr); */ + q.s.low = 0; + q.s.high = n.s.low << (n_udword_bits - sr); + /* r.all = n.all >> sr; */ + r.s.high = n.s.high >> sr; + r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr); + } + else /* d.s.low != 0 */ + { + if (d.s.high == 0) + { + /* K X + * --- + * 0 K + */ + if ((d.s.low & (d.s.low - 1)) == 0) /* if d is a power of 2 */ + { + if (rem) + *rem = n.s.low & (d.s.low - 1); + if (d.s.low == 1) + return n.all; + unsigned sr = __builtin_ctzll(d.s.low); + q.s.high = n.s.high >> sr; + q.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr); + return q.all; + } + /* K X + * --- + * 0 K + */ + sr = 1 + n_udword_bits + __builtin_clzll(d.s.low) + - __builtin_clzll(n.s.high); + /* 2 <= sr <= n_utword_bits - 1 + * q.all = n.all << (n_utword_bits - sr); + * r.all = n.all >> sr; + * if (sr == n_udword_bits) + * { + * q.s.low = 0; + * q.s.high = n.s.low; + * r.s.high = 0; + * r.s.low = n.s.high; + * } + * else if (sr < n_udword_bits) // 2 <= sr <= n_udword_bits - 1 + * { + * q.s.low = 0; + * q.s.high = n.s.low << (n_udword_bits - sr); + * r.s.high = n.s.high >> sr; + * r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr); + * } + * else // n_udword_bits + 1 <= sr <= n_utword_bits - 1 + * { + * q.s.low = n.s.low << (n_utword_bits - sr); + * q.s.high = (n.s.high << (n_utword_bits - sr)) | + * (n.s.low >> (sr - n_udword_bits)); + * r.s.high = 0; + * r.s.low = n.s.high >> (sr - n_udword_bits); + * } + */ + q.s.low = (n.s.low << (n_utword_bits - sr)) & + ((di_int)(int)(n_udword_bits - sr) >> (n_udword_bits-1)); + q.s.high = ((n.s.low << ( n_udword_bits - sr)) & + ((di_int)(int)(sr - n_udword_bits - 1) >> (n_udword_bits-1))) | + (((n.s.high << (n_utword_bits - sr)) | + (n.s.low >> (sr - n_udword_bits))) & + ((di_int)(int)(n_udword_bits - sr) >> (n_udword_bits-1))); + r.s.high = (n.s.high >> sr) & + ((di_int)(int)(sr - n_udword_bits) >> (n_udword_bits-1)); + r.s.low = ((n.s.high >> (sr - n_udword_bits)) & + ((di_int)(int)(n_udword_bits - sr - 1) >> (n_udword_bits-1))) | + (((n.s.high << (n_udword_bits - sr)) | + (n.s.low >> sr)) & + ((di_int)(int)(sr - n_udword_bits) >> (n_udword_bits-1))); + } + else + { + /* K X + * --- + * K K + */ + sr = __builtin_clzll(d.s.high) - __builtin_clzll(n.s.high); + /*0 <= sr <= n_udword_bits - 1 or sr large */ + if (sr > n_udword_bits - 1) + { + if (rem) + *rem = n.all; + return 0; + } + ++sr; + /* 1 <= sr <= n_udword_bits */ + /* q.all = n.all << (n_utword_bits - sr); */ + q.s.low = 0; + q.s.high = n.s.low << (n_udword_bits - sr); + /* r.all = n.all >> sr; + * if (sr < n_udword_bits) + * { + * r.s.high = n.s.high >> sr; + * r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr); + * } + * else + * { + * r.s.high = 0; + * r.s.low = n.s.high; + * } + */ + r.s.high = (n.s.high >> sr) & + ((di_int)(int)(sr - n_udword_bits) >> (n_udword_bits-1)); + r.s.low = (n.s.high << (n_udword_bits - sr)) | + ((n.s.low >> sr) & + ((di_int)(int)(sr - n_udword_bits) >> (n_udword_bits-1))); + } + } + /* Not a special case + * q and r are initialized with: + * q.all = n.all << (n_utword_bits - sr); + * r.all = n.all >> sr; + * 1 <= sr <= n_utword_bits - 1 + */ + su_int carry = 0; + for (; sr > 0; --sr) + { + /* r:q = ((r:q) << 1) | carry */ + r.s.high = (r.s.high << 1) | (r.s.low >> (n_udword_bits - 1)); + r.s.low = (r.s.low << 1) | (q.s.high >> (n_udword_bits - 1)); + q.s.high = (q.s.high << 1) | (q.s.low >> (n_udword_bits - 1)); + q.s.low = (q.s.low << 1) | carry; + /* carry = 0; + * if (r.all >= d.all) + * { + * r.all -= d.all; + * carry = 1; + * } + */ + const ti_int s = (ti_int)(d.all - r.all - 1) >> (n_utword_bits - 1); + carry = s & 1; + r.all -= d.all & s; + } + q.all = (q.all << 1) | carry; + if (rem) + *rem = r.all; + return q.all; +} + +#endif /* __x86_64 */ |