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Diffstat (limited to 'lib/mulvdi3.c')
-rw-r--r-- | lib/mulvdi3.c | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/lib/mulvdi3.c b/lib/mulvdi3.c new file mode 100644 index 000000000..862a8c006 --- /dev/null +++ b/lib/mulvdi3.c @@ -0,0 +1,56 @@ +//===-- mulvdi3.c - Implement __mulvdi3 -----------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements __mulvdi3 for the compiler_rt library. +// +//===----------------------------------------------------------------------===// + +#include "int_lib.h" +#include <stdlib.h> + +// Returns: a * b + +// Effects: aborts if a * b overflows + +di_int +__mulvdi3(di_int a, di_int b) +{ + const int N = (int)(sizeof(di_int) * CHAR_BIT); + const di_int MIN = (di_int)1 << (N-1); + const di_int MAX = ~MIN; + if (a == MIN) + { + if (b == 0 || b == 1) + return a * b; + abort(); + } + if (b == MIN) + { + if (a == 0 || a == 1) + return a * b; + abort(); + } + di_int sa = a >> (N - 1); + di_int abs_a = (a ^ sa) - sa; + di_int sb = b >> (N - 1); + di_int abs_b = (b ^ sb) - sb; + if (abs_a < 2 || abs_b < 2) + return a * b; + if (sa == sb) + { + if (abs_a > MAX / abs_b) + abort(); + } + else + { + if (abs_a > MIN / -abs_b) + abort(); + } + return a * b; +} |