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Diffstat (limited to 'lib/mulvti3.c')
-rw-r--r-- | lib/mulvti3.c | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/lib/mulvti3.c b/lib/mulvti3.c new file mode 100644 index 000000000..82efe8caa --- /dev/null +++ b/lib/mulvti3.c @@ -0,0 +1,60 @@ +//===-- mulvti3.c - Implement __mulvti3 -----------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements __mulvti3 for the compiler_rt library. +// +//===----------------------------------------------------------------------===// + +#if __x86_64 + +#include "int_lib.h" +#include <stdlib.h> + +// Returns: a * b + +// Effects: aborts if a * b overflows + +ti_int +__mulvti3(ti_int a, ti_int b) +{ + const int N = (int)(sizeof(ti_int) * CHAR_BIT); + const ti_int MIN = (ti_int)1 << (N-1); + const ti_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(); + } + ti_int sa = a >> (N - 1); + ti_int abs_a = (a ^ sa) - sa; + ti_int sb = b >> (N - 1); + ti_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; +} + +#endif |