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Diffstat (limited to 'lib/multi3.c')
-rw-r--r-- | lib/multi3.c | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/lib/multi3.c b/lib/multi3.c new file mode 100644 index 000000000..8ba6550b6 --- /dev/null +++ b/lib/multi3.c @@ -0,0 +1,57 @@ +//===-- multi3.c - Implement __multi3 -------------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements __multi3 for the compiler_rt library. +// +//===----------------------------------------------------------------------===// + +#if __x86_64 + +#include "int_lib.h" + +// Returns: a * b + +static +ti_int +__mulddi3(du_int a, du_int b) +{ + twords r; + const int bits_in_dword_2 = (int)(sizeof(di_int) * CHAR_BIT) / 2; + const du_int lower_mask = (du_int)~0 >> bits_in_dword_2; + r.low = (a & lower_mask) * (b & lower_mask); + du_int t = r.low >> bits_in_dword_2; + r.low &= lower_mask; + t += (a >> bits_in_dword_2) * (b & lower_mask); + r.low += (t & lower_mask) << bits_in_dword_2; + r.high = t >> bits_in_dword_2; + t = r.low >> bits_in_dword_2; + r.low &= lower_mask; + t += (b >> bits_in_dword_2) * (a & lower_mask); + r.low += (t & lower_mask) << bits_in_dword_2; + r.high += t >> bits_in_dword_2; + r.high += (a >> bits_in_dword_2) * (b >> bits_in_dword_2); + return r.all; +} + +// Returns: a * b + +ti_int +__multi3(ti_int a, ti_int b) +{ + twords x; + x.all = a; + twords y; + y.all = b; + twords r; + r.all = __mulddi3(x.low, y.low); + r.high += x.high * y.low + x.low * y.high; + return r.all; +} + +#endif |