59 lines
1.5 KiB
C
59 lines
1.5 KiB
C
/* ===-- multi3.c - Implement __multi3 -------------------------------------===
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*
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* The LLVM Compiler Infrastructure
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*
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* This file is dual licensed under the MIT and the University of Illinois Open
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* Source Licenses. See LICENSE.TXT for details.
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*
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* ===----------------------------------------------------------------------===
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* This file implements __multi3 for the compiler_rt library.
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*
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* ===----------------------------------------------------------------------===
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*/
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#include "int_lib.h"
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#if __x86_64
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/* Returns: a * b */
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static
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ti_int
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__mulddi3(du_int a, du_int b)
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{
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twords r;
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const int bits_in_dword_2 = (int)(sizeof(di_int) * CHAR_BIT) / 2;
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const du_int lower_mask = (du_int)~0 >> bits_in_dword_2;
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r.s.low = (a & lower_mask) * (b & lower_mask);
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du_int t = r.s.low >> bits_in_dword_2;
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r.s.low &= lower_mask;
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t += (a >> bits_in_dword_2) * (b & lower_mask);
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r.s.low += (t & lower_mask) << bits_in_dword_2;
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r.s.high = t >> bits_in_dword_2;
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t = r.s.low >> bits_in_dword_2;
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r.s.low &= lower_mask;
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t += (b >> bits_in_dword_2) * (a & lower_mask);
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r.s.low += (t & lower_mask) << bits_in_dword_2;
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r.s.high += t >> bits_in_dword_2;
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r.s.high += (a >> bits_in_dword_2) * (b >> bits_in_dword_2);
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return r.all;
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}
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/* Returns: a * b */
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ti_int
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__multi3(ti_int a, ti_int b)
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{
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twords x;
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x.all = a;
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twords y;
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y.all = b;
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twords r;
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r.all = __mulddi3(x.s.low, y.s.low);
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r.s.high += x.s.high * y.s.low + x.s.low * y.s.high;
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return r.all;
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}
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#endif /* __x86_64 */
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