61 lines
1.4 KiB
C
61 lines
1.4 KiB
C
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/* ===-- mulvti3.c - Implement __mulvti3 -----------------------------------===
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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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*
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* This file implements __mulvti3 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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/* Effects: aborts if a * b overflows */
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ti_int
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__mulvti3(ti_int a, ti_int b)
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{
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const int N = (int)(sizeof(ti_int) * CHAR_BIT);
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const ti_int MIN = (ti_int)1 << (N-1);
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const ti_int MAX = ~MIN;
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if (a == MIN)
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{
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if (b == 0 || b == 1)
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return a * b;
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compilerrt_abort();
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}
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if (b == MIN)
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{
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if (a == 0 || a == 1)
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return a * b;
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compilerrt_abort();
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}
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ti_int sa = a >> (N - 1);
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ti_int abs_a = (a ^ sa) - sa;
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ti_int sb = b >> (N - 1);
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ti_int abs_b = (b ^ sb) - sb;
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if (abs_a < 2 || abs_b < 2)
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return a * b;
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if (sa == sb)
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{
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if (abs_a > MAX / abs_b)
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compilerrt_abort();
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}
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else
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{
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if (abs_a > MIN / -abs_b)
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compilerrt_abort();
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}
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return a * b;
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}
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#endif
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