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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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#ifdef CRT_HAS_128BIT |
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/* Returns: a * b */ |
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/* Effects: aborts if a * b overflows */ |
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COMPILER_RT_ABI 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 /* CRT_HAS_128BIT */ |