forked from OSchip/llvm-project
57 lines
1.3 KiB
C
57 lines
1.3 KiB
C
//===-- mulvsi3.c - Implement __mulvsi3 -----------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements __mulvsi3 for the compiler_rt library.
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//
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//===----------------------------------------------------------------------===//
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#include "int_lib.h"
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#include <stdlib.h>
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// Returns: a * b
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// Effects: aborts if a * b overflows
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si_int
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__mulvsi3(si_int a, si_int b)
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{
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const int N = (int)(sizeof(si_int) * CHAR_BIT);
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const si_int MIN = (si_int)1 << (N-1);
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const si_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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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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abort();
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}
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si_int sa = a >> (N - 1);
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si_int abs_a = (a ^ sa) - sa;
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si_int sb = b >> (N - 1);
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si_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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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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abort();
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}
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return a * b;
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}
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