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When compiling the builtins with the undefined behavior sanitizer and running testcases you end up with the following warning: UBSan: ashlti3.c:33:35: left shift of 1 by 63 places cannot be represented in type 'di_int' (aka 'long long') UBSan: ashrti3.c:34:34: left shift of negative value -81985529216486891 This can be avoided by doing the shift in a matching unsigned variant of the type. The same kind of patterns are found in ashldi3.c and ashrdi3.c This was found in an out of tree target. Reviewed By: MaskRay Differential Revision: https://reviews.llvm.org/D158819
40 lines
1.2 KiB
C
40 lines
1.2 KiB
C
//===-- ashlti3.c - Implement __ashlti3 -----------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements __ashlti3 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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#ifdef CRT_HAS_128BIT
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// Returns: a << b
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// Precondition: 0 <= b < bits_in_tword
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COMPILER_RT_ABI ti_int __ashlti3(ti_int a, int b) {
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const int bits_in_dword = (int)(sizeof(di_int) * CHAR_BIT);
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twords input;
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twords result;
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input.all = a;
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if (b & bits_in_dword) /* bits_in_dword <= b < bits_in_tword */ {
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result.s.low = 0;
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result.s.high = input.s.low << (b - bits_in_dword);
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} else /* 0 <= b < bits_in_dword */ {
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if (b == 0)
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return a;
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result.s.low = input.s.low << b;
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result.s.high =
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((du_int)input.s.high << b) | (input.s.low >> (bits_in_dword - b));
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}
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return result.all;
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}
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#endif // CRT_HAS_128BIT
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