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When compiling compiler-rt with -fsanitize=undefined and running testcases you end up with the following warnings: UBSan: absvdi2.c:21:23: left shift of 1 by 63 places cannot be represented in type 'di_int' (aka 'long long') UBSan: absvsi2.c:21:23: left shift of 1 by 31 places cannot be represented in type 'si_int' (aka 'long') UBSan: negvdi2.c:20:32: left shift of 1 by 63 places cannot be represented in type 'di_int' (aka 'long long') UBSan: negvsi2.c:20:32: left shift of 1 by 31 places cannot be represented in type 'si_int' (aka 'long') This can be avoided by doing the shift in a matching unsigned variant of the type. This was found in an out of tree target. Reviewed By: MaskRay Differential Revision: https://reviews.llvm.org/D146932
26 lines
825 B
C
26 lines
825 B
C
//===-- absvdi2.c - Implement __absvdi2 -----------------------------------===//
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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 __absvdi2 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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// Returns: absolute value
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// Effects: aborts if abs(x) < 0
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COMPILER_RT_ABI di_int __absvdi2(di_int a) {
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const int N = (int)(sizeof(di_int) * CHAR_BIT);
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if (a == ((di_int)((du_int)1 << (N - 1))))
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compilerrt_abort();
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const di_int t = a >> (N - 1);
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return (a ^ t) - t;
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}
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