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8178348: left_n_bits(0) invokes undefined behavior

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Reviewed-by: dholmes, coleenp
This commit is contained in:
Harold Seigel 2021-03-12 19:00:36 +00:00
parent 0b10c6b415
commit 4b5c664b4c
2 changed files with 1 additions and 5 deletions
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5
src/hotspot/share/utilities/globalDefinitions.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 1997, 2020, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -390,6 +390,3 @@ STATIC_ASSERT(nth_bit(1|2) == 0x8);
STATIC_ASSERT(right_n_bits(3) == 0x7);
STATIC_ASSERT(right_n_bits(1|2) == 0x7);
STATIC_ASSERT(left_n_bits(3) == (intptr_t) LP64_ONLY(0xE000000000000000) NOT_LP64(0xE0000000));
STATIC_ASSERT(left_n_bits(1|2) == (intptr_t) LP64_ONLY(0xE000000000000000) NOT_LP64(0xE0000000));

1
src/hotspot/share/utilities/globalDefinitions.hpp
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@ -982,7 +982,6 @@ const intptr_t OneBit = 1; // only right_most bit set in a word
// (note: #define used only so that they can be used in enum constant definitions)
#define nth_bit(n) (((n) >= BitsPerWord) ? 0 : (OneBit << (n)))
#define right_n_bits(n) (nth_bit(n) - 1)
#define left_n_bits(n) (right_n_bits(n) << (((n) >= BitsPerWord) ? 0 : (BitsPerWord - (n))))
// bit-operations using a mask m
inline void set_bits (intptr_t& x, intptr_t m) { x |= m; }