hotspot/src/cpu/x86/vm/bytes_x86.hpp
author ysr
Tue, 10 Aug 2010 14:53:35 -0700
changeset 6253 228a0240f71e
parent 5547 f4b087cbb361
child 7397 5b173b4ca846
permissions -rw-r--r--
6973570: OrderAccess::storestore() scales poorly on multi-socket x64 and sparc: cache-line ping-ponging Summary: volatile store to static variable removed in favour of a volatile store to stack to avoid excessive cache coherency traffic; verified that the volatile store is not elided by any of our current compilers. Reviewed-by: dholmes, dice, jcoomes, kvn
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/*
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 * Copyright (c) 1997, 2001, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 *
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 */
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class Bytes: AllStatic {
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 private:
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#ifndef AMD64
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  // Helper function for swap_u8
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  static inline u8   swap_u8_base(u4 x, u4 y);        // compiler-dependent implementation
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#endif // AMD64
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 public:
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  // Returns true if the byte ordering used by Java is different from the native byte ordering
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  // of the underlying machine. For example, this is true for Intel x86, but false for Solaris
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  // on Sparc.
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  static inline bool is_Java_byte_ordering_different(){ return true; }
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  // Efficient reading and writing of unaligned unsigned data in platform-specific byte ordering
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  // (no special code is needed since x86 CPUs can access unaligned data)
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  static inline u2   get_native_u2(address p)         { return *(u2*)p; }
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  static inline u4   get_native_u4(address p)         { return *(u4*)p; }
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  static inline u8   get_native_u8(address p)         { return *(u8*)p; }
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  static inline void put_native_u2(address p, u2 x)   { *(u2*)p = x; }
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  static inline void put_native_u4(address p, u4 x)   { *(u4*)p = x; }
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  static inline void put_native_u8(address p, u8 x)   { *(u8*)p = x; }
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  // Efficient reading and writing of unaligned unsigned data in Java
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  // byte ordering (i.e. big-endian ordering). Byte-order reversal is
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  // needed since x86 CPUs use little-endian format.
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  static inline u2   get_Java_u2(address p)           { return swap_u2(get_native_u2(p)); }
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  static inline u4   get_Java_u4(address p)           { return swap_u4(get_native_u4(p)); }
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  static inline u8   get_Java_u8(address p)           { return swap_u8(get_native_u8(p)); }
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  static inline void put_Java_u2(address p, u2 x)     { put_native_u2(p, swap_u2(x)); }
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  static inline void put_Java_u4(address p, u4 x)     { put_native_u4(p, swap_u4(x)); }
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  static inline void put_Java_u8(address p, u8 x)     { put_native_u8(p, swap_u8(x)); }
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  // Efficient swapping of byte ordering
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  static inline u2   swap_u2(u2 x);                   // compiler-dependent implementation
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  static inline u4   swap_u4(u4 x);                   // compiler-dependent implementation
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  static inline u8   swap_u8(u8 x);
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};
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// The following header contains the implementations of swap_u2, swap_u4, and swap_u8[_base]
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#include "incls/_bytes_pd.inline.hpp.incl"