view src/os_cpu/linux_zero/vm/os_linux_zero.hpp @ 8977:59bbf36a21f9

8211387: [Zero] atomic_copy64: Use ldrexd for atomic reads on ARMv7 Reviewed-by: dholmes, aph Contributed-by: Andrew Haley <>
author sgehwolf
date Tue, 02 Oct 2018 17:17:43 +0200
parents b2fa3e69edc9
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 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2007, 2008, 2010 Red Hat, Inc.
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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  static void setup_fpu() {}

  static bool is_allocatable(size_t bytes);

  // Used to register dynamic code cache area with the OS
  // Note: Currently only used in 64 bit Windows implementations
  static bool register_code_area(char *low, char *high) { return true; }

  // Atomically copy 64 bits of data
  static void atomic_copy64(volatile void *src, volatile void *dst) {
#if defined(PPC32) && !defined(__SPE__)
    double tmp;
    asm volatile ("lfd  %0, %2\n"
                  "stfd %0, %1\n"
                  : "=&f"(tmp), "=Q"(*(volatile double*)dst)
                  : "Q"(*(volatile double*)src));
#elif defined(PPC32) && defined(__SPE__)
    long tmp;
    asm volatile ("evldd  %0, %2\n"
                  "evstdd %0, %1\n"
                  : "=&r"(tmp), "=Q"(*(volatile long*)dst)
                  : "Q"(*(volatile long*)src));
#elif defined(S390) && !defined(_LP64)
    double tmp;
    asm volatile ("ld  %0, %2\n"
                  "std %0, %1\n"
                  : "=&f"(tmp), "=Q"(*(volatile double*)dst)
                  : "Q"(*(volatile double*)src));
#elif defined(__ARM_ARCH_7A__)
    // Note that a ldrexd + clrex combination is only needed for
    // correctness on the OS level (context-switches). In this
    // case, clrex *may* be beneficial for performance. For now
    // don't bother with clrex as this is Zero.
    jlong tmp;
    asm volatile ("ldrexd  %0, [%1]\n"
                  : "=r"(tmp)
                  : "r"(src), "m"(src));
    *(jlong *) dst = tmp;
    *(jlong *) dst = *(jlong *) src;