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https://https.git.savannah.gnu.org/git/gnulib.git
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Collin Funk
365 lines
10 KiB
C
365 lines
10 KiB
C
/* Simple atomic operations for multithreading.
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Copyright (C) 2020-2026 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Bruno Haible <bruno@clisp.org>, 2021. */
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#include <config.h>
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/* Specification. */
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#include "simple-atomic.h"
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#if 0x590 <= __SUNPRO_C && __STDC__
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# define asm __asm
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#endif
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#if defined _WIN32 && ! defined __CYGWIN__
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/* Native Windows. */
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# include <windows.h>
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void
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memory_barrier (void)
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{
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/* MemoryBarrier
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<https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-memorybarrier> */
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MemoryBarrier ();
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}
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unsigned int
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atomic_compare_and_swap (unsigned int volatile *vp,
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unsigned int cmp,
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unsigned int newval)
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{
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/* InterlockedCompareExchange
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<https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchange> */
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return InterlockedCompareExchange ((LONG volatile *) vp,
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(LONG) newval, (LONG) cmp);
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}
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uintptr_t
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atomic_compare_and_swap_ptr (uintptr_t volatile *vp,
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uintptr_t cmp,
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uintptr_t newval)
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{
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/* InterlockedCompareExchangePointer
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<https://docs.microsoft.com/en-us/windows/win32/api/winnt/nf-winnt-interlockedcompareexchangepointer> */
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return (uintptr_t)
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InterlockedCompareExchangePointer ((void * volatile *) vp,
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(void *) newval, (void *) cmp);
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}
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#elif HAVE_PTHREAD_H
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/* Some other platform that supports multi-threading.
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We don't use the C11 <stdatomic.h> (available in GCC >= 4.9) because it would
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require to link with -latomic. */
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# if (((__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)) \
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|| __clang_major__ >= 3) \
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&& HAVE_ATOMIC_COMPARE_AND_SWAP_GCC41)
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/* Use GCC built-ins (available on many platforms with GCC >= 4.1 or
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clang >= 3.0).
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Documentation:
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<https://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Atomic-Builtins.html> */
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void
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memory_barrier (void)
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{
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__sync_synchronize ();
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}
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unsigned int
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atomic_compare_and_swap (unsigned int volatile *vp,
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unsigned int cmp,
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unsigned int newval)
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{
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return __sync_val_compare_and_swap (vp, cmp, newval);
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}
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uintptr_t
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atomic_compare_and_swap_ptr (uintptr_t volatile *vp,
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uintptr_t cmp,
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uintptr_t newval)
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{
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return __sync_val_compare_and_swap (vp, cmp, newval);
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}
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# elif defined _AIX
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/* AIX */
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/* For older versions of GCC or xlc, use inline assembly.
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__compare_and_swap and __compare_and_swaplp are not sufficient here. */
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void
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memory_barrier (void)
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{
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asm volatile ("sync");
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}
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unsigned int
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atomic_compare_and_swap (unsigned int volatile *vp,
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unsigned int cmp,
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unsigned int newval)
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{
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asm volatile ("sync");
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unsigned int oldval;
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asm volatile (
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# if defined __GNUC__ || defined __clang__
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"1: lwarx %0,0,%1\n"
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" cmpw 0,%0,%2\n"
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" bne 0,2f\n"
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" stwcx. %3,0,%1\n"
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" bne 0,1b\n"
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"2:"
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# else /* another label syntax */
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".L01: lwarx %0,0,%1\n"
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" cmpw 0,%0,%2\n"
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" bne 0,.L02\n"
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" stwcx. %3,0,%1\n"
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" bne 0,.L01\n"
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".L02:"
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# endif
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: "=&r" (oldval)
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: "r" (vp), "r" (cmp), "r" (newval)
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: "cr0");
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asm volatile ("isync");
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return oldval;
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}
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uintptr_t
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atomic_compare_and_swap_ptr (uintptr_t volatile *vp,
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uintptr_t cmp,
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uintptr_t newval)
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{
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asm volatile ("sync");
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uintptr_t oldval;
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asm volatile (
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# if defined __GNUC__ || defined __clang__
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# if defined __powerpc64__ || defined __LP64__
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"1: ldarx %0,0,%1\n"
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" cmpd 0,%0,%2\n"
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" bne 0,2f\n"
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" stdcx. %3,0,%1\n"
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" bne 0,1b\n"
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"2:"
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# else
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"1: lwarx %0,0,%1\n"
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" cmpw 0,%0,%2\n"
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" bne 0,2f\n"
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" stwcx. %3,0,%1\n"
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" bne 0,1b\n"
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"2:"
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# endif
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# else /* another label syntax */
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# if defined __powerpc64__ || defined __LP64__
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".L01: ldarx %0,0,%1\n"
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" cmpd 0,%0,%2\n"
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" bne 0,.L02\n"
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" stdcx. %3,0,%1\n"
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" bne 0,.L01\n"
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".L02:"
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# else
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".L01: lwarx %0,0,%1\n"
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" cmpw 0,%0,%2\n"
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" bne 0,.L02\n"
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" stwcx. %3,0,%1\n"
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" bne 0,.L01\n"
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".L02:"
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# endif
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# endif
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: "=&r" (oldval)
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: "r" (vp), "r" (cmp), "r" (newval)
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: "cr0");
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asm volatile ("isync");
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return oldval;
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}
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# elif ((defined __GNUC__ || defined __clang__ || defined __SUNPRO_C) && (defined __sparc || defined __i386 || defined __x86_64__)) || (defined __TINYC__ && (defined __i386 || defined __x86_64__))
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/* For older versions of GCC or clang, use inline assembly.
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GCC, clang, and the Oracle Studio C 12 compiler understand GCC's extended
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asm syntax, but the plain Oracle Studio C 11 compiler understands only
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simple asm. */
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void
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memory_barrier (void)
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{
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# if defined __GNUC__ || defined __clang__ || __SUNPRO_C >= 0x590 || defined __TINYC__
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# if defined __i386 || defined __x86_64__
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# if defined __TINYC__ && defined __i386
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/* Cannot use the SSE instruction "mfence" with this compiler. */
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asm volatile ("lock orl $0,(%esp)");
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# else
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asm volatile ("mfence");
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# endif
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# endif
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# if defined __sparc
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asm volatile ("membar 2");
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# endif
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# else
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# if defined __i386 || defined __x86_64__
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asm ("mfence");
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# endif
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# if defined __sparc
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asm ("membar 2");
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# endif
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# endif
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}
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unsigned int
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atomic_compare_and_swap (unsigned int volatile *vp,
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unsigned int cmp,
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unsigned int newval)
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{
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# if defined __GNUC__ || defined __clang__ || __SUNPRO_C >= 0x590 || defined __TINYC__
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unsigned int oldval;
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# if defined __i386 || defined __x86_64__
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asm volatile (" lock\n cmpxchgl %3,(%1)"
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: "=a" (oldval) : "r" (vp), "a" (cmp), "r" (newval) : "memory");
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# endif
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# if defined __sparc
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asm volatile (" cas [%1],%2,%3\n"
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" mov %3,%0"
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: "=r" (oldval) : "r" (vp), "r" (cmp), "r" (newval) : "memory");
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# endif
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return oldval;
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# else /* __SUNPRO_C */
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# if defined __x86_64__
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asm (" movl %esi,%eax\n"
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" lock\n cmpxchgl %edx,(%rdi)");
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# elif defined __i386
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asm (" movl 16(%ebp),%ecx\n"
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" movl 12(%ebp),%eax\n"
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" movl 8(%ebp),%edx\n"
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" lock\n cmpxchgl %ecx,(%edx)");
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# endif
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# if defined __sparc
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asm (" cas [%i0],%i1,%i2\n"
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" mov %i2,%i0");
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# endif
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# endif
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}
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uintptr_t
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atomic_compare_and_swap_ptr (uintptr_t volatile *vp,
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uintptr_t cmp,
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uintptr_t newval)
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{
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# if defined __GNUC__ || defined __clang__ || __SUNPRO_C >= 0x590 || defined __TINYC__
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uintptr_t oldval;
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# if defined __x86_64__
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asm volatile (" lock\n cmpxchgq %3,(%1)"
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: "=a" (oldval) : "r" (vp), "a" (cmp), "r" (newval) : "memory");
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# elif defined __i386
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asm volatile (" lock\n cmpxchgl %3,(%1)"
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: "=a" (oldval) : "r" (vp), "a" (cmp), "r" (newval) : "memory");
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# endif
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# if defined __sparc && (defined __sparcv9 || defined __arch64__)
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asm volatile (" casx [%1],%2,%3\n"
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" mov %3,%0"
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: "=r" (oldval) : "r" (vp), "r" (cmp), "r" (newval) : "memory");
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# elif defined __sparc
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asm volatile (" cas [%1],%2,%3\n"
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" mov %3,%0"
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: "=r" (oldval) : "r" (vp), "r" (cmp), "r" (newval) : "memory");
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# endif
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return oldval;
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# else /* __SUNPRO_C */
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# if defined __x86_64__
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asm (" movq %rsi,%rax\n"
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" lock\n cmpxchgq %rdx,(%rdi)");
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# elif defined __i386
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asm (" movl 16(%ebp),%ecx\n"
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" movl 12(%ebp),%eax\n"
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" movl 8(%ebp),%edx\n"
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" lock\n cmpxchgl %ecx,(%edx)");
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# endif
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# if defined __sparc && (defined __sparcv9 || defined __arch64__)
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asm (" casx [%i0],%i1,%i2\n"
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" mov %i2,%i0");
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# elif defined __sparc
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asm (" cas [%i0],%i1,%i2\n"
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" mov %i2,%i0");
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# endif
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# endif
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}
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# else
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/* Fallback code. It has some race conditions. The unit test will fail. */
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void
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memory_barrier (void)
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{
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}
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unsigned int
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atomic_compare_and_swap (unsigned int volatile *vp,
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unsigned int cmp,
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unsigned int newval)
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{
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unsigned int oldval = *vp;
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if (oldval == cmp)
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*vp = newval;
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return oldval;
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}
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uintptr_t
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atomic_compare_and_swap_ptr (uintptr_t volatile *vp,
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uintptr_t cmp,
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uintptr_t newval)
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{
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uintptr_t oldval = *vp;
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if (oldval == cmp)
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*vp = newval;
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return oldval;
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}
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# endif
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#else
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/* A platform that does not support multi-threading. */
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void
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memory_barrier (void)
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{
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}
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unsigned int
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atomic_compare_and_swap (unsigned int volatile *vp,
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unsigned int cmp,
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unsigned int newval)
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{
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unsigned int oldval = *vp;
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if (oldval == cmp)
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*vp = newval;
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return oldval;
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}
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uintptr_t
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atomic_compare_and_swap_ptr (uintptr_t volatile *vp,
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uintptr_t cmp,
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uintptr_t newval)
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{
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uintptr_t oldval = *vp;
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if (oldval == cmp)
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*vp = newval;
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return oldval;
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}
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#endif
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