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/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, you can obtain one at https://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
#ifndef ISC_ATOMIC_H
#define ISC_ATOMIC_H 1
#include <inttypes.h>
#include <isc/platform.h>
#include <isc/types.h>
#ifdef ISC_PLATFORM_USEGCCASM
/*
* This routine atomically increments the value stored in 'p' by 'val', and
* returns the previous value.
*/
static __inline__ int32_t
isc_atomic_xadd(int32_t *p, int32_t val) {
int32_t prev = val;
__asm__ volatile(
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
"xadd %0, %1"
:"=q"(prev)
:"m"(*p), "0"(prev)
:"memory", "cc");
return (prev);
}
#ifdef ISC_PLATFORM_HAVEXADDQ
static __inline__ int64_t
isc_atomic_xaddq(int64_t *p, int64_t val) {
int64_t prev = val;
__asm__ volatile(
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
"xaddq %0, %1"
:"=q"(prev)
:"m"(*p), "0"(prev)
:"memory", "cc");
return (prev);
}
#endif /* ISC_PLATFORM_HAVEXADDQ */
/*
* This routine atomically stores the value 'val' in 'p' (32-bit version).
*/
static __inline__ void
isc_atomic_store(int32_t *p, int32_t val) {
__asm__ volatile(
#ifdef ISC_PLATFORM_USETHREADS
/*
* xchg should automatically lock memory, but we add it
* explicitly just in case (it at least doesn't harm)
*/
"lock;"
#endif
"xchgl %1, %0"
:
: "r"(val), "m"(*p)
: "memory");
}
#ifdef ISC_PLATFORM_HAVEATOMICSTOREQ
/*
* This routine atomically stores the value 'val' in 'p' (64-bit version).
*/
static __inline__ void
isc_atomic_storeq(int64_t *p, int64_t val) {
__asm__ volatile(
#ifdef ISC_PLATFORM_USETHREADS
/*
* xchg should automatically lock memory, but we add it
* explicitly just in case (it at least doesn't harm)
*/
"lock;"
#endif
"xchgq %1, %0"
:
: "r"(val), "m"(*p)
: "memory");
}
#endif /* ISC_PLATFORM_HAVEATOMICSTOREQ */
/*
* This routine atomically replaces the value in 'p' with 'val', if the
* original value is equal to 'cmpval'. The original value is returned in any
* case.
*/
static __inline__ int32_t
isc_atomic_cmpxchg(int32_t *p, int32_t cmpval, int32_t val) {
__asm__ volatile(
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
"cmpxchgl %1, %2"
: "=a"(cmpval)
: "r"(val), "m"(*p), "a"(cmpval)
: "memory");
return (cmpval);
}
#elif defined(ISC_PLATFORM_USESTDASM)
/*
* The following are "generic" assembly code which implements the same
* functionality in case the gcc extension cannot be used. It should be
* better to avoid inlining below, since we directly refer to specific
* positions of the stack frame, which would not actually point to the
* intended address in the embedded mnemonic.
*/
static int32_t
isc_atomic_xadd(int32_t *p, int32_t val) {
(void)(p);
(void)(val);
__asm (
"movl 8(%ebp), %ecx\n"
"movl 12(%ebp), %edx\n"
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
"xadd %edx, (%ecx)\n"
/*
* set the return value directly in the register so that we
* can avoid guessing the correct position in the stack for a
* local variable.
*/
"movl %edx, %eax"
);
}
static void
isc_atomic_store(int32_t *p, int32_t val) {
(void)(p);
(void)(val);
__asm (
"movl 8(%ebp), %ecx\n"
"movl 12(%ebp), %edx\n"
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
"xchgl (%ecx), %edx\n"
);
}
static int32_t
isc_atomic_cmpxchg(int32_t *p, int32_t cmpval, int32_t val) {
(void)(p);
(void)(cmpval);
(void)(val);
__asm (
"movl 8(%ebp), %ecx\n"
"movl 12(%ebp), %eax\n" /* must be %eax for cmpxchgl */
"movl 16(%ebp), %edx\n"
#ifdef ISC_PLATFORM_USETHREADS
"lock;"
#endif
/*
* If (%ecx) == %eax then (%ecx) := %edx.
% %eax is set to old (%ecx), which will be the return value.
*/
"cmpxchgl %edx, (%ecx)"
);
}
#else /* !ISC_PLATFORM_USEGCCASM && !ISC_PLATFORM_USESTDASM */
#error "unsupported compiler. disable atomic ops by --disable-atomic"
#endif
#endif /* ISC_ATOMIC_H */
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