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qemu/atomic128: Add x86_64 atomic128-ldst.h

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With CPUINFO_ATOMIC_VMOVDQA, we can perform proper atomic
load/store without cmpxchg16b.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2023-05-19 21:12:34 -07:00
parent 6479dd74f1
commit 480dfba2c9
1 changed files with 68 additions and 0 deletions
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68
host/include/x86_64/host/atomic128-ldst.h Normal file
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/*
* SPDX-License-Identifier: GPL-2.0-or-later
* Load/store for 128-bit atomic operations, x86_64 version.
*
* Copyright (C) 2023 Linaro, Ltd.
*
* See docs/devel/atomics.rst for discussion about the guarantees each
* atomic primitive is meant to provide.
*/
#ifndef AARCH64_ATOMIC128_LDST_H
#define AARCH64_ATOMIC128_LDST_H
#ifdef CONFIG_INT128_TYPE
#include "host/cpuinfo.h"
#include "tcg/debug-assert.h"
/*
* Through clang 16, with -mcx16, __atomic_load_n is incorrectly
* expanded to a read-write operation: lock cmpxchg16b.
*/
#define HAVE_ATOMIC128_RO likely(cpuinfo & CPUINFO_ATOMIC_VMOVDQA)
#define HAVE_ATOMIC128_RW 1
static inline Int128 atomic16_read_ro(const Int128 *ptr)
{
Int128Alias r;
tcg_debug_assert(HAVE_ATOMIC128_RO);
asm("vmovdqa %1, %0" : "=x" (r.i) : "m" (*ptr));
return r.s;
}
static inline Int128 atomic16_read_rw(Int128 *ptr)
{
__int128_t *ptr_align = __builtin_assume_aligned(ptr, 16);
Int128Alias r;
if (HAVE_ATOMIC128_RO) {
asm("vmovdqa %1, %0" : "=x" (r.i) : "m" (*ptr_align));
} else {
r.i = __sync_val_compare_and_swap_16(ptr_align, 0, 0);
}
return r.s;
}
static inline void atomic16_set(Int128 *ptr, Int128 val)
{
__int128_t *ptr_align = __builtin_assume_aligned(ptr, 16);
Int128Alias new = { .s = val };
if (HAVE_ATOMIC128_RO) {
asm("vmovdqa %1, %0" : "=m"(*ptr_align) : "x" (new.i));
} else {
__int128_t old;
do {
old = *ptr_align;
} while (!__sync_bool_compare_and_swap_16(ptr_align, old, new.i));
}
}
#else
/* Provide QEMU_ERROR stubs. */
#include "host/include/generic/host/atomic128-ldst.h"
#endif
#endif /* AARCH64_ATOMIC128_LDST_H */