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qemu/atomic128: Split atomic16_read

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Create both atomic16_read_ro and atomic16_read_rw.
Previously we pretended that we had atomic16_read in system mode,
because we "know" that all ram is always writable to the host.
Now, expose read-only and read-write versions all of the time.

For aarch64, do not fall back to __atomic_read_16 even if
supported by the compiler, to work around a clang bug.

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 18:30:28 -07:00
parent 4deb39ebb3
commit 21c38f31c0
3 changed files with 36 additions and 18 deletions
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21
host/include/aarch64/host/atomic128-ldst.h
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@ -11,10 +11,18 @@
#ifndef AARCH64_ATOMIC128_LDST_H
#define AARCH64_ATOMIC128_LDST_H
/* Through gcc 10, aarch64 has no support for 128-bit atomics. */
#if !defined(CONFIG_ATOMIC128) && !defined(CONFIG_USER_ONLY)
/* We can do better than cmpxchg for AArch64. */
static inline Int128 atomic16_read(Int128 *ptr)
/*
* Through gcc 10, aarch64 has no support for 128-bit atomics.
* Through clang 16, without -march=armv8.4-a, __atomic_load_16
* is incorrectly expanded to a read-write operation.
*/
#define HAVE_ATOMIC128_RO 0
#define HAVE_ATOMIC128_RW 1
Int128 QEMU_ERROR("unsupported atomic") atomic16_read_ro(const Int128 *ptr);
static inline Int128 atomic16_read_rw(Int128 *ptr)
{
uint64_t l, h;
uint32_t tmp;
@ -41,9 +49,4 @@ static inline void atomic16_set(Int128 *ptr, Int128 val)
: [l] "r"(l), [h] "r"(h));
}
# define HAVE_ATOMIC128 1
#else
#include "host/include/generic/host/atomic128-ldst.h"
#endif
#endif /* AARCH64_ATOMIC128_LDST_H */

31
host/include/generic/host/atomic128-ldst.h
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@ -12,16 +12,25 @@
#define HOST_ATOMIC128_LDST_H
#if defined(CONFIG_ATOMIC128)
# define HAVE_ATOMIC128_RO 1
# define HAVE_ATOMIC128_RW 1
static inline Int128 ATTRIBUTE_ATOMIC128_OPT
atomic16_read(Int128 *ptr)
atomic16_read_ro(const Int128 *ptr)
{
__int128_t *ptr_align = __builtin_assume_aligned(ptr, 16);
const __int128_t *ptr_align = __builtin_assume_aligned(ptr, 16);
Int128Alias r;
r.i = qatomic_read__nocheck(ptr_align);
return r.s;
}
static inline Int128 ATTRIBUTE_ATOMIC128_OPT
atomic16_read_rw(Int128 *ptr)
{
return atomic16_read_ro(ptr);
}
static inline void ATTRIBUTE_ATOMIC128_OPT
atomic16_set(Int128 *ptr, Int128 val)
{
@ -32,10 +41,14 @@ atomic16_set(Int128 *ptr, Int128 val)
qatomic_set__nocheck(ptr_align, v.i);
}
# define HAVE_ATOMIC128 1
#elif defined(CONFIG_CMPXCHG128) && !defined(CONFIG_USER_ONLY)
#elif defined(CONFIG_CMPXCHG128)
# define HAVE_ATOMIC128_RO 0
# define HAVE_ATOMIC128_RW 1
Int128 QEMU_ERROR("unsupported atomic") atomic16_read_ro(const Int128 *ptr);
static inline Int128 ATTRIBUTE_ATOMIC128_OPT
atomic16_read(Int128 *ptr)
atomic16_read_rw(Int128 *ptr)
{
/* Maybe replace 0 with 0, returning the old value. */
Int128 z = int128_make64(0);
@ -52,12 +65,14 @@ atomic16_set(Int128 *ptr, Int128 val)
} while (int128_ne(old, cmp));
}
# define HAVE_ATOMIC128 1
#else
# define HAVE_ATOMIC128_RO 0
# define HAVE_ATOMIC128_RW 0
/* Fallback definitions that must be optimized away, or error. */
Int128 QEMU_ERROR("unsupported atomic") atomic16_read(Int128 *ptr);
Int128 QEMU_ERROR("unsupported atomic") atomic16_read_ro(const Int128 *ptr);
Int128 QEMU_ERROR("unsupported atomic") atomic16_read_rw(Int128 *ptr);
void QEMU_ERROR("unsupported atomic") atomic16_set(Int128 *ptr, Int128 val);
# define HAVE_ATOMIC128 0
#endif
#endif /* HOST_ATOMIC128_LDST_H */

2
target/s390x/tcg/mem_helper.c
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@ -1780,7 +1780,7 @@ static uint32_t do_csst(CPUS390XState *env, uint32_t r3, uint64_t a1,
max = 3;
#endif
if ((HAVE_CMPXCHG128 ? 0 : fc + 2 > max) ||
(HAVE_ATOMIC128 ? 0 : sc > max)) {
(HAVE_ATOMIC128_RW ? 0 : sc > max)) {
cpu_loop_exit_atomic(env_cpu(env), ra);
}
}