34aee9c946
When compiling QEMU with Clang 17 on a s390x, the compilation fails:
In file included from ../accel/tcg/cputlb.c:32:
In file included from /root/qemu/include/exec/helper-proto-common.h:10:
In file included from /root/qemu/include/qemu/atomic128.h:62:
/root/qemu/host/include/generic/host/atomic128-ldst.h:68:15: error:
__sync builtin operation MUST have natural alignment (consider using __
atomic). [-Werror,-Wsync-alignment]
68 | } while (!__sync_bool_compare_and_swap_16(ptr_align, old, new.i));
| ^
In file included from ../accel/tcg/cputlb.c:32:
In file included from /root/qemu/include/exec/helper-proto-common.h:10:
In file included from /root/qemu/include/qemu/atomic128.h:61:
/root/qemu/host/include/generic/host/atomic128-cas.h:36:11: error:
__sync builtin operation MUST have natural alignment (consider using __a
tomic). [-Werror,-Wsync-alignment]
36 | r.i = __sync_val_compare_and_swap_16(ptr_align, c.i, n.i);
| ^
2 errors generated.
It's arguably a bug in Clang since we already use __builtin_assume_aligned()
to tell the compiler that the pointer is properly aligned. But according to
https://github.com/llvm/llvm-project/issues/69146 it seems like the Clang
folks don't see an easy fix on their side and recommend to use a type
declared with __attribute__((aligned(16))) to work around this problem.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1934
Message-ID: <20231108085954.313071-1-thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
82 lines
2.0 KiB
C
82 lines
2.0 KiB
C
/*
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* SPDX-License-Identifier: GPL-2.0-or-later
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* Load/store for 128-bit atomic operations, generic version.
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*
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* Copyright (C) 2018, 2023 Linaro, Ltd.
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*
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* See docs/devel/atomics.rst for discussion about the guarantees each
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* atomic primitive is meant to provide.
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*/
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#ifndef HOST_ATOMIC128_LDST_H
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#define HOST_ATOMIC128_LDST_H
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#if defined(CONFIG_ATOMIC128)
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# define HAVE_ATOMIC128_RO 1
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# define HAVE_ATOMIC128_RW 1
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static inline Int128 ATTRIBUTE_ATOMIC128_OPT
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atomic16_read_ro(const Int128 *ptr)
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{
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const __int128_t *ptr_align = __builtin_assume_aligned(ptr, 16);
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Int128Alias r;
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r.i = qatomic_read__nocheck(ptr_align);
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return r.s;
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}
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static inline Int128 ATTRIBUTE_ATOMIC128_OPT
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atomic16_read_rw(Int128 *ptr)
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{
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return atomic16_read_ro(ptr);
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}
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static inline void ATTRIBUTE_ATOMIC128_OPT
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atomic16_set(Int128 *ptr, Int128 val)
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{
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__int128_t *ptr_align = __builtin_assume_aligned(ptr, 16);
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Int128Alias v;
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v.s = val;
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qatomic_set__nocheck(ptr_align, v.i);
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}
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#elif defined(CONFIG_CMPXCHG128)
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# define HAVE_ATOMIC128_RO 0
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# define HAVE_ATOMIC128_RW 1
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Int128 QEMU_ERROR("unsupported atomic") atomic16_read_ro(const Int128 *ptr);
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static inline Int128 ATTRIBUTE_ATOMIC128_OPT
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atomic16_read_rw(Int128 *ptr)
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{
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/* Maybe replace 0 with 0, returning the old value. */
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Int128 z = int128_make64(0);
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return atomic16_cmpxchg(ptr, z, z);
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}
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static inline void ATTRIBUTE_ATOMIC128_OPT
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atomic16_set(Int128 *ptr, Int128 val)
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{
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Int128Aligned *ptr_align = __builtin_assume_aligned(ptr, 16);
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__int128_t old;
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Int128Alias new;
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new.s = val;
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do {
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old = *ptr_align;
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} while (!__sync_bool_compare_and_swap_16(ptr_align, old, new.i));
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}
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#else
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# define HAVE_ATOMIC128_RO 0
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# define HAVE_ATOMIC128_RW 0
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/* Fallback definitions that must be optimized away, or error. */
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Int128 QEMU_ERROR("unsupported atomic") atomic16_read_ro(const Int128 *ptr);
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Int128 QEMU_ERROR("unsupported atomic") atomic16_read_rw(Int128 *ptr);
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void QEMU_ERROR("unsupported atomic") atomic16_set(Int128 *ptr, Int128 val);
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#endif
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#endif /* HOST_ATOMIC128_LDST_H */
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