From 34aee9c94691f529cd952f9483a6b357ca098042 Mon Sep 17 00:00:00 2001 From: Thomas Huth Date: Wed, 8 Nov 2023 09:59:54 +0100 Subject: [PATCH] host/include/generic/host/atomic128: Fix compilation problem with Clang 17 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Richard Henderson Signed-off-by: Thomas Huth --- host/include/generic/host/atomic128-cas.h | 2 +- host/include/generic/host/atomic128-ldst.h | 2 +- include/qemu/int128.h | 2 ++ 3 files changed, 4 insertions(+), 2 deletions(-) diff --git a/host/include/generic/host/atomic128-cas.h b/host/include/generic/host/atomic128-cas.h index 991d3da082..6b40cc2271 100644 --- a/host/include/generic/host/atomic128-cas.h +++ b/host/include/generic/host/atomic128-cas.h @@ -28,7 +28,7 @@ atomic16_cmpxchg(Int128 *ptr, Int128 cmp, Int128 new) static inline Int128 ATTRIBUTE_ATOMIC128_OPT atomic16_cmpxchg(Int128 *ptr, Int128 cmp, Int128 new) { - __int128_t *ptr_align = __builtin_assume_aligned(ptr, 16); + Int128Aligned *ptr_align = __builtin_assume_aligned(ptr, 16); Int128Alias r, c, n; c.s = cmp; diff --git a/host/include/generic/host/atomic128-ldst.h b/host/include/generic/host/atomic128-ldst.h index 80fff0643a..691e6a8531 100644 --- a/host/include/generic/host/atomic128-ldst.h +++ b/host/include/generic/host/atomic128-ldst.h @@ -58,7 +58,7 @@ atomic16_read_rw(Int128 *ptr) static inline void ATTRIBUTE_ATOMIC128_OPT atomic16_set(Int128 *ptr, Int128 val) { - __int128_t *ptr_align = __builtin_assume_aligned(ptr, 16); + Int128Aligned *ptr_align = __builtin_assume_aligned(ptr, 16); __int128_t old; Int128Alias new; diff --git a/include/qemu/int128.h b/include/qemu/int128.h index 73624e8be7..174bd7dafb 100644 --- a/include/qemu/int128.h +++ b/include/qemu/int128.h @@ -10,6 +10,7 @@ */ #if defined(CONFIG_INT128) && !defined(CONFIG_TCG_INTERPRETER) typedef __int128_t Int128; +typedef __int128_t __attribute__((aligned(16))) Int128Aligned; static inline Int128 int128_make64(uint64_t a) { @@ -224,6 +225,7 @@ static inline Int128 int128_rems(Int128 a, Int128 b) #else /* !CONFIG_INT128 */ typedef struct Int128 Int128; +typedef struct Int128 __attribute__((aligned(16))) Int128Aligned; /* * We guarantee that the in-memory byte representation of an