tcg: access cpu->icount_decr.u16.high with atomics

Consistently access u16.high with atomics to avoid
undefined behaviour in MTTCG.

Note that icount_decr.u16.low is only used in icount mode,
so regular accesses to it are OK.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <20181010144853.13005-2-cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/qom/cpu.c b/qom/cpu.c
index f7746546d0..9ad1372d57 100644
--- a/qom/cpu.c
+++ b/qom/cpu.c
@@ -265,7 +265,7 @@ static void cpu_common_reset(CPUState *cpu)
     cpu->mem_io_pc = 0;
     cpu->mem_io_vaddr = 0;
     cpu->icount_extra = 0;
-    cpu->icount_decr.u32 = 0;
+    atomic_set(&cpu->icount_decr.u32, 0);
     cpu->can_do_io = 1;
     cpu->exception_index = -1;
     cpu->crash_occurred = false;