On Mon, Aug 24, 2026 at 12:19:15PM +0800, BillXiang wrote:
> Hi Richard, I've read your code in accel/tcg/ldst_atomicity.c.inc. Do
> you think it would be better to make the load/store_atomic* public?
They do not fit by default, as we need to still process unaligned cases?
I wished we can use qemu_mem_move() directly that just got introduced.. but
it does slightly more than wanted. Maybe something like this? Below diff
dropped ldsw_he_p() alone the way as it's never used.
Thanks,
===8<===
diff --git a/include/qemu/bswap.h b/include/qemu/bswap.h
index 387d65c0b0..04a0f63612 100644
--- a/include/qemu/bswap.h
+++ b/include/qemu/bswap.h
@@ -1,6 +1,7 @@
#ifndef BSWAP_H
#define BSWAP_H
+#include "qemu/atomic.h"
#include "qemu/target-info.h"
#include "exec/memop.h"
@@ -238,62 +239,52 @@ static inline void stb_p(void *ptr, uint8_t v)
*(uint8_t *)ptr = v;
}
-/*
- * Any compiler worth its salt will turn these memcpy into native unaligned
- * operations. Thus we don't need to play games with packed attributes, or
- * inline byte-by-byte stores.
- * Some compilation environments (eg some fortify-source implementations)
- * may intercept memcpy() in a way that defeats the compiler optimization,
- * though, so we use __builtin_memcpy() to give ourselves the best chance
- * of good performance.
- */
-
-static inline int lduw_he_p(const void *ptr)
-{
- uint16_t r;
- __builtin_memcpy(&r, ptr, sizeof(r));
- return r;
-}
-
-static inline int ldsw_he_p(const void *ptr)
-{
- int16_t r;
- __builtin_memcpy(&r, ptr, sizeof(r));
- return r;
-}
+#define LD_HE_P(type, size) \
+ static inline type \
+ glue(glue(ld, size), _he_p)(const void *ptr) \
+ { \
+ type v; \
+ if (unlikely((uintptr_t)ptr & (sizeof(v) - 1))) { \
+ __builtin_memcpy(&v, ptr, sizeof(v)); \
+ } else { \
+ v = qatomic_read((type *)ptr); \
+ } \
+ return v; \
+ }
-static inline void stw_he_p(void *ptr, uint16_t v)
-{
- __builtin_memcpy(ptr, &v, sizeof(v));
-}
+#define ST_HE_P(type, size) \
+ static inline void \
+ glue(glue(st, size), _he_p)(void *ptr, type v) \
+ { \
+ if (unlikely((uintptr_t)ptr & (sizeof(v) - 1))) { \
+ __builtin_memcpy(ptr, &v, sizeof(v)); \
+ } else { \
+ qatomic_set((type *)ptr, v); \
+ } \
+ }
-static inline void st24_he_p(void *ptr, uint32_t v)
-{
- __builtin_memcpy(ptr, &v, 3);
-}
+LD_HE_P(uint16_t, 16)
+LD_HE_P(uint32_t, 32)
+LD_HE_P(uint64_t, 64)
+ST_HE_P(uint16_t, 16)
+ST_HE_P(uint32_t, 32)
+ST_HE_P(uint64_t, 64)
-static inline int ldl_he_p(const void *ptr)
-{
- int32_t r;
- __builtin_memcpy(&r, ptr, sizeof(r));
- return r;
-}
+#undef LD_HE_P
+#undef ST_HE_P
+#undef ADDR_ALIGNED
-static inline void stl_he_p(void *ptr, uint32_t v)
-{
- __builtin_memcpy(ptr, &v, sizeof(v));
-}
+#define lduw_he_p ld16_he_p
+#define ldl_he_p ld32_he_p
+#define ldq_he_p ld64_he_p
-static inline uint64_t ldq_he_p(const void *ptr)
-{
- uint64_t r;
- __builtin_memcpy(&r, ptr, sizeof(r));
- return r;
-}
+#define stw_he_p st16_he_p
+#define stl_he_p st32_he_p
+#define stq_he_p st64_he_p
-static inline void stq_he_p(void *ptr, uint64_t v)
+static inline void st24_he_p(void *ptr, uint32_t v)
{
- __builtin_memcpy(ptr, &v, sizeof(v));
+ __builtin_memcpy(ptr, &v, 3);
}
static inline int lduw_le_p(const void *ptr)
--
2.54.0
--
Peter Xu
