From 24be3369ad63c3882be42dd510a45bad52816fd1 Mon Sep 17 00:00:00 2001
From: Thomas Huth <thuth@redhat.com>
Date: Tue, 11 Apr 2023 20:34:17 +0200
Subject: [PATCH] include/exec: Provide the tswap() functions for target
 independent code, too
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In some cases of target independent code, it would be useful to have access
to the functions that swap endianess in case it differs between guest and
host. Thus re-implement the tswapXX() functions in a new header that can be
included separately. The check whether the swapping is needed continues to
be done at compile-time for target specific code, while it is done at
run-time in target-independent code.

Message-Id: <20230411183418.1640500-3-thuth@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 include/exec/cpu-all.h | 64 +------------------------------------
 include/exec/tswap.h   | 72 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+), 63 deletions(-)
 create mode 100644 include/exec/tswap.h

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 090922e4a8..ad824fee52 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -21,6 +21,7 @@
 
 #include "exec/cpu-common.h"
 #include "exec/memory.h"
+#include "exec/tswap.h"
 #include "qemu/thread.h"
 #include "hw/core/cpu.h"
 #include "qemu/rcu.h"
@@ -44,69 +45,6 @@
 #define BSWAP_NEEDED
 #endif
 
-#ifdef BSWAP_NEEDED
-
-static inline uint16_t tswap16(uint16_t s)
-{
-    return bswap16(s);
-}
-
-static inline uint32_t tswap32(uint32_t s)
-{
-    return bswap32(s);
-}
-
-static inline uint64_t tswap64(uint64_t s)
-{
-    return bswap64(s);
-}
-
-static inline void tswap16s(uint16_t *s)
-{
-    *s = bswap16(*s);
-}
-
-static inline void tswap32s(uint32_t *s)
-{
-    *s = bswap32(*s);
-}
-
-static inline void tswap64s(uint64_t *s)
-{
-    *s = bswap64(*s);
-}
-
-#else
-
-static inline uint16_t tswap16(uint16_t s)
-{
-    return s;
-}
-
-static inline uint32_t tswap32(uint32_t s)
-{
-    return s;
-}
-
-static inline uint64_t tswap64(uint64_t s)
-{
-    return s;
-}
-
-static inline void tswap16s(uint16_t *s)
-{
-}
-
-static inline void tswap32s(uint32_t *s)
-{
-}
-
-static inline void tswap64s(uint64_t *s)
-{
-}
-
-#endif
-
 #if TARGET_LONG_SIZE == 4
 #define tswapl(s) tswap32(s)
 #define tswapls(s) tswap32s((uint32_t *)(s))
diff --git a/include/exec/tswap.h b/include/exec/tswap.h
new file mode 100644
index 0000000000..68944a880b
--- /dev/null
+++ b/include/exec/tswap.h
@@ -0,0 +1,72 @@
+/*
+ * Macros for swapping a value if the endianness is different
+ * between the target and the host.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#ifndef TSWAP_H
+#define TSWAP_H
+
+#include "hw/core/cpu.h"
+#include "qemu/bswap.h"
+
+/*
+ * If we're in target-specific code, we can hard-code the swapping
+ * condition, otherwise we have to do (slower) run-time checks.
+ */
+#ifdef NEED_CPU_H
+#define target_needs_bswap()  (HOST_BIG_ENDIAN != TARGET_BIG_ENDIAN)
+#else
+#define target_needs_bswap()  (target_words_bigendian() != HOST_BIG_ENDIAN)
+#endif
+
+static inline uint16_t tswap16(uint16_t s)
+{
+    if (target_needs_bswap()) {
+        return bswap16(s);
+    } else {
+        return s;
+    }
+}
+
+static inline uint32_t tswap32(uint32_t s)
+{
+    if (target_needs_bswap()) {
+        return bswap32(s);
+    } else {
+        return s;
+    }
+}
+
+static inline uint64_t tswap64(uint64_t s)
+{
+    if (target_needs_bswap()) {
+        return bswap64(s);
+    } else {
+        return s;
+    }
+}
+
+static inline void tswap16s(uint16_t *s)
+{
+    if (target_needs_bswap()) {
+        *s = bswap16(*s);
+    }
+}
+
+static inline void tswap32s(uint32_t *s)
+{
+    if (target_needs_bswap()) {
+        *s = bswap32(*s);
+    }
+}
+
+static inline void tswap64s(uint64_t *s)
+{
+    if (target_needs_bswap()) {
+        *s = bswap64(*s);
+    }
+}
+
+#endif  /* TSWAP_H */