Fix wrong endianness of wasm header in WasmModuleWriter on big-endian platforms

src/base/bits.h

Index: src/base/bits.h
diff --git a/src/base/bits.h b/src/base/bits.h
index 2e6527b0548ec54f6640cc629d06c0a729959fe3..0db2778b6709395b687930aeb9861042dbfca3e4 100644
--- a/src/base/bits.h
+++ b/src/base/bits.h
@@ -131,6 +131,67 @@ inline unsigned CountTrailingZeros32(uint32_t value) {
 #endif
 }
 
+inline int16_t ChangeEndianness(int16_t value) {
+#if V8_HAS_BUILTIN_BSWAP16
+  return __builtin_bswap16(value);
+#else
+  return (value << 8) | ((value >> 8) & 0xFF);
+#endif
+}
+
+inline uint16_t ChangeEndianness(uint16_t value) {
+#if V8_HAS_BUILTIN_BSWAP16
+  return __builtin_bswap16(value);
+#else
+  return (value << 8) | (value >> 8);
+#endif
+}
+
+inline int32_t ChangeEndianness(int32_t value) {
+#if V8_HAS_BUILTIN_BSWAP32
+  return __builtin_bswap32(value);
+#else
+  int32_t tmp;
+  tmp = ((value << 8) & 0xFF00FF00) | ((value >> 8) & 0xFF00FF);
+  return (tmp << 16) | ((tmp >> 16) & 0xFFFF);
+#endif
+}
+
+inline uint32_t ChangeEndianness(uint32_t value) {
+#if V8_HAS_BUILTIN_BSWAP32
+  return __builtin_bswap32(value);
+#else
+  int32_t tmp;
+  tmp = ((value << 8) & 0xFF00FF00) | ((value >> 8) & 0xFF00FF);
+  return (tmp << 16) | (tmp >> 16);
+#endif
+}
+
+inline int64_t ChangeEndianness(int64_t value) {
+#if V8_HAS_BUILTIN_BSWAP64
+  return __builtin_bswap64(value);
+#else
+  int64_t tmp;
+  tmp = ((value << 8) & 0xFF00FF00FF00FF00ULL) |
+        ((value >> 8) & 0x00FF00FF00FF00FFULL);
+  tmp = ((tmp << 16) & 0xFFFF0000FFFF0000ULL) |
+        ((tmp >> 16) & 0x0000FFFF0000FFFFULL);
+  return (tmp << 32) | ((tmp >> 32) & 0xFFFFFFFFULL);
+#endif
+}
+
+inline int64_t ChangeEndianness(uint64_t value) {
+#if V8_HAS_BUILTIN_BSWAP64
+  return __builtin_bswap64(value);
+#else
+  int64_t tmp;
+  tmp = ((value << 8) & 0xFF00FF00FF00FF00ULL) |
+        ((value >> 8) & 0x00FF00FF00FF00FFULL);
+  tmp = ((tmp << 16) & 0xFFFF0000FFFF0000ULL) |
+        ((tmp >> 16) & 0x0000FFFF0000FFFFULL);
+  return (tmp << 32) | (tmp >> 32);
+#endif
+}
 
 // CountTrailingZeros64(value) returns the number of zero bits preceding the
 // least significant 1 bit in |value| if |value| is non-zero, otherwise it