Use common helper functions for unaligned loads.

src/lj_def.h

@@ -184,6 +184,28 @@ static LJ_AINLINE uint64_t lj_bswap64(uint64_t x)
 #error "missing define for lj_bswap()"
 #endif
 
+typedef union __attribute__((packed)) Unaligned16 {
+  uint16_t u;
+  uint8_t b[2];
+} Unaligned16;
+
+typedef union __attribute__((packed)) Unaligned32 {
+  uint32_t u;
+  uint8_t b[4];
+} Unaligned32;
+
+/* Unaligned load of uint16_t. */
+static LJ_AINLINE uint16_t lj_getu16(const void *p)
+{
+  return ((const Unaligned16 *)p)->u;
+}
+
+/* Unaligned load of uint32_t. */
+static LJ_AINLINE uint32_t lj_getu32(const void *p)
+{
+  return ((const Unaligned32 *)p)->u;
+}
+
 #elif defined(_MSC_VER)
 
 #define LJ_NORET	__declspec(noreturn)
@@ -208,6 +230,10 @@ static LJ_AINLINE uint32_t lj_fls(uint32_t x)
 #define lj_bswap(x)	(_byteswap_ulong((x)))
 #define lj_bswap64(x)	(_byteswap_uint64((x)))
 
+/* MSVC is only supported on x86/x64, where unaligned loads are always ok. */
+#define lj_getu16(p)	(*(uint16_t *)(p))
+#define lj_getu32(p)	(*(uint32_t *)(p))
+
 #else
 #error "missing defines for your compiler"
 #endif

src/lj_opt_fold.c

@@ -1647,16 +1647,13 @@ LJFOLDF(comm_bxor)
 static TRef kfold_xload(jit_State *J, IRIns *ir, const void *p)
 {
   int32_t k;
-#if !LJ_TARGET_X86ORX64
-#error "Missing support for unaligned loads"
-#endif
   switch (irt_type(ir->t)) {
   case IRT_NUM: return lj_ir_knum_u64(J, *(uint64_t *)p);
   case IRT_I8: k = (int32_t)*(int8_t *)p; break;
   case IRT_U8: k = (int32_t)*(uint8_t *)p; break;
-  case IRT_I16: k = (int32_t)*(int16_t *)p; break;
-  case IRT_U16: k = (int32_t)*(uint16_t *)p; break;
-  case IRT_INT: case IRT_U32: k = *(int32_t *)p; break;
+  case IRT_I16: k = (int32_t)(int16_t)lj_getu16(p); break;
+  case IRT_U16: k = (int32_t)(uint16_t)lj_getu16(p); break;
+  case IRT_INT: case IRT_U32: k = (int32_t)lj_getu32(p); break;
   case IRT_I64: case IRT_U64: return lj_ir_kint64(J, *(uint64_t *)p);
   default: return 0;
   }

src/lj_str.c

@@ -43,18 +43,6 @@ int32_t LJ_FASTCALL lj_str_cmp(GCstr *a, GCstr *b)
   return (int32_t)(a->len - b->len);
 }
 
-typedef union
-#ifdef __GNUC__
-__attribute__((packed))
-#endif
-Unaligned32 { uint32_t u; uint8_t b[4]; } Unaligned32;
-
-/* Unaligned read of uint32_t. */
-static LJ_AINLINE uint32_t str_getu32(const void *p)
-{
-  return ((const Unaligned32 *)p)->u;
-}
-
 /* Fast string data comparison. Caveat: unaligned access to 1st string! */
 static LJ_AINLINE int str_fastcmp(const char *a, const char *b, MSize len)
 {
@@ -62,7 +50,7 @@ static LJ_AINLINE int str_fastcmp(const char *a, const char *b, MSize len)
   lua_assert(len > 0);
   lua_assert((((uintptr_t)a + len) & (LJ_PAGESIZE-1)) <= LJ_PAGESIZE-4);
   do {  /* Note: innocuous access up to end of string + 3. */
-    uint32_t v = str_getu32(a+i) ^ *(const uint32_t *)(b+i);
+    uint32_t v = lj_getu32(a+i) ^ *(const uint32_t *)(b+i);
     if (v) {
       i -= len;
 #if LJ_LE
@@ -115,11 +103,11 @@ GCstr *lj_str_new(lua_State *L, const char *str, size_t lenx)
   g = G(L);
   /* Compute string hash. Constants taken from lookup3 hash by Bob Jenkins. */
   if (len >= 4) {  /* Caveat: unaligned access! */
-    a = str_getu32(str);
-    h ^= str_getu32(str+len-4);
-    b = str_getu32(str+(len>>1)-2);
+    a = lj_getu32(str);
+    h ^= lj_getu32(str+len-4);
+    b = lj_getu32(str+(len>>1)-2);
     h ^= b; h -= lj_rol(b, 14);
-    b += str_getu32(str+(len>>2)-1);
+    b += lj_getu32(str+(len>>2)-1);
   } else if (len > 0) {
     a = *(const uint8_t *)str;
     h ^= *(const uint8_t *)(str+len-1);