Bug 1409295 part 5 - Use memcpy on little endian platforms. r=luke

--HG--
extra : rebase_source : 2e2bd1267a7d84d8458d6ec7cafef795ee5b6295

js/src/jsopcode.h

@@ -12,6 +12,7 @@
  */
 
 #include "mozilla/Attributes.h"
+#include "mozilla/EndianUtils.h"
 
 #include "jsbytecode.h"
 #include "jstypes.h"
@@ -136,14 +137,24 @@ UINT16_LO(uint16_t i)
 static MOZ_ALWAYS_INLINE uint16_t
 GET_UINT16(const jsbytecode* pc)
 {
+#if MOZ_LITTLE_ENDIAN
+    uint16_t result;
+    memcpy(&result, pc + 1, sizeof(result));
+    return result;
+#else
     return uint16_t((pc[2] << 8) | pc[1]);
+#endif
 }
 
 static MOZ_ALWAYS_INLINE void
 SET_UINT16(jsbytecode* pc, uint16_t i)
 {
+#if MOZ_LITTLE_ENDIAN
+    memcpy(pc + 1, &i, sizeof(i));
+#else
     pc[1] = UINT16_LO(i);
     pc[2] = UINT16_HI(i);
+#endif
 }
 
 static const unsigned UINT16_LIMIT      = 1 << 16;
@@ -153,19 +164,32 @@ static const unsigned JUMP_OFFSET_LEN   = 4;
 static const int32_t JUMP_OFFSET_MIN    = INT32_MIN;
 static const int32_t JUMP_OFFSET_MAX    = INT32_MAX;
 
-static MOZ_ALWAYS_INLINE unsigned
+static MOZ_ALWAYS_INLINE uint32_t
 GET_UINT24(const jsbytecode* pc)
 {
+#if MOZ_LITTLE_ENDIAN
+    // Do a single 32-bit load (for opcode and operand), then shift off the
+    // opcode.
+    uint32_t result;
+    memcpy(&result, pc, 4);
+    return result >> 8;
+#else
     return unsigned((pc[3] << 16) | (pc[2] << 8) | pc[1]);
+#endif
 }
 
 static MOZ_ALWAYS_INLINE void
-SET_UINT24(jsbytecode* pc, unsigned i)
+SET_UINT24(jsbytecode* pc, uint32_t i)
 {
     MOZ_ASSERT(i < (1 << 24));
+
+#if MOZ_LITTLE_ENDIAN
+    memcpy(pc + 1, &i, 3);
+#else
     pc[1] = jsbytecode(i);
     pc[2] = jsbytecode(i >> 8);
     pc[3] = jsbytecode(i >> 16);
+#endif
 }
 
 static MOZ_ALWAYS_INLINE int8_t
@@ -177,19 +201,29 @@ GET_INT8(const jsbytecode* pc)
 static MOZ_ALWAYS_INLINE uint32_t
 GET_UINT32(const jsbytecode* pc)
 {
+#if MOZ_LITTLE_ENDIAN
+    uint32_t result;
+    memcpy(&result, pc + 1, sizeof(result));
+    return result;
+#else
     return  (uint32_t(pc[4]) << 24) |
             (uint32_t(pc[3]) << 16) |
             (uint32_t(pc[2]) << 8)  |
             uint32_t(pc[1]);
+#endif
 }
 
 static MOZ_ALWAYS_INLINE void
 SET_UINT32(jsbytecode* pc, uint32_t u)
 {
+#if MOZ_LITTLE_ENDIAN
+    memcpy(pc + 1, &u, sizeof(u));
+#else
     pc[1] = jsbytecode(u);
     pc[2] = jsbytecode(u >> 8);
     pc[3] = jsbytecode(u >> 16);
     pc[4] = jsbytecode(u >> 24);
+#endif
 }
 
 static MOZ_ALWAYS_INLINE int32_t