Revert "Remove V8_HOST_CAN_READ_UNALIGNED and its uses."

src/deoptimizer.h

Index: src/deoptimizer.h
diff --git a/src/deoptimizer.h b/src/deoptimizer.h
index 602a21a0e20b199e7ca9a229b79c0be5be9c4783..5d401deedd6c8d9f06c15b7f9b61a3f352680176 100644
--- a/src/deoptimizer.h
+++ b/src/deoptimizer.h
@@ -17,17 +17,19 @@ namespace internal {
 
 
 static inline double read_double_value(Address p) {
+#ifdef V8_HOST_CAN_READ_UNALIGNED
+  return Memory::double_at(p);
+#else  // V8_HOST_CAN_READ_UNALIGNED
   // Prevent gcc from using load-double (mips ldc1) on (possibly)
   // non-64-bit aligned address.
-  // We assume that the address is 32-bit aligned.
-  DCHECK(IsAligned(reinterpret_cast<intptr_t>(p), kInt32Size));
   union conversion {
     double d;
     uint32_t u[2];
   } c;
-  c.u[0] = Memory::uint32_at(p);
-  c.u[1] = Memory::uint32_at(p + 4);
+  c.u[0] = *reinterpret_cast<uint32_t*>(p);
+  c.u[1] = *reinterpret_cast<uint32_t*>(p + 4);
   return c.d;
+#endif  // V8_HOST_CAN_READ_UNALIGNED
 }