Reland "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 8b4b26397e322f7817b33124d5f7ef06c93fb88e..4becf6e305e1ce29a36eac853688445a169aa21c 100644
--- a/src/deoptimizer.h
+++ b/src/deoptimizer.h
@@ -17,19 +17,17 @@ 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] = *reinterpret_cast<uint32_t*>(p);
-  c.u[1] = *reinterpret_cast<uint32_t*>(p + 4);
+  c.u[0] = Memory::uint32_at(p);
+  c.u[1] = Memory::uint32_at(p + 4);
   return c.d;
-#endif  // V8_HOST_CAN_READ_UNALIGNED
 }