Ruby: Correct DataBlock =operator

The =operator for the DataBlock class was incorrectly interpreting the class
member m_alloc. This variable stands for whether the assigned memory for the
data block needs to be freed or not by the class itself. It seems that the
=operator interpreted the variable as whether the memory is assigned to the
data block. This wrong interpretation was causing values not to propagate
to RubySystem::m_mem_vec_ptr. This caused major issues with restoring from
checkpoints when using a protocol which verified that the cache data was
consistent with the backing store (i.e. MOESI-hammer).

src/mem/ruby/common/DataBlock.cc

@@ -87,14 +87,6 @@ DataBlock::setData(uint8* data, int offset, int len)
 DataBlock &
 DataBlock::operator=(const DataBlock & obj)
 {
-    if (this == &obj) {
-        // assert(false);
-    } else {
-        if (!m_alloc)
-            m_data = new uint8[RubySystem::getBlockSizeBytes()];
     memcpy(m_data, obj.m_data, RubySystem::getBlockSizeBytes());
-        m_alloc = true;
-    }
-
     return *this;
 }

src/mem/ruby/common/DataBlock.hh

@@ -29,6 +29,7 @@
 #ifndef __MEM_RUBY_COMMON_DATABLOCK_HH__
 #define __MEM_RUBY_COMMON_DATABLOCK_HH__
 
+#include <cassert>
 #include <iomanip>
 #include <iostream>
 
@@ -72,6 +73,7 @@ class DataBlock
 inline void
 DataBlock::assign(uint8* data)
 {
+    assert(data != NULL);
     if (m_alloc) {
         delete [] m_data;
     }