A compute instruction to be executed is to use a memory operand in a computation. An address associated with the memory operand is to be used to locate a portion of memory from which data is to be obtained and placed in the memory operand. A determination is made as to whether the portion of memory extends across a specified memory boundary. Based on the portion of memory extending across the specified memory boundary, the portion of memory includes a plurality of memory units and a check is made as to whether at least one specified memory unit is accessible and whether at least one specified memory unit is inaccessible. Based on the checking indicating the at least one specified memory unit is accessible and the at least one specified memory unit is inaccessible accessing the at least one specified memory unit that is accessible and placing data from the at least one specified memory unit that is accessible in one or more locations in the memory operand, and for the at least one unit of memory that is inaccessible, placing default data in one or more other locations of the memory operand.