1. A method of executing program instructions, the method comprising: receiving, in a processor, an instruction; generating an exception in response to determining that the received instruction will cause the processor to read data from or write data to a portion of memory that is shared by one or more processes; and executing, in response to the exception by the processor, an exception handling routine with alternate instructions in place of the received instruction, the alternate instructions causing the processor to: read the data from the portion of memory in a first format and transform the data to a second format when the received instruction will cause the processor to read data from the portion of memory; and when the received instruction will cause the processor to write the data to the portion of memory, transform the data to the second format and write the data to the portion of memory in the second format.