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Unformatted text preview: re forming the interface between the processor and the memory system. For example, suppose a processor always fetches 8 bytes from memory with an address that must be a multiple of 8. If we can guarantee that any double will be aligned to have its address be a multiple of 8, then the value can be read or written with a single memory operation. Otherwise, we may need to perform two memory accesses, since the object might be split across two 8-byte memory blocks. The IA32 hardware will work correctly regardless of the alignment of data. However, Intel recommends that data be aligned to improve memory system performance. Linux follows an alignment policy where 2-byte data types (e.g., short) must have an address that is a multiple of 2, while any larger data types (e.g., int, int *, float, and double) must have an address that is a multiple of 4. Note that this requirement means that the least signiﬁcant bit of the address of an object of type short must equal 0. Similarly, any object of...
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- Spring '10
- The American