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Must the data be 16-byte aligned so that it can be processed by the SSE instruction without segmentation fault? The compiler I tried is gcc with option -msse2. I want use _mm_cmpgt_epi32 to compare a large int array. I found that it can not be executed at any location of the array except the position with subscript of the multiples of 4.
Yes, when you load and store data to/from SSE registers it needs to be 16 byte aligned, unless you use the misaligned versions of the load/store instructions, e.g.
_mm_loadu_si128/_mm_storeu_si128. There is typically a performance penalty for using these misaligned load/store instructions however, so one would normally try to ensure correct data alignment at all times and only use misaligned loads/stores as a last resort.