gcc didn't add vectorization as part of -O3 until 4.3.  It's still not nearly as aggressive in vectorization as icc, even if -ffast-math is set.  The gcc -ftree-vectorizer-verbose option resembles icc -vec-report, except that the default is no report.  Even when the same loops are vectorized, icc usually generates over twice as much additional code with vectorization as gcc, due to multiple versions for alignment, and more unrolling.  The i7 architecture removes several of the reasons for differences in the gcc and icc implementations of vectorization, but it hasn't made much difference in the compilers so far.