Brian McGrew wrote: >Dell is > shipping us new Precision T5500 workstations with the Intel Xeon 5500 > processor and the new "QPI" architecture. > > What version of gcc do I need to support QPI? > What flags to I need to build gcc with to support QPI? > What -march, -mcpu or -mtune (or other) options to I need to build my > codebase to support QPI? You don't necessarily have to change gcc, but your version is aging. The incentive for going to x86_64, if you haven't done so, is increasing. -msse4 is good for either Xeon 5400 or 5500 series. I believe that became available in 4.3. -mssse3 is undesirable for the 5500 (but this is not a politically correct position), while -msse3 is OK. If you upgrade gcc and use more auto-vectorization, -march=barcelona becomes advantageous, as there is a hardware register added to support unaligned 128-bit loads. gcc doesn't deal directly with QPI, any more than it did with FSB on 5400 series, or HyperTransport on AMD. I find --param max-unroll-times=4 useful; the increased effectiveness of Loop Stream Detection makes limited unrolling work well over a wide range of loop counts and complexities.
