On Mon, Dec 12, 2011 at 06:05:57PM -0800, Sriraman Tallam wrote: > Do not vectorize loops on Core2 that need to use unaligned > vector load/stores. > * tree-vect-stmts.c (is_slow_vect_unaligned_load_store): New function. > (vect_analyze_stmt): Check if the vectorizable load/store is slow. > * target.def (TARGET_SLOW_UNALIGNED_VECTOR_MEMOP): New target hook. > * doc/m.texi.in: Document new target hook: > TARGET_SLOW_UNALIGNED_VECTOR_MEMOP > * doc/m.texi: Regenerate. > * config/i386/i386.c (ix86_slow_unaligned_vector_memop): New function. > (TARGET_SLOW_UNALIGNED_VECTOR_MEMOP): New macro.
IMHO it would be better if it didn't prevent vectorization of the loops altogether, but lead to using aligned stores with an alignment check before the vectorized loop if possible. Also, are unaligned loads equally expensive to unaligned stores? See http://gcc.gnu.org/PR49442 for further info, this really should be done using some cost model rather than a boolean hook. Jakub
