> Ping? > > David > > On Sat, Aug 3, 2013 at 12:36 PM, Xinliang David Li <davi...@google.com> wrote: > > Hi, GCC/i386 currently has about 73 boolean parameters/knobs (defined > > in ix86_tune_features[], indexed by ix86_tune_indices) to perform > > micro-arch specific performance tuning. However such settings are hard > > coded (fixed with a given -mtune setting) and is very hard to do > > performance experiment. > > > > The attached patch fixes the problem. The patch introduces a new > > option -mtune-ctrl=. Its parameter is a comma separated list of > > feature names to turn on associated features. Feature name can be > > prefixed by ^ to do the opposite. For instance, > > > > -mtune-ctrl=prologue_using_move,epilogue_using_move,^pad_returns > > > > tells the compiler to use move instructions in prologue/epilogue > > (instead of push/pop), and *not* pad return instructions. > > > > To facilitate the change, the feature tuning enums defined in i386.h > > are moved to a new file x86-tune.def and this file can be used to > > generate both the enums and names of the features. > > > > > > Ok for trunk?
Yes, this patch seems fine to me (as an undocumented option we should not be obliged to fix any ices from non-sential combinations of flags and in fact I do not really know of any). I wonder if we can't feed initial_ix86_tune_features so we get rid of two places that needs to be kept in sync when adding new knob? Honza > > > > > > thanks, > > > > David > > > > 2013-08-03 Xinliang David Li <davi...@google.com> > > > > * config/i386/i386.opt: New option -mtune-ctrl=. > > * config/i386/x86-tune.def: New file. > > * config/i386/i386.h: include x86-tune.def. > > * config/i386/i386.c (ix86_option_override_internal): > > Parsing -mtune-ctrl= option and set tune features.
