On Thu, Apr 12, 2012 at 1:05 PM, Igor Zamyatin <izamya...@gmail.com> wrote: > On Wed, Apr 11, 2012 at 12:39 PM, Richard Guenther > <richard.guent...@gmail.com> wrote: >> On Tue, Apr 10, 2012 at 8:43 PM, Igor Zamyatin <izamya...@gmail.com> wrote: >>> Hi All! >>> >>> Here is a patch that enables unroll at O2 for Atom. >>> >>> This gives good performance boost on EEMBC 2.0 (~+8% in Geomean for 32 >>> bits) with quite moderate code size increase (~5% for EEMBC2.0, 32 >>> bits). >> >> 5% is not moderate. Your patch does enable unrolling at -O2 but not -O3, >> why? Why do you disable register renaming? check_imull requires a function >> comment. > > Sure, enabling unroll for O3 could be the next step. > We can't avoid code size increase with unroll - what number do you > think will be appropriate? > Register renaming was the reason of several degradations during tuning process > Comment for check_imull was added > >> >> This completely looks like a hack for EEMBC2.0, so it's definitely not ok. > > Why? EEMBC was measured and result provided here just because this > benchmark considers to be very relevant for Atom
I'd say that SPEC INT (2000 / 2006) is more relevant for Atom (SPEC FP would be irrelevant OTOH). Similar code size for, say, Mozilla Firefox or GCC itself would be important. >> -O2 is not supposed to give best benchmark results. > > O2 is wide-used so performance improvement could be important for users. But not at a 5% size cost. Please also always check the compile-time effect which is important for -O2 as well. Richard. >> >> Thanks, >> Richard. >> >>> >>> Tested for i386 and x86-64, ok for trunk? > > Updated patch attached > >>> >>> Thanks, >>> Igor >>> >>> ChangeLog: >>> >>> 2012-04-10 Yakovlev Vladimir <vladimir.b.yakov...@intel.com> >>> >>> * gcc/config/i386/i386.c (check_imul): New routine. >>> (ix86_loop_unroll_adjust): New target hook. >>> (ix86_option_override_internal): Enable unrolling on Atom at -O2. >>> (TARGET_LOOP_UNROLL_ADJUST): New define.
