Hi Uros, This fix is for all x86 platforms, we tested it on core2/corei7, atom/atom2 and AMD and got performance improvement +6% -- +11%. So I don' think we need to introduce additioanl tune feature.
Sorry for my typo with gcc version - I ment mainline only since 4.7 does not use LRA. Thanks. Yuri. 2012/12/12 Uros Bizjak <ubiz...@gmail.com>: > On Wed, Dec 12, 2012 at 12:27 PM, Yuri Rumyantsev <ysrum...@gmail.com> wrote: > >> This fix is aimed to remove performance degradation introduced by new >> LRA phase that in fact is combining problem. Gcc combiner does >> propagation of memory load to if-then-else gimple that was splitted >> back by old reload phase. LRA does not perform such splitting. To >> avoid performance slowdown on important benchmark (this is true for >> all x86 targets) we decided to enhance 'ix86_legitimate_combined_insn' >> with a check on such propagation and consider such conditional >> instruction with memory operand as illegal one from performance point >> of view. > > Is this true for all x86 targets? I have no objections to the > implementation, but these fine-tunings should be declared in > ix86_tune_features[] array, and used as conditions involving > TARGET_xxx in the code. Please see many examples in the i386 source > dir. > >> Is it OK for 4.8 and mainline? > > Hm, currently 4.8 _is_ mainline. Did you mean 4.7? > > Thanks, > Uros.
