On Fri, Oct 14, 2016 at 8:28 PM, Andrew Pinski <pins...@gmail.com> wrote: > On Thu, Sep 22, 2016 at 12:10 PM, Pat Haugen > <pthau...@linux.vnet.ibm.com> wrote: >> I noticed the loop unroller peels an extra copy of the loop before it enters >> the switch block code to round the iteration count to a multiple of the >> unroll factor. This peeled copy is only needed for the case where the exit >> test is at the beginning of the loop since in that case it inserts the test >> for zero peel iterations before that peeled copy. >> >> This patch bumps the iteration count by 1 for loops with the exit at the end >> so that it represents the number of times the loop body is executed, and >> therefore removes the need to always execute that first peeled copy. With >> this change, when the number of executions of the loop is an even multiple >> of the unroll factor then the code will jump to the unrolled loop >> immediately instead of executing all the switch code and peeled copies of >> the loop and then falling into the unrolled loop. This change also reduces >> code size by removing a peeled copy of the loop. >> >> Bootstrap/regtest on powerpc64le with no new regressions. Ok for trunk? > > This patch or > PR rtl-optimization/68212 > * cfgloopmanip.c (duplicate_loop_to_header_edge): Use preheader edge > frequency when computing scale factor for peeled copies. > * loop-unroll.c (unroll_loop_runtime_iterations): Fix freq/count > values for switch/peel blocks/edges. > > Caused a ~2.7-3.5% regression in coremarks with -funroll-all-loops.
I should say on ThunderX (aarch64-linux-gnu). Thanks, Andrew > > Thanks, > Andrew > >> >> >> >> 2016-09-22 Pat Haugen <pthau...@us.ibm.com> >> >> * loop-unroll.c (unroll_loop_runtime_iterations): Condition initial >> loop peel to loops with exit test at the beginning. >> >>
