Ping. Thanks! -Zhenqiang
> -----Original Message----- > From: gcc-patches-ow...@gcc.gnu.org [mailto:gcc-patches- > ow...@gcc.gnu.org] On Behalf Of Zhenqiang Chen > Sent: Tuesday, August 14, 2012 2:50 PM > To: gcc-patches@gcc.gnu.org > Subject: [PATCH] Enable bbro for -Os > > Hi, > > Basic block reordering is disabled for -Os from gcc 4.7 since the pass will lead > to big code size regression. But benchmarks logs also show there are lots of > regression due to poor code layout compared with 4.6. > > The patch is to enable bbro for -Os. When optimizing for size, it > * avoid duplicating block. > * keep its original order if there is no chance to fall through. > * ignore edge frequency and probability. > * handle predecessor first if its index is smaller to break long trace. > * only connect Trace n with Trace n + 1 to reduce long jump. > > Here are the CSiBE code size benchmark results: > * For ARM, code size reduces 0.21%. > * For MIPS, code size reduces 0.25%. > * For PPC, code size reduces 0.33%. > * For X86, code size reduces 0.22%. > > The patch does not impact bbro when optimizing for speed. To verify it, I > "objdump -d" all obj files from CSiBE (compiled with -O2) for > ARM/MIPS/PPC/X86. The assembler with the patch is the same as it without > the patch. > > No make check regression on ARM. > > Is it OK for trunk? > > Thanks! > -Zhenqiang > > ChangeLog > 2012-08-14 Zhenqiang Chen <zhenqiang.c...@arm.com> > > * bb-reorder.c (connect_better_edge_p): New added. > (find_traces_1_round): When optimizing for size, ignore edge > frequency > and probability, and handle all in one round. > (bb_to_key): Use bb->index as key for size. > (better_edge_p): The smaller bb index is better for size. > (connect_traces): Connect block n with block n + 1; > connect trace m with trace m + 1 if falling through. > (copy_bb_p): Avoid duplicating blocks. > (gate_handle_reorder_blocks): Enable bbro when optimizing for -Os.
