http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39326
--- Comment #38 from Steven Bosscher <steven at gcc dot gnu.org> 2013-03-07 22:15:39 UTC --- Created attachment 29612 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29612 Punt on loops with more memory references than LIM can handle For the LIM problem, I'm thinking of a patch like this one (not tested yet). Basically, this means giving up on really large loops with many loads and/or stores. That's not an unreasonable thing to do anyway. Code motion from really big loops usually isn't an improvement. Richi, could you have a look at this, and see if I've got it all right, more-or-less? LIM is quite complicated and I'm not sure if I should look at, or update, the set of optimizable loops somewhere. With the patch, and with "-O2 -fgcse", I now have: gap_TlnLv4.c: In function 'RDFT_49152_1': gap_TlnLv4.c:37502:18: warning: -ftree-loop-im: number of memory references in loop exceeds the --param loops-max-datarefs-for-datadeps threshold [-Wdisabled-optimization] t12308[500] = t12304[6144*i0+1000]; ^ dead store elim1 : 57.70 ( 8%) dead store elim2 : 76.82 (10%) combiner : 360.07 (48%) reload CSE regs : 55.44 ( 7%) TOTAL : 743.77
