On Thu, Oct 27, 2011 at 12:24:46AM +1030, Alan Modra wrote: > more code than duplicating epilogues. From what I've seen, the > duplicate tails are generally very small. I guess I should dump out > some info so we can get a better idea.
There were 545 occurrences of shrink-wrap in the gcc/ dir for a -O2 powerpc-linux bootstrap. I counted active insns in duplicated blocks. 244 had zero insns (all the ones I looked at were just uses of r3), 96 had one insn (all the ones I looked at were setting r3), with the remainder being: cfgrtl.c.199r.pro_and_epilogue:Duplicating bb 6, 2 insns. tail call function.c.199r.pro_and_epilogue:Duplicating bb 17, 2 insns. setting a value via pointer (*poffset in instantiate_new_reg) insn-automata.c.199r.pro_and_epilogue:Duplicating bb 229, 2 insns. tail call varasm.c.199r.pro_and_epilogue:Duplicating bb 48, 2 insns. setting a global var rs6000.c.199r.pro_and_epilogue:Duplicating bb 300, 3 insns. tail call rs6000.c.199r.pro_and_epilogue:Duplicating bb 8, 3 insns. tail call toplev.c.199r.pro_and_epilogue:Duplicating bb 5, 4 insns. loading two word return value from "random_seed" var. reginfo.c.199r.pro_and_epilogue:Duplicating bb 4, 7 insns. setting a two word global var and r3 dbxout.c.199r.pro_and_epilogue:Duplicating bb 4, 8 insns. tail call dbxout.c.199r.pro_and_epilogue:Duplicating bb 4, 8 insns. tail call Note that having 350 duplicated blocks doesn't mean we had 350 extra cases of shrink-wrapping, because some tails were two blocks, and I recall seeing a case when developing my code where one function had two duplicated tails. Certainly many more shrink wrapped functions though. :-) -- Alan Modra Australia Development Lab, IBM
