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Re: PowerPC shrink-wrap support 3 of 3


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


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