[Bug c++/13871] New: g++ creates excessive amounts of NOTE_INSN_DELETED insns

["dann at godzilla dot ics dot uci dot edu" <gcc-bugzilla at gcc dot gnu dot org>]

Using the testcase in PR8361
gcc from CVS HEAD
x86-linux
g++ -O2 -fno-inline generate-3.4.ii -dr

count the total number of insns in the .01.rtl dump:
grep -c "^(" generate-3.4.ii.01.rtl
138865

count the number of NOTE_INSN_DELETED insns:

grep -c "^(note.*DELETED" generate-3.4.ii.01.rtl
36070

So 25% of the total number of insns created are NOTE_INSN_DELETED. 


Another data point, compare the RTL generated by gcc and g++ for the same
preprocessed file: combine.i 

   Total number of insns in the .01.rtl dump:
   gcc:33014
   g++:42638

   Total number of NOTE_INSN_DELETED insns in the .01.rtl dump:
   gcc:1966
   g++:9799

These NOTE_INSN_DELETED insns are deleted later in the compilation process, but 
they create extra garbage to be collected, and affect the spatial locality of 
insns.

-- 
           Summary: g++ creates excessive amounts of NOTE_INSN_DELETED insns
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dann at godzilla dot ics dot uci dot edu
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13871