some tree-ssa vs mainline stats

[Dan Nicolaescu]

I've done some empirical comparisons of GCC from CVS HEAD and the
tree-ssa branch. 
One comparison was for compiling a C file: combine.i,
the other one was for compiling a C++ file: generate-3.4.ii from PR8361

First the ggc_alloc-ed memory, printed using this patch
http://gcc.gnu.org/ml/gcc-patches/2003-06/msg01972.html



                                 generate-3.4.ii SSA  generate-3.4.ii HEAD
Total Overhead:                         83783064        34185222
Total Allocated:                       731518424       397362416
Total Overhead under   32B:              7872708          652308
Total Allocated under  32B:            332573472       194445000
Total Overhead under   64B:             29934672         6397392
Total Allocated under  64B:            482390040       265828848
Total Overhead under  128B:             40725380         9095252
Total Allocated under 128B:            585024728       314759152


                                   combine.i SSA  combine.i HEAD
Total Overhead:                          6631608         2010876
Total Allocated:                        72673776        48363184
Total Overhead under   32B:              2418024           14520
Total Allocated under  32B:             43772364        32016332
Total Overhead under   64B:              3824092          478592
Total Allocated under  64B:             55117808        37752656
Total Overhead under  128B:              4282744          611152
Total Allocated under 128B:             61364720        40886448

                                        all the values are in bytes     

Observations:
 - tree-ssa is allocating a lot more memory 
 - the overheads are a higher for tree-ssa, so it seems that it needs
   a few extra values added to ggc-page.c:extra_order_size_table


Total # of identifiers:
generate-3.4.ii SSA  84136 
generate-3.4.ii HEAD  8131 
combine.i       SSA  10987 
combine.i       HEAD  4389


Does tree-ssa create unique identifiers for each ssa name, or
something similar? Is that OK?

Total number # of insns in .00.rtl 
generate-3.4.ii SSA   417674
generate-3.4.ii HEAD  728202
combine.i       SSA    41528
combine.i       HEAD   35524


Total number # of NOTE_INSN_DELETED insns in .00.rtl
generate-3.4.ii SSA    64382
generate-3.4.ii HEAD  233290
combine.i       SSA	 407
combine.i       HEAD    1960

It seems strange that gcc HEAD emits so many NOTE_INSN_DELETED
insns.

wc -l for the generated assembly file
generate-3.4.ii SSA    104654
generate-3.4.ii HEAD   121585
combine.i       SSA     32971
combine.i       HEAD    30977