[Bug target/28481] regression from 3.x: 4.1.1 uses memory where it can use registers

["vda dot linux at googlemail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #4 from vda dot linux at googlemail dot com  2007-07-22 00:02 -------
With t.c being a timing program from comment #3 and serpent.c from attachment,
I build testing program for 3.4.3, 3.4.6 and 4.2.1, -Os and -O3, like this:

ver=NNN
gcc -Os -o serpent-${ver}-Os serpent.c t.c
gcc -Os -o serpent-${ver}-Os.o -c serpent.c
gcc -O3 -o serpent-${ver}-O3 serpent.c t.c
gcc -O3 -o serpent-${ver}-O3.o -c serpent.c

Performance regression on -O3 (runs at 2/3 speed of 3.4.x). Did four runs of
each:

343-O3
ops/second=712888
ops/second=722059
ops/second=718909
ops/second=713506
346-O3
ops/second=643833
ops/second=712619
ops/second=721724
ops/second=719445
421-O3
ops/second=495349
ops/second=496887
ops/second=490650
ops/second=494522

Size: improved relative to 3.4.x:

# size *-Os.o
   text    data     bss     dec     hex filename
   4302       0       0    4302    10ce serpent-343-Os.o
   4335       0       0    4335    10ef serpent-346-Os.o
   3877       0       0    3877     f25 serpent-421-Os.o

...but 3.4.x was even smaller at -O3 than 4.2.1 at -Os:

# size *-O3.o
   text    data     bss     dec     hex filename
   3292       0       0    3292     cdc serpent-343-O3.o
   3292       0       0    3292     cdc serpent-346-O3.o
   3877       0       0    3877     f25 serpent-421-O3.o

Actually, 4.2.1 seems to generate same code for -Os/-O2/-O3:

# size *421*.o
   text    data     bss     dec     hex filename
   3877       0       0    3877     f25 serpent-421-O2.o
   3877       0       0    3877     f25 serpent-421-O3.o
   3877       0       0    3877     f25 serpent-421-Os.o


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28481