[Bug rtl-optimization/33922] [4.3 Regression] slow compilation on ia64 (postreload scheduling)

["jakub at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #18 from jakub at gcc dot gnu dot org  2007-10-28 20:20 -------
Created an attachment (id=14429)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14429&action=view)
rws_insn.patch

Just a side note.  Maintaining the rws_insn array seems to be horribly
expensive to me, and for each regno only one bit is actually used just to check
one gcc_assert and only two regnos are actually checked in some other code.  So
memsetting and maintaining a 1604 bytes long array all the time seems to be an
overkill - a bitmap can do just fine or, if we just remove that gcc_assert
when not ENABLE_CHECKING, we need just 2 bits altogether instead of those 1604
bytes.
Doesn't help much on this testcase (as it is not addressing the algorithmic
issue), but is already noticeable.
 scheduling 2          :  10.60 (88%) usr   0.00 ( 0%) sys  10.60 (88%) wall   
1970 kB (15%) ggc
went down to
 scheduling 2          :   8.99 (86%) usr   0.01 (50%) sys   9.00 (86%) wall   
1970 kB (15%) ggc
with this patch and --enable-checking=release, so about 14% speedup in wall
time for the whole compilation of this file.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33922