This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: How long should -O1 compiles take?
- To: lucier at math dot purdue dot edu, law at cygnus dot com
- Subject: Re: How long should -O1 compiles take?
- From: Brad Lucier <lucier at math dot purdue dot edu>
- Date: Mon, 4 Oct 1999 20:59:01 -0500 (EST)
- Cc: gcc at gcc dot gnu dot org, hosking at cs dot purdue dot edu, feeley at iro dot umontreal dot ca
Jeff Law wrote:
> It's meant to optimize, but use less time/memory than -On for n > 1.
I'm wondering whether this actually affects decisions about what goes
into -O1. Here are some compile times for a file that contains one
large procedure as an automatically-generated finite-state machine;
flags were -O1 -mcpu=ultrasparc -fPIC on an UltraSPARC 250.
today's gcc-2.96 gcc-2.95.1 egcs-1.1.2
parse: 5.580000 5.460000 5.380000
integration: 0.000000 0.000000 0.000000
jump: 3.050000 3.000000 3.320000
cse: 2.950000 2.810000 4.580000
gcse: 0.000000 0.000000 0.000000
loop: 0.010000 0.010000 0.020000
cse2: 0.000000 0.000000 0.000000
branch-prob: 0.000000 0.000000 0.000000
flow: 176.880000 177.050000 38.220000
combine: 2.650000 2.410000 2.360000
regmove: 0.000000 0.000000 0.000000
sched: 0.000000 0.000000 0.000000
local-alloc: 1.550000 1.440000 1.360000
global-alloc: 89.310000 102.680000 2.450000
flow2: 177.160000 176.380000 N/A
sched2: 0.000000 0.000000 0.000000
dbranch: 1.440000 1.330000 0.820000
shorten-branch: 0.120000 0.110000 0.130000
stack-reg: 0.000000 0.000000 0.000000
final: 4.130000 4.000000 0.700000
varconst: 0.020000 0.010000 0.040000
symout: 0.000000 0.000000 0.000000
dump: 0.000000 0.000000 0.000000
gc: 0.000000 N/A N/A
user 464.64u 476.67u 55.75u
system 2.43s 2.19s 5.31s
Total: 7:47.49 8:00.20 1:01.59
Is the global register allocation that much better in gcc-2.96 that it
should take 89 seconds now instead of 2.45 seconds as in egcs-1.1.2?
Or is flow analysis/control so much better that gcc should be spending
353 seconds on it rather than 38 seconds? (I tried -fno-thread-jumps in
gcc-2.95.1 to try to reduce the compile time, but instead it increased
to 478.56u.)
Saying that it takes less time/memory than -On for n>1 doesn't seem to
be saying much.
Brad Lucier