-doipc is apparently not an adequate replacement for -dowls: ktrvariant.sac

Bugzilla Link	1086
Created on	Sep 24, 2013 19:53
Version	svn
OS	Linux
Architecture	PC
Attachments	ktrvariant.sac

Extended Description

Created an attachment (id=984)
source code to reproduce fault
This was observed on Build #18308, in the ipc unit test suite:
sac2c ktrvariant.sac  -O3 
sac@rattler:~/sac/testsuite/optimizations/ipc$ time a.out; echo $?
real	0m0.608s
user	0m0.600s
sys	0m0.000s
0
sac@rattler:~/sac/testsuite/optimizations/ipc$ sac2c ktrvariant.sac  -O3 -nowls
sac@rattler:~/sac/testsuite/optimizations/ipc$ time a.out; echo $?
real	0m1.978s
user	0m1.240s
sys	0m0.730s
0
sac@rattler:~/sac/testsuite/optimizations/ipc$ sac2c ktrvariant.sac  -O3 -noipc
sac@rattler:~/sac/testsuite/optimizations/ipc$ time a.out; echo $?
real	0m0.608s
user	0m0.590s
sys	0m0.010s
0
sac@rattler:~/sac/testsuite/optimizations/ipc$ sac2c ktrvariant.sac  -O3 -noipc -nowls 
sac@rattler:~/sac/testsuite/optimizations/ipc$ time a.out; echo $?
real	0m2.180s
user	0m1.490s
sys	0m0.680s
0
Bodo claimed, earlier today, that IPC should (my words) be able to
supplant WLS. The above timings show that, for this test, at least:
  1. If WLS is enabled, IPC does nothing more for us.
  2. If WLS is disabled, IPC is not able to do generate code that
     performs as well as WLS.