Performance anomaly in Livermore Loops when declarations are used

Bugzilla Link	707
Created on	May 11, 2010 18:13
Version	svn
OS	Linux
Architecture	PC

Extended Description

I've been running performance measurements of the Livermore Loops in sac.
When I compiled loop10.sac, I got a gazillion complaints about:
WARNING: Insufficient symbolic shape information available. Using explicit
WARNING: information to split index operation.
Looking at the code, we see in main():
  rep = FibreScanInt( stdin );
  n   = FibreScanInt( stdin );
I looked at n and rep, and noted that they are not declared,
but are passed to the Loop() function, where they are NOT referenced or set.
In the spirit of cleaning things up, I tried some simple tests:
(This is op counts, compiling with AWLF options on rbe's private code.)
Original:
6715137927
n and rep removed from Loop() call:
7905664809      !! WORSE !!
n and rep removed from Loop() call; "int rep; int n;" added to main():
7850187292         slightly better
When compiled with -O3...
Original:
loop10.sac.exe.O3.16831:MODIFIED.papiex.rattler.18553:PAPI_TOT_INS:		965058436
n and rep removed from Loop() call:
loop10.sac.exe.O3.16831:MODIFIED.papiex.rattler.18633:PAPI_TOT_INS:		947804966
n and rep removed from Loop() call; "int rep; int n;" added to main():
loop10.sac.exe.O3.16831:MODIFIED.papiex.rattler.18753:PAPI_TOT_INS:		934451791
I do not understand what's going on here.