The following testcase takes much longer to compile at -O1 and above using GCC 4.7.3 on x86_64-linux (in both 32-bit and 64-bit modes). 

It does not seem to affect 4.8 and the current trunk. 


$ gcc-4.7 -v
Using built-in specs.
COLLECT_GCC=gcc-4.7
COLLECT_LTO_WRAPPER=/usr/local/gcc-4.7/libexec/gcc/x86_64-unknown-linux-gnu/4.7.3/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-4.7.3/configure --enable-languages=c,c++,objc,obj-c++,fortran,lto --disable-checking --with-gmp=/usr/local/gcc-4.7 --with-mpfr=/usr/local/gcc-4.7 --with-mpc=/usr/local/gcc-4.7 --with-ppl=/usr/local/gcc-4.7 --with-cloog=/usr/local/gcc-4.7 --prefix=/usr/local/gcc-4.7
Thread model: posix
gcc version 4.7.3 (GCC) 
$ time gcc-4.7 -O0 small.c
0.02user 0.02system 0:00.05elapsed 86%CPU (0avgtext+0avgdata 38336maxresident)k
0inputs+32outputs (0major+6471minor)pagefaults 0swaps
$ time gcc-4.7 -O1 small.c
33.43user 0.12system 0:33.64elapsed 99%CPU (0avgtext+0avgdata 660976maxresident)k
0inputs+32outputs (0major+53023minor)pagefaults 0swaps
$ time gcc-4.8 -O1 small.c
0.02user 0.02system 0:00.05elapsed 85%CPU (0avgtext+0avgdata 36704maxresident)k
0inputs+32outputs (0major+6364minor)pagefaults 0swaps
$ time gcc-trunk -O1 small.c
0.04user 0.01system 0:00.07elapsed 82%CPU (0avgtext+0avgdata 42656maxresident)k
0inputs+32outputs (0major+6700minor)pagefaults 0swaps
$ 


-----------------------------


int a, b, c, d, e; 

int main ()
{
  for (a = 0; a < 10; a++)
    for (b = 0; b < 10; b++)
      for (c = 0; c < 10; c++)
	for (d = 0; d < 10; d++)
	  for (e = 0; e < 10; e++)
	    ;
  return 0;
}