[Bug rtl-optimization/38518] Excessive compile time with -O3

["dcb314 at hotmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38518

--- Comment #15 from David Binderman <dcb314 at hotmail dot com> ---
(In reply to David Binderman from comment #12)
> With recent gcc:
> 
> no -O flag: 2 seconds
> 
> -O2: 24 seconds
> 
> -O3: 247 seconds

Those numbers for a version of trunk gcc with lots of checking.

Without checking, I get gcc trunk with -O3 in 4 mins 56 seconds
and release gcc 7.1.1 in 3 minutes 38 seconds, so it still looks like it's
going backwards. 

From -ftime-report on trunk gcc with -O3:

$ grep "([0-9][0-9]\%) usr" report.out
 df live&initialized regs:  45.04 (16%) usr   0.06 ( 2%) sys  45.74 (15%) wall 
     0 kB ( 0%) ggc
 load CSE after reload   : 174.76 (60%) usr   0.07 ( 2%) sys 176.23 (60%) wall 
    10 kB ( 0%) ggc
$

So I think that confirms what Richard is seeing.