[Bug tree-optimization/46590] long compile time with -O2 and many loops

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46590

--- Comment #53 from Richard Biener <rguenth at gcc dot gnu.org> ---
After both are fixed there's still non-linearity from loop-invariant, this
time in the DF RD problem.

Doubling the testcase goes from 9.1s to 25.5s, doubling again to 82.2s

with RD going from

 df reaching defs                   :   0.67 (  7%)   0.01 (  3%)   0.72 (  8%)
      0 kB (  0%)

to

 df reaching defs                   :   3.79 ( 15%)   0.05 (  7%)   3.79 ( 14%)
      0 kB (  0%)

and

 df reaching defs                   :  11.47 ( 14%)  46.48 ( 88%)  58.41 ( 43%)
      0 kB (  0%)