[Bug tree-optimization/84552] [6/7/8 Regression] Compile time hog w/ -O2 -floop-nest-optimize -fno-tree-copy-prop -fno-tree-fre -fno-tree-loop-ivcanon

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84552

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P4                          |P2
   Target Milestone|8.0                         |6.5
            Summary|[8 Regression] Compile time |[6/7/8 Regression] Compile
                   |hog w/ -O2                  |time hog w/ -O2
                   |-floop-nest-optimize        |-floop-nest-optimize
                   |-fno-tree-copy-prop         |-fno-tree-copy-prop
                   |-fno-tree-fre               |-fno-tree-fre
                   |-fno-tree-loop-ivcanon      |-fno-tree-loop-ivcanon

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
So this is really a latent issue and not dependent on -floop-nest-optimize.  It
materializes during unrolling where we perform SCEV analysis on not up-to-date
SSA form when analyzing.