[Bug rtl-optimization/117922] [15/16 Regression] fold-mem-offsets pass is slow and memory hungry because UD/UD chain usage and the RD df problem

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117922

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |deferred
   Target Milestone|15.0                        |16.0
           Priority|P1                          |P2
            Summary|[15 Regression] 1000%       |[15/16 Regression]
                   |compilation time slow down  |fold-mem-offsets pass is
                   |on the testcase from        |slow and memory hungry
                   |pr26854                     |because UD/UD chain usage
                   |                            |and the RD df problem

--- Comment #26 from Richard Biener <rguenth at gcc dot gnu.org> ---
So this should be mitigated for the PR26854 testcase - the heuristic of course
might not trigger for another one, showing a regression there.

The pass should be moved over to RTL-SSA as suggested, but that's a stage1
thing, so defering and re-wording the summary.