[Bug tree-optimization/122843] [16 Regression] Excessive compile time with flags -O2 -fpeel-loops -march=znver3

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122843

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 62901
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=62901&action=edit
debugging patch

A bit of debugging, dump when we re-simplify.

Applying pattern match.pd:2085, gimple-match-8.cc:1893
resimplify nop_expr_614
resimplify nop_expr_353
Applying pattern match.pd:5661, gimple-match-7.cc:7671
Applying pattern match.pd:5778, gimple-match-7.cc:7729
Applying pattern match.pd:2302, gimple-match-4.cc:2120
resimplify nop_expr_353
Applying pattern match.pd:2302, gimple-match-4.cc:2120
Applying pattern match.pd:2085, gimple-match-8.cc:1893
resimplify nop_expr_575
resimplify nop_expr_353
Applying pattern match.pd:5661, gimple-match-7.cc:7671
Applying pattern match.pd:5778, gimple-match-7.cc:7729

I'll note the testcase is a bit big, but likely a GIMPLE testcase from before
forwprop4 could cut it down for easier analysis.