[Bug ipa/65076] [5 Regression] 16% tramp3d-v4.cpp compile time regression

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65076

--- Comment #19 from Richard Biener <rguenth at gcc dot gnu.org> ---
I've meanwhile disabled pass_chkp_instrumentation_passes by default.

The fixup_cfg in pass_build_ssa_passes doesn't do anything on tramp3d
(and bootstrap/testing shows no issue removing it either).

Adding a local_pure_const to the end of build_ssa_passes unfortunately
makes us ICE in cgraph node verification during early inlining (we have
a dangling call-stmt without a BB on a cgraph edge).  Not sure how that
happens as we fixup the cfg and rebuild cgraph edges before early inlining.
Looks like re-building cgraph edges fixes that.

This brings down the number of clobbers and stmts to 4.9 level.

Index: gcc/passes.def
===================================================================
--- gcc/passes.def      (revision 221660)
+++ gcc/passes.def      (working copy)
@@ -54,10 +54,12 @@ along with GCC; see the file COPYING3.
   NEXT_PASS (pass_build_ssa_passes);
   PUSH_INSERT_PASSES_WITHIN (pass_build_ssa_passes)
       NEXT_PASS (pass_fixup_cfg);
+      NEXT_PASS (pass_rebuild_cgraph_edges);
       NEXT_PASS (pass_init_datastructures);
       NEXT_PASS (pass_build_ssa);
       NEXT_PASS (pass_ubsan);
       NEXT_PASS (pass_early_warn_uninitialized);
+      NEXT_PASS (pass_local_pure_const);
   POP_INSERT_PASSES ()

   NEXT_PASS (pass_chkp_instrumentation_passes);

as opposed to the also possible patch (which doesn't change anything but
compile-time):

Index: gcc/passes.def
===================================================================
--- gcc/passes.def      (revision 221657)
+++ gcc/passes.def      (working copy)
@@ -53,7 +53,6 @@ along with GCC; see the file COPYING3.
   NEXT_PASS (pass_ipa_chkp_early_produce_thunks);
   NEXT_PASS (pass_build_ssa_passes);
   PUSH_INSERT_PASSES_WITHIN (pass_build_ssa_passes)
-      NEXT_PASS (pass_fixup_cfg);
       NEXT_PASS (pass_init_datastructures);
       NEXT_PASS (pass_build_ssa);
       NEXT_PASS (pass_ubsan);