[gcc r14-2101] Fix profile of forwarders produced by cd-dce

[gcc r14-2101] Fix profile of forwarders produced by cd-dce

[Jan Hubicka]

https://gcc.gnu.org/g:c2ebccc97190a978a44e341516b488f02a78c598

commit r14-2101-gc2ebccc97190a978a44e341516b488f02a78c598
Author: Jan Hubicka <jh@suse.cz>
Date:   Mon Jun 26 18:29:39 2023 +0200

    Fix profile of forwarders produced by cd-dce
    
    compiling the testcase from PR109849 (which uses std:vector based stack to
    drive a loop) with profile feedbakc leads to profile mismatches introduced by
    tree-ssa-dce.  This is the new code to produce unified forwarder blocks for
    PHIs.
    
    I am not including the testcase itself since
    checking it for Invalid sum is probably going to be too fragile and this should
    show in our LNT testers. The patch however fixes the mismatch.
    
    Bootstrapped/regtested x86_64-linux and plan to commit it shortly.
    
    gcc/ChangeLog:
    
            PR tree-optimization/109849
            * tree-ssa-dce.cc (make_forwarders_with_degenerate_phis): Fix profile
            count of newly constructed forwarder block.

Diff:
---
 gcc/tree-ssa-dce.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc
index 2949957f883..f0b02456132 100644
--- a/gcc/tree-ssa-dce.cc
+++ b/gcc/tree-ssa-dce.cc
@@ -1865,12 +1865,15 @@ make_forwarders_with_degenerate_phis (function *fn)
 		    }
 		  free_dominance_info (fn, CDI_DOMINATORS);
 		  basic_block forwarder = split_edge (args[start].first);
+		  profile_count count = profile_count::zero ();
 		  for (unsigned j = start + 1; j < i; ++j)
 		    {
 		      edge e = args[j].first;
 		      redirect_edge_and_branch_force (e, forwarder);
 		      redirect_edge_var_map_clear (e);
+		      count += e->count ();
 		    }
+		  forwarder->count = count;
 		  if (vphi)
 		    {
 		      tree def = copy_ssa_name (vphi_args[0]);