Re: Fix profile of forwardes produced by cd-dce

[Richard Biener <rguenther@suse.de>]

On Mon, 26 Jun 2023, Jan Hubicka wrote:

> Hi,
> 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.

Thanks - can you also fix affected branches?

Richard.

> gcc/ChangeLog:
> 
> 	PR tree-optimization/109849
> 	* tree-ssa-dce.cc (make_forwarders_with_degenerate_phis): Fix profile
> 	count of newly constructed forwarder block.
> 
> 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]);
> 

-- 
Richard Biener <rguenther@suse.de>
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