Re: [PATCH] phiopt: Remove unnecessary checks from spaceship_replacement [PR106506]

[Richard Biener <rguenther@suse.de>]

On Thu, 11 Aug 2022, Jakub Jelinek wrote:

> Hi!
> 
> Those 2 checks were just me trying to be extra careful, the
> (phires & 1) == phires and variants it is folded to of course make only sense
> for the -1/0/1/2 result spaceship, for -1/0/1 one can just use comparisons of
> phires.  We only floating point spaceship if nans aren't honored, so the
> 2 case is ignored, and if it is, with Aldy's changes we can simplify the
> 2 case away from the phi but the (phires & 1) == phires stayed.  It is safe
> to treat the phires comparison as phires >= 0 even then.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

Thanks,
Richard.

> 2022-08-11  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR tree-optimization/106506
> 	* tree-ssa-phiopt.cc (spaceship_replacement): Don't punt for
> 	is_cast or orig_use_lhs cases if phi_bb has 3 predecessors.
> 
> 	* g++.dg/opt/pr94589-2.C: New test.
> 
> --- gcc/tree-ssa-phiopt.cc.jj	2022-08-10 09:06:53.000000000 +0200
> +++ gcc/tree-ssa-phiopt.cc	2022-08-10 15:33:32.414641593 +0200
> @@ -2448,8 +2448,6 @@ spaceship_replacement (basic_block cond_
>  	return false;
>        if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig_use_lhs))
>  	return false;
> -      if (EDGE_COUNT (phi_bb->preds) != 4)
> -	return false;
>        if (!single_imm_use (orig_use_lhs, &use_p, &use_stmt))
>  	return false;
>  
> @@ -2467,8 +2465,6 @@ spaceship_replacement (basic_block cond_
>        orig_use_lhs = gimple_assign_lhs (use_stmt);
>        if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig_use_lhs))
>  	return false;
> -      if (EDGE_COUNT (phi_bb->preds) != 4)
> -	return false;
>        if (!single_imm_use (orig_use_lhs, &use_p, &use_stmt))
>  	return false;
>      }
> --- gcc/testsuite/g++.dg/opt/pr94589-2.C.jj	2022-08-10 09:06:52.921213966 +0200
> +++ gcc/testsuite/g++.dg/opt/pr94589-2.C	2022-08-10 15:45:24.599319922 +0200
> @@ -1,7 +1,7 @@
>  // PR tree-optimization/94589
>  // { dg-do compile { target c++20 } }
>  // { dg-options "-O2 -g0 -ffast-math -fdump-tree-optimized" }
> -// { dg-final { scan-tree-dump-times "\[ij]_\[0-9]+\\(D\\) (?:<|<=|==|!=|>|>=) \[ij]_\[0-9]+\\(D\\)" 12 "optimized" { xfail *-*-* } } }
> +// { dg-final { scan-tree-dump-times "\[ij]_\[0-9]+\\(D\\) (?:<|<=|==|!=|>|>=) \[ij]_\[0-9]+\\(D\\)" 12 "optimized" } }
>  // { dg-final { scan-tree-dump-times "i_\[0-9]+\\(D\\) (?:<|<=|==|!=|>|>=) 5\\.0" 12 "optimized" } }
>  
>  #include <compare>
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg,
Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman;
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