[PATCH] phiopt, v2: Adjust instead of reset phires range

[Jakub Jelinek <jakub@redhat.com>]

On Thu, Dec 22, 2022 at 08:46:33PM +0100, Aldy Hernandez wrote:
> I haven't looked at your problem above, but have you tried using
> int_range_max (or even int_range<2>) instead of value_range above?
> 
> value_range is deprecated and uses the legacy anti-range business,
> which has a really hard time representing complex ranges, as well as
> union/intersecting them.

You're right.  With int_range_max it works as I expected.
And no, floating point isn't possible here.
If value_range is right now just the legacy single range or anti-range,
then it explains why it didn't work - while on the first testcase
we could have anti-range ~[0, 0], on the second case [-128, -1] U [1, 127]
is turned into simple legacy [-128, 127].

So, ok for trunk if this passes bootstrap/regtest?

2022-12-22  Jakub Jelinek  <jakub@redhat.com>
	    Aldy Hernandez  <aldyh@redhat.com>

	* tree-ssa-phiopt.cc (value_replacement): Instead of resetting
	phires range info, union it with oarg.

--- gcc/tree-ssa-phiopt.cc.jj	2022-12-22 12:52:36.588469821 +0100
+++ gcc/tree-ssa-phiopt.cc	2022-12-22 13:11:51.145060050 +0100
@@ -1492,11 +1492,25 @@ value_replacement (basic_block cond_bb,
 		    break;
 		  }
 	      if (equal_p)
-		/* After the optimization PHI result can have value
-		   which it couldn't have previously.
-		   We could instead of resetting it union the range
-		   info with oarg.  */
-		reset_flow_sensitive_info (gimple_phi_result (phi));
+		{
+		  tree phires = gimple_phi_result (phi);
+		  if (SSA_NAME_RANGE_INFO (phires))
+		    {
+		      /* After the optimization PHI result can have value
+			 which it couldn't have previously.  */
+		      int_range_max r;
+		      if (get_global_range_query ()->range_of_expr (r, phires,
+								    phi))
+			{
+			  int_range<2> tmp (carg, carg);
+			  r.union_ (tmp);
+			  reset_flow_sensitive_info (phires);
+			  set_range_info (phires, r);
+			}
+		      else
+			reset_flow_sensitive_info (phires);
+		    }
+		}
 	      if (equal_p && MAY_HAVE_DEBUG_BIND_STMTS)
 		{
 		  imm_use_iterator imm_iter;


	Jakub