From: Richard Biener <rguenther@suse.de>
Date: Thu, 23 Nov 2023 08:49:59 +0000 (+0100)
Subject: tree-optimization/112344 - relax final value-replacement fix
X-Git-Tag: basepoints/gcc-15~4326
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a7d82b45edeed99a850595eee0e59d16c4df7aff;p=thirdparty%2Fgcc.git

tree-optimization/112344 - relax final value-replacement fix

The following tries to reduce the number of cases we use an unsigned
type for the addition when we know the original signed increment was
OK which is when the total unsigned increment computed fits the signed
type as well.

This fixes the observed testsuite fallout.

	PR tree-optimization/112344
	* tree-chrec.cc (chrec_apply): Only use an unsigned add
	when the overall increment doesn't fit the signed type.
---

diff --git a/gcc/tree-chrec.cc b/gcc/tree-chrec.cc
index f4ba130ba200..e2864e8d1310 100644
--- a/gcc/tree-chrec.cc
+++ b/gcc/tree-chrec.cc
@@ -646,9 +646,21 @@ chrec_apply (unsigned var,
 	      res = chrec_fold_multiply (utype,
 					 chrec_convert (utype, chrecr, NULL),
 					 res);
-	      res = chrec_fold_plus (utype,
-				     chrec_convert (utype, chrecl, NULL), res);
-	      res = chrec_convert (type, res, NULL);
+	      /* When the resulting increment fits the original type
+		 do the increment in it.  */
+	      if (TREE_CODE (res) == INTEGER_CST
+		  && int_fits_type_p (res, TREE_TYPE (chrecr)))
+		{
+		  res = chrec_convert (TREE_TYPE (chrecr), res, NULL);
+		  res = chrec_fold_plus (type, chrecl, res);
+		}
+	      else
+		{
+		  res = chrec_fold_plus (utype,
+					 chrec_convert (utype, chrecl, NULL),
+					 res);
+		  res = chrec_convert (type, res, NULL);
+		}
 	    }
 	}
       else if (TREE_CODE (x) == INTEGER_CST