From: Richard Biener <rguenther@suse.de>
Date: Tue, 26 Jul 2022 09:02:13 +0000 (+0200)
Subject: Improve ptr_derefs_may_alias_p for the case of &STRING_CST
X-Git-Tag: basepoints/gcc-14~5368
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=67248ad043b366d30e97cb6c192593057e798805;p=thirdparty%2Fgcc.git

Improve ptr_derefs_may_alias_p for the case of &STRING_CST

When the first pointer happens to be a pointer to a STRING_CST we
give up too early since the 2nd pointer handling could still end
up with a DECL for example which can disambiguate against a STRING_CST
just fine.

	* tree-ssa-alias.cc (ptr_derefs_may_alias_p): If ptr1
	points to a constant continue checking ptr2.
---

diff --git a/gcc/tree-ssa-alias.cc b/gcc/tree-ssa-alias.cc
index 390cd875074..b4c65da5718 100644
--- a/gcc/tree-ssa-alias.cc
+++ b/gcc/tree-ssa-alias.cc
@@ -349,7 +349,9 @@ ptr_derefs_may_alias_p (tree ptr1, tree ptr2)
       else if (base
 	       && DECL_P (base))
 	return ptr_deref_may_alias_decl_p (ptr2, base);
-      else
+      /* Try ptr2 when ptr1 points to a constant.  */
+      else if (base
+	       && !CONSTANT_CLASS_P (base))
 	return true;
     }
   if (TREE_CODE (ptr2) == ADDR_EXPR)