From: Richard Biener <rguenther@suse.de>
Date: Thu, 16 May 2024 10:35:28 +0000 (+0200)
Subject: wrong code with points-to and volatile
X-Git-Tag: basepoints/gcc-16~8974
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a9251ab3c91c8c559d0306838575a666ae62dff4;p=thirdparty%2Fgcc.git

wrong code with points-to and volatile

The following fixes points-to analysis which ignores the fact that
volatile qualified refs can result in any pointer.

	* tree-ssa-structalias.cc (get_constraint_for_1): For
	volatile referenced or decls use ANYTHING.

	* gcc.dg/tree-ssa/alias-38.c: New testcase.
---

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/alias-38.c b/gcc/testsuite/gcc.dg/tree-ssa/alias-38.c
new file mode 100644
index 00000000000..a5c41493473
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/alias-38.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int x;
+int y;
+
+int main ()
+{
+  int *volatile p = &x;
+  return (p != &y);
+}
+
+/* { dg-final { scan-tree-dump " != &y" "optimized" } } */
+/* { dg-final { scan-tree-dump-not "return 1;" "optimized" } } */
diff --git a/gcc/tree-ssa-structalias.cc b/gcc/tree-ssa-structalias.cc
index bb59c6a7c02..0bac1a1f045 100644
--- a/gcc/tree-ssa-structalias.cc
+++ b/gcc/tree-ssa-structalias.cc
@@ -3575,6 +3575,10 @@ get_constraint_for_1 (tree t, vec<ce_s> *results, bool address_p,
       }
     case tcc_reference:
       {
+	if (TREE_THIS_VOLATILE (t))
+	  /* Fall back to anything.  */
+	  break;
+
 	switch (TREE_CODE (t))
 	  {
 	  case MEM_REF:
@@ -3676,6 +3680,9 @@ get_constraint_for_1 (tree t, vec<ce_s> *results, bool address_p,
       }
     case tcc_declaration:
       {
+	if (VAR_P (t) && TREE_THIS_VOLATILE (t))
+	  /* Fall back to anything.  */
+	  break;
 	get_constraint_for_ssa_var (t, results, address_p);
 	return;
       }