re PR tree-optimization/15738 ([tree-ssa] Convert strrchr(s, c) to strchr(s, c)…

re PR tree-optimization/15738 ([tree-ssa] Convert strrchr(s, c) to strchr(s, c) if c is known to be 0)

	PR tree-optimization/15738.
	* builtins.c (fold_builtin_strchr): Transform
	strrchr (s, '\0') to strchr (s, '\0').

From-SVN: r82572

gcc/ChangeLog

+2004-06-02  Kazu Hirata  <kazu@cs.umass.edu>
+
+	PR tree-optimization/15738.
+	* builtins.c (fold_builtin_strchr): Transform
+	strrchr (s, '\0') to strchr (s, '\0').
+
 2004-06-02  Steven Bosscher  <stevenb@suse.de>
 
 	* i386.c (ix86_adjust_cost): Don't increase the cost for

gcc/builtins.c

@@ -7123,6 +7123,21 @@ fold_builtin_strchr (tree exp, bool actually_strrchr)
 						 ssize_int (r - p1))));
 	}
 
+      if (actually_strrchr)
+	{
+	  tree fn;
+
+	  if (!integer_zerop (s2))
+	    return 0;
+
+	  fn = implicit_built_in_decls[BUILT_IN_STRCHR];
+	  if (!fn)
+	    return 0;
+
+	  /* Transform strrchr(s1, '\0') to strchr(s1, '\0').  */
+	  return build_function_call_expr (fn, arglist);
+	}
+
       return 0;
     }
 }