re PR tree-optimization/79547 (duplicate strlen calls with same argument not folded)

2017-04-21  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/79547
	* tree-ssa-structalias.c (find_func_aliases_for_builtin_call):
	Handle strlen, strcmp, strncmp, strcasecmp, strncasecmp, memcmp,
	bcmp, strspn, strcspn, __builtin_object_size and __builtin_constant_p
	without any constraints.

	* gcc.dg/tree-ssa/strlen-2.c: New testcase.

From-SVN: r247062

gcc/ChangeLog

 2017-04-21  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/79547
+	* tree-ssa-structalias.c (find_func_aliases_for_builtin_call):
+	Handle strlen, strcmp, strncmp, strcasecmp, strncasecmp, memcmp,
+	bcmp, strspn, strcspn, __builtin_object_size and __builtin_constant_p
+	without any constraints.
+
+2017-04-21  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/78847
 	* fold-const.c (split_tree): Handle POINTER_PLUS_EXPR.
 

gcc/testsuite/ChangeLog

 2017-04-21  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/79547
+	* gcc.dg/tree-ssa/strlen-2.c: New testcase.
+
+2017-04-21  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/78847
 	* g++.dg/tree-ssa/pr78847.C: New testcase.
 

gcc/testsuite/gcc.dg/tree-ssa/strlen-2.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+void f (unsigned);
+
+void f3 (void)
+{
+  char s[] = "1234";
+
+  f (__builtin_strlen (s));
+  f (__builtin_strlen (s));
+  f (__builtin_strlen (s));
+}
+
+/* { dg-final { scan-tree-dump-times "strlen" 0 "strlen" } } */

gcc/tree-ssa-structalias.c

@@ -4474,6 +4474,40 @@ find_func_aliases_for_builtin_call (struct function *fn, gcall *t)
 	    process_all_all_constraints (lhsc, rhsc);
 	  }
 	return true;
+      /* Pure functions that return something not based on any object and
+         that use the memory pointed to by their arguments (but not
+	 transitively).  */
+      case BUILT_IN_STRCMP:
+      case BUILT_IN_STRNCMP:
+      case BUILT_IN_STRCASECMP:
+      case BUILT_IN_STRNCASECMP:
+      case BUILT_IN_MEMCMP:
+      case BUILT_IN_BCMP:
+      case BUILT_IN_STRSPN:
+      case BUILT_IN_STRCSPN:
+	{
+	  varinfo_t uses = get_call_use_vi (t);
+	  make_any_offset_constraints (uses);
+	  make_constraint_to (uses->id, gimple_call_arg (t, 0));
+	  make_constraint_to (uses->id, gimple_call_arg (t, 1));
+	  /* No constraints are necessary for the return value.  */
+	  return true;
+	}
+      case BUILT_IN_STRLEN:
+	{
+	  varinfo_t uses = get_call_use_vi (t);
+	  make_any_offset_constraints (uses);
+	  make_constraint_to (uses->id, gimple_call_arg (t, 0));
+	  /* No constraints are necessary for the return value.  */
+	  return true;
+	}
+      case BUILT_IN_OBJECT_SIZE:
+      case BUILT_IN_CONSTANT_P:
+	{
+	  /* No constraints are necessary for the return value or the
+	     arguments.  */
+	  return true;
+	}
       /* Trampolines are special - they set up passing the static
 	 frame.  */
       case BUILT_IN_INIT_TRAMPOLINE: