Re: [PATCH] Fix PR79547

[Richard Biener <rguenther@suse.de>]

On Thu, 16 Feb 2017, Richard Biener wrote:

> 
> I am testing the following patch for PR79547.  Those builtins do not
> return anything that can be used to re-construct the pointer(s) passed
> to them.
> 
> Queued for GCC 8.

Actually we need calluse constraints.  Thus adjusted as follows.

Richard.

2017-02-17  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.

Index: gcc/testsuite/gcc.dg/tree-ssa/strlen-2.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/strlen-2.c	(nonexistent)
+++ gcc/testsuite/gcc.dg/tree-ssa/strlen-2.c	(working copy)
@@ -0,0 +1,15 @@
+/* { 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" 1 "strlen" } } */
Index: gcc/tree-ssa-structalias.c
===================================================================
--- gcc/tree-ssa-structalias.c	(revision 245501)
+++ gcc/tree-ssa-structalias.c	(working copy)
@@ -4474,6 +4474,40 @@ find_func_aliases_for_builtin_call (stru
 	    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: