[PATCH] Cleanup STRING_CST handing in PTA

[Richard Biener <rguenther at suse dot de>]

points-to is one place that needs special handling of us
allowing &"string" as operands (rather than having a
CONST_DECL for each string literal).  The following patch
realizes that readonly_id is only used for string literals
and adjusts code accordingly.

Bootstrap and regtest running on x86_64-unknown-linux-gnu.

Richard.

2014-08-15  Richard Biener  <rguenther@suse.de>

	* tree-ssa-structalias.c (readonly_id): Rename to string_id.
	(get_constraint_for_ssa_var): Remove dead code.
	(get_constraint_for_1): Adjust.
	(find_what_var_points_to): Likewise.
	(init_base_vars): Likewise.  STRING_CSTs do not contain pointers.

Index: gcc/tree-ssa-structalias.c
===================================================================
--- gcc/tree-ssa-structalias.c	(revision 214007)
+++ gcc/tree-ssa-structalias.c	(working copy)
@@ -344,7 +344,7 @@ vi_next (varinfo_t vi)
 
 /* Static IDs for the special variables.  Variable ID zero is unused
    and used as terminator for the sub-variable chain.  */
-enum { nothing_id = 1, anything_id = 2, readonly_id = 3,
+enum { nothing_id = 1, anything_id = 2, string_id = 3,
        escaped_id = 4, nonlocal_id = 5,
        storedanything_id = 6, integer_id = 7 };
 
@@ -2938,14 +2938,6 @@ get_constraint_for_ssa_var (tree t, vec<
   cexpr.var = vi->id;
   cexpr.type = SCALAR;
   cexpr.offset = 0;
-  /* If we determine the result is "anything", and we know this is readonly,
-     say it points to readonly memory instead.  */
-  if (cexpr.var == anything_id && TREE_READONLY (t))
-    {
-      gcc_unreachable ();
-      cexpr.type = ADDRESSOF;
-      cexpr.var = readonly_id;
-    }
 
   /* If we are not taking the address of the constraint expr, add all
      sub-fiels of the variable as well.  */
@@ -3380,10 +3372,11 @@ get_constraint_for_1 (tree t, vec<ce_s>
       return;
     }
 
-  /* String constants are read-only.  */
+  /* String constants are read-only, ideally we'd have a CONST_DECL
+     for those.  */
   if (TREE_CODE (t) == STRING_CST)
     {
-      temp.var = readonly_id;
+      temp.var = string_id;
       temp.type = SCALAR;
       temp.offset = 0;
       results->safe_push (temp);
@@ -6112,8 +6105,8 @@ find_what_var_points_to (varinfo_t orig_
 	  else if (vi->is_heap_var)
 	    /* We represent heapvars in the points-to set properly.  */
 	    ;
-	  else if (vi->id == readonly_id)
-	    /* Nobody cares.  */
+	  else if (vi->id == string_id)
+	    /* Nobody cares - STRING_CSTs are read-only entities.  */
 	    ;
 	  else if (vi->id == anything_id
 		   || vi->id == integer_id)
@@ -6501,7 +6494,7 @@ init_base_vars (void)
   struct constraint_expr lhs, rhs;
   varinfo_t var_anything;
   varinfo_t var_nothing;
-  varinfo_t var_readonly;
+  varinfo_t var_string;
   varinfo_t var_escaped;
   varinfo_t var_nonlocal;
   varinfo_t var_storedanything;
@@ -6547,27 +6540,17 @@ init_base_vars (void)
      but this one are redundant.  */
   constraints.safe_push (new_constraint (lhs, rhs));
 
-  /* Create the READONLY variable, used to represent that a variable
-     points to readonly memory.  */
-  var_readonly = new_var_info (NULL_TREE, "READONLY");
-  gcc_assert (var_readonly->id == readonly_id);
-  var_readonly->is_artificial_var = 1;
-  var_readonly->offset = 0;
-  var_readonly->size = ~0;
-  var_readonly->fullsize = ~0;
-  var_readonly->is_special_var = 1;
-
-  /* readonly memory points to anything, in order to make deref
-     easier.  In reality, it points to anything the particular
-     readonly variable can point to, but we don't track this
-     separately. */
-  lhs.type = SCALAR;
-  lhs.var = readonly_id;
-  lhs.offset = 0;
-  rhs.type = ADDRESSOF;
-  rhs.var = readonly_id;  /* FIXME */
-  rhs.offset = 0;
-  process_constraint (new_constraint (lhs, rhs));
+  /* Create the STRING variable, used to represent that a variable
+     points to a string literal.  String literals don't contain
+     pointers so STRING doesn't point to anything.  */
+  var_string = new_var_info (NULL_TREE, "STRING");
+  gcc_assert (var_string->id == string_id);
+  var_string->is_artificial_var = 1;
+  var_string->offset = 0;
+  var_string->size = ~0;
+  var_string->fullsize = ~0;
+  var_string->is_special_var = 1;
+  var_string->may_have_pointers = 0;
 
   /* Create the ESCAPED variable, used to represent the set of escaped
      memory.  */