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Minor improvement to points-to analysis
- From: Diego Novillo <dnovillo at redhat dot com>
- To: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 30 Jul 2004 17:04:08 -0400
- Subject: Minor improvement to points-to analysis
- Organization: Red Hat Canada
Noticed while fixing the alias problem in Ada. We shouldn't just look
at invariant addresses.
This lets us find a few more points-to sets (~700 more in a bootstrap
and ~1300 in DLV). This means precisely zilch, but it's Friday and I
have nothing better to do.
I'm hoping that we will soon be able to get rid of this use-def chain
walker. Brian Booth is working on an improvement that may give us a bit
better points-to sets almost for free. We'll see if it pans out.
Bootstrapped and tested x86, alpha, ia64, x86-64 and ppc.
Diego.
* tree-ssa-alias.c (compute_points_to_and_addr_escape): If a
pointer escapes through a function call, assume that the
callee will dereference it.
(add_pointed_to_var): Assume that VALUE is always an
ADDR_EXPR.
(collect_points_to_info_r): Only call add_pointed_to_var if
the value is an ADDR_EXPR.
Index: tree-ssa-alias.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-alias.c,v
retrieving revision 2.21
diff -d -c -p -u -r2.21 tree-ssa-alias.c
--- tree-ssa-alias.c 30 Jul 2004 14:59:46 -0000 2.21
+++ tree-ssa-alias.c 30 Jul 2004 17:11:12 -0000
@@ -691,7 +691,10 @@ compute_points_to_and_addr_escape (struc
that pointer OP will be dereferenced in a store
operation inside the called function. */
if (get_call_expr_in (stmt))
- bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
+ {
+ bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
+ pi->is_dereferenced = 1;
+ }
}
}
@@ -1863,35 +1866,32 @@ static void
add_pointed_to_var (struct alias_info *ai, tree ptr, tree value)
{
struct ptr_info_def *pi = get_ptr_info (ptr);
+ tree pt_var;
+ size_t uid;
- if (TREE_CODE (value) == ADDR_EXPR)
- {
- tree pt_var;
- size_t uid;
+#if defined ENABLE_CHECKING
+ if (TREE_CODE (value) != ADDR_EXPR)
+ abort ();
+#endif
- pt_var = TREE_OPERAND (value, 0);
- if (TREE_CODE_CLASS (TREE_CODE (pt_var)) == 'r')
- pt_var = get_base_address (pt_var);
+ pt_var = TREE_OPERAND (value, 0);
+ if (TREE_CODE_CLASS (TREE_CODE (pt_var)) == 'r')
+ pt_var = get_base_address (pt_var);
- if (pt_var && SSA_VAR_P (pt_var))
- {
- uid = var_ann (pt_var)->uid;
- bitmap_set_bit (ai->addresses_needed, uid);
+ if (pt_var && SSA_VAR_P (pt_var))
+ {
+ uid = var_ann (pt_var)->uid;
+ bitmap_set_bit (ai->addresses_needed, uid);
- /* If PTR has already been found to point anywhere, don't
- add the variable to PTR's points-to set. */
- if (!pi->pt_anything)
- {
- if (pi->pt_vars == NULL)
- pi->pt_vars = BITMAP_GGC_ALLOC ();
- bitmap_set_bit (pi->pt_vars, uid);
- }
+ /* If PTR has already been found to point anywhere, don't
+ add the variable to PTR's points-to set. */
+ if (!pi->pt_anything)
+ {
+ if (pi->pt_vars == NULL)
+ pi->pt_vars = BITMAP_GGC_ALLOC ();
+ bitmap_set_bit (pi->pt_vars, uid);
}
- else
- add_pointed_to_expr (ptr, value);
}
- else
- add_pointed_to_expr (ptr, value);
}
@@ -1922,8 +1922,8 @@ collect_points_to_info_r (tree var, tree
tree rhs = TREE_OPERAND (stmt, 1);
STRIP_NOPS (rhs);
- /* Found P_i = CONST. */
- if (is_gimple_min_invariant (rhs))
+ /* Found P_i = ADDR_EXPR */
+ if (TREE_CODE (rhs) == ADDR_EXPR)
add_pointed_to_var (ai, var, rhs);
/* Found P_i = Q_j. */
@@ -1944,9 +1944,9 @@ collect_points_to_info_r (tree var, tree
else if (TREE_CODE (op1) == SSA_NAME
&& POINTER_TYPE_P (TREE_TYPE (op1)))
merge_pointed_to_info (ai, var, op1);
- else if (is_gimple_min_invariant (op0))
+ else if (TREE_CODE (op0) == ADDR_EXPR)
add_pointed_to_var (ai, var, op0);
- else if (is_gimple_min_invariant (op1))
+ else if (TREE_CODE (op1) == ADDR_EXPR)
add_pointed_to_var (ai, var, op1);
else
add_pointed_to_expr (var, rhs);
@@ -1978,7 +1978,7 @@ collect_points_to_info_r (tree var, tree
variable that we are analyzing is the LHS of the PHI node. */
tree lhs = PHI_RESULT (stmt);
- if (is_gimple_min_invariant (var))
+ if (TREE_CODE (var) == ADDR_EXPR)
add_pointed_to_var (ai, lhs, var);
else if (TREE_CODE (var) == SSA_NAME)
{
@@ -1987,6 +1987,8 @@ collect_points_to_info_r (tree var, tree
else
set_pt_anything (lhs);
}
+ else if (is_gimple_min_invariant (var))
+ add_pointed_to_expr (lhs, var);
else
abort ();
}