/* Forward propagation of expressions for single use variables.
- Copyright (C) 2004, 2005, 2007 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2005, 2007, 2008 Free Software Foundation, Inc.
This file is part of GCC.
0 /* letter */
};
-
-/* Structure to keep track of the value of a dereferenced PHI result
- and the set of virtual operands used for that dereference. */
-
-struct phiprop_d
-{
- tree value;
- tree vop_stmt;
-};
-
-/* Verify if the value recorded for NAME in PHIVN is still valid at
- the start of basic block BB. */
-
-static bool
-phivn_valid_p (struct phiprop_d *phivn, tree name, basic_block bb)
-{
- tree vop_stmt = phivn[SSA_NAME_VERSION (name)].vop_stmt;
- ssa_op_iter ui;
- tree vuse;
-
- /* The def stmts of all virtual uses need to be post-dominated
- by bb. */
- FOR_EACH_SSA_TREE_OPERAND (vuse, vop_stmt, ui, SSA_OP_VUSE)
- {
- tree use_stmt;
- imm_use_iterator ui2;
- bool ok = true;
-
- FOR_EACH_IMM_USE_STMT (use_stmt, ui2, vuse)
- {
- /* If BB does not dominate a VDEF, the value is invalid. */
- if (((TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
- && !ZERO_SSA_OPERANDS (use_stmt, SSA_OP_VDEF))
- || TREE_CODE (use_stmt) == PHI_NODE)
- && !dominated_by_p (CDI_DOMINATORS, bb_for_stmt (use_stmt), bb))
- {
- ok = false;
- BREAK_FROM_IMM_USE_STMT (ui2);
- }
- }
- if (!ok)
- return false;
- }
-
- return true;
-}
-
-/* Insert a new phi node for the dereference of PHI at basic_block
- BB with the virtual operands from USE_STMT. */
-
-static tree
-phiprop_insert_phi (basic_block bb, tree phi, tree use_stmt,
- struct phiprop_d *phivn, size_t n)
-{
- tree res, new_phi;
- edge_iterator ei;
- edge e;
-
- /* Build a new PHI node to replace the definition of
- the indirect reference lhs. */
- res = GIMPLE_STMT_OPERAND (use_stmt, 0);
- SSA_NAME_DEF_STMT (res) = new_phi = create_phi_node (res, bb);
-
- /* Add PHI arguments for each edge inserting loads of the
- addressable operands. */
- FOR_EACH_EDGE (e, ei, bb->preds)
- {
- tree old_arg, new_var, tmp;
-
- old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
- while (TREE_CODE (old_arg) == SSA_NAME
- && (SSA_NAME_VERSION (old_arg) >= n
- || phivn[SSA_NAME_VERSION (old_arg)].value == NULL_TREE))
- {
- tree def_stmt = SSA_NAME_DEF_STMT (old_arg);
- old_arg = GIMPLE_STMT_OPERAND (def_stmt, 1);
- }
-
- if (TREE_CODE (old_arg) == SSA_NAME)
- /* Reuse a formerly created dereference. */
- new_var = phivn[SSA_NAME_VERSION (old_arg)].value;
- else
- {
- old_arg = TREE_OPERAND (old_arg, 0);
- new_var = create_tmp_var (TREE_TYPE (old_arg), NULL);
- tmp = build2 (GIMPLE_MODIFY_STMT, void_type_node,
- NULL_TREE, unshare_expr (old_arg));
- if (TREE_CODE (TREE_TYPE (old_arg)) == COMPLEX_TYPE
- || TREE_CODE (TREE_TYPE (old_arg)) == VECTOR_TYPE)
- DECL_GIMPLE_REG_P (new_var) = 1;
- add_referenced_var (new_var);
- new_var = make_ssa_name (new_var, tmp);
- GIMPLE_STMT_OPERAND (tmp, 0) = new_var;
-
- bsi_insert_on_edge (e, tmp);
-
- update_stmt (tmp);
- mark_symbols_for_renaming (tmp);
- }
-
- add_phi_arg (new_phi, new_var, e);
- }
-
- update_stmt (new_phi);
-
- return res;
-}
-
-/* Propagate between the phi node arguments of PHI in BB and phi result
- users. For now this matches
- # p_2 = PHI <&x, &y>
- <Lx>:;
- p_3 = p_2;
- z_2 = *p_3;
- and converts it to
- # z_2 = PHI <x, y>
- <Lx>:;
- Returns true if a transformation was done and edge insertions
- need to be committed. Global data PHIVN and N is used to track
- past transformation results. We need to be especially careful here
- with aliasing issues as we are moving memory reads. */
-
-static bool
-propagate_with_phi (basic_block bb, tree phi, struct phiprop_d *phivn, size_t n)
-{
- tree ptr = PHI_RESULT (phi);
- tree use_stmt, res = NULL_TREE;
- block_stmt_iterator bsi;
- imm_use_iterator ui;
- use_operand_p arg_p, use;
- ssa_op_iter i;
- bool phi_inserted;
-
- if (MTAG_P (SSA_NAME_VAR (ptr))
- || !POINTER_TYPE_P (TREE_TYPE (ptr))
- || !is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr))))
- return false;
-
- /* Check if we can "cheaply" dereference all phi arguments. */
- FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE)
- {
- tree arg = USE_FROM_PTR (arg_p);
- /* Walk the ssa chain until we reach a ssa name we already
- created a value for or we reach a definition of the form
- ssa_name_n = &var; */
- while (TREE_CODE (arg) == SSA_NAME
- && !SSA_NAME_IS_DEFAULT_DEF (arg)
- && (SSA_NAME_VERSION (arg) >= n
- || phivn[SSA_NAME_VERSION (arg)].value == NULL_TREE))
- {
- tree def_stmt = SSA_NAME_DEF_STMT (arg);
- if (TREE_CODE (def_stmt) != GIMPLE_MODIFY_STMT)
- return false;
- arg = GIMPLE_STMT_OPERAND (def_stmt, 1);
- }
- if ((TREE_CODE (arg) != ADDR_EXPR
- /* Avoid to have to decay *&a to a[0] later. */
- || !is_gimple_reg_type (TREE_TYPE (TREE_OPERAND (arg, 0))))
- && !(TREE_CODE (arg) == SSA_NAME
- && phivn[SSA_NAME_VERSION (arg)].value != NULL_TREE
- && phivn_valid_p (phivn, arg, bb)))
- return false;
- }
-
- /* Find a dereferencing use. First follow (single use) ssa
- copy chains for ptr. */
- while (single_imm_use (ptr, &use, &use_stmt)
- && TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
- && GIMPLE_STMT_OPERAND (use_stmt, 1) == ptr
- && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME)
- ptr = GIMPLE_STMT_OPERAND (use_stmt, 0);
-
- /* Replace the first dereference of *ptr if there is one and if we
- can move the loads to the place of the ptr phi node. */
- phi_inserted = false;
- FOR_EACH_IMM_USE_STMT (use_stmt, ui, ptr)
- {
- ssa_op_iter ui2;
- tree vuse;
-
- /* Check whether this is a load of *ptr. */
- if (!(TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
- && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME
- && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == INDIRECT_REF
- && TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0) == ptr
- /* We cannot replace a load that may throw or is volatile. */
- && !tree_can_throw_internal (use_stmt)))
- continue;
-
- /* Check if we can move the loads. The def stmts of all virtual uses
- need to be post-dominated by bb. */
- FOR_EACH_SSA_TREE_OPERAND (vuse, use_stmt, ui2, SSA_OP_VUSE)
- {
- tree def_stmt = SSA_NAME_DEF_STMT (vuse);
- if (!SSA_NAME_IS_DEFAULT_DEF (vuse)
- && (bb_for_stmt (def_stmt) == bb
- || !dominated_by_p (CDI_DOMINATORS,
- bb, bb_for_stmt (def_stmt))))
- goto next;
- }
-
- /* Found a proper dereference. Insert a phi node if this
- is the first load transformation. */
- if (!phi_inserted)
- {
- res = phiprop_insert_phi (bb, phi, use_stmt, phivn, n);
-
- /* Remember the value we created for *ptr. */
- phivn[SSA_NAME_VERSION (ptr)].value = res;
- phivn[SSA_NAME_VERSION (ptr)].vop_stmt = use_stmt;
-
- /* Remove old stmt. The phi is taken care of by DCE, if we
- want to delete it here we also have to delete all intermediate
- copies. */
- bsi = bsi_for_stmt (use_stmt);
- bsi_remove (&bsi, 0);
-
- phi_inserted = true;
- }
- else
- {
- /* Further replacements are easy, just make a copy out of the
- load. */
- GIMPLE_STMT_OPERAND (use_stmt, 1) = res;
- update_stmt (use_stmt);
- }
-
-next:;
- /* Continue searching for a proper dereference. */
- }
-
- return phi_inserted;
-}
-
-/* Helper walking the dominator tree starting from BB and processing
- phi nodes with global data PHIVN and N. */
-
-static bool
-tree_ssa_phiprop_1 (basic_block bb, struct phiprop_d *phivn, size_t n)
-{
- bool did_something = false;
- basic_block son;
- tree phi;
-
- for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
- did_something |= propagate_with_phi (bb, phi, phivn, n);
-
- for (son = first_dom_son (CDI_DOMINATORS, bb);
- son;
- son = next_dom_son (CDI_DOMINATORS, son))
- did_something |= tree_ssa_phiprop_1 (son, phivn, n);
-
- return did_something;
-}
-
-/* Main entry for phiprop pass. */
-
-static unsigned int
-tree_ssa_phiprop (void)
-{
- struct phiprop_d *phivn;
-
- calculate_dominance_info (CDI_DOMINATORS);
-
- phivn = XCNEWVEC (struct phiprop_d, num_ssa_names);
-
- if (tree_ssa_phiprop_1 (ENTRY_BLOCK_PTR, phivn, num_ssa_names))
- bsi_commit_edge_inserts ();
-
- free (phivn);
-
- return 0;
-}
-
-static bool
-gate_phiprop (void)
-{
- return 1;
-}
-
-struct tree_opt_pass pass_phiprop = {
- "phiprop", /* name */
- gate_phiprop, /* gate */
- tree_ssa_phiprop, /* execute */
- NULL, /* sub */
- NULL, /* next */
- 0, /* static_pass_number */
- TV_TREE_FORWPROP, /* tv_id */
- PROP_cfg | PROP_ssa, /* properties_required */
- 0, /* properties_provided */
- 0, /* properties_destroyed */
- 0, /* todo_flags_start */
- TODO_dump_func
- | TODO_ggc_collect
- | TODO_update_ssa
- | TODO_verify_ssa, /* todo_flags_finish */
- 0 /* letter */
-};
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