-/* Const/copy propagation and SSA_NAME replacement support routines.
- Copyright (C) 2004 Free Software Foundation, Inc.
+/* Copy propagation and SSA_NAME replacement support routines.
+ Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010
+ Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2, or (at your option)
+the Free Software Foundation; either version 3, or (at your option)
any later version.
GCC is distributed in the hope that it will be useful,
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING. If not, write to
-the Free Software Foundation, 59 Temple Place - Suite 330,
-Boston, MA 02111-1307, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "tm.h"
#include "tree.h"
#include "flags.h"
-#include "rtl.h"
#include "tm_p.h"
-#include "ggc.h"
#include "basic-block.h"
#include "output.h"
-#include "errors.h"
-#include "expr.h"
#include "function.h"
-#include "diagnostic.h"
+#include "tree-pretty-print.h"
+#include "gimple-pretty-print.h"
#include "timevar.h"
#include "tree-dump.h"
#include "tree-flow.h"
#include "tree-pass.h"
+#include "tree-ssa-propagate.h"
#include "langhooks.h"
+#include "cfgloop.h"
-/* This file provides a handful of interfaces for performing const/copy
- propagation and simple expression replacement which keep variable
- annotations up-to-date.
+/* This file implements the copy propagation pass and provides a
+ handful of interfaces for performing const/copy propagation and
+ simple expression replacement which keep variable annotations
+ up-to-date.
We require that for any copy operation where the RHS and LHS have
- a non-null memory tag that the memory tag be the same. It is OK
+ a non-null memory tag the memory tag be the same. It is OK
for one or both of the memory tags to be NULL.
We also require tracking if a variable is dereferenced in a load or
replacements of one SSA_NAME with a different SSA_NAME to use the
APIs defined in this file. */
-/* Given two SSA_NAMEs, replace the one pointed to by OP_P with VAR.
+/* Return true if we may propagate ORIG into DEST, false otherwise. */
- If *OP_P is a pointer, copy the memory tag used originally by *OP_P into
- VAR. This is needed in cases where VAR had never been dereferenced in the
- program.
-
- If FOR_PROPAGATION is true, then perform additional checks to ensure
- that const/copy propagation of var for *OP_P is valid. */
-
-static void
-replace_ssa_names (tree *op_p,
- tree var,
- bool for_propagation ATTRIBUTE_UNUSED)
+bool
+may_propagate_copy (tree dest, tree orig)
{
-#if defined ENABLE_CHECKING
- if (for_propagation && !may_propagate_copy (*op_p, var))
- abort ();
-#endif
-
- /* If VAR doesn't have a memory tag, copy the one from the original
- operand. Also copy the dereferenced flags. */
- if (POINTER_TYPE_P (TREE_TYPE (*op_p)))
+ tree type_d = TREE_TYPE (dest);
+ tree type_o = TREE_TYPE (orig);
+
+ /* If ORIG flows in from an abnormal edge, it cannot be propagated. */
+ if (TREE_CODE (orig) == SSA_NAME
+ && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig))
+ return false;
+
+ /* If DEST is an SSA_NAME that flows from an abnormal edge, then it
+ cannot be replaced. */
+ if (TREE_CODE (dest) == SSA_NAME
+ && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (dest))
+ return false;
+
+ /* Do not copy between types for which we *do* need a conversion. */
+ if (!useless_type_conversion_p (type_d, type_o))
+ return false;
+
+ /* Propagating virtual operands is always ok. */
+ if (TREE_CODE (dest) == SSA_NAME && !is_gimple_reg (dest))
{
- var_ann_t new_ann = var_ann (SSA_NAME_VAR (var));
- var_ann_t orig_ann = var_ann (SSA_NAME_VAR (*op_p));
-
- if (new_ann->type_mem_tag == NULL_TREE)
- new_ann->type_mem_tag = orig_ann->type_mem_tag;
- else if (orig_ann->type_mem_tag == NULL_TREE)
- orig_ann->type_mem_tag = new_ann->type_mem_tag;
- else if (new_ann->type_mem_tag != orig_ann->type_mem_tag)
- abort ();
+ /* But only between virtual operands. */
+ gcc_assert (TREE_CODE (orig) == SSA_NAME && !is_gimple_reg (orig));
+
+ return true;
}
- *op_p = var;
+ /* Anything else is OK. */
+ return true;
}
+/* Like may_propagate_copy, but use as the destination expression
+ the principal expression (typically, the RHS) contained in
+ statement DEST. This is more efficient when working with the
+ gimple tuples representation. */
+
+bool
+may_propagate_copy_into_stmt (gimple dest, tree orig)
+{
+ tree type_d;
+ tree type_o;
+
+ /* If the statement is a switch or a single-rhs assignment,
+ then the expression to be replaced by the propagation may
+ be an SSA_NAME. Fortunately, there is an explicit tree
+ for the expression, so we delegate to may_propagate_copy. */
+
+ if (gimple_assign_single_p (dest))
+ return may_propagate_copy (gimple_assign_rhs1 (dest), orig);
+ else if (gimple_code (dest) == GIMPLE_SWITCH)
+ return may_propagate_copy (gimple_switch_index (dest), orig);
+
+ /* In other cases, the expression is not materialized, so there
+ is no destination to pass to may_propagate_copy. On the other
+ hand, the expression cannot be an SSA_NAME, so the analysis
+ is much simpler. */
+
+ if (TREE_CODE (orig) == SSA_NAME
+ && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (orig))
+ return false;
+
+ if (is_gimple_assign (dest))
+ type_d = TREE_TYPE (gimple_assign_lhs (dest));
+ else if (gimple_code (dest) == GIMPLE_COND)
+ type_d = boolean_type_node;
+ else if (is_gimple_call (dest)
+ && gimple_call_lhs (dest) != NULL_TREE)
+ type_d = TREE_TYPE (gimple_call_lhs (dest));
+ else
+ gcc_unreachable ();
+
+ type_o = TREE_TYPE (orig);
+
+ if (!useless_type_conversion_p (type_d, type_o))
+ return false;
+
+ return true;
+}
+
+/* Similarly, but we know that we're propagating into an ASM_EXPR. */
+
+bool
+may_propagate_copy_into_asm (tree dest)
+{
+ /* Hard register operands of asms are special. Do not bypass. */
+ return !(TREE_CODE (dest) == SSA_NAME
+ && TREE_CODE (SSA_NAME_VAR (dest)) == VAR_DECL
+ && DECL_HARD_REGISTER (SSA_NAME_VAR (dest)));
+}
+
+
/* Common code for propagate_value and replace_exp.
- Replace *OP_P with VAL. FOR_PROPAGATION indicates if the replacement
- is done to propagate a value or not. */
+ Replace use operand OP_P with VAL. FOR_PROPAGATION indicates if the
+ replacement is done to propagate a value or not. */
static void
-replace_exp_1 (tree *op_p, tree val, bool for_propagation)
+replace_exp_1 (use_operand_p op_p, tree val,
+ bool for_propagation ATTRIBUTE_UNUSED)
{
+#if defined ENABLE_CHECKING
+ tree op = USE_FROM_PTR (op_p);
+
+ gcc_assert (!(for_propagation
+ && TREE_CODE (op) == SSA_NAME
+ && TREE_CODE (val) == SSA_NAME
+ && !may_propagate_copy (op, val)));
+#endif
+
if (TREE_CODE (val) == SSA_NAME)
- {
- if (TREE_CODE (*op_p) == SSA_NAME)
- replace_ssa_names (op_p, val, for_propagation);
- else
- *op_p = val;
- }
+ SET_USE (op_p, val);
else
- *op_p = lhd_unsave_expr_now (val);
+ SET_USE (op_p, unsave_expr_now (val));
}
+
/* Propagate the value VAL (assumed to be a constant or another SSA_NAME)
- into the operand pointed by OP_P.
+ into the operand pointed to by OP_P.
Use this version for const/copy propagation as it will perform additional
checks to ensure validity of the const/copy propagation. */
void
-propagate_value (tree *op_p, tree val)
+propagate_value (use_operand_p op_p, tree val)
{
replace_exp_1 (op_p, val, true);
}
Use this version when not const/copy propagating values. For example,
PRE uses this version when building expressions as they would appear
- in specific blocks taking into account actions of PHI nodes. */
+ in specific blocks taking into account actions of PHI nodes.
+
+ The statement in which an expression has been replaced should be
+ folded using fold_stmt_inplace. */
void
-replace_exp (tree *op_p, tree val)
+replace_exp (use_operand_p op_p, tree val)
{
replace_exp_1 (op_p, val, false);
}
-/* Replace *OP_P in STMT with any known equivalent value for *OP_P from
- CONST_AND_COPIES. */
+
+/* Propagate the value VAL (assumed to be a constant or another SSA_NAME)
+ into the tree pointed to by OP_P.
+
+ Use this version for const/copy propagation when SSA operands are not
+ available. It will perform the additional checks to ensure validity of
+ the const/copy propagation, but will not update any operand information.
+ Be sure to mark the stmt as modified. */
+
+void
+propagate_tree_value (tree *op_p, tree val)
+{
+ gcc_checking_assert (!(TREE_CODE (val) == SSA_NAME
+ && *op_p
+ && TREE_CODE (*op_p) == SSA_NAME
+ && !may_propagate_copy (*op_p, val)));
+
+ if (TREE_CODE (val) == SSA_NAME)
+ *op_p = val;
+ else
+ *op_p = unsave_expr_now (val);
+}
+
+
+/* Like propagate_tree_value, but use as the operand to replace
+ the principal expression (typically, the RHS) contained in the
+ statement referenced by iterator GSI. Note that it is not
+ always possible to update the statement in-place, so a new
+ statement may be created to replace the original. */
+
+void
+propagate_tree_value_into_stmt (gimple_stmt_iterator *gsi, tree val)
+{
+ gimple stmt = gsi_stmt (*gsi);
+
+ if (is_gimple_assign (stmt))
+ {
+ tree expr = NULL_TREE;
+ if (gimple_assign_single_p (stmt))
+ expr = gimple_assign_rhs1 (stmt);
+ propagate_tree_value (&expr, val);
+ gimple_assign_set_rhs_from_tree (gsi, expr);
+ }
+ else if (gimple_code (stmt) == GIMPLE_COND)
+ {
+ tree lhs = NULL_TREE;
+ tree rhs = build_zero_cst (TREE_TYPE (val));
+ propagate_tree_value (&lhs, val);
+ gimple_cond_set_code (stmt, NE_EXPR);
+ gimple_cond_set_lhs (stmt, lhs);
+ gimple_cond_set_rhs (stmt, rhs);
+ }
+ else if (is_gimple_call (stmt)
+ && gimple_call_lhs (stmt) != NULL_TREE)
+ {
+ gimple new_stmt;
+
+ tree expr = NULL_TREE;
+ propagate_tree_value (&expr, val);
+ new_stmt = gimple_build_assign (gimple_call_lhs (stmt), expr);
+ move_ssa_defining_stmt_for_defs (new_stmt, stmt);
+ gsi_replace (gsi, new_stmt, false);
+ }
+ else if (gimple_code (stmt) == GIMPLE_SWITCH)
+ propagate_tree_value (gimple_switch_index_ptr (stmt), val);
+ else
+ gcc_unreachable ();
+}
+
+/*---------------------------------------------------------------------------
+ Copy propagation
+---------------------------------------------------------------------------*/
+/* Lattice for copy-propagation. The lattice is initialized to
+ UNDEFINED (value == NULL) for SSA names that can become a copy
+ of something or VARYING (value == self) if not (see get_copy_of_val
+ and stmt_may_generate_copy). Other values make the name a COPY
+ of that value.
+
+ When visiting a statement or PHI node the lattice value for an
+ SSA name can transition from UNDEFINED to COPY to VARYING. */
+
+struct prop_value_d {
+ /* Copy-of value. */
+ tree value;
+};
+typedef struct prop_value_d prop_value_t;
+
+static prop_value_t *copy_of;
+
+
+/* Return true if this statement may generate a useful copy. */
static bool
-cprop_operand (stmt_ann_t ann, tree *op_p, varray_type const_and_copies)
+stmt_may_generate_copy (gimple stmt)
+{
+ if (gimple_code (stmt) == GIMPLE_PHI)
+ return !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_phi_result (stmt));
+
+ if (gimple_code (stmt) != GIMPLE_ASSIGN)
+ return false;
+
+ /* If the statement has volatile operands, it won't generate a
+ useful copy. */
+ if (gimple_has_volatile_ops (stmt))
+ return false;
+
+ /* Statements with loads and/or stores will never generate a useful copy. */
+ if (gimple_vuse (stmt))
+ return false;
+
+ /* Otherwise, the only statements that generate useful copies are
+ assignments whose RHS is just an SSA name that doesn't flow
+ through abnormal edges. */
+ return ((gimple_assign_rhs_code (stmt) == SSA_NAME
+ && !SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (stmt)))
+ || is_gimple_min_invariant (gimple_assign_rhs1 (stmt)));
+}
+
+
+/* Return the copy-of value for VAR. */
+
+static inline prop_value_t *
+get_copy_of_val (tree var)
+{
+ prop_value_t *val = ©_of[SSA_NAME_VERSION (var)];
+
+ if (val->value == NULL_TREE
+ && !stmt_may_generate_copy (SSA_NAME_DEF_STMT (var)))
+ {
+ /* If the variable will never generate a useful copy relation,
+ make it its own copy. */
+ val->value = var;
+ }
+
+ return val;
+}
+
+/* Return the variable VAR is a copy of or VAR if VAR isn't the result
+ of a copy. */
+
+static inline tree
+valueize_val (tree var)
+{
+ if (TREE_CODE (var) == SSA_NAME)
+ {
+ tree val = get_copy_of_val (var)->value;
+ if (val)
+ return val;
+ }
+ return var;
+}
+
+/* Set VAL to be the copy of VAR. If that changed return true. */
+
+static inline bool
+set_copy_of_val (tree var, tree val)
+{
+ unsigned int ver = SSA_NAME_VERSION (var);
+ tree old;
+
+ /* Set FIRST to be the first link in COPY_OF[DEST]. If that
+ changed, return true. */
+ old = copy_of[ver].value;
+ copy_of[ver].value = val;
+
+ if (old != val
+ || (val && !operand_equal_p (old, val, 0)))
+ return true;
+
+ return false;
+}
+
+
+/* Dump the copy-of value for variable VAR to FILE. */
+
+static void
+dump_copy_of (FILE *file, tree var)
{
- bool may_have_exposed_new_symbols = false;
tree val;
- /* If the operand has a known constant value or it is known to be a
- copy of some other variable, use the value or copy stored in
- CONST_AND_COPIES. */
- val = VARRAY_TREE (const_and_copies, SSA_NAME_VERSION (*op_p));
- if (val)
+ print_generic_expr (file, var, dump_flags);
+ if (TREE_CODE (var) != SSA_NAME)
+ return;
+
+ val = copy_of[SSA_NAME_VERSION (var)].value;
+ fprintf (file, " copy-of chain: ");
+ print_generic_expr (file, var, 0);
+ fprintf (file, " ");
+ if (!val)
+ fprintf (file, "[UNDEFINED]");
+ else if (val == var)
+ fprintf (file, "[NOT A COPY]");
+ else
{
- tree op_type, val_type;
-
- /* Do not change the base variable in the virtual operand
- tables. That would make it impossible to reconstruct
- the renamed virtual operand if we later modify this
- statement. Also only allow the new value to be an SSA_NAME
- for propagation into virtual operands. */
- if (!is_gimple_reg (*op_p)
- && (get_virtual_var (val) != get_virtual_var (*op_p)
- || TREE_CODE (val) != SSA_NAME))
- return false;
-
- /* Get the toplevel type of each operand. */
- op_type = TREE_TYPE (*op_p);
- val_type = TREE_TYPE (val);
-
- /* While both types are pointers, get the type of the object
- pointed to. */
- while (POINTER_TYPE_P (op_type) && POINTER_TYPE_P (val_type))
- {
- op_type = TREE_TYPE (op_type);
- val_type = TREE_TYPE (val_type);
- }
+ fprintf (file, "-> ");
+ print_generic_expr (file, val, 0);
+ fprintf (file, " ");
+ fprintf (file, "[COPY]");
+ }
+}
+
+
+/* Evaluate the RHS of STMT. If it produces a valid copy, set the LHS
+ value and store the LHS into *RESULT_P. */
+
+static enum ssa_prop_result
+copy_prop_visit_assignment (gimple stmt, tree *result_p)
+{
+ tree lhs, rhs;
+
+ lhs = gimple_assign_lhs (stmt);
+ rhs = valueize_val (gimple_assign_rhs1 (stmt));
+
+ if (TREE_CODE (lhs) == SSA_NAME)
+ {
+ /* Straight copy between two SSA names. First, make sure that
+ we can propagate the RHS into uses of LHS. */
+ if (!may_propagate_copy (lhs, rhs))
+ return SSA_PROP_VARYING;
+
+ *result_p = lhs;
+ if (set_copy_of_val (*result_p, rhs))
+ return SSA_PROP_INTERESTING;
+ else
+ return SSA_PROP_NOT_INTERESTING;
+ }
+
+ return SSA_PROP_VARYING;
+}
- /* Make sure underlying types match before propagating a
- constant by converting the constant to the proper type. Note
- that convert may return a non-gimple expression, in which case
- we ignore this propagation opportunity. */
- if (!lang_hooks.types_compatible_p (op_type, val_type)
- && TREE_CODE (val) != SSA_NAME)
- {
- val = convert (TREE_TYPE (*op_p), val);
- if (!is_gimple_min_invariant (val)
- && TREE_CODE (val) != SSA_NAME)
- return false;
- }
- /* Certain operands are not allowed to be copy propagated due
- to their interaction with exception handling and some GCC
- extensions. */
- if (TREE_CODE (val) == SSA_NAME
- && !may_propagate_copy (*op_p, val))
- return false;
+/* Visit the GIMPLE_COND STMT. Return SSA_PROP_INTERESTING
+ if it can determine which edge will be taken. Otherwise, return
+ SSA_PROP_VARYING. */
- /* Dump details. */
+static enum ssa_prop_result
+copy_prop_visit_cond_stmt (gimple stmt, edge *taken_edge_p)
+{
+ enum ssa_prop_result retval = SSA_PROP_VARYING;
+ location_t loc = gimple_location (stmt);
+
+ tree op0 = gimple_cond_lhs (stmt);
+ tree op1 = gimple_cond_rhs (stmt);
+
+ /* The only conditionals that we may be able to compute statically
+ are predicates involving two SSA_NAMEs. */
+ if (TREE_CODE (op0) == SSA_NAME && TREE_CODE (op1) == SSA_NAME)
+ {
+ op0 = valueize_val (op0);
+ op1 = valueize_val (op1);
+
+ /* See if we can determine the predicate's value. */
if (dump_file && (dump_flags & TDF_DETAILS))
{
- fprintf (dump_file, " Replaced '");
- print_generic_expr (dump_file, *op_p, dump_flags);
- fprintf (dump_file, "' with %s '",
- (TREE_CODE (val) != SSA_NAME ? "constant" : "variable"));
- print_generic_expr (dump_file, val, dump_flags);
- fprintf (dump_file, "'\n");
+ fprintf (dump_file, "Trying to determine truth value of ");
+ fprintf (dump_file, "predicate ");
+ print_gimple_stmt (dump_file, stmt, 0, 0);
}
- /* If VAL is an ADDR_EXPR or a constant of pointer type, note
- that we may have exposed a new symbol for SSA renaming. */
- if (TREE_CODE (val) == ADDR_EXPR
- || (POINTER_TYPE_P (TREE_TYPE (*op_p))
- && is_gimple_min_invariant (val)))
- may_have_exposed_new_symbols = true;
+ /* We can fold COND and get a useful result only when we have
+ the same SSA_NAME on both sides of a comparison operator. */
+ if (op0 == op1)
+ {
+ tree folded_cond = fold_binary_loc (loc, gimple_cond_code (stmt),
+ boolean_type_node, op0, op1);
+ if (folded_cond)
+ {
+ basic_block bb = gimple_bb (stmt);
+ *taken_edge_p = find_taken_edge (bb, folded_cond);
+ if (*taken_edge_p)
+ retval = SSA_PROP_INTERESTING;
+ }
+ }
+ }
- propagate_value (op_p, val);
+ if (dump_file && (dump_flags & TDF_DETAILS) && *taken_edge_p)
+ fprintf (dump_file, "\nConditional will always take edge %d->%d\n",
+ (*taken_edge_p)->src->index, (*taken_edge_p)->dest->index);
- /* And note that we modified this statement. This is now
- safe, even if we changed virtual operands since we will
- rescan the statement and rewrite its operands again. */
- ann->modified = 1;
- }
- return may_have_exposed_new_symbols;
+ return retval;
}
-/* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
- known value for that SSA_NAME (or NULL if no value is known).
- Propagate values from CONST_AND_COPIES into the uses, vuses and
- vdef_ops of STMT. */
+/* Evaluate statement STMT. If the statement produces a new output
+ value, return SSA_PROP_INTERESTING and store the SSA_NAME holding
+ the new value in *RESULT_P.
-bool
-cprop_into_stmt (tree stmt, varray_type const_and_copies)
+ If STMT is a conditional branch and we can determine its truth
+ value, set *TAKEN_EDGE_P accordingly.
+
+ If the new value produced by STMT is varying, return
+ SSA_PROP_VARYING. */
+
+static enum ssa_prop_result
+copy_prop_visit_stmt (gimple stmt, edge *taken_edge_p, tree *result_p)
{
- bool may_have_exposed_new_symbols = false;
- stmt_ann_t ann = stmt_ann (stmt);
- size_t i, num_uses, num_vuses, num_vdefs;
- vuse_optype vuses;
- vdef_optype vdefs;
- use_optype uses;
-
- uses = USE_OPS (ann);
- num_uses = NUM_USES (uses);
- for (i = 0; i < num_uses; i++)
+ enum ssa_prop_result retval;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
{
- tree *op_p = USE_OP_PTR (uses, i);
- if (TREE_CODE (*op_p) == SSA_NAME)
- may_have_exposed_new_symbols
- |= cprop_operand (ann, op_p, const_and_copies);
+ fprintf (dump_file, "\nVisiting statement:\n");
+ print_gimple_stmt (dump_file, stmt, 0, dump_flags);
+ fprintf (dump_file, "\n");
}
- vuses = VUSE_OPS (ann);
- num_vuses = NUM_VUSES (vuses);
- for (i = 0; i < num_vuses; i++)
+ if (gimple_assign_single_p (stmt)
+ && TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME
+ && (TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
+ || is_gimple_min_invariant (gimple_assign_rhs1 (stmt))))
+ {
+ /* If the statement is a copy assignment, evaluate its RHS to
+ see if the lattice value of its output has changed. */
+ retval = copy_prop_visit_assignment (stmt, result_p);
+ }
+ else if (gimple_code (stmt) == GIMPLE_COND)
{
- tree *op_p = VUSE_OP_PTR (vuses, i);
- if (TREE_CODE (*op_p) == SSA_NAME)
- may_have_exposed_new_symbols
- |= cprop_operand (ann, op_p, const_and_copies);
+ /* See if we can determine which edge goes out of a conditional
+ jump. */
+ retval = copy_prop_visit_cond_stmt (stmt, taken_edge_p);
}
+ else
+ retval = SSA_PROP_VARYING;
- vdefs = VDEF_OPS (ann);
- num_vdefs = NUM_VDEFS (vdefs);
- for (i = 0; i < num_vdefs; i++)
+ if (retval == SSA_PROP_VARYING)
{
- tree *op_p = VDEF_OP_PTR (vdefs, i);
- if (TREE_CODE (*op_p) == SSA_NAME)
- may_have_exposed_new_symbols
- |= cprop_operand (ann, op_p, const_and_copies);
+ tree def;
+ ssa_op_iter i;
+
+ /* Any other kind of statement is not interesting for constant
+ propagation and, therefore, not worth simulating. */
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "No interesting values produced.\n");
+
+ /* The assignment is not a copy operation. Don't visit this
+ statement again and mark all the definitions in the statement
+ to be copies of nothing. */
+ FOR_EACH_SSA_TREE_OPERAND (def, stmt, i, SSA_OP_ALL_DEFS)
+ set_copy_of_val (def, def);
}
- return may_have_exposed_new_symbols;
-}
-/* CONST_AND_COPIES is a table which maps an SSA_NAME to the current
- known value for that SSA_NAME (or NULL if no value is known).
+ return retval;
+}
- NONZERO_VARS is the set SSA_NAMES known to have a nonzero value,
- even if we don't know their precise value.
- Propagate values from CONST_AND_COPIES and NONZERO_VARS into the PHI
- nodes of the successors of BB. */
+/* Visit PHI node PHI. If all the arguments produce the same value,
+ set it to be the value of the LHS of PHI. */
-void
-cprop_into_successor_phis (basic_block bb,
- varray_type const_and_copies,
- bitmap nonzero_vars)
+static enum ssa_prop_result
+copy_prop_visit_phi_node (gimple phi)
{
- edge e;
+ enum ssa_prop_result retval;
+ unsigned i;
+ prop_value_t phi_val = { NULL_TREE };
- /* This can get rather expensive if the implementation is naive in
- how it finds the phi alternative associated with a particular edge. */
- for (e = bb->succ; e; e = e->succ_next)
+ tree lhs = gimple_phi_result (phi);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
{
- tree phi;
- int phi_num_args;
- int hint;
+ fprintf (dump_file, "\nVisiting PHI node: ");
+ print_gimple_stmt (dump_file, phi, 0, dump_flags);
+ }
- /* If this is an abnormal edge, then we do not want to copy propagate
- into the PHI alternative associated with this edge. */
- if (e->flags & EDGE_ABNORMAL)
+ for (i = 0; i < gimple_phi_num_args (phi); i++)
+ {
+ prop_value_t *arg_val;
+ tree arg_value;
+ tree arg = gimple_phi_arg_def (phi, i);
+ edge e = gimple_phi_arg_edge (phi, i);
+
+ /* We don't care about values flowing through non-executable
+ edges. */
+ if (!(e->flags & EDGE_EXECUTABLE))
continue;
- phi = phi_nodes (e->dest);
- if (! phi)
- continue;
+ /* Names that flow through abnormal edges cannot be used to
+ derive copies. */
+ if (TREE_CODE (arg) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (arg))
+ {
+ phi_val.value = lhs;
+ break;
+ }
- /* There is no guarantee that for any two PHI nodes in a block that
- the phi alternative associated with a particular edge will be
- at the same index in the phi alternative array.
-
- However, it is very likely they will be the same. So we keep
- track of the index of the alternative where we found the edge in
- the previous phi node and check that index first in the next
- phi node. If that hint fails, then we actually search all
- the entries. */
- phi_num_args = PHI_NUM_ARGS (phi);
- hint = phi_num_args;
- for ( ; phi; phi = TREE_CHAIN (phi))
+ if (dump_file && (dump_flags & TDF_DETAILS))
{
- int i;
- tree new;
- tree *orig_p;
-
- /* If the hint is valid (!= phi_num_args), see if it points
- us to the desired phi alternative. */
- if (hint != phi_num_args && PHI_ARG_EDGE (phi, hint) == e)
- ;
- else
- {
- /* The hint was either invalid or did not point to the
- correct phi alternative. Search all the alternatives
- for the correct one. Update the hint. */
- for (i = 0; i < phi_num_args; i++)
- if (PHI_ARG_EDGE (phi, i) == e)
- break;
- hint = i;
- }
+ fprintf (dump_file, "\tArgument #%d: ", i);
+ dump_copy_of (dump_file, arg);
+ fprintf (dump_file, "\n");
+ }
-#ifdef ENABLE_CHECKING
- /* If we did not find the proper alternative, then something is
- horribly wrong. */
- if (hint == phi_num_args)
- abort ();
-#endif
+ if (TREE_CODE (arg) == SSA_NAME)
+ {
+ arg_val = get_copy_of_val (arg);
- /* The alternative may be associated with a constant, so verify
- it is an SSA_NAME before doing anything with it. */
- orig_p = &PHI_ARG_DEF (phi, hint);
- if (TREE_CODE (*orig_p) != SSA_NAME)
+ /* If we didn't visit the definition of arg yet treat it as
+ UNDEFINED. This also handles PHI arguments that are the
+ same as lhs. We'll come here again. */
+ if (!arg_val->value)
continue;
- /* If the alternative is known to have a nonzero value, record
- that fact in the PHI node itself for future use. */
- if (bitmap_bit_p (nonzero_vars, SSA_NAME_VERSION (*orig_p)))
- PHI_ARG_NONZERO (phi, i) = true;
-
- /* If we have *ORIG_P in our constant/copy table, then replace
- ORIG_P with its value in our constant/copy table. */
- new = VARRAY_TREE (const_and_copies, SSA_NAME_VERSION (*orig_p));
- if (new
- && (TREE_CODE (new) == SSA_NAME
- || is_gimple_min_invariant (new))
- && may_propagate_copy (*orig_p, new))
- propagate_value (orig_p, new);
+ arg_value = arg_val->value;
+ }
+ else
+ arg_value = valueize_val (arg);
+
+ /* Avoid copy propagation from an inner into an outer loop.
+ Otherwise, this may move loop variant variables outside of
+ their loops and prevent coalescing opportunities. If the
+ value was loop invariant, it will be hoisted by LICM and
+ exposed for copy propagation.
+ ??? The value will be always loop invariant.
+ In loop-closed SSA form do not copy-propagate through
+ PHI nodes in blocks with a loop exit edge predecessor. */
+ if (current_loops
+ && TREE_CODE (arg_value) == SSA_NAME
+ && (loop_depth_of_name (arg_value) > loop_depth_of_name (lhs)
+ || (loops_state_satisfies_p (LOOP_CLOSED_SSA)
+ && loop_exit_edge_p (e->src->loop_father, e))))
+ {
+ phi_val.value = lhs;
+ break;
+ }
+
+ /* If the LHS didn't have a value yet, make it a copy of the
+ first argument we find. */
+ if (phi_val.value == NULL_TREE)
+ {
+ phi_val.value = arg_value;
+ continue;
+ }
+
+ /* If PHI_VAL and ARG don't have a common copy-of chain, then
+ this PHI node cannot be a copy operation. */
+ if (phi_val.value != arg_value
+ && !operand_equal_p (phi_val.value, arg_value, 0))
+ {
+ phi_val.value = lhs;
+ break;
}
}
+
+ if (phi_val.value
+ && may_propagate_copy (lhs, phi_val.value)
+ && set_copy_of_val (lhs, phi_val.value))
+ retval = (phi_val.value != lhs) ? SSA_PROP_INTERESTING : SSA_PROP_VARYING;
+ else
+ retval = SSA_PROP_NOT_INTERESTING;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "PHI node ");
+ dump_copy_of (dump_file, lhs);
+ fprintf (dump_file, "\nTelling the propagator to ");
+ if (retval == SSA_PROP_INTERESTING)
+ fprintf (dump_file, "add SSA edges out of this PHI and continue.");
+ else if (retval == SSA_PROP_VARYING)
+ fprintf (dump_file, "add SSA edges out of this PHI and never visit again.");
+ else
+ fprintf (dump_file, "do nothing with SSA edges and keep iterating.");
+ fprintf (dump_file, "\n\n");
+ }
+
+ return retval;
}
+
+
+/* Initialize structures used for copy propagation. */
+
+static void
+init_copy_prop (void)
+{
+ basic_block bb;
+
+ copy_of = XCNEWVEC (prop_value_t, num_ssa_names);
+
+ FOR_EACH_BB (bb)
+ {
+ gimple_stmt_iterator si;
+ int depth = bb->loop_depth;
+
+ for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si))
+ {
+ gimple stmt = gsi_stmt (si);
+ ssa_op_iter iter;
+ tree def;
+
+ /* The only statements that we care about are those that may
+ generate useful copies. We also need to mark conditional
+ jumps so that their outgoing edges are added to the work
+ lists of the propagator.
+
+ Avoid copy propagation from an inner into an outer loop.
+ Otherwise, this may move loop variant variables outside of
+ their loops and prevent coalescing opportunities. If the
+ value was loop invariant, it will be hoisted by LICM and
+ exposed for copy propagation.
+ ??? This doesn't make sense. */
+ if (stmt_ends_bb_p (stmt))
+ prop_set_simulate_again (stmt, true);
+ else if (stmt_may_generate_copy (stmt)
+ /* Since we are iterating over the statements in
+ BB, not the phi nodes, STMT will always be an
+ assignment. */
+ && loop_depth_of_name (gimple_assign_rhs1 (stmt)) <= depth)
+ prop_set_simulate_again (stmt, true);
+ else
+ prop_set_simulate_again (stmt, false);
+
+ /* Mark all the outputs of this statement as not being
+ the copy of anything. */
+ FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
+ if (!prop_simulate_again_p (stmt))
+ set_copy_of_val (def, def);
+ }
+
+ for (si = gsi_start_phis (bb); !gsi_end_p (si); gsi_next (&si))
+ {
+ gimple phi = gsi_stmt (si);
+ tree def;
+
+ def = gimple_phi_result (phi);
+ if (!is_gimple_reg (def))
+ prop_set_simulate_again (phi, false);
+ else
+ prop_set_simulate_again (phi, true);
+
+ if (!prop_simulate_again_p (phi))
+ set_copy_of_val (def, def);
+ }
+ }
+}
+
+/* Callback for substitute_and_fold to get at the final copy-of values. */
+
+static tree
+get_value (tree name)
+{
+ tree val = copy_of[SSA_NAME_VERSION (name)].value;
+ if (val && val != name)
+ return val;
+ return NULL_TREE;
+}
+
+/* Deallocate memory used in copy propagation and do final
+ substitution. */
+
+static void
+fini_copy_prop (void)
+{
+ unsigned i;
+
+ /* Set the final copy-of value for each variable by traversing the
+ copy-of chains. */
+ for (i = 1; i < num_ssa_names; i++)
+ {
+ tree var = ssa_name (i);
+ if (!var
+ || !copy_of[i].value
+ || copy_of[i].value == var)
+ continue;
+
+ /* In theory the points-to solution of all members of the
+ copy chain is their intersection. For now we do not bother
+ to compute this but only make sure we do not lose points-to
+ information completely by setting the points-to solution
+ of the representative to the first solution we find if
+ it doesn't have one already. */
+ if (copy_of[i].value != var
+ && TREE_CODE (copy_of[i].value) == SSA_NAME
+ && POINTER_TYPE_P (TREE_TYPE (var))
+ && SSA_NAME_PTR_INFO (var)
+ && !SSA_NAME_PTR_INFO (copy_of[i].value))
+ duplicate_ssa_name_ptr_info (copy_of[i].value, SSA_NAME_PTR_INFO (var));
+ }
+
+ /* Don't do DCE if we have loops. That's the simplest way to not
+ destroy the scev cache. */
+ substitute_and_fold (get_value, NULL, !current_loops);
+
+ free (copy_of);
+}
+
+
+/* Main entry point to the copy propagator.
+
+ PHIS_ONLY is true if we should only consider PHI nodes as generating
+ copy propagation opportunities.
+
+ The algorithm propagates the value COPY-OF using ssa_propagate. For
+ every variable X_i, COPY-OF(X_i) indicates which variable is X_i created
+ from. The following example shows how the algorithm proceeds at a
+ high level:
+
+ 1 a_24 = x_1
+ 2 a_2 = PHI <a_24, x_1>
+ 3 a_5 = PHI <a_2>
+ 4 x_1 = PHI <x_298, a_5, a_2>
+
+ The end result should be that a_2, a_5, a_24 and x_1 are a copy of
+ x_298. Propagation proceeds as follows.
+
+ Visit #1: a_24 is copy-of x_1. Value changed.
+ Visit #2: a_2 is copy-of x_1. Value changed.
+ Visit #3: a_5 is copy-of x_1. Value changed.
+ Visit #4: x_1 is copy-of x_298. Value changed.
+ Visit #1: a_24 is copy-of x_298. Value changed.
+ Visit #2: a_2 is copy-of x_298. Value changed.
+ Visit #3: a_5 is copy-of x_298. Value changed.
+ Visit #4: x_1 is copy-of x_298. Stable state reached.
+
+ When visiting PHI nodes, we only consider arguments that flow
+ through edges marked executable by the propagation engine. So,
+ when visiting statement #2 for the first time, we will only look at
+ the first argument (a_24) and optimistically assume that its value
+ is the copy of a_24 (x_1). */
+
+static unsigned int
+execute_copy_prop (void)
+{
+ init_copy_prop ();
+ ssa_propagate (copy_prop_visit_stmt, copy_prop_visit_phi_node);
+ fini_copy_prop ();
+ return 0;
+}
+
+static bool
+gate_copy_prop (void)
+{
+ return flag_tree_copy_prop != 0;
+}
+
+struct gimple_opt_pass pass_copy_prop =
+{
+ {
+ GIMPLE_PASS,
+ "copyprop", /* name */
+ gate_copy_prop, /* gate */
+ execute_copy_prop, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_TREE_COPY_PROP, /* tv_id */
+ PROP_ssa | PROP_cfg, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_cleanup_cfg
+ | TODO_ggc_collect
+ | TODO_verify_ssa
+ | TODO_update_ssa /* todo_flags_finish */
+ }
+};
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