-/* 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. */
-
/* Return true if we may propagate ORIG into DEST, false otherwise. */
bool
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 (!tree_ssa_useless_type_conversion_1 (type_d, type_o))
+ if (!useless_type_conversion_p (type_d, type_o))
return false;
- /* FIXME. GIMPLE is allowing pointer assignments and comparisons of
- pointers that have different alias sets. This means that these
- pointers will have different memory tags associated to them.
-
- If we allow copy propagation in these cases, statements de-referencing
- the new pointer will now have a reference to a different memory tag
- with potentially incorrect SSA information.
-
- This was showing up in libjava/java/util/zip/ZipFile.java with code
- like:
-
- struct java.io.BufferedInputStream *T.660;
- struct java.io.BufferedInputStream *T.647;
- struct java.io.InputStream *is;
- struct java.io.InputStream *is.662;
- [ ... ]
- T.660 = T.647;
- is = T.660; <-- This ought to be type-casted
- is.662 = is;
-
- Also, f/name.c exposed a similar problem with a COND_EXPR predicate
- that was causing DOM to generate and equivalence with two pointers of
- alias-incompatible types:
-
- struct _ffename_space *n;
- struct _ffename *ns;
- [ ... ]
- if (n == ns)
- goto lab;
- ...
- lab:
- return n;
-
- I think that GIMPLE should emit the appropriate type-casts. For the
- time being, blocking copy-propagation in these cases is the safe thing
- to do. */
- if (TREE_CODE (dest) == SSA_NAME && TREE_CODE (orig) == SSA_NAME
- && POINTER_TYPE_P (type_d) && POINTER_TYPE_P (type_o))
+ /* Propagating virtual operands is always ok. */
+ if (TREE_CODE (dest) == SSA_NAME && !is_gimple_reg (dest))
{
- tree mt_dest = var_ann (SSA_NAME_VAR (dest))->type_mem_tag;
- tree mt_orig = var_ann (SSA_NAME_VAR (orig))->type_mem_tag;
- if (mt_dest && mt_orig && mt_dest != mt_orig)
- return false;
- else if (!lang_hooks.types_compatible_p (type_d, type_o))
- return false;
- else if (get_alias_set (TREE_TYPE (type_d)) !=
- get_alias_set (TREE_TYPE (type_o)))
- return false;
+ /* But only between virtual operands. */
+ gcc_assert (TREE_CODE (orig) == SSA_NAME && !is_gimple_reg (orig));
+
+ return true;
}
- /* If the destination is a SSA_NAME for a virtual operand, then we have
- some special cases to handle. */
- if (TREE_CODE (dest) == SSA_NAME && !is_gimple_reg (dest))
- {
- /* If both operands are SSA_NAMEs referring to virtual operands, then
- we can always propagate. */
- if (TREE_CODE (orig) == SSA_NAME)
- {
- if (!is_gimple_reg (orig))
- return true;
+ /* Anything else is OK. */
+ return true;
+}
-#ifdef ENABLE_CHECKING
- /* If we have one real and one virtual operand, then something has
- gone terribly wrong. */
- gcc_assert (!is_gimple_reg (orig));
-#endif
- }
+/* 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. */
- /* We have a "copy" from something like a constant into a virtual
- operand. Reject these. */
- return false;
- }
+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 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 or if it
- represents a hard register, then it cannot be replaced. */
- if (TREE_CODE (dest) == SSA_NAME
- && (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (dest)
- || DECL_HARD_REGISTER (SSA_NAME_VAR (dest))))
+ 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;
- /* Anything else is OK. */
return true;
}
{
/* 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)));
}
-/* Given two SSA_NAMEs pointers ORIG and NEW such that we are copy
- propagating NEW into ORIG, consolidate aliasing information so that
- they both share the same memory tags. */
-
-static void
-merge_alias_info (tree orig, tree new)
-{
- tree new_sym = SSA_NAME_VAR (new);
- tree orig_sym = SSA_NAME_VAR (orig);
- var_ann_t new_ann = var_ann (new_sym);
- var_ann_t orig_ann = var_ann (orig_sym);
-
- gcc_assert (POINTER_TYPE_P (TREE_TYPE (orig)));
- gcc_assert (POINTER_TYPE_P (TREE_TYPE (new)));
-#if defined ENABLE_CHECKING
- gcc_assert (lang_hooks.types_compatible_p (TREE_TYPE (orig),
- TREE_TYPE (new)));
-
- /* If the pointed-to alias sets are different, these two pointers
- would never have the same memory tag. In this case, NEW should
- not have been propagated into ORIG. */
- gcc_assert (get_alias_set (TREE_TYPE (TREE_TYPE (new_sym)))
- == get_alias_set (TREE_TYPE (TREE_TYPE (orig_sym))));
-#endif
-
- /* Merge type-based alias info. */
- 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
- gcc_assert (new_ann->type_mem_tag == orig_ann->type_mem_tag);
-}
-
-
/* Common code for propagate_value and replace_exp.
Replace use operand OP_P with VAL. FOR_PROPAGATION indicates if the
static void
replace_exp_1 (use_operand_p op_p, tree val,
- bool for_propagation ATTRIBUTE_UNUSED)
+ bool for_propagation ATTRIBUTE_UNUSED)
{
+#if defined ENABLE_CHECKING
tree op = USE_FROM_PTR (op_p);
-#if defined ENABLE_CHECKING
gcc_assert (!(for_propagation
&& TREE_CODE (op) == SSA_NAME
&& TREE_CODE (val) == SSA_NAME
#endif
if (TREE_CODE (val) == SSA_NAME)
- {
- if (TREE_CODE (op) == SSA_NAME && POINTER_TYPE_P (TREE_TYPE (op)))
- merge_alias_info (op, val);
- SET_USE (op_p, val);
- }
+ SET_USE (op_p, val);
else
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. */
replace_exp_1 (op_p, val, true);
}
+/* Replace *OP_P with value VAL (assumed to be a constant or another SSA_NAME).
+
+ 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.
+
+ The statement in which an expression has been replaced should be
+ folded using fold_stmt_inplace. */
+
+void
+replace_exp (use_operand_p op_p, tree val)
+{
+ replace_exp_1 (op_p, val, false);
+}
+
/* Propagate the value VAL (assumed to be a constant or another SSA_NAME)
- into the tree pointed by OP_P.
+ 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
void
propagate_tree_value (tree *op_p, tree val)
{
-#if defined ENABLE_CHECKING
- gcc_assert (!(TREE_CODE (val) == SSA_NAME
- && TREE_CODE (*op_p) == SSA_NAME
- && !may_propagate_copy (*op_p, val)));
-#endif
+ 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)
{
- if (TREE_CODE (*op_p) == SSA_NAME && POINTER_TYPE_P (TREE_TYPE (*op_p)))
- merge_alias_info (*op_p, val);
- *op_p = val;
+ 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
- *op_p = unsave_expr_now (val);
+ 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.
-/* Replace *OP_P with value VAL (assumed to be a constant or another SSA_NAME).
+ When visiting a statement or PHI node the lattice value for an
+ SSA name can transition from UNDEFINED to COPY to VARYING. */
- 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. */
+struct prop_value_d {
+ /* Copy-of value. */
+ tree value;
+};
+typedef struct prop_value_d prop_value_t;
-void
-replace_exp (use_operand_p op_p, tree val)
+static prop_value_t *copy_of;
+
+
+/* Return true if this statement may generate a useful copy. */
+
+static bool
+stmt_may_generate_copy (gimple stmt)
{
- replace_exp_1 (op_p, val, false);
+ 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)
+{
+ tree 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
+ {
+ 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;
+}
+
+
+/* Visit the GIMPLE_COND STMT. Return SSA_PROP_INTERESTING
+ if it can determine which edge will be taken. Otherwise, return
+ SSA_PROP_VARYING. */
+
+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, "Trying to determine truth value of ");
+ fprintf (dump_file, "predicate ");
+ print_gimple_stmt (dump_file, stmt, 0, 0);
+ }
+
+ /* 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;
+ }
+ }
+ }
+
+ 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);
+
+ return retval;
+}
+
+
+/* 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.
+
+ 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)
+{
+ enum ssa_prop_result retval;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "\nVisiting statement:\n");
+ print_gimple_stmt (dump_file, stmt, 0, dump_flags);
+ fprintf (dump_file, "\n");
+ }
+
+ 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)
+ {
+ /* 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;
+
+ if (retval == SSA_PROP_VARYING)
+ {
+ 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 retval;
+}
+
+
+/* Visit PHI node PHI. If all the arguments produce the same value,
+ set it to be the value of the LHS of PHI. */
+
+static enum ssa_prop_result
+copy_prop_visit_phi_node (gimple phi)
+{
+ enum ssa_prop_result retval;
+ unsigned i;
+ prop_value_t phi_val = { NULL_TREE };
+
+ tree lhs = gimple_phi_result (phi);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "\nVisiting PHI node: ");
+ print_gimple_stmt (dump_file, phi, 0, dump_flags);
+ }
+
+ 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;
+
+ /* 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;
+ }
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "\tArgument #%d: ", i);
+ dump_copy_of (dump_file, arg);
+ fprintf (dump_file, "\n");
+ }
+
+ if (TREE_CODE (arg) == SSA_NAME)
+ {
+ arg_val = get_copy_of_val (arg);
+
+ /* 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;
+
+ 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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