/* SSA Dominator optimizations for trees
- Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006
+ Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
Free Software Foundation, Inc.
Contributed by Diego Novillo <dnovillo@redhat.com>
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, 51 Franklin Street, Fifth Floor,
-Boston, MA 02110-1301, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
expressions are removed from AVAIL_EXPRS. Else we may change the
hash code for an expression and be unable to find/remove it from
AVAIL_EXPRS. */
-static VEC(tree,heap) *stmts_to_rescan;
+typedef tree *tree_p;
+DEF_VEC_P(tree_p);
+DEF_VEC_ALLOC_P(tree_p,heap);
+
+static VEC(tree_p,heap) *stmts_to_rescan;
/* Structure for entries in the expression hash table.
restored during finalization of this block. */
static VEC(tree,heap) *const_and_copies_stack;
-/* Bitmap of SSA_NAMEs known to have a nonzero value, even if we do not
- know their exact value. */
-static bitmap nonzero_vars;
-
-/* Stack of SSA_NAMEs which need their NONZERO_VARS property cleared
- when the current block is finalized.
-
- A NULL entry is used to mark the end of names needing their
- entry in NONZERO_VARS cleared during finalization of this block. */
-static VEC(tree,heap) *nonzero_vars_stack;
-
/* Track whether or not we have changed the control flow graph. */
static bool cfg_altered;
static void remove_local_expressions_from_table (void);
static void restore_vars_to_original_value (void);
static edge single_incoming_edge_ignoring_loop_edges (basic_block);
-static void restore_nonzero_vars_to_original_value (void);
-static inline bool unsafe_associative_fp_binop (tree);
/* Allocate an EDGE_INFO for edge E and attach it to E.
every new symbol exposed, its corresponding bit will be set in
VARS_TO_RENAME. */
-static void
+static unsigned int
tree_ssa_dominator_optimize (void)
{
struct dom_walk_data walk_data;
unsigned int i;
- struct loops loops_info;
memset (&opt_stats, 0, sizeof (opt_stats));
avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free);
avail_exprs_stack = VEC_alloc (tree, heap, 20);
const_and_copies_stack = VEC_alloc (tree, heap, 20);
- nonzero_vars_stack = VEC_alloc (tree, heap, 20);
- stmts_to_rescan = VEC_alloc (tree, heap, 20);
- nonzero_vars = BITMAP_ALLOC (NULL);
+ stmts_to_rescan = VEC_alloc (tree_p, heap, 20);
need_eh_cleanup = BITMAP_ALLOC (NULL);
/* Setup callbacks for the generic dominator tree walker. */
init_walk_dominator_tree (&walk_data);
calculate_dominance_info (CDI_DOMINATORS);
+ cfg_altered = false;
- /* We need to know which edges exit loops so that we can
- aggressively thread through loop headers to an exit
- edge. */
- flow_loops_find (&loops_info);
- mark_loop_exit_edges (&loops_info);
- flow_loops_free (&loops_info);
-
- /* Clean up the CFG so that any forwarder blocks created by loop
- canonicalization are removed. */
- cleanup_tree_cfg ();
- calculate_dominance_info (CDI_DOMINATORS);
+ /* We need to know loop structures in order to avoid destroying them
+ in jump threading. Note that we still can e.g. thread through loop
+ headers to an exit edge, or through loop header to the loop body, assuming
+ that we update the loop info. */
+ loop_optimizer_init (LOOPS_HAVE_SIMPLE_LATCHES);
/* We need accurate information regarding back edges in the CFG
- for jump threading. */
+ for jump threading; this may include back edges that are not part of
+ a single loop. */
mark_dfs_back_edges ();
-
+
/* Recursively walk the dominator tree optimizing statements. */
walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
free_all_edge_infos ();
/* Thread jumps, creating duplicate blocks as needed. */
- cfg_altered |= thread_through_all_blocks ();
+ cfg_altered |= thread_through_all_blocks (first_pass_instance);
+
+ if (cfg_altered)
+ free_dominance_info (CDI_DOMINATORS);
/* Removal of statements may make some EH edges dead. Purge
such edges from the CFG as needed. */
if (!bitmap_empty_p (need_eh_cleanup))
{
- cfg_altered |= tree_purge_all_dead_eh_edges (need_eh_cleanup);
+ unsigned i;
+ bitmap_iterator bi;
+
+ /* Jump threading may have created forwarder blocks from blocks
+ needing EH cleanup; the new successor of these blocks, which
+ has inherited from the original block, needs the cleanup. */
+ EXECUTE_IF_SET_IN_BITMAP (need_eh_cleanup, 0, i, bi)
+ {
+ basic_block bb = BASIC_BLOCK (i);
+ if (single_succ_p (bb) == 1
+ && (single_succ_edge (bb)->flags & EDGE_EH) == 0)
+ {
+ bitmap_clear_bit (need_eh_cleanup, i);
+ bitmap_set_bit (need_eh_cleanup, single_succ (bb)->index);
+ }
+ }
+
+ tree_purge_all_dead_eh_edges (need_eh_cleanup);
bitmap_zero (need_eh_cleanup);
}
- if (cfg_altered)
- free_dominance_info (CDI_DOMINATORS);
-
/* Finally, remove everything except invariants in SSA_NAME_VALUE.
Long term we will be able to let everything in SSA_NAME_VALUE
SSA_NAME_VALUE (name) = NULL;
}
+ statistics_counter_event (cfun, "Redundant expressions eliminated",
+ opt_stats.num_re);
+ statistics_counter_event (cfun, "Constants propagated",
+ opt_stats.num_const_prop);
+ statistics_counter_event (cfun, "Copies propagated",
+ opt_stats.num_copy_prop);
+
/* Debugging dumps. */
if (dump_file && (dump_flags & TDF_STATS))
dump_dominator_optimization_stats (dump_file);
+ loop_optimizer_finalize ();
+
/* Delete our main hashtable. */
htab_delete (avail_exprs);
/* And finalize the dominator walker. */
fini_walk_dominator_tree (&walk_data);
- /* Free nonzero_vars. */
- BITMAP_FREE (nonzero_vars);
+ /* Free asserted bitmaps and stacks. */
BITMAP_FREE (need_eh_cleanup);
VEC_free (tree, heap, avail_exprs_stack);
VEC_free (tree, heap, const_and_copies_stack);
- VEC_free (tree, heap, nonzero_vars_stack);
- VEC_free (tree, heap, stmts_to_rescan);
+ VEC_free (tree_p, heap, stmts_to_rescan);
+ return 0;
}
static bool
return flag_tree_dom != 0;
}
-struct tree_opt_pass pass_dominator =
+struct gimple_opt_pass pass_dominator =
{
+ {
+ GIMPLE_PASS,
"dom", /* name */
gate_dominator, /* gate */
tree_ssa_dominator_optimize, /* execute */
TODO_dump_func
| TODO_update_ssa
| TODO_cleanup_cfg
- | TODO_verify_ssa, /* todo_flags_finish */
- 0 /* letter */
+ | TODO_verify_ssa /* todo_flags_finish */
+ }
};
far to unwind when we finalize this block. */
VEC_safe_push (tree, heap, avail_exprs_stack, NULL_TREE);
VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE);
- VEC_safe_push (tree, heap, nonzero_vars_stack, NULL_TREE);
record_equivalences_from_incoming_edge (bb);
else if (TREE_CODE (expr) == RETURN_EXPR && TREE_OPERAND (expr, 0))
{
element->stmt = expr;
- element->rhs = TREE_OPERAND (TREE_OPERAND (expr, 0), 1);
+ element->rhs = GIMPLE_STMT_OPERAND (TREE_OPERAND (expr, 0), 1);
}
else if (TREE_CODE (expr) == GOTO_EXPR)
{
else
{
element->stmt = expr;
- element->rhs = TREE_OPERAND (expr, 1);
+ element->rhs = GENERIC_TREE_OPERAND (expr, 1);
}
element->lhs = lhs;
}
}
-/* Use the SSA_NAMES in LOCALS to restore TABLE to its original
- state, stopping when there are LIMIT entries left in LOCALs. */
-
-static void
-restore_nonzero_vars_to_original_value (void)
-{
- while (VEC_length (tree, nonzero_vars_stack) > 0)
- {
- tree name = VEC_pop (tree, nonzero_vars_stack);
-
- if (name == NULL)
- break;
-
- bitmap_clear_bit (nonzero_vars, SSA_NAME_VERSION (name));
- }
-}
-
/* Use the source/dest pairs in CONST_AND_COPIES_STACK to restore
CONST_AND_COPIES to its original state, stopping when we hit a
NULL marker. */
/* A trivial wrapper so that we can present the generic jump
threading code with a simple API for simplifying statements. */
static tree
-simplify_stmt_for_jump_threading (tree stmt)
+simplify_stmt_for_jump_threading (tree stmt, tree within_stmt ATTRIBUTE_UNUSED)
{
return lookup_avail_expr (stmt, false);
}
walk_data->global_data = dummy_cond;
}
- thread_across_edge (walk_data->global_data, e, false,
+ thread_across_edge ((tree) walk_data->global_data, e, false,
&const_and_copies_stack,
simplify_stmt_for_jump_threading);
}
/* If we have an outgoing edge to a block with multiple incoming and
- outgoing edges, then we may be able to thread the edge. ie, we
+ outgoing edges, then we may be able to thread the edge, i.e., we
may be able to statically determine which of the outgoing edges
will be traversed when the incoming edge from BB is traversed. */
if (single_succ_p (bb)
}
remove_local_expressions_from_table ();
- restore_nonzero_vars_to_original_value ();
restore_vars_to_original_value ();
/* If we queued any statements to rescan in this block, then
go ahead and rescan them now. */
- while (VEC_length (tree, stmts_to_rescan) > 0)
+ while (VEC_length (tree_p, stmts_to_rescan) > 0)
{
- tree stmt = VEC_last (tree, stmts_to_rescan);
+ tree *stmt_p = VEC_last (tree_p, stmts_to_rescan);
+ tree stmt = *stmt_p;
basic_block stmt_bb = bb_for_stmt (stmt);
if (stmt_bb != bb)
break;
- VEC_pop (tree, stmts_to_rescan);
- mark_new_vars_to_rename (stmt);
+ VEC_pop (tree_p, stmts_to_rescan);
+ pop_stmt_changes (stmt_p);
}
}
Ignoring any alternatives which are the same as the result, if
all the alternatives are equal, then the PHI node creates an
- equivalence.
-
- Additionally, if all the PHI alternatives are known to have a nonzero
- value, then the result of this PHI is known to have a nonzero value,
- even if we do not know its exact value. */
+ equivalence. */
static void
record_equivalences_from_phis (basic_block bb)
if (i == PHI_NUM_ARGS (phi)
&& may_propagate_copy (lhs, rhs))
SSA_NAME_VALUE (lhs) = rhs;
-
- /* Now see if we know anything about the nonzero property for the
- result of this PHI. */
- for (i = 0; i < PHI_NUM_ARGS (phi); i++)
- {
- if (!PHI_ARG_NONZERO (phi, i))
- break;
- }
-
- if (i == PHI_NUM_ARGS (phi))
- bitmap_set_bit (nonzero_vars, SSA_NAME_VERSION (PHI_RESULT (phi)));
}
}
void
dump_dominator_optimization_stats (FILE *file)
{
- long n_exprs;
-
fprintf (file, "Total number of statements: %6ld\n\n",
opt_stats.num_stmts);
fprintf (file, "Exprs considered for dominator optimizations: %6ld\n",
opt_stats.num_exprs_considered);
- n_exprs = opt_stats.num_exprs_considered;
- if (n_exprs == 0)
- n_exprs = 1;
-
- fprintf (file, " Redundant expressions eliminated: %6ld (%.0f%%)\n",
- opt_stats.num_re, PERCENT (opt_stats.num_re,
- n_exprs));
- fprintf (file, " Constants propagated: %6ld\n",
- opt_stats.num_const_prop);
- fprintf (file, " Copies propagated: %6ld\n",
- opt_stats.num_copy_prop);
-
fprintf (file, "\nHash table statistics:\n");
fprintf (file, " avail_exprs: ");
htab_collisions (htab));
}
-/* Record the fact that VAR has a nonzero value, though we may not know
- its exact value. Note that if VAR is already known to have a nonzero
- value, then we do nothing. */
-
-static void
-record_var_is_nonzero (tree var)
-{
- int indx = SSA_NAME_VERSION (var);
-
- if (bitmap_bit_p (nonzero_vars, indx))
- return;
-
- /* Mark it in the global table. */
- bitmap_set_bit (nonzero_vars, indx);
-
- /* Record this SSA_NAME so that we can reset the global table
- when we leave this block. */
- VEC_safe_push (tree, heap, nonzero_vars_stack, var);
-}
-
/* Enter a statement into the true/false expression hash table indicating
that the condition COND has the value VALUE. */
{
case LT_EXPR:
case GT_EXPR:
- edge_info->max_cond_equivalences = 12;
- edge_info->cond_equivalences = XNEWVEC (tree, 12);
+ if (FLOAT_TYPE_P (TREE_TYPE (op0)))
+ {
+ edge_info->max_cond_equivalences = 12;
+ edge_info->cond_equivalences = XNEWVEC (tree, 12);
+ build_and_record_new_cond (ORDERED_EXPR, op0, op1,
+ &edge_info->cond_equivalences[8]);
+ build_and_record_new_cond (LTGT_EXPR, op0, op1,
+ &edge_info->cond_equivalences[10]);
+ }
+ else
+ {
+ edge_info->max_cond_equivalences = 8;
+ edge_info->cond_equivalences = XNEWVEC (tree, 8);
+ }
+
build_and_record_new_cond ((TREE_CODE (cond) == LT_EXPR
? LE_EXPR : GE_EXPR),
op0, op1, &edge_info->cond_equivalences[4]);
- build_and_record_new_cond (ORDERED_EXPR, op0, op1,
- &edge_info->cond_equivalences[6]);
build_and_record_new_cond (NE_EXPR, op0, op1,
- &edge_info->cond_equivalences[8]);
- build_and_record_new_cond (LTGT_EXPR, op0, op1,
- &edge_info->cond_equivalences[10]);
+ &edge_info->cond_equivalences[6]);
break;
case GE_EXPR:
case LE_EXPR:
- edge_info->max_cond_equivalences = 6;
- edge_info->cond_equivalences = XNEWVEC (tree, 6);
- build_and_record_new_cond (ORDERED_EXPR, op0, op1,
- &edge_info->cond_equivalences[4]);
+ if (FLOAT_TYPE_P (TREE_TYPE (op0)))
+ {
+ edge_info->max_cond_equivalences = 6;
+ edge_info->cond_equivalences = XNEWVEC (tree, 6);
+ build_and_record_new_cond (ORDERED_EXPR, op0, op1,
+ &edge_info->cond_equivalences[4]);
+ }
+ else
+ {
+ edge_info->max_cond_equivalences = 4;
+ edge_info->cond_equivalences = XNEWVEC (tree, 4);
+ }
break;
case EQ_EXPR:
- edge_info->max_cond_equivalences = 10;
- edge_info->cond_equivalences = XNEWVEC (tree, 10);
- build_and_record_new_cond (ORDERED_EXPR, op0, op1,
- &edge_info->cond_equivalences[4]);
+ if (FLOAT_TYPE_P (TREE_TYPE (op0)))
+ {
+ edge_info->max_cond_equivalences = 10;
+ edge_info->cond_equivalences = XNEWVEC (tree, 10);
+ build_and_record_new_cond (ORDERED_EXPR, op0, op1,
+ &edge_info->cond_equivalences[8]);
+ }
+ else
+ {
+ edge_info->max_cond_equivalences = 8;
+ edge_info->cond_equivalences = XNEWVEC (tree, 8);
+ }
build_and_record_new_cond (LE_EXPR, op0, op1,
- &edge_info->cond_equivalences[6]);
+ &edge_info->cond_equivalences[4]);
build_and_record_new_cond (GE_EXPR, op0, op1,
- &edge_info->cond_equivalences[8]);
+ &edge_info->cond_equivalences[6]);
break;
case UNORDERED_EXPR:
(by depth), then use that.
Otherwise it doesn't matter which value we choose, just so
long as we canonicalize on one value. */
- if (TREE_INVARIANT (y))
+ if (is_gimple_min_invariant (y))
;
- else if (TREE_INVARIANT (x) || (loop_depth_of_name (x) <= loop_depth_of_name (y)))
+ else if (is_gimple_min_invariant (x)
+ || (loop_depth_of_name (x) <= loop_depth_of_name (y)))
prev_x = x, x = y, y = prev_x, prev_x = prev_y;
- else if (prev_x && TREE_INVARIANT (prev_x))
+ else if (prev_x && is_gimple_min_invariant (prev_x))
x = y, y = prev_x, prev_x = prev_y;
else if (prev_y && TREE_CODE (prev_y) != VALUE_HANDLE)
y = prev_y;
record_const_or_copy_1 (x, y, prev_x);
}
-/* Return true, if it is ok to do folding of an associative expression.
- EXP is the tree for the associative expression. */
-
-static inline bool
-unsafe_associative_fp_binop (tree exp)
-{
- enum tree_code code = TREE_CODE (exp);
- return !(!flag_unsafe_math_optimizations
- && (code == MULT_EXPR || code == PLUS_EXPR
- || code == MINUS_EXPR)
- && FLOAT_TYPE_P (TREE_TYPE (exp)));
-}
-
/* Returns true when STMT is a simple iv increment. It detects the
following situation:
tree lhs, rhs, preinc, phi;
unsigned i;
- if (TREE_CODE (stmt) != MODIFY_EXPR)
+ if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT)
return false;
- lhs = TREE_OPERAND (stmt, 0);
+ lhs = GIMPLE_STMT_OPERAND (stmt, 0);
if (TREE_CODE (lhs) != SSA_NAME)
return false;
- rhs = TREE_OPERAND (stmt, 1);
+ rhs = GIMPLE_STMT_OPERAND (stmt, 1);
if (TREE_CODE (rhs) != PLUS_EXPR
&& TREE_CODE (rhs) != MINUS_EXPR)
/* 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).
- 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. */
+ Propagate values from CONST_AND_COPIES into the PHI nodes of the
+ successors of BB. */
static void
-cprop_into_successor_phis (basic_block bb, bitmap nonzero_vars)
+cprop_into_successor_phis (basic_block bb)
{
edge e;
edge_iterator ei;
indx = e->dest_idx;
for ( ; phi; phi = PHI_CHAIN (phi))
{
- tree new;
+ tree new_val;
use_operand_p orig_p;
- tree orig;
+ tree orig_val;
/* 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_PTR (phi, indx);
- orig = USE_FROM_PTR (orig_p);
- if (TREE_CODE (orig) != SSA_NAME)
+ orig_val = USE_FROM_PTR (orig_p);
+ if (TREE_CODE (orig_val) != SSA_NAME)
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)))
- PHI_ARG_NONZERO (phi, indx) = true;
-
/* If we have *ORIG_P in our constant/copy table, then replace
ORIG_P with its value in our constant/copy table. */
- new = SSA_NAME_VALUE (orig);
- if (new
- && new != orig
- && (TREE_CODE (new) == SSA_NAME
- || is_gimple_min_invariant (new))
- && may_propagate_copy (orig, new))
- propagate_value (orig_p, new);
+ new_val = SSA_NAME_VALUE (orig_val);
+ if (new_val
+ && new_val != orig_val
+ && (TREE_CODE (new_val) == SSA_NAME
+ || is_gimple_min_invariant (new_val))
+ && may_propagate_copy (orig_val, new_val))
+ propagate_value (orig_p, new_val);
}
}
}
tree op1 = TREE_OPERAND (cond, 1);
/* Special case comparing booleans against a constant as we
- know the value of OP0 on both arms of the branch. i.e., we
+ know the value of OP0 on both arms of the branch, i.e., we
can record an equivalence for OP0 rather than COND. */
if ((TREE_CODE (cond) == EQ_EXPR || TREE_CODE (cond) == NE_EXPR)
&& TREE_CODE (op0) == SSA_NAME
basic_block bb)
{
record_edge_info (bb);
- cprop_into_successor_phis (bb, nonzero_vars);
+ cprop_into_successor_phis (bb);
}
/* Search for redundant computations in STMT. If any are found, then
bool retval = false;
bool modify_expr_p = false;
- if (TREE_CODE (stmt) == MODIFY_EXPR)
- def = TREE_OPERAND (stmt, 0);
+ if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
+ def = GIMPLE_STMT_OPERAND (stmt, 0);
/* Certain expressions on the RHS can be optimized away, but can not
themselves be entered into the hash tables. */
if (! def
|| TREE_CODE (def) != SSA_NAME
|| SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
- || !ZERO_SSA_OPERANDS (stmt, SSA_OP_VMAYDEF)
+ || !ZERO_SSA_OPERANDS (stmt, SSA_OP_VDEF)
/* Do not record equivalences for increments of ivs. This would create
overlapping live ranges for a very questionable gain. */
|| simple_iv_increment_p (stmt))
expr_p = &SWITCH_COND (stmt);
else if (TREE_CODE (stmt) == RETURN_EXPR && TREE_OPERAND (stmt, 0))
{
- expr_p = &TREE_OPERAND (TREE_OPERAND (stmt, 0), 1);
+ expr_p = &GIMPLE_STMT_OPERAND (TREE_OPERAND (stmt, 0), 1);
modify_expr_p = true;
}
else
{
- expr_p = &TREE_OPERAND (stmt, 1);
+ expr_p = &GENERIC_TREE_OPERAND (stmt, 1);
modify_expr_p = true;
}
if (cached_lhs
&& ((TREE_CODE (cached_lhs) != SSA_NAME
&& (modify_expr_p
- || tree_ssa_useless_type_conversion_1 (TREE_TYPE (*expr_p),
- TREE_TYPE (cached_lhs))))
+ || useless_type_conversion_p (TREE_TYPE (*expr_p),
+ TREE_TYPE (cached_lhs))))
|| may_propagate_copy (*expr_p, cached_lhs)))
{
if (dump_file && (dump_flags & TDF_DETAILS))
retval = true;
if (modify_expr_p
- && !tree_ssa_useless_type_conversion_1 (TREE_TYPE (*expr_p),
- TREE_TYPE (cached_lhs)))
+ && !useless_type_conversion_p (TREE_TYPE (*expr_p),
+ TREE_TYPE (cached_lhs)))
cached_lhs = fold_convert (TREE_TYPE (*expr_p), cached_lhs);
propagate_tree_value (expr_p, cached_lhs);
return retval;
}
-/* STMT, a MODIFY_EXPR, may create certain equivalences, in either
+/* STMT, a GIMPLE_MODIFY_STMT, may create certain equivalences, in either
the available expressions table or the const_and_copies table.
Detect and record those equivalences. */
static void
-record_equivalences_from_stmt (tree stmt,
- int may_optimize_p,
- stmt_ann_t ann)
+record_equivalences_from_stmt (tree stmt, int may_optimize_p, stmt_ann_t ann)
{
- tree lhs = TREE_OPERAND (stmt, 0);
+ tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
enum tree_code lhs_code = TREE_CODE (lhs);
- int i;
if (lhs_code == SSA_NAME)
{
- tree rhs = TREE_OPERAND (stmt, 1);
+ tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
/* Strip away any useless type conversions. */
STRIP_USELESS_TYPE_CONVERSION (rhs);
&& (TREE_CODE (rhs) == SSA_NAME
|| is_gimple_min_invariant (rhs)))
SSA_NAME_VALUE (lhs) = rhs;
-
- if (tree_expr_nonzero_p (rhs))
- record_var_is_nonzero (lhs);
}
- /* Look at both sides for pointer dereferences. If we find one, then
- the pointer must be nonnull and we can enter that equivalence into
- the hash tables. */
- if (flag_delete_null_pointer_checks)
- for (i = 0; i < 2; i++)
- {
- tree t = TREE_OPERAND (stmt, i);
-
- /* Strip away any COMPONENT_REFs. */
- while (TREE_CODE (t) == COMPONENT_REF)
- t = TREE_OPERAND (t, 0);
-
- /* Now see if this is a pointer dereference. */
- if (INDIRECT_REF_P (t))
- {
- tree op = TREE_OPERAND (t, 0);
-
- /* If the pointer is a SSA variable, then enter new
- equivalences into the hash table. */
- while (TREE_CODE (op) == SSA_NAME)
- {
- tree def = SSA_NAME_DEF_STMT (op);
-
- record_var_is_nonzero (op);
-
- /* And walk up the USE-DEF chains noting other SSA_NAMEs
- which are known to have a nonzero value. */
- if (def
- && TREE_CODE (def) == MODIFY_EXPR
- && TREE_CODE (TREE_OPERAND (def, 1)) == NOP_EXPR)
- op = TREE_OPERAND (TREE_OPERAND (def, 1), 0);
- else
- break;
- }
- }
- }
-
/* A memory store, even an aliased store, creates a useful
equivalence. By exchanging the LHS and RHS, creating suitable
vops and recording the result in the available expression table,
we may be able to expose more redundant loads. */
if (!ann->has_volatile_ops
- && (TREE_CODE (TREE_OPERAND (stmt, 1)) == SSA_NAME
- || is_gimple_min_invariant (TREE_OPERAND (stmt, 1)))
+ && stmt_references_memory_p (stmt)
+ && (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == SSA_NAME
+ || is_gimple_min_invariant (GIMPLE_STMT_OPERAND (stmt, 1)))
&& !is_gimple_reg (lhs))
{
- tree rhs = TREE_OPERAND (stmt, 1);
- tree new;
-
- /* FIXME: If the LHS of the assignment is a bitfield and the RHS
- is a constant, we need to adjust the constant to fit into the
- type of the LHS. If the LHS is a bitfield and the RHS is not
- a constant, then we can not record any equivalences for this
- statement since we would need to represent the widening or
- narrowing of RHS. This fixes gcc.c-torture/execute/921016-1.c
- and should not be necessary if GCC represented bitfields
- properly. */
- if (lhs_code == COMPONENT_REF
- && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
- {
- if (TREE_CONSTANT (rhs))
- rhs = widen_bitfield (rhs, TREE_OPERAND (lhs, 1), lhs);
- else
- rhs = NULL;
-
- /* If the value overflowed, then we can not use this equivalence. */
- if (rhs && ! is_gimple_min_invariant (rhs))
- rhs = NULL;
- }
-
- if (rhs)
- {
- /* Build a new statement with the RHS and LHS exchanged. */
- new = build2 (MODIFY_EXPR, TREE_TYPE (stmt), rhs, lhs);
+ tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
+ tree new_stmt;
- create_ssa_artficial_load_stmt (new, stmt);
+ /* Build a new statement with the RHS and LHS exchanged. */
+ new_stmt = build_gimple_modify_stmt (rhs, lhs);
+ create_ssa_artificial_load_stmt (new_stmt, stmt, true);
- /* Finally enter the statement into the available expression
- table. */
- lookup_avail_expr (new, true);
- }
+ /* Finally enter the statement into the available expression
+ table. */
+ lookup_avail_expr (new_stmt, true);
}
}
propagation opportunity. */
if (TREE_CODE (val) != SSA_NAME)
{
- if (!lang_hooks.types_compatible_p (op_type, val_type))
+ if (!useless_type_conversion_p (op_type, val_type))
{
val = fold_convert (TREE_TYPE (op), val);
if (!is_gimple_min_invariant (val))
known value for that SSA_NAME (or NULL if no value is known).
Propagate values from CONST_AND_COPIES into the uses, vuses and
- v_may_def_ops of STMT. */
+ vdef_ops of STMT. */
static bool
cprop_into_stmt (tree stmt)
ann = stmt_ann (stmt);
opt_stats.num_stmts++;
may_have_exposed_new_symbols = false;
+ push_stmt_changes (bsi_stmt_ptr (si));
if (dump_file && (dump_flags & TDF_DETAILS))
{
print_generic_stmt (dump_file, stmt, TDF_SLIM);
}
- /* Const/copy propagate into USES, VUSES and the RHS of V_MAY_DEFs. */
+ /* Const/copy propagate into USES, VUSES and the RHS of VDEFs. */
may_have_exposed_new_symbols = cprop_into_stmt (stmt);
/* If the statement has been modified with constant replacements,
may_optimize_p = (!ann->has_volatile_ops
&& ((TREE_CODE (stmt) == RETURN_EXPR
&& TREE_OPERAND (stmt, 0)
- && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR
+ && TREE_CODE (TREE_OPERAND (stmt, 0))
+ == GIMPLE_MODIFY_STMT
&& ! (TREE_SIDE_EFFECTS
- (TREE_OPERAND (TREE_OPERAND (stmt, 0), 1))))
- || (TREE_CODE (stmt) == MODIFY_EXPR
- && ! TREE_SIDE_EFFECTS (TREE_OPERAND (stmt, 1)))
+ (GIMPLE_STMT_OPERAND
+ (TREE_OPERAND (stmt, 0), 1))))
+ || (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
+ && ! TREE_SIDE_EFFECTS (GIMPLE_STMT_OPERAND (stmt,
+ 1)))
|| TREE_CODE (stmt) == COND_EXPR
|| TREE_CODE (stmt) == SWITCH_EXPR));
may_have_exposed_new_symbols |= eliminate_redundant_computations (stmt);
/* Record any additional equivalences created by this statement. */
- if (TREE_CODE (stmt) == MODIFY_EXPR)
- record_equivalences_from_stmt (stmt,
- may_optimize_p,
- ann);
+ if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
+ record_equivalences_from_stmt (stmt, may_optimize_p, ann);
/* If STMT is a COND_EXPR and it was modified, then we may know
where it goes. If that is the case, then mark the CFG as altered.
Ultimately I suspect we're going to need to change the interface
into the SSA_NAME manager. */
-
if (ann->modified)
{
tree val = NULL;
}
if (may_have_exposed_new_symbols)
- VEC_safe_push (tree, heap, stmts_to_rescan, bsi_stmt (si));
+ {
+ /* Queue the statement to be re-scanned after all the
+ AVAIL_EXPRS have been processed. The change buffer stack for
+ all the pushed statements will be processed when this queue
+ is emptied. */
+ VEC_safe_push (tree_p, heap, stmts_to_rescan, bsi_stmt_ptr (si));
+ }
+ else
+ {
+ /* Otherwise, just discard the recently pushed change buffer. If
+ not, the STMTS_TO_RESCAN queue will get out of synch with the
+ change buffer stack. */
+ discard_stmt_changes (bsi_stmt_ptr (si));
+ }
}
/* Search for an existing instance of STMT in the AVAIL_EXPRS table. If
is also added to the stack pointed to by BLOCK_AVAIL_EXPRS_P, so that they
can be removed when we finish processing this block and its children.
- NOTE: This function assumes that STMT is a MODIFY_EXPR node that
+ NOTE: This function assumes that STMT is a GIMPLE_MODIFY_STMT node that
contains no CALL_EXPR on its RHS and makes no volatile nor
aliased references. */
tree temp;
struct expr_hash_elt *element = XNEW (struct expr_hash_elt);
- lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
+ lhs = TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
+ ? GIMPLE_STMT_OPERAND (stmt, 0) : NULL;
initialize_hash_element (stmt, lhs, element);
return NULL_TREE;
}
- /* If this is an equality test against zero, see if we have recorded a
- nonzero value for the variable in question. */
- if ((TREE_CODE (element->rhs) == EQ_EXPR
- || TREE_CODE (element->rhs) == NE_EXPR)
- && TREE_CODE (TREE_OPERAND (element->rhs, 0)) == SSA_NAME
- && integer_zerop (TREE_OPERAND (element->rhs, 1)))
- {
- int indx = SSA_NAME_VERSION (TREE_OPERAND (element->rhs, 0));
-
- if (bitmap_bit_p (nonzero_vars, indx))
- {
- tree t = element->rhs;
- free (element);
- return constant_boolean_node (TREE_CODE (t) != EQ_EXPR,
- TREE_TYPE (t));
- }
- }
-
/* Finally try to find the expression in the main expression hash table. */
slot = htab_find_slot_with_hash (avail_exprs, element, element->hash,
(insert ? INSERT : NO_INSERT));
}
/* Hashing and equality functions for AVAIL_EXPRS. The table stores
- MODIFY_EXPR statements. We compute a value number for expressions using
- the code of the expression and the SSA numbers of its operands. */
+ GIMPLE_MODIFY_STMT statements. We compute a value number for expressions
+ using the code of the expression and the SSA numbers of its operands. */
static hashval_t
avail_expr_hash (const void *p)
{
- tree stmt = ((struct expr_hash_elt *)p)->stmt;
- tree rhs = ((struct expr_hash_elt *)p)->rhs;
+ tree stmt = ((const struct expr_hash_elt *)p)->stmt;
+ tree rhs = ((const struct expr_hash_elt *)p)->rhs;
tree vuse;
ssa_op_iter iter;
hashval_t val = 0;
static int
avail_expr_eq (const void *p1, const void *p2)
{
- tree stmt1 = ((struct expr_hash_elt *)p1)->stmt;
- tree rhs1 = ((struct expr_hash_elt *)p1)->rhs;
- tree stmt2 = ((struct expr_hash_elt *)p2)->stmt;
- tree rhs2 = ((struct expr_hash_elt *)p2)->rhs;
+ tree stmt1 = ((const struct expr_hash_elt *)p1)->stmt;
+ tree rhs1 = ((const struct expr_hash_elt *)p1)->rhs;
+ tree stmt2 = ((const struct expr_hash_elt *)p2)->stmt;
+ tree rhs2 = ((const struct expr_hash_elt *)p2)->rhs;
/* If they are the same physical expression, return true. */
if (rhs1 == rhs2 && stmt1 == stmt2)
/* In case of a collision, both RHS have to be identical and have the
same VUSE operands. */
- if ((TREE_TYPE (rhs1) == TREE_TYPE (rhs2)
- || lang_hooks.types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2)))
+ if (types_compatible_p (TREE_TYPE (rhs1), TREE_TYPE (rhs2))
&& operand_equal_p (rhs1, rhs2, OEP_PURE_SAME))
{
bool ret = compare_ssa_operands_equal (stmt1, stmt2, SSA_OP_VUSE);
- gcc_assert (!ret || ((struct expr_hash_elt *)p1)->hash
- == ((struct expr_hash_elt *)p2)->hash);
+ gcc_assert (!ret || ((const struct expr_hash_elt *)p1)->hash
+ == ((const struct expr_hash_elt *)p2)->hash);
return ret;
}
return false;
}
+
+/* PHI-ONLY copy and constant propagation. This pass is meant to clean
+ up degenerate PHIs created by or exposed by jump threading. */
+
+/* Given PHI, return its RHS if the PHI is a degenerate, otherwise return
+ NULL. */
+
+static tree
+degenerate_phi_result (tree phi)
+{
+ tree lhs = PHI_RESULT (phi);
+ tree val = NULL;
+ int i;
+
+ /* Ignoring arguments which are the same as LHS, if all the remaining
+ arguments are the same, then the PHI is a degenerate and has the
+ value of that common argument. */
+ for (i = 0; i < PHI_NUM_ARGS (phi); i++)
+ {
+ tree arg = PHI_ARG_DEF (phi, i);
+
+ if (arg == lhs)
+ continue;
+ else if (!val)
+ val = arg;
+ else if (!operand_equal_p (arg, val, 0))
+ break;
+ }
+ return (i == PHI_NUM_ARGS (phi) ? val : NULL);
+}
+
+/* Given a tree node T, which is either a PHI_NODE or GIMPLE_MODIFY_STMT,
+ remove it from the IL. */
+
+static void
+remove_stmt_or_phi (tree t)
+{
+ if (TREE_CODE (t) == PHI_NODE)
+ remove_phi_node (t, NULL, true);
+ else
+ {
+ block_stmt_iterator bsi = bsi_for_stmt (t);
+ bsi_remove (&bsi, true);
+ release_defs (t);
+ }
+}
+
+/* Given a tree node T, which is either a PHI_NODE or GIMPLE_MODIFY_STMT,
+ return the "rhs" of the node, in the case of a non-degenerate
+ PHI, NULL is returned. */
+
+static tree
+get_rhs_or_phi_arg (tree t)
+{
+ if (TREE_CODE (t) == PHI_NODE)
+ return degenerate_phi_result (t);
+ else if (TREE_CODE (t) == GIMPLE_MODIFY_STMT)
+ return GIMPLE_STMT_OPERAND (t, 1);
+ gcc_unreachable ();
+}
+
+
+/* Given a tree node T, which is either a PHI_NODE or a GIMPLE_MODIFY_STMT,
+ return the "lhs" of the node. */
+
+static tree
+get_lhs_or_phi_result (tree t)
+{
+ if (TREE_CODE (t) == PHI_NODE)
+ return PHI_RESULT (t);
+ else if (TREE_CODE (t) == GIMPLE_MODIFY_STMT)
+ return GIMPLE_STMT_OPERAND (t, 0);
+ gcc_unreachable ();
+}
+
+/* Propagate RHS into all uses of LHS (when possible).
+
+ RHS and LHS are derived from STMT, which is passed in solely so
+ that we can remove it if propagation is successful.
+
+ When propagating into a PHI node or into a statement which turns
+ into a trivial copy or constant initialization, set the
+ appropriate bit in INTERESTING_NAMEs so that we will visit those
+ nodes as well in an effort to pick up secondary optimization
+ opportunities. */
+
+static void
+propagate_rhs_into_lhs (tree stmt, tree lhs, tree rhs, bitmap interesting_names)
+{
+ /* First verify that propagation is valid and isn't going to move a
+ loop variant variable outside its loop. */
+ if (! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs)
+ && (TREE_CODE (rhs) != SSA_NAME
+ || ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs))
+ && may_propagate_copy (lhs, rhs)
+ && loop_depth_of_name (lhs) >= loop_depth_of_name (rhs))
+ {
+ use_operand_p use_p;
+ imm_use_iterator iter;
+ tree use_stmt;
+ bool all = true;
+
+ /* Dump details. */
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " Replacing '");
+ print_generic_expr (dump_file, lhs, dump_flags);
+ fprintf (dump_file, "' with %s '",
+ (TREE_CODE (rhs) != SSA_NAME ? "constant" : "variable"));
+ print_generic_expr (dump_file, rhs, dump_flags);
+ fprintf (dump_file, "'\n");
+ }
+
+ /* Walk over every use of LHS and try to replace the use with RHS.
+ At this point the only reason why such a propagation would not
+ be successful would be if the use occurs in an ASM_EXPR. */
+ FOR_EACH_IMM_USE_STMT (use_stmt, iter, lhs)
+ {
+
+ /* It's not always safe to propagate into an ASM_EXPR. */
+ if (TREE_CODE (use_stmt) == ASM_EXPR
+ && ! may_propagate_copy_into_asm (lhs))
+ {
+ all = false;
+ continue;
+ }
+
+ /* Dump details. */
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " Original statement:");
+ print_generic_expr (dump_file, use_stmt, dump_flags);
+ fprintf (dump_file, "\n");
+ }
+
+ push_stmt_changes (&use_stmt);
+
+ /* Propagate the RHS into this use of the LHS. */
+ FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
+ propagate_value (use_p, rhs);
+
+ /* Special cases to avoid useless calls into the folding
+ routines, operand scanning, etc.
+
+ First, propagation into a PHI may cause the PHI to become
+ a degenerate, so mark the PHI as interesting. No other
+ actions are necessary.
+
+ Second, if we're propagating a virtual operand and the
+ propagation does not change the underlying _DECL node for
+ the virtual operand, then no further actions are necessary. */
+ if (TREE_CODE (use_stmt) == PHI_NODE
+ || (! is_gimple_reg (lhs)
+ && TREE_CODE (rhs) == SSA_NAME
+ && SSA_NAME_VAR (lhs) == SSA_NAME_VAR (rhs)))
+ {
+ /* Dump details. */
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " Updated statement:");
+ print_generic_expr (dump_file, use_stmt, dump_flags);
+ fprintf (dump_file, "\n");
+ }
+
+ /* Propagation into a PHI may expose new degenerate PHIs,
+ so mark the result of the PHI as interesting. */
+ if (TREE_CODE (use_stmt) == PHI_NODE)
+ {
+ tree result = get_lhs_or_phi_result (use_stmt);
+ bitmap_set_bit (interesting_names, SSA_NAME_VERSION (result));
+ }
+
+ discard_stmt_changes (&use_stmt);
+ continue;
+ }
+
+ /* From this point onward we are propagating into a
+ real statement. Folding may (or may not) be possible,
+ we may expose new operands, expose dead EH edges,
+ etc. */
+ fold_stmt_inplace (use_stmt);
+
+ /* Sometimes propagation can expose new operands to the
+ renamer. Note this will call update_stmt at the
+ appropriate time. */
+ pop_stmt_changes (&use_stmt);
+
+ /* Dump details. */
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " Updated statement:");
+ print_generic_expr (dump_file, use_stmt, dump_flags);
+ fprintf (dump_file, "\n");
+ }
+
+ /* If we replaced a variable index with a constant, then
+ we would need to update the invariant flag for ADDR_EXPRs. */
+ if (TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
+ && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == ADDR_EXPR)
+ recompute_tree_invariant_for_addr_expr
+ (GIMPLE_STMT_OPERAND (use_stmt, 1));
+
+ /* If we cleaned up EH information from the statement,
+ mark its containing block as needing EH cleanups. */
+ if (maybe_clean_or_replace_eh_stmt (use_stmt, use_stmt))
+ {
+ bitmap_set_bit (need_eh_cleanup, bb_for_stmt (use_stmt)->index);
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " Flagged to clear EH edges.\n");
+ }
+
+ /* Propagation may expose new trivial copy/constant propagation
+ opportunities. */
+ 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)) == SSA_NAME
+ || is_gimple_min_invariant (GIMPLE_STMT_OPERAND (use_stmt,
+ 1))))
+ {
+ tree result = get_lhs_or_phi_result (use_stmt);
+ bitmap_set_bit (interesting_names, SSA_NAME_VERSION (result));
+ }
+
+ /* Propagation into these nodes may make certain edges in
+ the CFG unexecutable. We want to identify them as PHI nodes
+ at the destination of those unexecutable edges may become
+ degenerates. */
+ else if (TREE_CODE (use_stmt) == COND_EXPR
+ || TREE_CODE (use_stmt) == SWITCH_EXPR
+ || TREE_CODE (use_stmt) == GOTO_EXPR)
+ {
+ tree val;
+
+ if (TREE_CODE (use_stmt) == COND_EXPR)
+ val = COND_EXPR_COND (use_stmt);
+ else if (TREE_CODE (use_stmt) == SWITCH_EXPR)
+ val = SWITCH_COND (use_stmt);
+ else
+ val = GOTO_DESTINATION (use_stmt);
+
+ if (is_gimple_min_invariant (val))
+ {
+ basic_block bb = bb_for_stmt (use_stmt);
+ edge te = find_taken_edge (bb, val);
+ edge_iterator ei;
+ edge e;
+ block_stmt_iterator bsi;
+
+ /* Remove all outgoing edges except TE. */
+ for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei));)
+ {
+ if (e != te)
+ {
+ tree phi;
+
+ /* Mark all the PHI nodes at the destination of
+ the unexecutable edge as interesting. */
+ for (phi = phi_nodes (e->dest);
+ phi;
+ phi = PHI_CHAIN (phi))
+ {
+ tree result = PHI_RESULT (phi);
+ int version = SSA_NAME_VERSION (result);
+
+ bitmap_set_bit (interesting_names, version);
+ }
+
+ te->probability += e->probability;
+
+ te->count += e->count;
+ remove_edge (e);
+ cfg_altered = true;
+ }
+ else
+ ei_next (&ei);
+ }
+
+ bsi = bsi_last (bb_for_stmt (use_stmt));
+ bsi_remove (&bsi, true);
+
+ /* And fixup the flags on the single remaining edge. */
+ te->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
+ te->flags &= ~EDGE_ABNORMAL;
+ te->flags |= EDGE_FALLTHRU;
+ if (te->probability > REG_BR_PROB_BASE)
+ te->probability = REG_BR_PROB_BASE;
+ }
+ }
+ }
+
+ /* Ensure there is nothing else to do. */
+ gcc_assert (!all || has_zero_uses (lhs));
+
+ /* If we were able to propagate away all uses of LHS, then
+ we can remove STMT. */
+ if (all)
+ remove_stmt_or_phi (stmt);
+ }
+}
+
+/* T is either a PHI node (potentially a degenerate PHI node) or
+ a statement that is a trivial copy or constant initialization.
+
+ Attempt to eliminate T by propagating its RHS into all uses of
+ its LHS. This may in turn set new bits in INTERESTING_NAMES
+ for nodes we want to revisit later.
+
+ All exit paths should clear INTERESTING_NAMES for the result
+ of T. */
+
+static void
+eliminate_const_or_copy (tree t, bitmap interesting_names)
+{
+ tree lhs = get_lhs_or_phi_result (t);
+ tree rhs;
+ int version = SSA_NAME_VERSION (lhs);
+
+ /* If the LHS of this statement or PHI has no uses, then we can
+ just eliminate it. This can occur if, for example, the PHI
+ was created by block duplication due to threading and its only
+ use was in the conditional at the end of the block which was
+ deleted. */
+ if (has_zero_uses (lhs))
+ {
+ bitmap_clear_bit (interesting_names, version);
+ remove_stmt_or_phi (t);
+ return;
+ }
+
+ /* Get the RHS of the assignment or PHI node if the PHI is a
+ degenerate. */
+ rhs = get_rhs_or_phi_arg (t);
+ if (!rhs)
+ {
+ bitmap_clear_bit (interesting_names, version);
+ return;
+ }
+
+ propagate_rhs_into_lhs (t, lhs, rhs, interesting_names);
+
+ /* Note that T may well have been deleted by now, so do
+ not access it, instead use the saved version # to clear
+ T's entry in the worklist. */
+ bitmap_clear_bit (interesting_names, version);
+}
+
+/* The first phase in degenerate PHI elimination.
+
+ Eliminate the degenerate PHIs in BB, then recurse on the
+ dominator children of BB. */
+
+static void
+eliminate_degenerate_phis_1 (basic_block bb, bitmap interesting_names)
+{
+ tree phi, next;
+ basic_block son;
+
+ for (phi = phi_nodes (bb); phi; phi = next)
+ {
+ next = PHI_CHAIN (phi);
+ eliminate_const_or_copy (phi, interesting_names);
+ }
+
+ /* Recurse into the dominator children of BB. */
+ for (son = first_dom_son (CDI_DOMINATORS, bb);
+ son;
+ son = next_dom_son (CDI_DOMINATORS, son))
+ eliminate_degenerate_phis_1 (son, interesting_names);
+}
+
+
+/* A very simple pass to eliminate degenerate PHI nodes from the
+ IL. This is meant to be fast enough to be able to be run several
+ times in the optimization pipeline.
+
+ Certain optimizations, particularly those which duplicate blocks
+ or remove edges from the CFG can create or expose PHIs which are
+ trivial copies or constant initializations.
+
+ While we could pick up these optimizations in DOM or with the
+ combination of copy-prop and CCP, those solutions are far too
+ heavy-weight for our needs.
+
+ This implementation has two phases so that we can efficiently
+ eliminate the first order degenerate PHIs and second order
+ degenerate PHIs.
+
+ The first phase performs a dominator walk to identify and eliminate
+ the vast majority of the degenerate PHIs. When a degenerate PHI
+ is identified and eliminated any affected statements or PHIs
+ are put on a worklist.
+
+ The second phase eliminates degenerate PHIs and trivial copies
+ or constant initializations using the worklist. This is how we
+ pick up the secondary optimization opportunities with minimal
+ cost. */
+
+static unsigned int
+eliminate_degenerate_phis (void)
+{
+ bitmap interesting_names;
+ bitmap interesting_names1;
+
+ /* Bitmap of blocks which need EH information updated. We can not
+ update it on-the-fly as doing so invalidates the dominator tree. */
+ need_eh_cleanup = BITMAP_ALLOC (NULL);
+
+ /* INTERESTING_NAMES is effectively our worklist, indexed by
+ SSA_NAME_VERSION.
+
+ A set bit indicates that the statement or PHI node which
+ defines the SSA_NAME should be (re)examined to determine if
+ it has become a degenerate PHI or trivial const/copy propagation
+ opportunity.
+
+ Experiments have show we generally get better compilation
+ time behavior with bitmaps rather than sbitmaps. */
+ interesting_names = BITMAP_ALLOC (NULL);
+ interesting_names1 = BITMAP_ALLOC (NULL);
+
+ calculate_dominance_info (CDI_DOMINATORS);
+ cfg_altered = false;
+
+ /* First phase. Eliminate degenerate PHIs via a dominator
+ walk of the CFG.
+
+ Experiments have indicated that we generally get better
+ compile-time behavior by visiting blocks in the first
+ phase in dominator order. Presumably this is because walking
+ in dominator order leaves fewer PHIs for later examination
+ by the worklist phase. */
+ eliminate_degenerate_phis_1 (ENTRY_BLOCK_PTR, interesting_names);
+
+ /* Second phase. Eliminate second order degenerate PHIs as well
+ as trivial copies or constant initializations identified by
+ the first phase or this phase. Basically we keep iterating
+ until our set of INTERESTING_NAMEs is empty. */
+ while (!bitmap_empty_p (interesting_names))
+ {
+ unsigned int i;
+ bitmap_iterator bi;
+
+ /* EXECUTE_IF_SET_IN_BITMAP does not like its bitmap
+ changed during the loop. Copy it to another bitmap and
+ use that. */
+ bitmap_copy (interesting_names1, interesting_names);
+
+ EXECUTE_IF_SET_IN_BITMAP (interesting_names1, 0, i, bi)
+ {
+ tree name = ssa_name (i);
+
+ /* Ignore SSA_NAMEs that have been released because
+ their defining statement was deleted (unreachable). */
+ if (name)
+ eliminate_const_or_copy (SSA_NAME_DEF_STMT (ssa_name (i)),
+ interesting_names);
+ }
+ }
+
+ if (cfg_altered)
+ free_dominance_info (CDI_DOMINATORS);
+
+ /* Propagation of const and copies may make some EH edges dead. Purge
+ such edges from the CFG as needed. */
+ if (!bitmap_empty_p (need_eh_cleanup))
+ {
+ tree_purge_all_dead_eh_edges (need_eh_cleanup);
+ BITMAP_FREE (need_eh_cleanup);
+ }
+
+ BITMAP_FREE (interesting_names);
+ BITMAP_FREE (interesting_names1);
+ return 0;
+}
+
+struct gimple_opt_pass pass_phi_only_cprop =
+{
+ {
+ GIMPLE_PASS,
+ "phicprop", /* name */
+ gate_dominator, /* gate */
+ eliminate_degenerate_phis, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_TREE_PHI_CPROP, /* tv_id */
+ PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_cleanup_cfg
+ | TODO_dump_func
+ | TODO_ggc_collect
+ | TODO_verify_ssa
+ | TODO_verify_stmts
+ | TODO_update_ssa /* todo_flags_finish */
+ }
+};
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