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);
need_eh_cleanup = BITMAP_ALLOC (NULL);
/* Setup callbacks for the generic dominator tree walker. */
/* 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);
+ loop_optimizer_init (0);
+ if (current_loops)
+ {
+ mark_loop_exit_edges ();
+ loop_optimizer_finalize ();
+ }
/* Clean up the CFG so that any forwarder blocks created by loop
canonicalization are removed. */
/* 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);
+ return 0;
}
static bool
TV_TREE_SSA_DOMINATOR_OPTS, /* tv_id */
PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
0, /* properties_provided */
- 0, /* properties_destroyed */
+ PROP_smt_usage, /* properties_destroyed */
0, /* todo_flags_start */
TODO_dump_func
| TODO_update_ssa
| TODO_cleanup_cfg
- | TODO_verify_ssa, /* todo_flags_finish */
+ | TODO_verify_ssa
+ | TODO_update_smt_usage, /* todo_flags_finish */
0 /* letter */
};
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);
}
}
-/* 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. */
/* If we don't already have a dummy condition, build it now. */
if (! walk_data->global_data)
{
- tree dummy_cond = build2 (NE, boolean_type_node,
+ tree dummy_cond = build2 (NE_EXPR, boolean_type_node,
integer_zero_node, integer_zero_node);
dummy_cond = build3 (COND_EXPR, void_type_node, dummy_cond, NULL, NULL);
walk_data->global_data = dummy_cond;
}
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
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)));
}
}
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:
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:
/* 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;
if (TREE_CODE (orig) != 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);
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
{
tree lhs = TREE_OPERAND (stmt, 0);
enum tree_code lhs_code = TREE_CODE (lhs);
- int i;
if (lhs_code == SSA_NAME)
{
&& (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,
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));
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 MODIFY_EXPR,
+ remove it from the IL. */
+
+static void
+remove_stmt_or_phi (tree t)
+{
+ if (TREE_CODE (t) == PHI_NODE)
+ remove_phi_node (t, NULL);
+ else
+ {
+ block_stmt_iterator bsi = bsi_for_stmt (t);
+ bsi_remove (&bsi, true);
+ }
+}
+
+/* Given a tree node T, which is either a PHI_NODE or MODIFY_EXPR,
+ 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) == MODIFY_EXPR)
+ return TREE_OPERAND (t, 1);
+ gcc_unreachable ();
+}
+
+
+/* Given a tree node T, which is either a PHI_NODE or a MODIFY_EXPR,
+ 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) == MODIFY_EXPR)
+ return TREE_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");
+ }
+
+ /* 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));
+ }
+ 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. */
+ mark_new_vars_to_rename (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) == MODIFY_EXPR
+ && TREE_CODE (TREE_OPERAND (use_stmt, 1)) == ADDR_EXPR)
+ recompute_tree_invariant_for_addr_expr (TREE_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) == MODIFY_EXPR
+ && TREE_CODE (TREE_OPERAND (use_stmt, 0)) == SSA_NAME
+ && (TREE_CODE (TREE_OPERAND (use_stmt, 1)) == SSA_NAME
+ || is_gimple_min_invariant (TREE_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 = 1;
+ }
+ 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 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);
+
+ /* 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. */
+ calculate_dominance_info (CDI_DOMINATORS);
+ 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 (interesting_names, 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);
+ }
+ }
+
+ /* 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))
+ {
+ cfg_altered |= tree_purge_all_dead_eh_edges (need_eh_cleanup);
+ BITMAP_FREE (need_eh_cleanup);
+ }
+
+ BITMAP_FREE (interesting_names);
+ if (cfg_altered)
+ free_dominance_info (CDI_DOMINATORS);
+ return 0;
+}
+
+struct tree_opt_pass pass_phi_only_cprop =
+{
+ "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 */
+ PROP_smt_usage, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_cleanup_cfg | TODO_dump_func
+ | TODO_ggc_collect | TODO_verify_ssa
+ | TODO_verify_stmts | TODO_update_smt_usage
+ | TODO_update_ssa, /* todo_flags_finish */
+ 0 /* letter */
+};