/* SSA Dominator optimizations for trees
- Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
+ Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
Contributed by Diego Novillo <dnovillo@redhat.com>
This file is part of GCC.
#include "tm_p.h"
#include "ggc.h"
#include "basic-block.h"
+#include "cfgloop.h"
#include "output.h"
#include "errors.h"
#include "expr.h"
of the form SSA_NAME COND CONST we create a new vrp_element to record
how the condition affects the possible values SSA_NAME may have.
- Each record contains the condition tested (COND), and the the range of
+ Each record contains the condition tested (COND), and the range of
values the variable may legitimately have if COND is true. Note the
range of values may be a smaller range than COND specifies if we have
recorded other ranges for this variable. Each record also contains the
in this basic block. We use this during finalization to know
which variables need their VRP data updated. */
-/* Stack of SSA_NAMEs which had their values constrainted by operations
+/* Stack of SSA_NAMEs which had their values constrained by operations
in this basic block. During finalization of this block we use this
list to determine which variables need their VRP data updated.
{
struct dom_walk_data walk_data;
unsigned int i;
+ struct loops loops_info;
memset (&opt_stats, 0, sizeof (opt_stats));
for (i = 0; i < num_referenced_vars; i++)
var_ann (referenced_var (i))->current_def = NULL;
- /* Mark loop edges so we avoid threading across loop boundaries.
- This may result in transforming natural loop into irreducible
- region. */
- mark_dfs_back_edges ();
-
/* Create our hash tables. */
avail_exprs = htab_create (1024, real_avail_expr_hash, avail_expr_eq, free);
vrp_data = htab_create (ceil_log2 (num_ssa_names), vrp_hash, vrp_eq, free);
nonzero_vars_stack = VEC_alloc (tree_on_heap, 20);
vrp_variables_stack = VEC_alloc (tree_on_heap, 20);
stmts_to_rescan = VEC_alloc (tree_on_heap, 20);
- nonzero_vars = BITMAP_XMALLOC ();
- need_eh_cleanup = BITMAP_XMALLOC ();
+ nonzero_vars = BITMAP_ALLOC (NULL);
+ need_eh_cleanup = BITMAP_ALLOC (NULL);
/* Setup callbacks for the generic dominator tree walker. */
walk_data.walk_stmts_backward = false;
calculate_dominance_info (CDI_DOMINATORS);
+ /* 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 ();
+
/* If we prove certain blocks are unreachable, then we want to
repeat the dominator optimization process as PHI nodes may
have turned into copies which allows better propagation of
/* Optimize the dominator tree. */
cfg_altered = false;
+ /* We need accurate information regarding back edges in the CFG
+ for jump threading. */
+ mark_dfs_back_edges ();
+
/* Recursively walk the dominator tree optimizing statements. */
walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
free_all_edge_infos ();
+ {
+ block_stmt_iterator bsi;
+ basic_block bb;
+ FOR_EACH_BB (bb)
+ {
+ for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
+ {
+ update_stmt_if_modified (bsi_stmt (bsi));
+ }
+ }
+ }
/* Thread jumps, creating duplicate blocks as needed. */
- cfg_altered = thread_through_all_blocks ();
+ cfg_altered |= thread_through_all_blocks ();
/* Removal of statements may make some EH edges dead. Purge
such edges from the CFG as needed. */
bitmap_zero (need_eh_cleanup);
}
- free_dominance_info (CDI_DOMINATORS);
- cfg_altered = cleanup_tree_cfg ();
+ if (cfg_altered)
+ free_dominance_info (CDI_DOMINATORS);
+
+ cfg_altered |= cleanup_tree_cfg ();
+
+ if (rediscover_loops_after_threading)
+ {
+ /* Rerun basic loop analysis to discover any newly
+ created loops and update the set of exit edges. */
+ rediscover_loops_after_threading = false;
+ flow_loops_find (&loops_info);
+ mark_loop_exit_edges (&loops_info);
+ flow_loops_free (&loops_info);
+
+ /* Remove any forwarder blocks inserted by loop
+ header canonicalization. */
+ cleanup_tree_cfg ();
+ }
+
calculate_dominance_info (CDI_DOMINATORS);
rewrite_ssa_into_ssa ();
for (i = 0; i < num_referenced_vars; i++)
var_ann (referenced_var (i))->current_def = NULL;
+
+ /* Finally, remove everything except invariants in SSA_NAME_VALUE.
+
+ This must be done before we iterate as we might have a
+ reference to an SSA_NAME which was removed by the call to
+ rewrite_ssa_into_ssa.
+
+ Long term we will be able to let everything in SSA_NAME_VALUE
+ persist. However, for now, we know this is the safe thing to do. */
+ for (i = 0; i < num_ssa_names; i++)
+ {
+ tree name = ssa_name (i);
+ tree value;
+
+ if (!name)
+ continue;
+
+ value = SSA_NAME_VALUE (name);
+ if (value && !is_gimple_min_invariant (value))
+ SSA_NAME_VALUE (name) = NULL;
+ }
}
- while (cfg_altered);
+ while (optimize > 1 && cfg_altered);
/* Debugging dumps. */
if (dump_file && (dump_flags & TDF_STATS))
fini_walk_dominator_tree (&walk_data);
/* Free nonzero_vars. */
- BITMAP_XFREE (nonzero_vars);
- BITMAP_XFREE (need_eh_cleanup);
-
- /* Finally, remove everything except invariants in SSA_NAME_VALUE.
-
- Long term we will be able to let everything in SSA_NAME_VALUE
- persist. However, for now, we know this is the safe thing to
- do. */
- for (i = 0; i < num_ssa_names; i++)
- {
- tree name = ssa_name (i);
- tree value;
-
- if (!name)
- continue;
-
- value = SSA_NAME_VALUE (name);
- if (value && !is_gimple_min_invariant (value))
- SSA_NAME_VALUE (name) = NULL;
- }
+ BITMAP_FREE (nonzero_vars);
+ BITMAP_FREE (need_eh_cleanup);
VEC_free (tree_on_heap, block_defs_stack);
VEC_free (tree_on_heap, avail_exprs_stack);
{
tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
tree dst = PHI_RESULT (phi);
+
+ /* If the desired argument is not the same as this PHI's result
+ and it is set by a PHI in this block, then we can not thread
+ through this block. */
+ if (src != dst
+ && TREE_CODE (src) == SSA_NAME
+ && TREE_CODE (SSA_NAME_DEF_STMT (src)) == PHI_NODE
+ && bb_for_stmt (SSA_NAME_DEF_STMT (src)) == e->dest)
+ return;
+
record_const_or_copy (dst, src);
register_new_def (dst, &block_defs_stack);
}
stmt_ann_t ann = stmt_ann (stmt);
use_optype uses = USE_OPS (ann);
vuse_optype vuses = VUSE_OPS (ann);
- tree *uses_copy = xcalloc (NUM_USES (uses), sizeof (tree));
- tree *vuses_copy = xcalloc (NUM_VUSES (vuses), sizeof (tree));
+ tree *uses_copy = xmalloc (NUM_USES (uses) * sizeof (tree));
+ tree *vuses_copy = xmalloc (NUM_VUSES (vuses) * sizeof (tree));
unsigned int i;
/* Make a copy of the uses into USES_COPY, then cprop into
arm will be taken. */
if (stmt
&& (TREE_CODE (stmt) == COND_EXPR
- || TREE_CODE (stmt) == SWITCH_EXPR))
+ || TREE_CODE (stmt) == SWITCH_EXPR
+ || TREE_CODE (stmt) == GOTO_EXPR))
{
tree cond, cached_lhs;
- edge e1;
- edge_iterator ei;
-
- /* Do not forward entry edges into the loop. In the case loop
- has multiple entry edges we may end up in constructing irreducible
- region.
- ??? We may consider forwarding the edges in the case all incoming
- edges forward to the same destination block. */
- if (!e->flags & EDGE_DFS_BACK)
- {
- FOR_EACH_EDGE (e1, ei, e->dest->preds)
- if (e1->flags & EDGE_DFS_BACK)
- break;
- if (e1)
- return;
- }
/* Now temporarily cprop the operands and try to find the resulting
expression in the hash tables. */
if (TREE_CODE (stmt) == COND_EXPR)
cond = COND_EXPR_COND (stmt);
+ else if (TREE_CODE (stmt) == GOTO_EXPR)
+ cond = GOTO_DESTINATION (stmt);
else
cond = SWITCH_COND (stmt);
{
tree last;
- /* If we are at a leaf node in the dominator graph, see if we can thread
+ /* If we are at a leaf node in the dominator tree, see if we can thread
the edge from BB through its successor.
Do this before we remove entries from our equivalence tables. */
- if (EDGE_COUNT (bb->succs) == 1
- && (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) == 0
- && (get_immediate_dominator (CDI_DOMINATORS, EDGE_SUCC (bb, 0)->dest) != bb
- || phi_nodes (EDGE_SUCC (bb, 0)->dest)))
+ if (single_succ_p (bb)
+ && (single_succ_edge (bb)->flags & EDGE_ABNORMAL) == 0
+ && (get_immediate_dominator (CDI_DOMINATORS, single_succ (bb)) != bb
+ || phi_nodes (single_succ (bb))))
{
- thread_across_edge (walk_data, EDGE_SUCC (bb, 0));
+ thread_across_edge (walk_data, single_succ_edge (bb));
+ }
+ else if ((last = last_stmt (bb))
+ && TREE_CODE (last) == GOTO_EXPR
+ && TREE_CODE (TREE_OPERAND (last, 0)) == SSA_NAME)
+ {
+ edge_iterator ei;
+ edge e;
+
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ thread_across_edge (walk_data, e);
+ }
}
else if ((last = last_stmt (bb))
&& TREE_CODE (last) == COND_EXPR
{
tree t = PHI_ARG_DEF (phi, i);
- /* Ignore alternatives which are the same as our LHS. */
- if (operand_equal_for_phi_arg_p (lhs, t))
+ /* Ignore alternatives which are the same as our LHS. Since
+ LHS is a PHI_RESULT, it is known to be a SSA_NAME, so we
+ can simply compare pointers. */
+ if (lhs == t)
continue;
/* If we have not processed an alternative yet, then set
basic_block parent;
struct edge_info *edge_info;
- /* If our parent block ended with a control statment, then we may be
+ /* If our parent block ended with a control statement, then we may be
able to record some equivalences based on which outgoing edge from
the parent was followed. */
parent = get_immediate_dominator (CDI_DOMINATORS, bb);
initialize_hash_element (cond, value, element);
slot = htab_find_slot_with_hash (avail_exprs, (void *)element,
- element->hash, true);
+ element->hash, INSERT);
if (*slot == NULL)
{
*slot = (void *) element;
/* Build a new conditional using NEW_CODE, OP0 and OP1 and store
the new conditional into *p, then store a boolean_true_node
- into the the *(p + 1). */
+ into *(p + 1). */
static void
build_and_record_new_cond (enum tree_code new_code, tree op0, tree op1, tree *p)
&& FLOAT_TYPE_P (TREE_TYPE (exp)));
}
+/* Returns true when STMT is a simple iv increment. It detects the
+ following situation:
+
+ i_1 = phi (..., i_2)
+ i_2 = i_1 +/- ... */
+
+static bool
+simple_iv_increment_p (tree stmt)
+{
+ tree lhs, rhs, preinc, phi;
+ unsigned i;
+
+ if (TREE_CODE (stmt) != MODIFY_EXPR)
+ return false;
+
+ lhs = TREE_OPERAND (stmt, 0);
+ if (TREE_CODE (lhs) != SSA_NAME)
+ return false;
+
+ rhs = TREE_OPERAND (stmt, 1);
+
+ if (TREE_CODE (rhs) != PLUS_EXPR
+ && TREE_CODE (rhs) != MINUS_EXPR)
+ return false;
+
+ preinc = TREE_OPERAND (rhs, 0);
+ if (TREE_CODE (preinc) != SSA_NAME)
+ return false;
+
+ phi = SSA_NAME_DEF_STMT (preinc);
+ if (TREE_CODE (phi) != PHI_NODE)
+ return false;
+
+ for (i = 0; i < (unsigned) PHI_NUM_ARGS (phi); i++)
+ if (PHI_ARG_DEF (phi, i) == lhs)
+ return true;
+
+ return false;
+}
+
/* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
hash tables. Try to simplify the RHS using whatever equivalences
we may have recorded.
{
tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
+ /* If the statement defines an induction variable, do not propagate
+ its value, so that we do not create overlapping life ranges. */
+ if (simple_iv_increment_p (rhs_def_stmt))
+ goto dont_fold_assoc;
+
/* See if the RHS_DEF_STMT has the same form as our statement. */
if (TREE_CODE (rhs_def_stmt) == MODIFY_EXPR)
{
/* If this is not a real stmt, ann will be NULL and we
avoid processing the operands. */
if (ann)
- modify_stmt (stmt);
+ mark_stmt_modified (stmt);
/* Lookup the condition and return its known value if it
exists. */
tree tmp_high, tmp_low;
int dummy;
- /* The last element has not been processed. Process it now. */
- extract_range_from_cond (element->cond, &tmp_high,
- &tmp_low, &dummy);
-
+ /* The last element has not been processed. Process it now.
+ record_range should ensure for cond inverted is not set.
+ This call can only fail if cond is x < min or x > max,
+ which fold should have optimized into false.
+ If that doesn't happen, just pretend all values are
+ in the range. */
+ if (! extract_range_from_cond (element->cond, &tmp_high,
+ &tmp_low, &dummy))
+ gcc_unreachable ();
+ else
+ gcc_assert (dummy == 0);
+
/* If this is the only element, then no merging is necessary,
the high/low values from extract_range_from_cond are all
we need. */
if (!fail)
{
SWITCH_COND (stmt) = def;
- modify_stmt (stmt);
+ mark_stmt_modified (stmt);
return lookup_avail_expr (stmt, insert);
}
edge e;
edge_iterator ei;
- /* This can get rather expensive if the implementation is naive in
- how it finds the phi alternative associated with a particular edge. */
FOR_EACH_EDGE (e, ei, bb->succs)
{
tree phi;
}
}
- if (is_gimple_min_invariant (op0)
- && (TREE_CODE (op1) == SSA_NAME
- || is_gimple_min_invariant (op1)))
+ else if (is_gimple_min_invariant (op0)
+ && (TREE_CODE (op1) == SSA_NAME
+ || is_gimple_min_invariant (op1)))
{
tree inverted = invert_truthvalue (cond);
struct edge_info *edge_info;
}
}
- if (TREE_CODE (op0) == SSA_NAME
- && (is_gimple_min_invariant (op1)
- || TREE_CODE (op1) == SSA_NAME))
+ else if (TREE_CODE (op0) == SSA_NAME
+ && (is_gimple_min_invariant (op1)
+ || TREE_CODE (op1) == SSA_NAME))
{
tree inverted = invert_truthvalue (cond);
struct edge_info *edge_info;
|| ! def
|| TREE_CODE (def) != SSA_NAME
|| SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def)
- || NUM_V_MAY_DEFS (v_may_defs) != 0)
+ || NUM_V_MAY_DEFS (v_may_defs) != 0
+ /* Do not record equivalences for increments of ivs. This would create
+ overlapping live ranges for a very questionable gain. */
+ || simple_iv_increment_p (stmt))
insert = false;
/* Check if the expression has been computed before. */
retval = true;
propagate_tree_value (expr_p, cached_lhs);
- modify_stmt (stmt);
+ mark_stmt_modified (stmt);
}
return retval;
}
extensions. */
else if (!may_propagate_copy (op, val))
return false;
+
+ /* Do not propagate copies if the propagated value is at a deeper loop
+ depth than the propagatee. 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. */
+ if (loop_depth_of_name (val) > loop_depth_of_name (op))
+ return false;
/* Dump details. */
if (dump_file && (dump_flags & TDF_DETAILS))
/* And note that we modified this statement. This is now
safe, even if we changed virtual operands since we will
rescan the statement and rewrite its operands again. */
- modify_stmt (stmt);
+ mark_stmt_modified (stmt);
}
return may_have_exposed_new_symbols;
}
stmt = bsi_stmt (si);
- get_stmt_operands (stmt);
+ update_stmt_if_modified (stmt);
ann = stmt_ann (stmt);
opt_stats.num_stmts++;
may_have_exposed_new_symbols = false;
/* And make sure we record the fact that we modified this
statement. */
- modify_stmt (stmt);
+ mark_stmt_modified (stmt);
return cached_lhs;
}
void **slot;
tree lhs;
tree temp;
- struct expr_hash_elt *element = xcalloc (sizeof (struct expr_hash_elt), 1);
+ struct expr_hash_elt *element = xmalloc (sizeof (struct expr_hash_elt));
lhs = TREE_CODE (stmt) == MODIFY_EXPR ? TREE_OPERAND (stmt, 0) : NULL;
tree op1 = TREE_OPERAND (cond, 1);
tree high, low, type;
int inverted;
-
+
+ type = TREE_TYPE (op1);
+
/* Experiments have shown that it's rarely, if ever useful to
record ranges for enumerations. Presumably this is due to
the fact that they're rarely used directly. They are typically
cast into an integer type and used that way. */
- if (TREE_CODE (TREE_TYPE (op1)) != INTEGER_TYPE)
+ if (TREE_CODE (type) != INTEGER_TYPE
+ /* We don't know how to deal with types with variable bounds. */
+ || TREE_CODE (TYPE_MIN_VALUE (type)) != INTEGER_CST
+ || TREE_CODE (TYPE_MAX_VALUE (type)) != INTEGER_CST)
return 0;
- type = TREE_TYPE (op1);
-
switch (TREE_CODE (cond))
{
case EQ_EXPR:
break;
case GT_EXPR:
- low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
high = TYPE_MAX_VALUE (type);
+ if (!tree_int_cst_lt (op1, high))
+ return 0;
+ low = int_const_binop (PLUS_EXPR, op1, integer_one_node, 1);
inverted = 0;
break;
break;
case LT_EXPR:
- high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
low = TYPE_MIN_VALUE (type);
+ if (!tree_int_cst_lt (low, op1))
+ return 0;
+ high = int_const_binop (MINUS_EXPR, op1, integer_one_node, 1);
inverted = 0;
break;
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