/* Code sinking for trees
- Copyright (C) 2001, 2002, 2003, 2004, 2007, 2008, 2009
+ Copyright (C) 2001, 2002, 2003, 2004, 2007, 2008, 2009, 2010
Free Software Foundation, Inc.
Contributed by Daniel Berlin <dan@dberlin.org>
#include "system.h"
#include "coretypes.h"
#include "tm.h"
-#include "ggc.h"
#include "tree.h"
#include "basic-block.h"
-#include "diagnostic.h"
+#include "gimple-pretty-print.h"
#include "tree-inline.h"
#include "tree-flow.h"
#include "gimple.h"
#include "fibheap.h"
#include "hashtab.h"
#include "tree-iterator.h"
-#include "real.h"
#include "alloc-pool.h"
#include "tree-pass.h"
#include "flags.h"
#include "bitmap.h"
#include "langhooks.h"
#include "cfgloop.h"
+#include "params.h"
/* TODO:
1. Sinking store only using scalar promotion (IE without moving the RHS):
else
y = *q;
-
+
should become
sinktemp = p;
p = p + 1;
y = *q
}
Store copy propagation will take care of the store elimination above.
-
+
2. Sinking using Partial Dead Code Elimination. */
static struct
-{
+{
/* The number of statements sunk down the flowgraph by code sinking. */
int sunk;
-
+
} sink_stats;
{
FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var)
{
+ if (is_gimple_debug (USE_STMT (use_p)))
+ continue;
if (firstuse == NULL)
firstuse = USE_STMT (use_p);
else
/* Check virtual definitions. If we get here, the only virtual
definitions we should see are those generated by assignment or call
statements. */
- if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_VIRTUAL_DEFS))
+ if (gimple_vdef (stmt))
{
tree lhs;
return true;
}
- else if (INDIRECT_REF_P (lhs))
- return may_point_to_global_var (TREE_OPERAND (lhs, 0));
+ else if (INDIRECT_REF_P (lhs)
+ || TREE_CODE (lhs) == MEM_REF
+ || TREE_CODE (lhs) == TARGET_MEM_REF)
+ return ptr_deref_may_alias_global_p (TREE_OPERAND (lhs, 0));
+ else if (CONSTANT_CLASS_P (lhs))
+ return true;
else
gcc_unreachable ();
}
/* Find the nearest common dominator of all of the immediate uses in IMM. */
static basic_block
-nearest_common_dominator_of_uses (gimple stmt)
-{
+nearest_common_dominator_of_uses (gimple stmt, bool *debug_stmts)
+{
bitmap blocks = BITMAP_ALLOC (NULL);
basic_block commondom;
unsigned int j;
useblock = gimple_phi_arg_edge (usestmt, idx)->src;
}
+ else if (is_gimple_debug (usestmt))
+ {
+ *debug_stmts = true;
+ continue;
+ }
else
{
useblock = gimple_bb (usestmt);
}
commondom = BASIC_BLOCK (bitmap_first_set_bit (blocks));
EXECUTE_IF_SET_IN_BITMAP (blocks, 0, j, bi)
- commondom = nearest_common_dominator (CDI_DOMINATORS, commondom,
+ commondom = nearest_common_dominator (CDI_DOMINATORS, commondom,
BASIC_BLOCK (j));
BITMAP_FREE (blocks);
return commondom;
}
-/* Given a statement (STMT) and the basic block it is currently in (FROMBB),
+/* Given EARLY_BB and LATE_BB, two blocks in a path through the dominator
+ tree, return the best basic block between them (inclusive) to place
+ statements.
+
+ We want the most control dependent block in the shallowest loop nest.
+
+ If the resulting block is in a shallower loop nest, then use it. Else
+ only use the resulting block if it has significantly lower execution
+ frequency than EARLY_BB to avoid gratutious statement movement. We
+ consider statements with VOPS more desirable to move.
+
+ This pass would obviously benefit from PDO as it utilizes block
+ frequencies. It would also benefit from recomputing frequencies
+ if profile data is not available since frequencies often get out
+ of sync with reality. */
+
+static basic_block
+select_best_block (basic_block early_bb,
+ basic_block late_bb,
+ gimple stmt)
+{
+ basic_block best_bb = late_bb;
+ basic_block temp_bb = late_bb;
+ int threshold;
+
+ while (temp_bb != early_bb)
+ {
+ /* If we've moved into a lower loop nest, then that becomes
+ our best block. */
+ if (temp_bb->loop_depth < best_bb->loop_depth)
+ best_bb = temp_bb;
+
+ /* Walk up the dominator tree, hopefully we'll find a shallower
+ loop nest. */
+ temp_bb = get_immediate_dominator (CDI_DOMINATORS, temp_bb);
+ }
+
+ /* If we found a shallower loop nest, then we always consider that
+ a win. This will always give us the most control dependent block
+ within that loop nest. */
+ if (best_bb->loop_depth < early_bb->loop_depth)
+ return best_bb;
+
+ /* Get the sinking threshold. If the statement to be moved has memory
+ operands, then increase the threshold by 7% as those are even more
+ profitable to avoid, clamping at 100%. */
+ threshold = PARAM_VALUE (PARAM_SINK_FREQUENCY_THRESHOLD);
+ if (gimple_vuse (stmt) || gimple_vdef (stmt))
+ {
+ threshold += 7;
+ if (threshold > 100)
+ threshold = 100;
+ }
+
+ /* If BEST_BB is at the same nesting level, then require it to have
+ significantly lower execution frequency to avoid gratutious movement. */
+ if (best_bb->loop_depth == early_bb->loop_depth
+ && best_bb->frequency < (early_bb->frequency * threshold / 100.0))
+ return best_bb;
+
+ /* No better block found, so return EARLY_BB, which happens to be the
+ statement's original block. */
+ return early_bb;
+}
+
+/* Given a statement (STMT) and the basic block it is currently in (FROMBB),
determine the location to sink the statement to, if any.
Returns true if there is such location; in that case, TOGSI points to the
statement before that STMT should be moved. */
gimple_stmt_iterator *togsi)
{
gimple use;
- tree def;
use_operand_p one_use = NULL_USE_OPERAND_P;
basic_block sinkbb;
use_operand_p use_p;
def_operand_p def_p;
ssa_op_iter iter;
imm_use_iterator imm_iter;
- enum tree_code code;
- FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
- {
- FOR_EACH_IMM_USE_FAST (one_use, imm_iter, def)
- {
- break;
- }
- if (one_use != NULL_USE_OPERAND_P)
- break;
- }
+ /* We only can sink assignments. */
+ if (!is_gimple_assign (stmt))
+ return false;
- /* Return if there are no immediate uses of this stmt. */
- if (one_use == NULL_USE_OPERAND_P)
+ /* We only can sink stmts with a single definition. */
+ def_p = single_ssa_def_operand (stmt, SSA_OP_ALL_DEFS);
+ if (def_p == NULL_DEF_OPERAND_P)
return false;
- if (gimple_code (stmt) != GIMPLE_ASSIGN)
+ /* Return if there are no immediate uses of this stmt. */
+ if (has_zero_uses (DEF_FROM_PTR (def_p)))
return false;
/* There are a few classes of things we can't or don't move, some because we
don't have code to handle it, some because it's not profitable and some
- because it's not legal.
-
+ because it's not legal.
+
We can't sink things that may be global stores, at least not without
calculating a lot more information, because we may cause it to no longer
be seen by an external routine that needs it depending on where it gets
- moved to.
-
+ moved to.
+
We don't want to sink loads from memory.
We can't sink statements that end basic blocks without splitting the
incoming edge for the sink location to place it there.
- We can't sink statements that have volatile operands.
+ We can't sink statements that have volatile operands.
We don't want to sink dead code, so anything with 0 immediate uses is not
sunk.
to use specific hard registers.
*/
- code = gimple_assign_rhs_code (stmt);
if (stmt_ends_bb_p (stmt)
|| gimple_has_side_effects (stmt)
- || code == EXC_PTR_EXPR
- || code == FILTER_EXPR
- || is_hidden_global_store (stmt)
|| gimple_has_volatile_ops (stmt)
- || !ZERO_SSA_OPERANDS (stmt, SSA_OP_VUSE)
+ || (gimple_vuse (stmt) && !gimple_vdef (stmt))
|| (cfun->has_local_explicit_reg_vars
&& TYPE_MODE (TREE_TYPE (gimple_assign_lhs (stmt))) == BLKmode))
return false;
-
- FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
- {
- tree def = DEF_FROM_PTR (def_p);
- if (is_global_var (SSA_NAME_VAR (def))
- || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def))
- return false;
- }
-
+
+ if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (DEF_FROM_PTR (def_p)))
+ return false;
+
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
{
tree use = USE_FROM_PTR (use_p);
if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (use))
return false;
}
-
+
+ use = NULL;
+
+ /* If stmt is a store the one and only use needs to be the VOP
+ merging PHI node. */
+ if (gimple_vdef (stmt))
+ {
+ FOR_EACH_IMM_USE_FAST (use_p, imm_iter, DEF_FROM_PTR (def_p))
+ {
+ gimple use_stmt = USE_STMT (use_p);
+
+ /* A killing definition is not a use. */
+ if (gimple_assign_single_p (use_stmt)
+ && gimple_vdef (use_stmt)
+ && operand_equal_p (gimple_assign_lhs (stmt),
+ gimple_assign_lhs (use_stmt), 0))
+ {
+ /* If use_stmt is or might be a nop assignment then USE_STMT
+ acts as a use as well as definition. */
+ if (stmt != use_stmt
+ && ref_maybe_used_by_stmt_p (use_stmt,
+ gimple_assign_lhs (stmt)))
+ return false;
+ continue;
+ }
+
+ if (gimple_code (use_stmt) != GIMPLE_PHI)
+ return false;
+
+ if (use
+ && use != use_stmt)
+ return false;
+
+ use = use_stmt;
+ }
+ if (!use)
+ return false;
+ }
/* If all the immediate uses are not in the same place, find the nearest
common dominator of all the immediate uses. For PHI nodes, we have to
find the nearest common dominator of all of the predecessor blocks, since
that is where insertion would have to take place. */
- if (!all_immediate_uses_same_place (stmt))
+ else if (!all_immediate_uses_same_place (stmt))
{
- basic_block commondom = nearest_common_dominator_of_uses (stmt);
-
+ bool debug_stmts = false;
+ basic_block commondom = nearest_common_dominator_of_uses (stmt,
+ &debug_stmts);
+
if (commondom == frombb)
return false;
/* Our common dominator has to be dominated by frombb in order to be a
trivially safe place to put this statement, since it has multiple
- uses. */
+ uses. */
if (!dominated_by_p (CDI_DOMINATORS, commondom, frombb))
return false;
-
- /* It doesn't make sense to move to a dominator that post-dominates
- frombb, because it means we've just moved it into a path that always
- executes if frombb executes, instead of reducing the number of
- executions . */
- if (dominated_by_p (CDI_POST_DOMINATORS, frombb, commondom))
- {
- if (dump_file && (dump_flags & TDF_DETAILS))
- fprintf (dump_file, "Not moving store, common dominator post-dominates from block.\n");
- return false;
- }
- if (commondom == frombb || commondom->loop_depth > frombb->loop_depth)
- return false;
- if (dump_file && (dump_flags & TDF_DETAILS))
- {
- fprintf (dump_file, "Common dominator of all uses is %d\n",
- commondom->index);
- }
+ commondom = select_best_block (frombb, commondom, stmt);
+
+ if (commondom == frombb)
+ return false;
+
*togsi = gsi_after_labels (commondom);
+
return true;
}
-
- use = USE_STMT (one_use);
- if (gimple_code (use) != GIMPLE_PHI)
+ else
{
- sinkbb = gimple_bb (use);
- if (sinkbb == frombb || sinkbb->loop_depth > frombb->loop_depth
- || sinkbb->loop_father != frombb->loop_father)
- return false;
+ FOR_EACH_IMM_USE_FAST (one_use, imm_iter, DEF_FROM_PTR (def_p))
+ {
+ if (is_gimple_debug (USE_STMT (one_use)))
+ continue;
+ break;
+ }
+ use = USE_STMT (one_use);
- *togsi = gsi_for_stmt (use);
- return true;
- }
+ if (gimple_code (use) != GIMPLE_PHI)
+ {
+ sinkbb = gimple_bb (use);
+ sinkbb = select_best_block (frombb, gimple_bb (use), stmt);
- /* Note that at this point, all uses must be in the same statement, so it
- doesn't matter which def op we choose, pick the first one. */
- FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
- break;
+ if (sinkbb == frombb)
+ return false;
- sinkbb = find_bb_for_arg (use, def);
- if (!sinkbb)
- return false;
+ *togsi = gsi_for_stmt (use);
- /* This will happen when you have
- a_3 = PHI <a_13, a_26>
-
- a_26 = VDEF <a_3>
+ return true;
+ }
+ }
- If the use is a phi, and is in the same bb as the def,
- we can't sink it. */
+ sinkbb = find_bb_for_arg (use, DEF_FROM_PTR (def_p));
- if (gimple_bb (use) == frombb)
+ /* This can happen if there are multiple uses in a PHI. */
+ if (!sinkbb)
return false;
- if (sinkbb == frombb || sinkbb->loop_depth > frombb->loop_depth
- || sinkbb->loop_father != frombb->loop_father)
+
+ sinkbb = select_best_block (frombb, sinkbb, stmt);
+ if (!sinkbb || sinkbb == frombb)
+ return false;
+
+ /* If the latch block is empty, don't make it non-empty by sinking
+ something into it. */
+ if (sinkbb == frombb->loop_father->latch
+ && empty_block_p (sinkbb))
return false;
*togsi = gsi_after_labels (sinkbb);
edge_iterator ei;
edge e;
bool last = true;
-
+
/* If this block doesn't dominate anything, there can't be any place to sink
the statements to. */
if (first_dom_son (CDI_DOMINATORS, bb) == NULL)
for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);)
{
- gimple stmt = gsi_stmt (gsi);
+ gimple stmt = gsi_stmt (gsi);
gimple_stmt_iterator togsi;
if (!statement_sink_location (stmt, bb, &togsi))
gsi_prev (&gsi);
last = false;
continue;
- }
+ }
if (dump_file)
{
fprintf (dump_file, "Sinking ");
fprintf (dump_file, " from bb %d to bb %d\n",
bb->index, (gsi_bb (togsi))->index);
}
-
+
+ /* Update virtual operands of statements in the path we
+ do not sink to. */
+ if (gimple_vdef (stmt))
+ {
+ imm_use_iterator iter;
+ use_operand_p use_p;
+ gimple vuse_stmt;
+
+ FOR_EACH_IMM_USE_STMT (vuse_stmt, iter, gimple_vdef (stmt))
+ if (gimple_code (vuse_stmt) != GIMPLE_PHI)
+ FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
+ SET_USE (use_p, gimple_vuse (stmt));
+ }
+
/* If this is the end of the basic block, we need to insert at the end
of the basic block. */
if (gsi_end_p (togsi))
last = false;
if (!gsi_end_p (gsi))
gsi_prev (&gsi);
-
+
}
earlyout:
for (son = first_dom_son (CDI_POST_DOMINATORS, bb);
{
sink_code_in_bb (son);
}
-}
+}
/* Perform code sinking.
This moves code down the flowgraph when we know it would be
executions of the statement.
IE given
-
+
a_1 = b + c;
if (<something>)
{
execute_sink_code (void)
{
loop_optimizer_init (LOOPS_NORMAL);
-
+ split_critical_edges ();
connect_infinite_loops_to_exit ();
memset (&sink_stats, 0, sizeof (sink_stats));
calculate_dominance_info (CDI_DOMINATORS);
calculate_dominance_info (CDI_POST_DOMINATORS);
- sink_code_in_bb (EXIT_BLOCK_PTR);
+ sink_code_in_bb (EXIT_BLOCK_PTR);
statistics_counter_event (cfun, "Sunk statements", sink_stats.sunk);
free_dominance_info (CDI_POST_DOMINATORS);
remove_fake_exit_edges ();
0, /* static_pass_number */
TV_TREE_SINK, /* tv_id */
PROP_no_crit_edges | PROP_cfg
- | PROP_ssa | PROP_alias, /* properties_required */
+ | PROP_ssa, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_update_ssa
- | TODO_dump_func
- | TODO_ggc_collect
- | TODO_verify_ssa /* todo_flags_finish */
+ TODO_update_ssa
+ | TODO_verify_ssa
+ | TODO_verify_flow
+ | TODO_ggc_collect /* todo_flags_finish */
}
};
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