/* SSA Jump Threading
- Copyright (C) 2005-2013 Free Software Foundation, Inc.
+ Copyright (C) 2005-2015 Free Software Foundation, Inc.
Contributed by Jeff Law <law@redhat.com>
This file is part of GCC.
#include "system.h"
#include "coretypes.h"
#include "tm.h"
+#include "alias.h"
+#include "symtab.h"
#include "tree.h"
+#include "fold-const.h"
#include "flags.h"
#include "tm_p.h"
+#include "predict.h"
+#include "hard-reg-set.h"
+#include "function.h"
+#include "dominance.h"
#include "basic-block.h"
#include "cfgloop.h"
-#include "function.h"
#include "timevar.h"
#include "dumpfile.h"
-#include "tree-ssa.h"
+#include "tree-ssa-alias.h"
+#include "internal-fn.h"
+#include "gimple-expr.h"
+#include "gimple.h"
+#include "gimple-iterator.h"
+#include "gimple-ssa.h"
+#include "tree-cfg.h"
+#include "tree-phinodes.h"
+#include "ssa-iterators.h"
+#include "stringpool.h"
+#include "tree-ssanames.h"
#include "tree-ssa-propagate.h"
#include "tree-ssa-threadupdate.h"
#include "langhooks.h"
#include "params.h"
+#include "tree-ssa-scopedtables.h"
+#include "tree-ssa-threadedge.h"
+#include "tree-ssa-loop.h"
+#include "builtins.h"
+#include "cfg.h"
+#include "cfganal.h"
/* To avoid code explosion due to jump threading, we limit the
number of statements we are going to copy. This variable
{
if (SSA_NAME_VERSION (name) >= ssa_name_values.length ())
ssa_name_values.safe_grow_cleared (SSA_NAME_VERSION (name) + 1);
+ if (value && TREE_OVERFLOW_P (value))
+ value = drop_tree_overflow (value);
ssa_name_values[SSA_NAME_VERSION (name)] = value;
}
{
gimple_stmt_iterator gsi;
+ /* Special case. We can get blocks that are forwarders, but are
+ not optimized away because they forward from outside a loop
+ to the loop header. We want to thread through them as we can
+ sometimes thread to the loop exit, which is obviously profitable.
+ the interesting case here is when the block has PHIs. */
+ if (gsi_end_p (gsi_start_nondebug_bb (bb))
+ && !gsi_end_p (gsi_start_phis (bb)))
+ return true;
+
/* If BB has a single successor or a single predecessor, then
there is no threading opportunity. */
if (single_succ_p (bb) || single_pred_p (bb))
return op;
}
-/* We record temporary equivalences created by PHI nodes or
- statements within the target block. Doing so allows us to
- identify more jump threading opportunities, even in blocks
- with side effects.
-
- We keep track of those temporary equivalences in a stack
- structure so that we can unwind them when we're done processing
- a particular edge. This routine handles unwinding the data
- structures. */
-
-static void
-remove_temporary_equivalences (vec<tree> *stack)
-{
- while (stack->length () > 0)
- {
- tree prev_value, dest;
-
- dest = stack->pop ();
-
- /* A NULL value indicates we should stop unwinding, otherwise
- pop off the next entry as they're recorded in pairs. */
- if (dest == NULL)
- break;
-
- prev_value = stack->pop ();
- set_ssa_name_value (dest, prev_value);
- }
-}
-
-/* Record a temporary equivalence, saving enough information so that
- we can restore the state of recorded equivalences when we're
- done processing the current edge. */
-
-static void
-record_temporary_equivalence (tree x, tree y, vec<tree> *stack)
-{
- tree prev_x = SSA_NAME_VALUE (x);
-
- if (TREE_CODE (y) == SSA_NAME)
- {
- tree tmp = SSA_NAME_VALUE (y);
- y = tmp ? tmp : y;
- }
-
- set_ssa_name_value (x, y);
- stack->reserve (2);
- stack->quick_push (prev_x);
- stack->quick_push (x);
-}
-
/* Record temporary equivalences created by PHIs at the target of the
edge E. Record unwind information for the equivalences onto STACK.
If a PHI which prevents threading is encountered, then return FALSE
- indicating we should not thread this edge, else return TRUE. */
+ indicating we should not thread this edge, else return TRUE.
+
+ If SRC_MAP/DST_MAP exist, then mark the source and destination SSA_NAMEs
+ of any equivalences recorded. We use this to make invalidation after
+ traversing back edges less painful. */
static bool
-record_temporary_equivalences_from_phis (edge e, vec<tree> *stack)
+record_temporary_equivalences_from_phis (edge e, const_and_copies *const_and_copies)
{
- gimple_stmt_iterator gsi;
+ gphi_iterator gsi;
/* Each PHI creates a temporary equivalence, record them.
These are context sensitive equivalences and will be removed
later. */
for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi))
{
- gimple phi = gsi_stmt (gsi);
+ gphi *phi = gsi.phi ();
tree src = PHI_ARG_DEF_FROM_EDGE (phi, e);
tree dst = gimple_phi_result (phi);
if (!virtual_operand_p (dst))
stmt_count++;
- record_temporary_equivalence (dst, src, stack);
+ const_and_copies->record_const_or_copy (dst, src);
}
return true;
}
static gimple
record_temporary_equivalences_from_stmts_at_dest (edge e,
- vec<tree> *stack,
+ const_and_copies *const_and_copies,
tree (*simplify) (gimple,
- gimple))
+ gimple),
+ bool backedge_seen)
{
gimple stmt = NULL;
gimple_stmt_iterator gsi;
/* If the statement has volatile operands, then we assume we
can not thread through this block. This is overly
conservative in some ways. */
- if (gimple_code (stmt) == GIMPLE_ASM && gimple_asm_volatile_p (stmt))
+ if (gimple_code (stmt) == GIMPLE_ASM
+ && gimple_asm_volatile_p (as_a <gasm *> (stmt)))
return NULL;
/* If duplicating this block is going to cause too much code
&& (gimple_code (stmt) != GIMPLE_CALL
|| gimple_call_lhs (stmt) == NULL_TREE
|| TREE_CODE (gimple_call_lhs (stmt)) != SSA_NAME))
- continue;
+ {
+ /* STMT might still have DEFS and we need to invalidate any known
+ equivalences for them.
+
+ Consider if STMT is a GIMPLE_ASM with one or more outputs that
+ feeds a conditional inside a loop. We might derive an equivalence
+ due to the conditional. */
+ tree op;
+ ssa_op_iter iter;
+
+ if (backedge_seen)
+ FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
+ const_and_copies->invalidate (op);
+
+ continue;
+ }
/* The result of __builtin_object_size depends on all the arguments
of a phi node. Temporarily using only one edge produces invalid
if (fndecl
&& (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_OBJECT_SIZE
|| DECL_FUNCTION_CODE (fndecl) == BUILT_IN_CONSTANT_P))
- continue;
+ {
+ if (backedge_seen)
+ {
+ tree lhs = gimple_get_lhs (stmt);
+ const_and_copies->invalidate (lhs);
+ }
+ continue;
+ }
}
/* At this point we have a statement which assigns an RHS to an
/* Try to fold/lookup the new expression. Inserting the
expression into the hash table is unlikely to help. */
if (is_gimple_call (stmt))
- cached_lhs = fold_call_stmt (stmt, false);
+ cached_lhs = fold_call_stmt (as_a <gcall *> (stmt), false);
else
cached_lhs = fold_assignment_stmt (stmt);
}
/* Record the context sensitive equivalence if we were able
- to simplify this statement. */
+ to simplify this statement.
+
+ If we have traversed a backedge at some point during threading,
+ then always enter something here. Either a real equivalence,
+ or a NULL_TREE equivalence which is effectively invalidation of
+ prior equivalences. */
if (cached_lhs
&& (TREE_CODE (cached_lhs) == SSA_NAME
|| is_gimple_min_invariant (cached_lhs)))
- record_temporary_equivalence (gimple_get_lhs (stmt), cached_lhs, stack);
+ const_and_copies->record_const_or_copy (gimple_get_lhs (stmt), cached_lhs);
+ else if (backedge_seen)
+ const_and_copies->invalidate (gimple_get_lhs (stmt));
}
return stmt;
}
+/* Once we have passed a backedge in the CFG when threading, we do not want to
+ utilize edge equivalences for simplification purpose. They are no longer
+ necessarily valid. We use this callback rather than the ones provided by
+ DOM/VRP to achieve that effect. */
+static tree
+dummy_simplify (gimple stmt1 ATTRIBUTE_UNUSED, gimple stmt2 ATTRIBUTE_UNUSED)
+{
+ return NULL_TREE;
+}
+
/* Simplify the control statement at the end of the block E->dest.
To avoid allocating memory unnecessarily, a scratch GIMPLE_COND
static tree
simplify_control_stmt_condition (edge e,
gimple stmt,
- gimple dummy_cond,
+ gcond *dummy_cond,
tree (*simplify) (gimple, gimple),
bool handle_dominating_asserts)
{
/* Get the current value of both operands. */
if (TREE_CODE (op0) == SSA_NAME)
{
- tree tmp = SSA_NAME_VALUE (op0);
- if (tmp)
- op0 = tmp;
+ for (int i = 0; i < 2; i++)
+ {
+ if (TREE_CODE (op0) == SSA_NAME
+ && SSA_NAME_VALUE (op0))
+ op0 = SSA_NAME_VALUE (op0);
+ else
+ break;
+ }
}
if (TREE_CODE (op1) == SSA_NAME)
{
- tree tmp = SSA_NAME_VALUE (op1);
- if (tmp)
- op1 = tmp;
+ for (int i = 0; i < 2; i++)
+ {
+ if (TREE_CODE (op1) == SSA_NAME
+ && SSA_NAME_VALUE (op1))
+ op1 = SSA_NAME_VALUE (op1);
+ else
+ break;
+ }
}
if (handle_dominating_asserts)
miss threading opportunities. */
if (tree_swap_operands_p (op0, op1, false))
{
- tree tmp;
cond_code = swap_tree_comparison (cond_code);
- tmp = op0;
- op0 = op1;
- op1 = tmp;
+ std::swap (op0, op1);
}
/* Stuff the operator and operands into our dummy conditional
}
if (code == GIMPLE_SWITCH)
- cond = gimple_switch_index (stmt);
+ cond = gimple_switch_index (as_a <gswitch *> (stmt));
else if (code == GIMPLE_GOTO)
cond = gimple_goto_dest (stmt);
else
rather than use a relational operator. These are simpler to handle. */
if (TREE_CODE (cond) == SSA_NAME)
{
+ tree original_lhs = cond;
cached_lhs = cond;
/* Get the variable's current value from the equivalence chains.
It is possible to get loops in the SSA_NAME_VALUE chains
(consider threading the backedge of a loop where we have
a loop invariant SSA_NAME used in the condition. */
- if (cached_lhs
- && TREE_CODE (cached_lhs) == SSA_NAME
- && SSA_NAME_VALUE (cached_lhs))
- cached_lhs = SSA_NAME_VALUE (cached_lhs);
+ if (cached_lhs)
+ {
+ for (int i = 0; i < 2; i++)
+ {
+ if (TREE_CODE (cached_lhs) == SSA_NAME
+ && SSA_NAME_VALUE (cached_lhs))
+ cached_lhs = SSA_NAME_VALUE (cached_lhs);
+ else
+ break;
+ }
+ }
/* If we're dominated by a suitable ASSERT_EXPR, then
update CACHED_LHS appropriately. */
pass specific callback to try and simplify it further. */
if (cached_lhs && ! is_gimple_min_invariant (cached_lhs))
cached_lhs = (*simplify) (stmt, stmt);
+
+ /* We couldn't find an invariant. But, callers of this
+ function may be able to do something useful with the
+ unmodified destination. */
+ if (!cached_lhs)
+ cached_lhs = original_lhs;
}
else
cached_lhs = NULL;
return cached_lhs;
}
-/* Return TRUE if the statement at the end of e->dest depends on
- the output of any statement in BB. Otherwise return FALSE.
-
- This is used when we are threading a backedge and need to ensure
- that temporary equivalences from BB do not affect the condition
- in e->dest. */
-
-static bool
-cond_arg_set_in_bb (edge e, basic_block bb)
-{
- ssa_op_iter iter;
- use_operand_p use_p;
- gimple last = last_stmt (e->dest);
-
- /* E->dest does not have to end with a control transferring
- instruction. This can occur when we try to extend a jump
- threading opportunity deeper into the CFG. In that case
- it is safe for this check to return false. */
- if (!last)
- return false;
-
- if (gimple_code (last) != GIMPLE_COND
- && gimple_code (last) != GIMPLE_GOTO
- && gimple_code (last) != GIMPLE_SWITCH)
- return false;
-
- FOR_EACH_SSA_USE_OPERAND (use_p, last, iter, SSA_OP_USE | SSA_OP_VUSE)
- {
- tree use = USE_FROM_PTR (use_p);
-
- if (TREE_CODE (use) == SSA_NAME
- && gimple_code (SSA_NAME_DEF_STMT (use)) != GIMPLE_PHI
- && gimple_bb (SSA_NAME_DEF_STMT (use)) == bb)
- return true;
- }
- return false;
-}
-
/* Copy debug stmts from DEST's chain of single predecessors up to
SRC, so that we don't lose the bindings as PHI nodes are introduced
when DEST gains new predecessors. */
i++;
}
- vec<tree, va_stack> fewvars = vNULL;
- pointer_set_t *vars = NULL;
+ auto_vec<tree, alloc_count> fewvars;
+ hash_set<tree> *vars = NULL;
/* If we're already starting with 3/4 of alloc_count, go for a
- pointer_set, otherwise start with an unordered stack-allocated
+ hash_set, otherwise start with an unordered stack-allocated
VEC. */
if (i * 4 > alloc_count * 3)
- vars = pointer_set_create ();
- else if (alloc_count)
- vec_stack_alloc (tree, fewvars, alloc_count);
+ vars = new hash_set<tree>;
/* Now go through the initial debug stmts in DEST again, this time
actually inserting in VARS or FEWVARS. Don't bother checking for
gcc_unreachable ();
if (vars)
- pointer_set_insert (vars, var);
+ vars->add (var);
else
fewvars.quick_push (var);
}
or somesuch. Adding `&& bb == src' to the condition
below will preserve all potentially relevant debug
notes. */
- if (vars && pointer_set_insert (vars, var))
+ if (vars && vars->add (var))
continue;
else if (!vars)
{
fewvars.quick_push (var);
else
{
- vars = pointer_set_create ();
+ vars = new hash_set<tree>;
for (i = 0; i < alloc_count; i++)
- pointer_set_insert (vars, fewvars[i]);
+ vars->add (fewvars[i]);
fewvars.release ();
- pointer_set_insert (vars, var);
+ vars->add (var);
}
}
while (bb != src && single_pred_p (bb));
if (vars)
- pointer_set_destroy (vars);
+ delete vars;
else if (fewvars.exists ())
fewvars.release ();
}
try and simplify the condition at the end of TAKEN_EDGE->dest. */
static bool
thread_around_empty_blocks (edge taken_edge,
- gimple dummy_cond,
+ gcond *dummy_cond,
bool handle_dominating_asserts,
tree (*simplify) (gimple, gimple),
bitmap visited,
- vec<jump_thread_edge *> *path)
+ vec<jump_thread_edge *> *path,
+ bool *backedge_seen_p)
{
basic_block bb = taken_edge->dest;
gimple_stmt_iterator gsi;
gsi = gsi_start_nondebug_bb (bb);
/* If the block has no statements, but does have a single successor, then
- it's just a forwarding block and we can thread through it trivially.
+ it's just a forwarding block and we can thread through it trivially.
However, note that just threading through empty blocks with single
successors is not inherently profitable. For the jump thread to
By taking the return value from the recursive call, we get the
desired effect of returning TRUE when we found a profitable jump
- threading opportunity and FALSE otherwise.
+ threading opportunity and FALSE otherwise.
This is particularly important when this routine is called after
processing a joiner block. Returning TRUE too aggressively in
if (single_succ_p (bb))
{
taken_edge = single_succ_edge (bb);
- if ((taken_edge->flags & EDGE_DFS_BACK) == 0
- && !bitmap_bit_p (visited, taken_edge->dest->index))
+ if (!bitmap_bit_p (visited, taken_edge->dest->index))
{
jump_thread_edge *x
= new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK);
path->safe_push (x);
bitmap_set_bit (visited, taken_edge->dest->index);
+ *backedge_seen_p |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
+ if (*backedge_seen_p)
+ simplify = dummy_simplify;
return thread_around_empty_blocks (taken_edge,
dummy_cond,
handle_dominating_asserts,
simplify,
visited,
- path);
+ path,
+ backedge_seen_p);
}
}
&& gimple_code (stmt) != GIMPLE_SWITCH)
return false;
+ /* If we have traversed a backedge, then we do not want to look
+ at certain expressions in the table that can not be relied upon.
+ Luckily the only code that looked at those expressions is the
+ SIMPLIFY callback, which we replace if we can no longer use it. */
+ if (*backedge_seen_p)
+ simplify = dummy_simplify;
+
/* Extract and simplify the condition. */
cond = simplify_control_stmt_condition (taken_edge, stmt, dummy_cond,
simplify, handle_dominating_asserts);
jump_thread_edge *x
= new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK);
path->safe_push (x);
+ *backedge_seen_p |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
+ if (*backedge_seen_p)
+ simplify = dummy_simplify;
thread_around_empty_blocks (taken_edge,
dummy_cond,
handle_dominating_asserts,
simplify,
visited,
- path);
+ path,
+ backedge_seen_p);
+ return true;
+ }
+
+ return false;
+}
+
+/* Return true if the CFG contains at least one path from START_BB to END_BB.
+ When a path is found, record in PATH the blocks from END_BB to START_BB.
+ VISITED_BBS is used to make sure we don't fall into an infinite loop. Bound
+ the recursion to basic blocks belonging to LOOP. */
+
+static bool
+fsm_find_thread_path (basic_block start_bb, basic_block end_bb,
+ vec<basic_block, va_gc> *&path,
+ hash_set<basic_block> *visited_bbs, loop_p loop)
+{
+ if (loop != start_bb->loop_father)
+ return false;
+
+ if (start_bb == end_bb)
+ {
+ vec_safe_push (path, start_bb);
return true;
}
-
+
+ if (!visited_bbs->add (start_bb))
+ {
+ edge e;
+ edge_iterator ei;
+ FOR_EACH_EDGE (e, ei, start_bb->succs)
+ if (fsm_find_thread_path (e->dest, end_bb, path, visited_bbs, loop))
+ {
+ vec_safe_push (path, start_bb);
+ return true;
+ }
+ }
+
return false;
}
-
+
+static int max_threaded_paths;
+
+/* We trace the value of the variable EXPR back through any phi nodes looking
+ for places where it gets a constant value and save the path. Stop after
+ having recorded MAX_PATHS jump threading paths. */
+
+static void
+fsm_find_control_statement_thread_paths (tree expr,
+ hash_set<basic_block> *visited_bbs,
+ vec<basic_block, va_gc> *&path,
+ bool seen_loop_phi)
+{
+ tree var = SSA_NAME_VAR (expr);
+ gimple def_stmt = SSA_NAME_DEF_STMT (expr);
+ basic_block var_bb = gimple_bb (def_stmt);
+
+ if (var == NULL || var_bb == NULL)
+ return;
+
+ /* For the moment we assume that an SSA chain only contains phi nodes, and
+ eventually one of the phi arguments will be an integer constant. In the
+ future, this could be extended to also handle simple assignments of
+ arithmetic operations. */
+ if (gimple_code (def_stmt) != GIMPLE_PHI)
+ return;
+
+ /* Avoid infinite recursion. */
+ if (visited_bbs->add (var_bb))
+ return;
+
+ gphi *phi = as_a <gphi *> (def_stmt);
+ int next_path_length = 0;
+ basic_block last_bb_in_path = path->last ();
+
+ if (loop_containing_stmt (phi)->header == gimple_bb (phi))
+ {
+ /* Do not walk through more than one loop PHI node. */
+ if (seen_loop_phi)
+ return;
+ seen_loop_phi = true;
+ }
+
+ /* Following the chain of SSA_NAME definitions, we jumped from a definition in
+ LAST_BB_IN_PATH to a definition in VAR_BB. When these basic blocks are
+ different, append to PATH the blocks from LAST_BB_IN_PATH to VAR_BB. */
+ if (var_bb != last_bb_in_path)
+ {
+ edge e;
+ int e_count = 0;
+ edge_iterator ei;
+ vec<basic_block, va_gc> *next_path;
+ vec_alloc (next_path, n_basic_blocks_for_fn (cfun));
+
+ FOR_EACH_EDGE (e, ei, last_bb_in_path->preds)
+ {
+ hash_set<basic_block> *visited_bbs = new hash_set<basic_block>;
+
+ if (fsm_find_thread_path (var_bb, e->src, next_path, visited_bbs,
+ e->src->loop_father))
+ ++e_count;
+
+ delete visited_bbs;
+
+ /* If there is more than one path, stop. */
+ if (e_count > 1)
+ {
+ vec_free (next_path);
+ return;
+ }
+ }
+
+ /* Stop if we have not found a path: this could occur when the recursion
+ is stopped by one of the bounds. */
+ if (e_count == 0)
+ {
+ vec_free (next_path);
+ return;
+ }
+
+ /* Append all the nodes from NEXT_PATH to PATH. */
+ vec_safe_splice (path, next_path);
+ next_path_length = next_path->length ();
+ vec_free (next_path);
+ }
+
+ gcc_assert (path->last () == var_bb);
+
+ /* Iterate over the arguments of PHI. */
+ unsigned int i;
+ for (i = 0; i < gimple_phi_num_args (phi); i++)
+ {
+ tree arg = gimple_phi_arg_def (phi, i);
+ basic_block bbi = gimple_phi_arg_edge (phi, i)->src;
+
+ /* Skip edges pointing outside the current loop. */
+ if (!arg || var_bb->loop_father != bbi->loop_father)
+ continue;
+
+ if (TREE_CODE (arg) == SSA_NAME)
+ {
+ vec_safe_push (path, bbi);
+ /* Recursively follow SSA_NAMEs looking for a constant definition. */
+ fsm_find_control_statement_thread_paths (arg, visited_bbs, path,
+ seen_loop_phi);
+
+ path->pop ();
+ continue;
+ }
+
+ if (TREE_CODE (arg) != INTEGER_CST)
+ continue;
+
+ int path_length = path->length ();
+ /* A path with less than 2 basic blocks should not be jump-threaded. */
+ if (path_length < 2)
+ continue;
+
+ if (path_length > PARAM_VALUE (PARAM_MAX_FSM_THREAD_LENGTH))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "FSM jump-thread path not considered: "
+ "the number of basic blocks on the path "
+ "exceeds PARAM_MAX_FSM_THREAD_LENGTH.\n");
+ continue;
+ }
+
+ if (max_threaded_paths <= 0)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "FSM jump-thread path not considered: "
+ "the number of previously recorded FSM paths to thread "
+ "exceeds PARAM_MAX_FSM_THREAD_PATHS.\n");
+ continue;
+ }
+
+ /* Add BBI to the path. */
+ vec_safe_push (path, bbi);
+ ++path_length;
+
+ int n_insns = 0;
+ gimple_stmt_iterator gsi;
+ int j;
+ loop_p loop = (*path)[0]->loop_father;
+ bool path_crosses_loops = false;
+
+ /* Count the number of instructions on the path: as these instructions
+ will have to be duplicated, we will not record the path if there are
+ too many instructions on the path. Also check that all the blocks in
+ the path belong to a single loop. */
+ for (j = 1; j < path_length - 1; j++)
+ {
+ basic_block bb = (*path)[j];
+
+ if (bb->loop_father != loop)
+ {
+ path_crosses_loops = true;
+ break;
+ }
+
+ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ gimple stmt = gsi_stmt (gsi);
+ /* Do not count empty statements and labels. */
+ if (gimple_code (stmt) != GIMPLE_NOP
+ && gimple_code (stmt) != GIMPLE_LABEL
+ && !is_gimple_debug (stmt))
+ ++n_insns;
+ }
+ }
+
+ if (path_crosses_loops)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "FSM jump-thread path not considered: "
+ "the path crosses loops.\n");
+ path->pop ();
+ continue;
+ }
+
+ if (n_insns >= PARAM_VALUE (PARAM_MAX_FSM_THREAD_PATH_INSNS))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "FSM jump-thread path not considered: "
+ "the number of instructions on the path "
+ "exceeds PARAM_MAX_FSM_THREAD_PATH_INSNS.\n");
+ path->pop ();
+ continue;
+ }
+
+ vec<jump_thread_edge *> *jump_thread_path
+ = new vec<jump_thread_edge *> ();
+
+ /* Record the edges between the blocks in PATH. */
+ for (j = 0; j < path_length - 1; j++)
+ {
+ edge e = find_edge ((*path)[path_length - j - 1],
+ (*path)[path_length - j - 2]);
+ gcc_assert (e);
+ jump_thread_edge *x = new jump_thread_edge (e, EDGE_FSM_THREAD);
+ jump_thread_path->safe_push (x);
+ }
+
+ /* Add the edge taken when the control variable has value ARG. */
+ edge taken_edge = find_taken_edge ((*path)[0], arg);
+ jump_thread_edge *x
+ = new jump_thread_edge (taken_edge, EDGE_NO_COPY_SRC_BLOCK);
+ jump_thread_path->safe_push (x);
+
+ register_jump_thread (jump_thread_path);
+ --max_threaded_paths;
+
+ /* Remove BBI from the path. */
+ path->pop ();
+ }
+
+ /* Remove all the nodes that we added from NEXT_PATH. */
+ if (next_path_length)
+ vec_safe_truncate (path, (path->length () - next_path_length));
+}
+
/* We are exiting E->src, see if E->dest ends with a conditional
jump which has a known value when reached via E.
+ E->dest can have arbitrary side effects which, if threading is
+ successful, will be maintained.
+
Special care is necessary if E is a back edge in the CFG as we
may have already recorded equivalences for E->dest into our
various tables, including the result of the conditional at
limited in that case to avoid short-circuiting the loop
incorrectly.
- Note it is quite common for the first block inside a loop to
- end with a conditional which is either always true or always
- false when reached via the loop backedge. Thus we do not want
- to blindly disable threading across a loop backedge.
-
DUMMY_COND is a shared cond_expr used by condition simplification as scratch,
to avoid allocating memory.
STACK is used to undo temporary equivalences created during the walk of
E->dest.
- SIMPLIFY is a pass-specific function used to simplify statements. */
-
-void
-thread_across_edge (gimple dummy_cond,
- edge e,
- bool handle_dominating_asserts,
- vec<tree> *stack,
- tree (*simplify) (gimple, gimple))
+ SIMPLIFY is a pass-specific function used to simplify statements.
+
+ Our caller is responsible for restoring the state of the expression
+ and const_and_copies stacks.
+
+ Positive return value is success. Zero return value is failure, but
+ the block can still be duplicated as a joiner in a jump thread path,
+ negative indicates the block should not be duplicated and thus is not
+ suitable for a joiner in a jump threading path. */
+
+static int
+thread_through_normal_block (edge e,
+ gcond *dummy_cond,
+ bool handle_dominating_asserts,
+ const_and_copies *const_and_copies,
+ tree (*simplify) (gimple, gimple),
+ vec<jump_thread_edge *> *path,
+ bitmap visited,
+ bool *backedge_seen_p)
{
- gimple stmt;
-
- /* If E is a backedge, then we want to verify that the COND_EXPR,
- SWITCH_EXPR or GOTO_EXPR at the end of e->dest is not affected
- by any statements in e->dest. If it is affected, then it is not
- safe to thread this edge. */
- if (e->flags & EDGE_DFS_BACK)
- {
- if (cond_arg_set_in_bb (e, e->dest))
- goto fail;
- }
-
- stmt_count = 0;
-
- /* PHIs create temporary equivalences. */
- if (!record_temporary_equivalences_from_phis (e, stack))
- goto fail;
+ /* If we have traversed a backedge, then we do not want to look
+ at certain expressions in the table that can not be relied upon.
+ Luckily the only code that looked at those expressions is the
+ SIMPLIFY callback, which we replace if we can no longer use it. */
+ if (*backedge_seen_p)
+ simplify = dummy_simplify;
+
+ /* PHIs create temporary equivalences.
+ Note that if we found a PHI that made the block non-threadable, then
+ we need to bubble that up to our caller in the same manner we do
+ when we prematurely stop processing statements below. */
+ if (!record_temporary_equivalences_from_phis (e, const_and_copies))
+ return -1;
/* Now walk each statement recording any context sensitive
temporary equivalences we can detect. */
- stmt = record_temporary_equivalences_from_stmts_at_dest (e, stack, simplify);
+ gimple stmt
+ = record_temporary_equivalences_from_stmts_at_dest (e, const_and_copies, simplify,
+ *backedge_seen_p);
+
+ /* There's two reasons STMT might be null, and distinguishing
+ between them is important.
+
+ First the block may not have had any statements. For example, it
+ might have some PHIs and unconditionally transfer control elsewhere.
+ Such blocks are suitable for jump threading, particularly as a
+ joiner block.
+
+ The second reason would be if we did not process all the statements
+ in the block (because there were too many to make duplicating the
+ block profitable. If we did not look at all the statements, then
+ we may not have invalidated everything needing invalidation. Thus
+ we must signal to our caller that this block is not suitable for
+ use as a joiner in a threading path. */
if (!stmt)
- goto fail;
-
+ {
+ /* First case. The statement simply doesn't have any instructions, but
+ does have PHIs. */
+ if (gsi_end_p (gsi_start_nondebug_bb (e->dest))
+ && !gsi_end_p (gsi_start_phis (e->dest)))
+ return 0;
+
+ /* Second case. */
+ return -1;
+ }
+
/* If we stopped at a COND_EXPR or SWITCH_EXPR, see if we know which arm
will be taken. */
if (gimple_code (stmt) == GIMPLE_COND
cond = simplify_control_stmt_condition (e, stmt, dummy_cond, simplify,
handle_dominating_asserts);
- if (cond && is_gimple_min_invariant (cond))
+ if (!cond)
+ return 0;
+
+ if (is_gimple_min_invariant (cond))
{
edge taken_edge = find_taken_edge (e->dest, cond);
basic_block dest = (taken_edge ? taken_edge->dest : NULL);
- bitmap visited;
/* DEST could be NULL for a computed jump to an absolute
address. */
- if (dest == NULL || dest == e->dest)
- goto fail;
-
- vec<jump_thread_edge *> *path = new vec<jump_thread_edge *> ();
- jump_thread_edge *x
- = new jump_thread_edge (e, EDGE_START_JUMP_THREAD);
- path->safe_push (x);
+ if (dest == NULL
+ || dest == e->dest
+ || bitmap_bit_p (visited, dest->index))
+ return 0;
+
+ /* Only push the EDGE_START_JUMP_THREAD marker if this is
+ first edge on the path. */
+ if (path->length () == 0)
+ {
+ jump_thread_edge *x
+ = new jump_thread_edge (e, EDGE_START_JUMP_THREAD);
+ path->safe_push (x);
+ *backedge_seen_p |= ((e->flags & EDGE_DFS_BACK) != 0);
+ }
- x = new jump_thread_edge (taken_edge, EDGE_COPY_SRC_BLOCK);
+ jump_thread_edge *x
+ = new jump_thread_edge (taken_edge, EDGE_COPY_SRC_BLOCK);
path->safe_push (x);
+ *backedge_seen_p |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
+ if (*backedge_seen_p)
+ simplify = dummy_simplify;
/* See if we can thread through DEST as well, this helps capture
secondary effects of threading without having to re-run DOM or
- VRP. */
- if ((e->flags & EDGE_DFS_BACK) == 0
- || ! cond_arg_set_in_bb (taken_edge, e->dest))
- {
- /* We don't want to thread back to a block we have already
- visited. This may be overly conservative. */
- visited = BITMAP_ALLOC (NULL);
- bitmap_set_bit (visited, dest->index);
- bitmap_set_bit (visited, e->dest->index);
- thread_around_empty_blocks (taken_edge,
- dummy_cond,
- handle_dominating_asserts,
- simplify,
- visited,
- path);
- BITMAP_FREE (visited);
- }
+ VRP.
+
+ We don't want to thread back to a block we have already
+ visited. This may be overly conservative. */
+ bitmap_set_bit (visited, dest->index);
+ bitmap_set_bit (visited, e->dest->index);
+ thread_around_empty_blocks (taken_edge,
+ dummy_cond,
+ handle_dominating_asserts,
+ simplify,
+ visited,
+ path,
+ backedge_seen_p);
+ return 1;
+ }
+
+ if (!flag_expensive_optimizations
+ || optimize_function_for_size_p (cfun)
+ || TREE_CODE (cond) != SSA_NAME
+ || e->dest->loop_father != e->src->loop_father
+ || loop_depth (e->dest->loop_father) == 0)
+ return 0;
+
+ /* When COND cannot be simplified, try to find paths from a control
+ statement back through the PHI nodes which would affect that control
+ statement. */
+ vec<basic_block, va_gc> *bb_path;
+ vec_alloc (bb_path, n_basic_blocks_for_fn (cfun));
+ vec_safe_push (bb_path, e->dest);
+ hash_set<basic_block> *visited_bbs = new hash_set<basic_block>;
+
+ max_threaded_paths = PARAM_VALUE (PARAM_MAX_FSM_THREAD_PATHS);
+ fsm_find_control_statement_thread_paths (cond, visited_bbs, bb_path,
+ false);
+
+ delete visited_bbs;
+ vec_free (bb_path);
+ }
+ return 0;
+}
+
+/* We are exiting E->src, see if E->dest ends with a conditional
+ jump which has a known value when reached via E.
+
+ Special care is necessary if E is a back edge in the CFG as we
+ may have already recorded equivalences for E->dest into our
+ various tables, including the result of the conditional at
+ the end of E->dest. Threading opportunities are severely
+ limited in that case to avoid short-circuiting the loop
+ incorrectly.
+
+ Note it is quite common for the first block inside a loop to
+ end with a conditional which is either always true or always
+ false when reached via the loop backedge. Thus we do not want
+ to blindly disable threading across a loop backedge.
+
+ DUMMY_COND is a shared cond_expr used by condition simplification as scratch,
+ to avoid allocating memory.
- remove_temporary_equivalences (stack);
- propagate_threaded_block_debug_into (path->last ()->e->dest,
- e->dest);
- register_jump_thread (path);
+ HANDLE_DOMINATING_ASSERTS is true if we should try to replace operands of
+ the simplified condition with left-hand sides of ASSERT_EXPRs they are
+ used in.
+
+ STACK is used to undo temporary equivalences created during the walk of
+ E->dest.
+
+ SIMPLIFY is a pass-specific function used to simplify statements. */
+
+void
+thread_across_edge (gcond *dummy_cond,
+ edge e,
+ bool handle_dominating_asserts,
+ const_and_copies *const_and_copies,
+ tree (*simplify) (gimple, gimple))
+{
+ bitmap visited = BITMAP_ALLOC (NULL);
+ bool backedge_seen;
+
+ stmt_count = 0;
+
+ vec<jump_thread_edge *> *path = new vec<jump_thread_edge *> ();
+ bitmap_clear (visited);
+ bitmap_set_bit (visited, e->src->index);
+ bitmap_set_bit (visited, e->dest->index);
+ backedge_seen = ((e->flags & EDGE_DFS_BACK) != 0);
+ if (backedge_seen)
+ simplify = dummy_simplify;
+
+ int threaded = thread_through_normal_block (e, dummy_cond,
+ handle_dominating_asserts,
+ const_and_copies, simplify, path,
+ visited, &backedge_seen);
+ if (threaded > 0)
+ {
+ propagate_threaded_block_debug_into (path->last ()->e->dest,
+ e->dest);
+ const_and_copies->pop_to_marker ();
+ BITMAP_FREE (visited);
+ register_jump_thread (path);
+ return;
+ }
+ else
+ {
+ /* Negative and zero return values indicate no threading was possible,
+ thus there should be no edges on the thread path and no need to walk
+ through the vector entries. */
+ gcc_assert (path->length () == 0);
+ path->release ();
+ delete path;
+
+ /* A negative status indicates the target block was deemed too big to
+ duplicate. Just quit now rather than trying to use the block as
+ a joiner in a jump threading path.
+
+ This prevents unnecessary code growth, but more importantly if we
+ do not look at all the statements in the block, then we may have
+ missed some invalidations if we had traversed a backedge! */
+ if (threaded < 0)
+ {
+ BITMAP_FREE (visited);
+ const_and_copies->pop_to_marker ();
return;
}
}
edge taken_edge;
edge_iterator ei;
bool found;
- bitmap visited = BITMAP_ALLOC (NULL);
+
+ /* If E->dest has abnormal outgoing edges, then there's no guarantee
+ we can safely redirect any of the edges. Just punt those cases. */
+ FOR_EACH_EDGE (taken_edge, ei, e->dest->succs)
+ if (taken_edge->flags & EDGE_ABNORMAL)
+ {
+ const_and_copies->pop_to_marker ();
+ BITMAP_FREE (visited);
+ return;
+ }
/* Look at each successor of E->dest to see if we can thread through it. */
FOR_EACH_EDGE (taken_edge, ei, e->dest->succs)
{
+ /* Push a fresh marker so we can unwind the equivalences created
+ for each of E->dest's successors. */
+ const_and_copies->push_marker ();
+
/* Avoid threading to any block we have already visited. */
bitmap_clear (visited);
- bitmap_set_bit (visited, taken_edge->dest->index);
+ bitmap_set_bit (visited, e->src->index);
bitmap_set_bit (visited, e->dest->index);
+ bitmap_set_bit (visited, taken_edge->dest->index);
vec<jump_thread_edge *> *path = new vec<jump_thread_edge *> ();
/* Record whether or not we were able to thread through a successor
x = new jump_thread_edge (taken_edge, EDGE_COPY_SRC_JOINER_BLOCK);
path->safe_push (x);
found = false;
- if ((e->flags & EDGE_DFS_BACK) == 0
- || ! cond_arg_set_in_bb (path->last ()->e, e->dest))
- found = thread_around_empty_blocks (taken_edge,
- dummy_cond,
- handle_dominating_asserts,
- simplify,
- visited,
- path);
+ backedge_seen = ((e->flags & EDGE_DFS_BACK) != 0);
+ backedge_seen |= ((taken_edge->flags & EDGE_DFS_BACK) != 0);
+ if (backedge_seen)
+ simplify = dummy_simplify;
+ found = thread_around_empty_blocks (taken_edge,
+ dummy_cond,
+ handle_dominating_asserts,
+ simplify,
+ visited,
+ path,
+ &backedge_seen);
+
+ if (backedge_seen)
+ simplify = dummy_simplify;
+
+ if (!found)
+ found = thread_through_normal_block (path->last ()->e, dummy_cond,
+ handle_dominating_asserts,
+ const_and_copies, simplify, path, visited,
+ &backedge_seen) > 0;
/* If we were able to thread through a successor of E->dest, then
record the jump threading opportunity. */
}
else
{
- for (unsigned int i = 0; i < path->length (); i++)
- delete (*path)[i];
- path->release();
+ delete_jump_thread_path (path);
}
+
+ /* And unwind the equivalence table. */
+ const_and_copies->pop_to_marker ();
}
BITMAP_FREE (visited);
}
- fail:
- remove_temporary_equivalences (stack);
+ const_and_copies->pop_to_marker ();
}