+/* Function splitting pass
+ Copyright (C) 2010
+ Free Software Foundation, Inc.
+ Contributed by Jan Hubicka <jh@suse.cz>
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
+
+/* The purpose of this pass is to split function bodies to improve
+ inlining. I.e. for function of the form:
+
+ func (...)
+ {
+ if (cheap_test)
+ something_small
+ else
+ something_big
+ }
+
+ Produce:
+
+ func.part (...)
+ {
+ something_big
+ }
+
+ func (...)
+ {
+ if (cheap_test)
+ something_small
+ else
+ func.part (...);
+ }
+
+ When func becomes inlinable and when cheap_test is often true, inlining func,
+ but not fund.part leads to performance imrovement similar as inlining
+ original func while the code size growth is smaller.
+
+ The pass is organized in three stages:
+ 1) Collect local info about basic block into BB_INFO structure and
+ compute function body estimated size and time.
+ 2) Via DFS walk find all possible basic blocks where we can split
+ and chose best one.
+ 3) If split point is found, split at the specified BB by creating a clone
+ and updating function to call it.
+
+ The decisions what functions to split are in execute_split_functions
+ and consider_split.
+
+ There are several possible future improvements for this pass including:
+
+ 1) Splitting to break up large functions
+ 2) Splitting to reduce stack frame usage
+ 3) Allow split part of function to use values computed in the header part.
+ The values needs to be passed to split function, perhaps via same
+ interface as for nested functions or as argument.
+ 4) Support for simple rematerialization. I.e. when split part use
+ value computed in header from function parameter in very cheap way, we
+ can just recompute it.
+ 5) Support splitting of nested functions.
+ 6) Support non-SSA arguments.
+ 7) There is nothing preventing us from producing multiple parts of single function
+ when needed or splitting also the parts. */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree.h"
+#include "target.h"
+#include "cgraph.h"
+#include "ipa-prop.h"
+#include "tree-flow.h"
+#include "tree-pass.h"
+#include "flags.h"
+#include "timevar.h"
+#include "diagnostic.h"
+#include "tree-dump.h"
+#include "tree-inline.h"
+#include "fibheap.h"
+#include "params.h"
+#include "gimple-pretty-print.h"
+
+/* Per basic block info. */
+
+typedef struct
+{
+ unsigned int size;
+ unsigned int time;
+} bb_info;
+DEF_VEC_O(bb_info);
+DEF_VEC_ALLOC_O(bb_info,heap);
+
+static VEC(bb_info, heap) *bb_info_vec;
+
+/* Description of split point. */
+
+struct split_point
+{
+ /* Size of the partitions. */
+ unsigned int header_time, header_size, split_time, split_size;
+
+ /* SSA names that need to be passed into spit funciton. */
+ bitmap ssa_names_to_pass;
+
+ /* Basic block where we split (that will become entry point of new function. */
+ basic_block entry_bb;
+
+ /* Basic blocks we are splitting away. */
+ bitmap split_bbs;
+};
+
+/* Best split point found. */
+
+struct split_point best_split_point;
+
+/* Callback for walk_stmt_load_store_addr_ops. If T is non-ssa automatic
+ variable, check it if it is present in bitmap passed via DATA. */
+
+static bool
+test_nonssa_use (gimple stmt ATTRIBUTE_UNUSED, tree t,
+ void *data ATTRIBUTE_UNUSED)
+{
+ t = get_base_address (t);
+
+ if (t && !is_gimple_reg (t)
+ && ((TREE_CODE (t) == VAR_DECL
+ && auto_var_in_fn_p (t, current_function_decl))
+ || (TREE_CODE (t) == RESULT_DECL)
+ || (TREE_CODE (t) == PARM_DECL)))
+ return bitmap_bit_p ((bitmap)data, DECL_UID (t));
+ return false;
+}
+
+/* Dump split point CURRENT. */
+
+static void
+dump_split_point (FILE * file, struct split_point *current)
+{
+ fprintf (file,
+ "Split point at BB %i header time:%i header size: %i"
+ " split time: %i split size: %i\n bbs: ",
+ current->entry_bb->index, current->header_time,
+ current->header_size, current->split_time, current->split_size);
+ dump_bitmap (file, current->split_bbs);
+ fprintf (file, " SSA names to pass: ");
+ dump_bitmap (file, current->ssa_names_to_pass);
+}
+
+/* Look for all BBs in header that might lead to split part and verify that
+ they are not defining any of SSA vars used by split part.
+ Parameters are the same as for consider_split. */
+
+static bool
+verify_non_ssa_vars (struct split_point *current, bitmap non_ssa_vars,
+ basic_block return_bb)
+{
+ bitmap seen = BITMAP_ALLOC (NULL);
+ VEC (basic_block,heap) *worklist = NULL;
+ edge e;
+ edge_iterator ei;
+ bool ok = true;
+
+ FOR_EACH_EDGE (e, ei, current->entry_bb->preds)
+ if (e->src != ENTRY_BLOCK_PTR
+ && !bitmap_bit_p (current->split_bbs, e->src->index))
+ {
+ VEC_safe_push (basic_block, heap, worklist, e->src);
+ bitmap_set_bit (seen, e->src->index);
+ }
+
+ while (!VEC_empty (basic_block, worklist))
+ {
+ gimple_stmt_iterator bsi;
+ basic_block bb = VEC_pop (basic_block, worklist);
+
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ if (e->src != ENTRY_BLOCK_PTR
+ && !bitmap_bit_p (seen, e->src->index))
+ {
+ gcc_checking_assert (!bitmap_bit_p (current->split_bbs,
+ e->src->index));
+ VEC_safe_push (basic_block, heap, worklist, e->src);
+ bitmap_set_bit (seen, e->src->index);
+ }
+ for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+ {
+ if (is_gimple_debug (gsi_stmt (bsi)))
+ continue;
+ if (walk_stmt_load_store_addr_ops
+ (gsi_stmt (bsi), non_ssa_vars, test_nonssa_use,
+ test_nonssa_use, test_nonssa_use))
+ {
+ ok = false;
+ goto done;
+ }
+ }
+ for (bsi = gsi_start_phis (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+ {
+ if (walk_stmt_load_store_addr_ops
+ (gsi_stmt (bsi), non_ssa_vars, test_nonssa_use,
+ test_nonssa_use, test_nonssa_use))
+ {
+ ok = false;
+ goto done;
+ }
+ }
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ if (e->dest != return_bb)
+ continue;
+ for (bsi = gsi_start_phis (return_bb); !gsi_end_p (bsi);
+ gsi_next (&bsi))
+ {
+ gimple stmt = gsi_stmt (bsi);
+ tree op = gimple_phi_arg_def (stmt, e->dest_idx);
+
+ if (!is_gimple_reg (gimple_phi_result (stmt)))
+ continue;
+ if (TREE_CODE (op) != SSA_NAME
+ && test_nonssa_use (stmt, op, non_ssa_vars))
+ {
+ ok = false;
+ goto done;
+ }
+ }
+ }
+ }
+done:
+ BITMAP_FREE (seen);
+ VEC_free (basic_block, heap, worklist);
+ return ok;
+}
+
+/* We found an split_point CURRENT. NON_SSA_VARS is bitmap of all non ssa
+ variables used and RETURN_BB is return basic block.
+ See if we can split function here. */
+
+static void
+consider_split (struct split_point *current, bitmap non_ssa_vars,
+ basic_block return_bb)
+{
+ tree parm;
+ unsigned int num_args = 0;
+ unsigned int call_overhead;
+ edge e;
+ edge_iterator ei;
+ gimple_stmt_iterator bsi;
+ unsigned int i;
+ int incomming_freq = 0;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ dump_split_point (dump_file, current);
+
+ FOR_EACH_EDGE (e, ei, current->entry_bb->preds)
+ if (!bitmap_bit_p (current->split_bbs, e->src->index))
+ incomming_freq += EDGE_FREQUENCY (e);
+
+ /* Do not split when we would end up calling function anyway. */
+ if (incomming_freq
+ >= (ENTRY_BLOCK_PTR->frequency
+ * PARAM_VALUE (PARAM_PARTIAL_INLINING_ENTRY_PROBABILITY) / 100))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ " Refused: incomming frequency is too large.\n");
+ return;
+ }
+
+ if (!current->header_size)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " Refused: header empty\n");
+ gcc_unreachable ();
+ return;
+ }
+
+ /* Verify that PHI args on entry are either virutal or all their operands
+ incomming from header are the same. */
+ for (bsi = gsi_start_phis (current->entry_bb); !gsi_end_p (bsi); gsi_next (&bsi))
+ {
+ gimple stmt = gsi_stmt (bsi);
+ tree val = NULL;
+
+ if (!is_gimple_reg (gimple_phi_result (stmt)))
+ continue;
+ for (i = 0; i < gimple_phi_num_args (stmt); i++)
+ {
+ edge e = gimple_phi_arg_edge (stmt, i);
+ if (!bitmap_bit_p (current->split_bbs, e->src->index))
+ {
+ tree edge_val = gimple_phi_arg_def (stmt, i);
+ if (val && edge_val != val)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ " Refused: entry BB has PHI with multiple variants\n");
+ return;
+ }
+ val = edge_val;
+ }
+ }
+ }
+
+
+ /* See what argument we will pass to the split function and compute
+ call overhead. */
+ call_overhead = eni_size_weights.call_cost;
+ for (parm = DECL_ARGUMENTS (current_function_decl); parm;
+ parm = TREE_CHAIN (parm))
+ {
+ if (!is_gimple_reg (parm))
+ {
+ if (bitmap_bit_p (non_ssa_vars, DECL_UID (parm)))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ " Refused: need to pass non-ssa param values\n");
+ return;
+ }
+ }
+ else if (gimple_default_def (cfun, parm)
+ && bitmap_bit_p (current->ssa_names_to_pass,
+ SSA_NAME_VERSION (gimple_default_def
+ (cfun, parm))))
+ {
+ if (!VOID_TYPE_P (TREE_TYPE (parm)))
+ call_overhead += estimate_move_cost (TREE_TYPE (parm));
+ num_args++;
+ }
+ }
+ if (!VOID_TYPE_P (TREE_TYPE (current_function_decl)))
+ call_overhead += estimate_move_cost (TREE_TYPE (current_function_decl));
+
+ if (current->split_size <= call_overhead)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ " Refused: split size is smaller than call overhead\n");
+ return;
+ }
+ if (current->header_size + call_overhead
+ >= (unsigned int)(DECL_DECLARED_INLINE_P (current_function_decl)
+ ? MAX_INLINE_INSNS_SINGLE
+ : MAX_INLINE_INSNS_AUTO))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ " Refused: header size is too large for inline candidate\n");
+ return;
+ }
+
+ /* FIXME: we currently can pass only SSA function parameters to the split
+ arguments. Once parm_adjustment infrastructure is supported by cloning,
+ we can pass more than that. */
+ if (num_args != bitmap_count_bits (current->ssa_names_to_pass))
+ {
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ " Refused: need to pass non-param values\n");
+ return;
+ }
+
+ /* When there are non-ssa vars used in the split region, see if they
+ are used in the header region. If so, reject the split.
+ FIXME: we can use nested function support to access both. */
+ if (!bitmap_empty_p (non_ssa_vars)
+ && !verify_non_ssa_vars (current, non_ssa_vars, return_bb))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ " Refused: split part has non-ssa uses\n");
+ return;
+ }
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " Accepted!\n");
+
+ /* At the moment chose split point with lowest frequency and that leaves
+ out smallest size of header.
+ In future we might re-consider this heuristics. */
+ if (!best_split_point.split_bbs
+ || best_split_point.entry_bb->frequency > current->entry_bb->frequency
+ || (best_split_point.entry_bb->frequency == current->entry_bb->frequency
+ && best_split_point.split_size < current->split_size))
+
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, " New best split point!\n");
+ if (best_split_point.ssa_names_to_pass)
+ {
+ BITMAP_FREE (best_split_point.ssa_names_to_pass);
+ BITMAP_FREE (best_split_point.split_bbs);
+ }
+ best_split_point = *current;
+ best_split_point.ssa_names_to_pass = BITMAP_ALLOC (NULL);
+ bitmap_copy (best_split_point.ssa_names_to_pass,
+ current->ssa_names_to_pass);
+ best_split_point.split_bbs = BITMAP_ALLOC (NULL);
+ bitmap_copy (best_split_point.split_bbs, current->split_bbs);
+ }
+}
+
+/* Return basic block containing RETURN statement. We allow basic blocks
+ of the form:
+ <retval> = tmp_var;
+ return <retval>
+ but return_bb can not be more complex than this.
+ If nothing is found, return EXIT_BLOCK_PTR.
+
+ When there are multiple RETURN statement, chose one with return value,
+ since that one is more likely shared by multiple code paths.
+
+ Return BB is special, because for function splitting it is the only
+ basic block that is duplicated in between header and split part of the
+ function.
+
+ TODO: We might support multiple return blocks. */
+
+static basic_block
+find_return_bb (void)
+{
+ edge e;
+ edge_iterator ei;
+ basic_block return_bb = EXIT_BLOCK_PTR;
+
+ if (EDGE_COUNT (EXIT_BLOCK_PTR->preds) == 1)
+ FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
+ {
+ gimple_stmt_iterator bsi;
+ bool found_return = false;
+ tree retval = NULL_TREE;
+
+ for (bsi = gsi_last_bb (e->src); !gsi_end_p (bsi); gsi_prev (&bsi))
+ {
+ gimple stmt = gsi_stmt (bsi);
+ if (gimple_code (stmt) == GIMPLE_LABEL
+ || is_gimple_debug (stmt))
+ ;
+ else if (gimple_code (stmt) == GIMPLE_ASSIGN
+ && found_return
+ && gimple_assign_single_p (stmt)
+ && (auto_var_in_fn_p (gimple_assign_rhs1 (stmt),
+ current_function_decl)
+ || is_gimple_min_invariant
+ (gimple_assign_rhs1 (stmt)))
+ && retval == gimple_assign_lhs (stmt))
+ ;
+ else if (gimple_code (stmt) == GIMPLE_RETURN)
+ {
+ found_return = true;
+ retval = gimple_return_retval (stmt);
+ }
+ else
+ break;
+ }
+ if (gsi_end_p (bsi) && found_return)
+ {
+ if (retval)
+ return e->src;
+ else
+ return_bb = e->src;
+ }
+ }
+ return return_bb;
+}
+
+/* Given return basicblock RETURN_BB, see where return value is really
+ stored. */
+static tree
+find_retval (basic_block return_bb)
+{
+ gimple_stmt_iterator bsi;
+ for (bsi = gsi_start_bb (return_bb); !gsi_end_p (bsi); gsi_next (&bsi))
+ if (gimple_code (gsi_stmt (bsi)) == GIMPLE_RETURN)
+ return gimple_return_retval (gsi_stmt (bsi));
+ else if (gimple_code (gsi_stmt (bsi)) == GIMPLE_ASSIGN)
+ return gimple_assign_rhs1 (gsi_stmt (bsi));
+ return NULL;
+}
+
+/* Callback for walk_stmt_load_store_addr_ops. If T is non-ssa automatic
+ variable, mark it as used in bitmap passed via DATA.
+ Return true when access to T prevents splitting the function. */
+
+static bool
+mark_nonssa_use (gimple stmt ATTRIBUTE_UNUSED, tree t,
+ void *data ATTRIBUTE_UNUSED)
+{
+ t = get_base_address (t);
+
+ if (!t || is_gimple_reg (t))
+ return false;
+
+ /* At present we can't pass non-SSA arguments to split function.
+ FIXME: this can be relaxed by passing references to arguments. */
+ if (TREE_CODE (t) == PARM_DECL)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Can not split use of non-ssa function parameter.\n");
+ return true;
+ }
+
+ if ((TREE_CODE (t) == VAR_DECL && auto_var_in_fn_p (t, current_function_decl))
+ || (TREE_CODE (t) == RESULT_DECL))
+ bitmap_set_bit ((bitmap)data, DECL_UID (t));
+ return false;
+}
+
+/* Compute local properties of basic block BB we collect when looking for
+ split points. We look for ssa defs and store them in SET_SSA_NAMES,
+ for ssa uses and store them in USED_SSA_NAMES and for any non-SSA automatic
+ vars stored in NON_SSA_VARS.
+
+ When BB has edge to RETURN_BB, collect uses in RETURN_BB too.
+
+ Return false when BB contains something that prevents it from being put into
+ split function. */
+
+static bool
+visit_bb (basic_block bb, basic_block return_bb,
+ bitmap set_ssa_names, bitmap used_ssa_names,
+ bitmap non_ssa_vars)
+{
+ gimple_stmt_iterator bsi;
+ edge e;
+ edge_iterator ei;
+ bool can_split = true;
+
+ for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+ {
+ gimple stmt = gsi_stmt (bsi);
+ tree op;
+ ssa_op_iter iter;
+ tree decl;
+
+ if (is_gimple_debug (stmt))
+ continue;
+
+ /* FIXME: We can split regions containing EH. We can not however
+ split RESX, EH_DISPATCH and EH_POINTER referring to same region
+ into different partitions. This would require tracking of
+ EH regions and checking in consider_split_point if they
+ are not used elsewhere. */
+ if (gimple_code (stmt) == GIMPLE_RESX
+ && stmt_can_throw_external (stmt))
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Can not split external resx.\n");
+ can_split = false;
+ }
+ if (gimple_code (stmt) == GIMPLE_EH_DISPATCH)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Can not split eh dispatch.\n");
+ can_split = false;
+ }
+
+ /* Check builtins that prevent splitting. */
+ if (gimple_code (stmt) == GIMPLE_CALL
+ && (decl = gimple_call_fndecl (stmt)) != NULL_TREE
+ && DECL_BUILT_IN (decl)
+ && DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL)
+ switch (DECL_FUNCTION_CODE (decl))
+ {
+ /* FIXME: once we will allow passing non-parm values to split part,
+ we need to be sure to handle correct builtin_stack_save and
+ builtin_stack_restore. At the moment we are safe; there is no
+ way to store builtin_stack_save result in non-SSA variable
+ since all calls to those are compiler generated. */
+ case BUILT_IN_APPLY:
+ case BUILT_IN_VA_START:
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Can not split builtin_apply and va_start.\n");
+ can_split = false;
+ break;
+ case BUILT_IN_EH_POINTER:
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Can not split builtin_eh_pointer.\n");
+ can_split = false;
+ break;
+ default:
+ break;
+ }
+
+ FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
+ bitmap_set_bit (set_ssa_names, SSA_NAME_VERSION (op));
+ FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
+ bitmap_set_bit (used_ssa_names, SSA_NAME_VERSION (op));
+ can_split &= !walk_stmt_load_store_addr_ops (stmt, non_ssa_vars,
+ mark_nonssa_use,
+ mark_nonssa_use,
+ mark_nonssa_use);
+ }
+ for (bsi = gsi_start_phis (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+ {
+ gimple stmt = gsi_stmt (bsi);
+ unsigned int i;
+
+ if (is_gimple_debug (stmt))
+ continue;
+ if (!is_gimple_reg (gimple_phi_result (stmt)))
+ continue;
+ bitmap_set_bit (set_ssa_names,
+ SSA_NAME_VERSION (gimple_phi_result (stmt)));
+ for (i = 0; i < gimple_phi_num_args (stmt); i++)
+ {
+ tree op = gimple_phi_arg_def (stmt, i);
+ if (TREE_CODE (op) == SSA_NAME)
+ bitmap_set_bit (used_ssa_names, SSA_NAME_VERSION (op));
+ }
+ can_split &= !walk_stmt_load_store_addr_ops (stmt, non_ssa_vars,
+ mark_nonssa_use,
+ mark_nonssa_use,
+ mark_nonssa_use);
+ }
+ /* Record also uses comming from PHI operand in return BB. */
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e->dest == return_bb)
+ {
+ bool found_phi = false;
+ for (bsi = gsi_start_phis (return_bb); !gsi_end_p (bsi); gsi_next (&bsi))
+ {
+ gimple stmt = gsi_stmt (bsi);
+ tree op = gimple_phi_arg_def (stmt, e->dest_idx);
+
+ if (is_gimple_debug (stmt))
+ continue;
+ if (!is_gimple_reg (gimple_phi_result (stmt)))
+ continue;
+ found_phi = true;
+ if (TREE_CODE (op) == SSA_NAME)
+ bitmap_set_bit (used_ssa_names, SSA_NAME_VERSION (op));
+ else
+ can_split &= !mark_nonssa_use (stmt, op, non_ssa_vars);
+ }
+ if (!gsi_end_p (gsi_last_bb (return_bb)))
+ {
+ ssa_op_iter iter;
+ gimple stmt = gsi_stmt (gsi_last_bb (return_bb));
+ tree op;
+ if (!found_phi)
+ FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
+ bitmap_set_bit (used_ssa_names, SSA_NAME_VERSION (op));
+ can_split &= !walk_stmt_load_store_addr_ops (stmt, non_ssa_vars,
+ mark_nonssa_use,
+ mark_nonssa_use,
+ mark_nonssa_use);
+ }
+ }
+ return can_split;
+}
+
+/* Stack entry for recursive DFS walk in find_split_point. */
+
+typedef struct
+{
+ /* Basic block we are examining. */
+ basic_block bb;
+
+ /* SSA names set and used by the BB and all BBs reachable
+ from it via DFS walk. */
+ bitmap set_ssa_names, used_ssa_names;
+ bitmap non_ssa_vars;
+
+ /* All BBS visited from this BB via DFS walk. */
+ bitmap bbs_visited;
+
+ /* Last examined edge in DFS walk. Since we walk unoriented graph,
+ the value is up to sum of incomming and outgoing edges of BB. */
+ unsigned int edge_num;
+
+ /* Stack entry index of earliest BB reachable from current BB
+ or any BB visited later in DFS valk. */
+ int earliest;
+
+ /* Overall time and size of all BBs reached from this BB in DFS walk. */
+ int overall_time, overall_size;
+
+ /* When false we can not split on this BB. */
+ bool can_split;
+} stack_entry;
+DEF_VEC_O(stack_entry);
+DEF_VEC_ALLOC_O(stack_entry,heap);
+
+
+/* Find all articulations and call consider_split on them.
+ OVERALL_TIME and OVERALL_SIZE is time and size of the function.
+
+ We perform basic algorithm for finding an articulation in a graph
+ created from CFG by considering it to be an unoriented graph.
+
+ The articulation is discovered via DFS walk. We collect earliest
+ basic block on stack that is reachable via backward edge. Articulation
+ is any basic block such that there is no backward edge bypassing it.
+ To reduce stack usage we maintain heap allocated stack in STACK vector.
+ AUX pointer of BB is set to index it appears in the stack or -1 once
+ it is visited and popped off the stack.
+
+ The algorithm finds articulation after visiting the whole component
+ reachable by it. This makes it convenient to collect information about
+ the component used by consider_split. */
+
+static void
+find_split_points (int overall_time, int overall_size)
+{
+ stack_entry first;
+ VEC(stack_entry, heap) *stack = NULL;
+ basic_block bb;
+ basic_block return_bb = find_return_bb ();
+ struct split_point current;
+
+ current.header_time = overall_time;
+ current.header_size = overall_size;
+ current.split_time = 0;
+ current.split_size = 0;
+ current.ssa_names_to_pass = BITMAP_ALLOC (NULL);
+
+ first.bb = ENTRY_BLOCK_PTR;
+ first.edge_num = 0;
+ first.overall_time = 0;
+ first.overall_size = 0;
+ first.earliest = INT_MAX;
+ first.set_ssa_names = 0;
+ first.used_ssa_names = 0;
+ first.bbs_visited = 0;
+ VEC_safe_push (stack_entry, heap, stack, &first);
+ ENTRY_BLOCK_PTR->aux = (void *)(intptr_t)-1;
+
+ while (!VEC_empty (stack_entry, stack))
+ {
+ stack_entry *entry = VEC_last (stack_entry, stack);
+
+ /* We are walking an acyclic graph, so edge_num counts
+ succ and pred edges together. However when considering
+ articulation, we want to have processed everything reachable
+ from articulation but nothing that reaches into it. */
+ if (entry->edge_num == EDGE_COUNT (entry->bb->succs)
+ && entry->bb != ENTRY_BLOCK_PTR)
+ {
+ int pos = VEC_length (stack_entry, stack);
+ entry->can_split &= visit_bb (entry->bb, return_bb,
+ entry->set_ssa_names,
+ entry->used_ssa_names,
+ entry->non_ssa_vars);
+ if (pos <= entry->earliest && !entry->can_split
+ && dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file,
+ "found articulation at bb %i but can not split\n",
+ entry->bb->index);
+ if (pos <= entry->earliest && entry->can_split)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "found articulation at bb %i\n",
+ entry->bb->index);
+ current.entry_bb = entry->bb;
+ current.ssa_names_to_pass = BITMAP_ALLOC (NULL);
+ bitmap_and_compl (current.ssa_names_to_pass,
+ entry->used_ssa_names, entry->set_ssa_names);
+ current.header_time = overall_time - entry->overall_time;
+ current.header_size = overall_size - entry->overall_size;
+ current.split_time = entry->overall_time;
+ current.split_size = entry->overall_size;
+ current.split_bbs = entry->bbs_visited;
+ consider_split (¤t, entry->non_ssa_vars, return_bb);
+ BITMAP_FREE (current.ssa_names_to_pass);
+ }
+ }
+ /* Do actual DFS walk. */
+ if (entry->edge_num
+ < (EDGE_COUNT (entry->bb->succs)
+ + EDGE_COUNT (entry->bb->preds)))
+ {
+ edge e;
+ basic_block dest;
+ if (entry->edge_num < EDGE_COUNT (entry->bb->succs))
+ {
+ e = EDGE_SUCC (entry->bb, entry->edge_num);
+ dest = e->dest;
+ }
+ else
+ {
+ e = EDGE_PRED (entry->bb, entry->edge_num
+ - EDGE_COUNT (entry->bb->succs));
+ dest = e->src;
+ }
+
+ entry->edge_num++;
+
+ /* New BB to visit, push it to the stack. */
+ if (dest != return_bb && dest != EXIT_BLOCK_PTR
+ && !dest->aux)
+ {
+ stack_entry new_entry;
+
+ new_entry.bb = dest;
+ new_entry.edge_num = 0;
+ new_entry.overall_time
+ = VEC_index (bb_info, bb_info_vec, dest->index)->time;
+ new_entry.overall_size
+ = VEC_index (bb_info, bb_info_vec, dest->index)->size;
+ new_entry.earliest = INT_MAX;
+ new_entry.set_ssa_names = BITMAP_ALLOC (NULL);
+ new_entry.used_ssa_names = BITMAP_ALLOC (NULL);
+ new_entry.bbs_visited = BITMAP_ALLOC (NULL);
+ new_entry.non_ssa_vars = BITMAP_ALLOC (NULL);
+ new_entry.can_split = true;
+ bitmap_set_bit (new_entry.bbs_visited, dest->index);
+ VEC_safe_push (stack_entry, heap, stack, &new_entry);
+ dest->aux = (void *)(intptr_t)VEC_length (stack_entry, stack);
+ }
+ /* Back edge found, record the earliest point. */
+ else if ((intptr_t)dest->aux > 0
+ && (intptr_t)dest->aux < entry->earliest)
+ entry->earliest = (intptr_t)dest->aux;
+ }
+ /* We are done with examing the edges. pop off the value from stack and
+ merge stuff we cummulate during the walk. */
+ else if (entry->bb != ENTRY_BLOCK_PTR)
+ {
+ stack_entry *prev = VEC_index (stack_entry, stack,
+ VEC_length (stack_entry, stack) - 2);
+
+ entry->bb->aux = (void *)(intptr_t)-1;
+ prev->can_split &= entry->can_split;
+ if (prev->set_ssa_names)
+ {
+ bitmap_ior_into (prev->set_ssa_names, entry->set_ssa_names);
+ bitmap_ior_into (prev->used_ssa_names, entry->used_ssa_names);
+ bitmap_ior_into (prev->bbs_visited, entry->bbs_visited);
+ bitmap_ior_into (prev->non_ssa_vars, entry->non_ssa_vars);
+ }
+ if (prev->earliest > entry->earliest)
+ prev->earliest = entry->earliest;
+ prev->overall_time += entry->overall_time;
+ prev->overall_size += entry->overall_size;
+ BITMAP_FREE (entry->set_ssa_names);
+ BITMAP_FREE (entry->used_ssa_names);
+ BITMAP_FREE (entry->bbs_visited);
+ BITMAP_FREE (entry->non_ssa_vars);
+ VEC_pop (stack_entry, stack);
+ }
+ else
+ VEC_pop (stack_entry, stack);
+ }
+ ENTRY_BLOCK_PTR->aux = NULL;
+ FOR_EACH_BB (bb)
+ bb->aux = NULL;
+ BITMAP_FREE (current.ssa_names_to_pass);
+}
+
+/* Split function at SPLIT_POINT. */
+
+static void
+split_function (struct split_point *split_point)
+{
+ VEC (tree, heap) *args_to_pass = NULL;
+ bitmap args_to_skip = BITMAP_ALLOC (NULL);
+ tree parm;
+ int num = 0;
+ struct cgraph_node *node;
+ basic_block return_bb = find_return_bb ();
+ basic_block call_bb;
+ gimple_stmt_iterator gsi;
+ gimple call;
+ edge e;
+ edge_iterator ei;
+ tree retval = NULL, real_retval = NULL;
+ bool split_part_return_p = false;
+ gimple last_stmt = NULL;
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "\n\nSplitting function at:\n");
+ dump_split_point (dump_file, split_point);
+ }
+
+ /* Collect the parameters of new function and args_to_skip bitmap. */
+ for (parm = DECL_ARGUMENTS (current_function_decl);
+ parm; parm = TREE_CHAIN (parm), num++)
+ if (!is_gimple_reg (parm)
+ || !gimple_default_def (cfun, parm)
+ || !bitmap_bit_p (split_point->ssa_names_to_pass,
+ SSA_NAME_VERSION (gimple_default_def (cfun, parm))))
+ bitmap_set_bit (args_to_skip, num);
+ else
+ VEC_safe_push (tree, heap, args_to_pass, gimple_default_def (cfun, parm));
+
+ /* See if the split function will return. */
+ FOR_EACH_EDGE (e, ei, return_bb->preds)
+ if (bitmap_bit_p (split_point->split_bbs, e->src->index))
+ break;
+ if (e)
+ split_part_return_p = true;
+
+ /* If we return, we will need the return block. */
+ if (return_bb != EXIT_BLOCK_PTR && split_part_return_p)
+ bitmap_set_bit (split_point->split_bbs, return_bb->index);
+
+ /* Now create the actual clone. */
+ rebuild_cgraph_edges ();
+ node = cgraph_function_versioning (cgraph_node (current_function_decl),
+ NULL, NULL,
+ args_to_skip,
+ split_point->split_bbs,
+ split_point->entry_bb, "part");
+ /* For usual cloning it is enough to clear builtin only when signature
+ changes. For partial inlining we however can not expect the part
+ of builtin implementation to have same semantic as the whole. */
+ if (DECL_BUILT_IN (node->decl))
+ {
+ DECL_BUILT_IN_CLASS (node->decl) = NOT_BUILT_IN;
+ DECL_FUNCTION_CODE (node->decl) = (enum built_in_function) 0;
+ }
+ cgraph_node_remove_callees (cgraph_node (current_function_decl));
+ if (!split_part_return_p)
+ TREE_THIS_VOLATILE (node->decl) = 1;
+ if (dump_file)
+ dump_function_to_file (node->decl, dump_file, dump_flags);
+
+ /* Create the basic block we place call into. It is the entry basic block
+ split after last label. */
+ call_bb = split_point->entry_bb;
+ for (gsi = gsi_start_bb (call_bb); !gsi_end_p (gsi);)
+ if (gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL)
+ {
+ last_stmt = gsi_stmt (gsi);
+ gsi_next (&gsi);
+ }
+ else
+ break;
+ e = split_block (split_point->entry_bb, last_stmt);
+ remove_edge (e);
+
+ /* Produce the call statement. */
+ gsi = gsi_last_bb (call_bb);
+ call = gimple_build_call_vec (node->decl, args_to_pass);
+ gimple_set_block (call, DECL_INITIAL (current_function_decl));
+
+ /* We avoid address being taken on any variable used by split part,
+ so return slot optimization is always possible. Moreover this is
+ required to make DECL_BY_REFERENCE work. */
+ if (aggregate_value_p (DECL_RESULT (current_function_decl),
+ TREE_TYPE (current_function_decl)))
+ gimple_call_set_return_slot_opt (call, true);
+
+ /* Update return value. This is bit tricky. When we do not return,
+ do nothing. When we return we might need to update return_bb
+ or produce a new return statement. */
+ if (!split_part_return_p)
+ gsi_insert_after (&gsi, call, GSI_NEW_STMT);
+ else
+ {
+ e = make_edge (call_bb, return_bb,
+ return_bb == EXIT_BLOCK_PTR ? 0 : EDGE_FALLTHRU);
+ e->count = call_bb->count;
+ e->probability = REG_BR_PROB_BASE;
+
+ /* If there is return basic block, see what value we need to store
+ return value into and put call just before it. */
+ if (return_bb != EXIT_BLOCK_PTR)
+ {
+ real_retval = retval = find_retval (return_bb);
+
+ /* See if return value is computed by split part;
+ function might just return its argument, invariant or undefined
+ value. In this case we don't need to do any updating. */
+ if (real_retval
+ && !is_gimple_min_invariant (retval)
+ && (TREE_CODE (retval) != SSA_NAME
+ || (!SSA_NAME_IS_DEFAULT_DEF (retval)
+ || DECL_BY_REFERENCE
+ (DECL_RESULT (current_function_decl)))))
+ {
+ gimple_stmt_iterator psi;
+
+ /* See if we need new SSA_NAME for the result.
+ When DECL_BY_REFERENCE is true, retval is actually pointer to
+ return value and it is constant in whole function. */
+ if (TREE_CODE (retval) == SSA_NAME
+ && !DECL_BY_REFERENCE (DECL_RESULT (current_function_decl)))
+ {
+ retval = make_ssa_name (SSA_NAME_VAR (retval), call);
+
+ /* See if there is PHI defining return value. */
+ for (psi = gsi_start_phis (return_bb);
+ !gsi_end_p (psi); gsi_next (&psi))
+ if (is_gimple_reg (gimple_phi_result (gsi_stmt (psi))))
+ break;
+
+ /* When there is PHI, just update its value. */
+ if (TREE_CODE (retval) == SSA_NAME
+ && !gsi_end_p (psi))
+ add_phi_arg (gsi_stmt (psi), retval, e, UNKNOWN_LOCATION);
+ /* Otherwise update the return BB itself.
+ find_return_bb allows at most one assignment to return value,
+ so update first statement. */
+ else
+ {
+ gimple_stmt_iterator bsi;
+ for (bsi = gsi_start_bb (return_bb); !gsi_end_p (bsi);
+ gsi_next (&bsi))
+ if (gimple_code (gsi_stmt (bsi)) == GIMPLE_RETURN)
+ {
+ gimple_return_set_retval (gsi_stmt (bsi), retval);
+ break;
+ }
+ else if (gimple_code (gsi_stmt (bsi)) == GIMPLE_ASSIGN)
+ {
+ gimple_assign_set_rhs1 (gsi_stmt (bsi), retval);
+ break;
+ }
+ update_stmt (gsi_stmt (bsi));
+ }
+ }
+ if (DECL_BY_REFERENCE (DECL_RESULT (current_function_decl)))
+ gimple_call_set_lhs (call, build_simple_mem_ref (retval));
+ else
+ gimple_call_set_lhs (call, retval);
+ }
+ gsi_insert_after (&gsi, call, GSI_NEW_STMT);
+ }
+ /* We don't use return block (there is either no return in function or
+ multiple of them). So create new basic block with return statement.
+ */
+ else
+ {
+ gimple ret;
+ if (!VOID_TYPE_P (TREE_TYPE (TREE_TYPE (current_function_decl))))
+ {
+ retval = DECL_RESULT (current_function_decl);
+
+ /* We use temporary register to hold value when aggregate_value_p
+ is false. Similarly for DECL_BY_REFERENCE we must avoid extra
+ copy. */
+ if (!aggregate_value_p (retval, TREE_TYPE (current_function_decl))
+ && !DECL_BY_REFERENCE (retval))
+ retval = create_tmp_reg (TREE_TYPE (retval), NULL);
+ if (is_gimple_reg (retval))
+ {
+ /* When returning by reference, there is only one SSA name
+ assigned to RESULT_DECL (that is pointer to return value).
+ Look it up or create new one if it is missing. */
+ if (DECL_BY_REFERENCE (retval))
+ {
+ tree retval_name;
+ if ((retval_name = gimple_default_def (cfun, retval))
+ != NULL)
+ retval = retval_name;
+ else
+ {
+ retval_name = make_ssa_name (retval,
+ gimple_build_nop ());
+ set_default_def (retval, retval_name);
+ retval = retval_name;
+ }
+ }
+ /* Otherwise produce new SSA name for return value. */
+ else
+ retval = make_ssa_name (retval, call);
+ }
+ if (DECL_BY_REFERENCE (DECL_RESULT (current_function_decl)))
+ gimple_call_set_lhs (call, build_simple_mem_ref (retval));
+ else
+ gimple_call_set_lhs (call, retval);
+ }
+ gsi_insert_after (&gsi, call, GSI_NEW_STMT);
+ ret = gimple_build_return (retval);
+ gsi_insert_after (&gsi, ret, GSI_NEW_STMT);
+ }
+ }
+ free_dominance_info (CDI_DOMINATORS);
+ free_dominance_info (CDI_POST_DOMINATORS);
+ compute_inline_parameters (node);
+}
+
+/* Execute function splitting pass. */
+
+static unsigned int
+execute_split_functions (void)
+{
+ gimple_stmt_iterator bsi;
+ basic_block bb;
+ int overall_time = 0, overall_size = 0;
+ int todo = 0;
+ struct cgraph_node *node = cgraph_node (current_function_decl);
+
+ if (flags_from_decl_or_type (current_function_decl) & ECF_NORETURN)
+ {
+ if (dump_file)
+ fprintf (dump_file, "Not splitting: noreturn function.\n");
+ return 0;
+ }
+ if (MAIN_NAME_P (DECL_NAME (current_function_decl)))
+ {
+ if (dump_file)
+ fprintf (dump_file, "Not splitting: main function.\n");
+ return 0;
+ }
+ /* This can be relaxed; function might become inlinable after splitting
+ away the uninlinable part. */
+ if (!node->local.inlinable)
+ {
+ if (dump_file)
+ fprintf (dump_file, "Not splitting: not inlinable.\n");
+ return 0;
+ }
+ if (node->local.disregard_inline_limits)
+ {
+ if (dump_file)
+ fprintf (dump_file, "Not splitting: disregading inline limits.\n");
+ return 0;
+ }
+ /* This can be relaxed; most of versioning tests actually prevents
+ a duplication. */
+ if (!tree_versionable_function_p (current_function_decl))
+ {
+ if (dump_file)
+ fprintf (dump_file, "Not splitting: not versionable.\n");
+ return 0;
+ }
+ /* FIXME: we could support this. */
+ if (DECL_STRUCT_FUNCTION (current_function_decl)->static_chain_decl)
+ {
+ if (dump_file)
+ fprintf (dump_file, "Not splitting: nested function.\n");
+ return 0;
+ }
+
+ /* See if it makes sense to try to split.
+ It makes sense to split if we inline, that is if we have direct calls to
+ handle or direct calls are possibly going to appear as result of indirect
+ inlining or LTO.
+ Note that we are not completely conservative about disqualifying functions
+ called once. It is possible that the caller is called more then once and
+ then inlining would still benefit. */
+ if ((!node->callers || !node->callers->next_caller)
+ && !node->address_taken
+ && ((!flag_lto && !flag_whopr) || !node->local.externally_visible))
+ {
+ if (dump_file)
+ fprintf (dump_file, "Not splitting: not called directly "
+ "or called once.\n");
+ return 0;
+ }
+
+ /* FIXME: We can actually split if splitting reduces call overhead. */
+ if (!flag_inline_small_functions
+ && !DECL_DECLARED_INLINE_P (current_function_decl))
+ {
+ if (dump_file)
+ fprintf (dump_file, "Not splitting: not autoinlining and function"
+ " is not inline.\n");
+ return 0;
+ }
+
+ /* Compute local info about basic blocks and determine function size/time. */
+ VEC_safe_grow_cleared (bb_info, heap, bb_info_vec, last_basic_block + 1);
+ memset (&best_split_point, 0, sizeof (best_split_point));
+ FOR_EACH_BB (bb)
+ {
+ int time = 0;
+ int size = 0;
+ int freq = compute_call_stmt_bb_frequency (current_function_decl, bb);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "Basic block %i\n", bb->index);
+
+ for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
+ {
+ int this_time, this_size;
+ gimple stmt = gsi_stmt (bsi);
+
+ this_size = estimate_num_insns (stmt, &eni_size_weights);
+ this_time = estimate_num_insns (stmt, &eni_time_weights) * freq;
+ size += this_size;
+ time += this_time;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " freq:%6i size:%3i time:%3i ",
+ freq, this_size, this_time);
+ print_gimple_stmt (dump_file, stmt, 0, 0);
+ }
+ }
+ overall_time += time;
+ overall_size += size;
+ VEC_index (bb_info, bb_info_vec, bb->index)->time = time;
+ VEC_index (bb_info, bb_info_vec, bb->index)->size = size;
+ }
+ find_split_points (overall_time, overall_size);
+ if (best_split_point.split_bbs)
+ {
+ split_function (&best_split_point);
+ BITMAP_FREE (best_split_point.ssa_names_to_pass);
+ BITMAP_FREE (best_split_point.split_bbs);
+ todo = TODO_update_ssa | TODO_cleanup_cfg;
+ }
+ VEC_free (bb_info, heap, bb_info_vec);
+ bb_info_vec = NULL;
+ return todo;
+}
+
+static bool
+gate_split_functions (void)
+{
+ return flag_partial_inlining;
+}
+
+struct gimple_opt_pass pass_split_functions =
+{
+ {
+ GIMPLE_PASS,
+ "fnsplit", /* name */
+ gate_split_functions, /* gate */
+ execute_split_functions, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_IPA_FNSPLIT, /* tv_id */
+ PROP_cfg, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_dump_func /* todo_flags_finish */
+ }
+};
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