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Diffstat (limited to 'gcc/tree-outof-ssa.cc')
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diff --git a/gcc/tree-outof-ssa.cc b/gcc/tree-outof-ssa.cc new file mode 100644 index 0000000..65d4de3 --- /dev/null +++ b/gcc/tree-outof-ssa.cc @@ -0,0 +1,1329 @@ +/* Convert a program in SSA form into Normal form. + Copyright (C) 2004-2022 Free Software Foundation, Inc. + Contributed by Andrew Macleod <amacleod@redhat.com> + +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/>. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "backend.h" +#include "rtl.h" +#include "tree.h" +#include "gimple.h" +#include "cfghooks.h" +#include "ssa.h" +#include "tree-ssa.h" +#include "memmodel.h" +#include "emit-rtl.h" +#include "gimple-pretty-print.h" +#include "diagnostic-core.h" +#include "tree-dfa.h" +#include "stor-layout.h" +#include "cfgrtl.h" +#include "cfganal.h" +#include "tree-eh.h" +#include "gimple-iterator.h" +#include "tree-cfg.h" +#include "dumpfile.h" +#include "tree-ssa-live.h" +#include "tree-ssa-ter.h" +#include "tree-ssa-coalesce.h" +#include "tree-outof-ssa.h" +#include "dojump.h" + +/* FIXME: A lot of code here deals with expanding to RTL. All that code + should be in cfgexpand.c. */ +#include "explow.h" +#include "expr.h" + +/* Return TRUE if expression STMT is suitable for replacement. */ + +bool +ssa_is_replaceable_p (gimple *stmt) +{ + use_operand_p use_p; + tree def; + gimple *use_stmt; + + /* Only consider modify stmts. */ + if (!is_gimple_assign (stmt)) + return false; + + /* If the statement may throw an exception, it cannot be replaced. */ + if (stmt_could_throw_p (cfun, stmt)) + return false; + + /* Punt if there is more than 1 def. */ + def = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_DEF); + if (!def) + return false; + + /* Only consider definitions which have a single use. */ + if (!single_imm_use (def, &use_p, &use_stmt)) + return false; + + /* Used in this block, but at the TOP of the block, not the end. */ + if (gimple_code (use_stmt) == GIMPLE_PHI) + return false; + + /* There must be no VDEFs. */ + if (gimple_vdef (stmt)) + return false; + + /* Float expressions must go through memory if float-store is on. */ + if (flag_float_store + && FLOAT_TYPE_P (TREE_TYPE (def))) + return false; + + /* An assignment with a register variable on the RHS is not + replaceable. */ + if (gimple_assign_rhs_code (stmt) == VAR_DECL + && DECL_HARD_REGISTER (gimple_assign_rhs1 (stmt))) + return false; + + /* No function calls can be replaced. */ + if (is_gimple_call (stmt)) + return false; + + /* Leave any stmt with volatile operands alone as well. */ + if (gimple_has_volatile_ops (stmt)) + return false; + + return true; +} + + +/* Used to hold all the components required to do SSA PHI elimination. + The node and pred/succ list is a simple linear list of nodes and + edges represented as pairs of nodes. + + The predecessor and successor list: Nodes are entered in pairs, where + [0] ->PRED, [1]->SUCC. All the even indexes in the array represent + predecessors, all the odd elements are successors. + + Rationale: + When implemented as bitmaps, very large programs SSA->Normal times were + being dominated by clearing the interference graph. + + Typically this list of edges is extremely small since it only includes + PHI results and uses from a single edge which have not coalesced with + each other. This means that no virtual PHI nodes are included, and + empirical evidence suggests that the number of edges rarely exceed + 3, and in a bootstrap of GCC, the maximum size encountered was 7. + This also limits the number of possible nodes that are involved to + rarely more than 6, and in the bootstrap of gcc, the maximum number + of nodes encountered was 12. */ + +class elim_graph +{ +public: + elim_graph (var_map map); + + /* Size of the elimination vectors. */ + int size; + + /* List of nodes in the elimination graph. */ + auto_vec<int> nodes; + + /* The predecessor and successor edge list. */ + auto_vec<int> edge_list; + + /* Source locus on each edge */ + auto_vec<location_t> edge_locus; + + /* Visited vector. */ + auto_sbitmap visited; + + /* Stack for visited nodes. */ + auto_vec<int> stack; + + /* The variable partition map. */ + var_map map; + + /* Edge being eliminated by this graph. */ + edge e; + + /* List of constant copies to emit. These are pushed on in pairs. */ + auto_vec<int> const_dests; + auto_vec<tree> const_copies; + + /* Source locations for any constant copies. */ + auto_vec<location_t> copy_locus; +}; + + +/* For an edge E find out a good source location to associate with + instructions inserted on edge E. If E has an implicit goto set, + use its location. Otherwise search instructions in predecessors + of E for a location, and use that one. That makes sense because + we insert on edges for PHI nodes, and effects of PHIs happen on + the end of the predecessor conceptually. An exception is made + for EH edges because we don't want to drag the source location + of unrelated statements at the beginning of handlers; they would + be further reused for various EH constructs, which would damage + the coverage information. */ + +static void +set_location_for_edge (edge e) +{ + if (e->goto_locus) + set_curr_insn_location (e->goto_locus); + else if (e->flags & EDGE_EH) + { + basic_block bb = e->dest; + gimple_stmt_iterator gsi; + + do + { + for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gimple *stmt = gsi_stmt (gsi); + if (is_gimple_debug (stmt)) + continue; + if (gimple_has_location (stmt) || gimple_block (stmt)) + { + set_curr_insn_location (gimple_location (stmt)); + return; + } + } + /* Nothing found in this basic block. Make a half-assed attempt + to continue with another block. */ + if (single_succ_p (bb)) + bb = single_succ (bb); + else + bb = e->dest; + } + while (bb != e->dest); + } + else + { + basic_block bb = e->src; + gimple_stmt_iterator gsi; + + do + { + for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi)) + { + gimple *stmt = gsi_stmt (gsi); + if (is_gimple_debug (stmt)) + continue; + if (gimple_has_location (stmt) || gimple_block (stmt)) + { + set_curr_insn_location (gimple_location (stmt)); + return; + } + } + /* Nothing found in this basic block. Make a half-assed attempt + to continue with another block. */ + if (single_pred_p (bb)) + bb = single_pred (bb); + else + bb = e->src; + } + while (bb != e->src); + } +} + +/* Emit insns to copy SRC into DEST converting SRC if necessary. As + SRC/DEST might be BLKmode memory locations SIZEEXP is a tree from + which we deduce the size to copy in that case. */ + +static inline rtx_insn * +emit_partition_copy (rtx dest, rtx src, int unsignedsrcp, tree sizeexp) +{ + start_sequence (); + + if (GET_MODE (src) != VOIDmode && GET_MODE (src) != GET_MODE (dest)) + src = convert_to_mode (GET_MODE (dest), src, unsignedsrcp); + if (GET_MODE (src) == BLKmode) + { + gcc_assert (GET_MODE (dest) == BLKmode); + emit_block_move (dest, src, expr_size (sizeexp), BLOCK_OP_NORMAL); + } + else + emit_move_insn (dest, src); + do_pending_stack_adjust (); + + rtx_insn *seq = get_insns (); + end_sequence (); + + return seq; +} + +/* Insert a copy instruction from partition SRC to DEST onto edge E. */ + +static void +insert_partition_copy_on_edge (edge e, int dest, int src, location_t locus) +{ + tree var; + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, + "Inserting a partition copy on edge BB%d->BB%d : " + "PART.%d = PART.%d", + e->src->index, + e->dest->index, dest, src); + fprintf (dump_file, "\n"); + } + + gcc_assert (SA.partition_to_pseudo[dest]); + gcc_assert (SA.partition_to_pseudo[src]); + + set_location_for_edge (e); + /* If a locus is provided, override the default. */ + if (locus) + set_curr_insn_location (locus); + + var = partition_to_var (SA.map, src); + rtx_insn *seq = emit_partition_copy (copy_rtx (SA.partition_to_pseudo[dest]), + copy_rtx (SA.partition_to_pseudo[src]), + TYPE_UNSIGNED (TREE_TYPE (var)), + var); + + insert_insn_on_edge (seq, e); +} + +/* Insert a copy instruction from expression SRC to partition DEST + onto edge E. */ + +static void +insert_value_copy_on_edge (edge e, int dest, tree src, location_t locus) +{ + rtx dest_rtx, seq, x; + machine_mode dest_mode, src_mode; + int unsignedp; + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, + "Inserting a value copy on edge BB%d->BB%d : PART.%d = ", + e->src->index, + e->dest->index, dest); + print_generic_expr (dump_file, src, TDF_SLIM); + fprintf (dump_file, "\n"); + } + + dest_rtx = copy_rtx (SA.partition_to_pseudo[dest]); + gcc_assert (dest_rtx); + + set_location_for_edge (e); + /* If a locus is provided, override the default. */ + if (locus) + set_curr_insn_location (locus); + + start_sequence (); + + tree name = partition_to_var (SA.map, dest); + src_mode = TYPE_MODE (TREE_TYPE (src)); + dest_mode = GET_MODE (dest_rtx); + gcc_assert (src_mode == TYPE_MODE (TREE_TYPE (name))); + gcc_assert (!REG_P (dest_rtx) + || dest_mode == promote_ssa_mode (name, &unsignedp)); + + if (src_mode != dest_mode) + { + x = expand_expr (src, NULL, src_mode, EXPAND_NORMAL); + x = convert_modes (dest_mode, src_mode, x, unsignedp); + } + else if (src_mode == BLKmode) + { + x = dest_rtx; + store_expr (src, x, 0, false, false); + } + else + x = expand_expr (src, dest_rtx, dest_mode, EXPAND_NORMAL); + + if (x != dest_rtx) + emit_move_insn (dest_rtx, x); + do_pending_stack_adjust (); + + seq = get_insns (); + end_sequence (); + + insert_insn_on_edge (seq, e); +} + +/* Insert a copy instruction from RTL expression SRC to partition DEST + onto edge E. */ + +static void +insert_rtx_to_part_on_edge (edge e, int dest, rtx src, int unsignedsrcp, + location_t locus) +{ + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, + "Inserting a temp copy on edge BB%d->BB%d : PART.%d = ", + e->src->index, + e->dest->index, dest); + print_simple_rtl (dump_file, src); + fprintf (dump_file, "\n"); + } + + gcc_assert (SA.partition_to_pseudo[dest]); + + set_location_for_edge (e); + /* If a locus is provided, override the default. */ + if (locus) + set_curr_insn_location (locus); + + /* We give the destination as sizeexp in case src/dest are BLKmode + mems. Usually we give the source. As we result from SSA names + the left and right size should be the same (and no WITH_SIZE_EXPR + involved), so it doesn't matter. */ + rtx_insn *seq = emit_partition_copy (copy_rtx (SA.partition_to_pseudo[dest]), + src, unsignedsrcp, + partition_to_var (SA.map, dest)); + + insert_insn_on_edge (seq, e); +} + +/* Insert a copy instruction from partition SRC to RTL lvalue DEST + onto edge E. */ + +static void +insert_part_to_rtx_on_edge (edge e, rtx dest, int src, location_t locus) +{ + tree var; + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, + "Inserting a temp copy on edge BB%d->BB%d : ", + e->src->index, + e->dest->index); + print_simple_rtl (dump_file, dest); + fprintf (dump_file, "= PART.%d\n", src); + } + + gcc_assert (SA.partition_to_pseudo[src]); + + set_location_for_edge (e); + /* If a locus is provided, override the default. */ + if (locus) + set_curr_insn_location (locus); + + var = partition_to_var (SA.map, src); + rtx_insn *seq = emit_partition_copy (dest, + copy_rtx (SA.partition_to_pseudo[src]), + TYPE_UNSIGNED (TREE_TYPE (var)), + var); + + insert_insn_on_edge (seq, e); +} + + +/* Create an elimination graph for map. */ + +elim_graph::elim_graph (var_map map) : + nodes (30), edge_list (20), edge_locus (10), visited (map->num_partitions), + stack (30), map (map), const_dests (20), const_copies (20), copy_locus (10) +{ +} + + +/* Empty elimination graph G. */ + +static inline void +clear_elim_graph (elim_graph *g) +{ + g->nodes.truncate (0); + g->edge_list.truncate (0); + g->edge_locus.truncate (0); +} + + +/* Return the number of nodes in graph G. */ + +static inline int +elim_graph_size (elim_graph *g) +{ + return g->nodes.length (); +} + + +/* Add NODE to graph G, if it doesn't exist already. */ + +static inline void +elim_graph_add_node (elim_graph *g, int node) +{ + int x; + int t; + + FOR_EACH_VEC_ELT (g->nodes, x, t) + if (t == node) + return; + g->nodes.safe_push (node); +} + + +/* Add the edge PRED->SUCC to graph G. */ + +static inline void +elim_graph_add_edge (elim_graph *g, int pred, int succ, location_t locus) +{ + g->edge_list.safe_push (pred); + g->edge_list.safe_push (succ); + g->edge_locus.safe_push (locus); +} + + +/* Remove an edge from graph G for which NODE is the predecessor, and + return the successor node. -1 is returned if there is no such edge. */ + +static inline int +elim_graph_remove_succ_edge (elim_graph *g, int node, location_t *locus) +{ + int y; + unsigned x; + for (x = 0; x < g->edge_list.length (); x += 2) + if (g->edge_list[x] == node) + { + g->edge_list[x] = -1; + y = g->edge_list[x + 1]; + g->edge_list[x + 1] = -1; + *locus = g->edge_locus[x / 2]; + g->edge_locus[x / 2] = UNKNOWN_LOCATION; + return y; + } + *locus = UNKNOWN_LOCATION; + return -1; +} + + +/* Find all the nodes in GRAPH which are successors to NODE in the + edge list. VAR will hold the partition number found. CODE is the + code fragment executed for every node found. */ + +#define FOR_EACH_ELIM_GRAPH_SUCC(GRAPH, NODE, VAR, LOCUS, CODE) \ +do { \ + unsigned x_; \ + int y_; \ + for (x_ = 0; x_ < (GRAPH)->edge_list.length (); x_ += 2) \ + { \ + y_ = (GRAPH)->edge_list[x_]; \ + if (y_ != (NODE)) \ + continue; \ + (void) ((VAR) = (GRAPH)->edge_list[x_ + 1]); \ + (void) ((LOCUS) = (GRAPH)->edge_locus[x_ / 2]); \ + CODE; \ + } \ +} while (0) + + +/* Find all the nodes which are predecessors of NODE in the edge list for + GRAPH. VAR will hold the partition number found. CODE is the + code fragment executed for every node found. */ + +#define FOR_EACH_ELIM_GRAPH_PRED(GRAPH, NODE, VAR, LOCUS, CODE) \ +do { \ + unsigned x_; \ + int y_; \ + for (x_ = 0; x_ < (GRAPH)->edge_list.length (); x_ += 2) \ + { \ + y_ = (GRAPH)->edge_list[x_ + 1]; \ + if (y_ != (NODE)) \ + continue; \ + (void) ((VAR) = (GRAPH)->edge_list[x_]); \ + (void) ((LOCUS) = (GRAPH)->edge_locus[x_ / 2]); \ + CODE; \ + } \ +} while (0) + + +/* Add T to elimination graph G. */ + +static inline void +eliminate_name (elim_graph *g, int T) +{ + elim_graph_add_node (g, T); +} + +/* Return true if this phi argument T should have a copy queued when using + var_map MAP. PHI nodes should contain only ssa_names and invariants. A + test for ssa_name is definitely simpler, but don't let invalid contents + slip through in the meantime. */ + +static inline bool +queue_phi_copy_p (var_map map, tree t) +{ + if (TREE_CODE (t) == SSA_NAME) + { + if (var_to_partition (map, t) == NO_PARTITION) + return true; + return false; + } + gcc_checking_assert (is_gimple_min_invariant (t)); + return true; +} + +/* Build elimination graph G for basic block BB on incoming PHI edge + G->e. */ + +static void +eliminate_build (elim_graph *g) +{ + tree Ti; + int p0, pi; + gphi_iterator gsi; + + clear_elim_graph (g); + + for (gsi = gsi_start_phis (g->e->dest); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gphi *phi = gsi.phi (); + location_t locus; + + p0 = var_to_partition (g->map, gimple_phi_result (phi)); + /* Ignore results which are not in partitions. */ + if (p0 == NO_PARTITION) + continue; + + Ti = PHI_ARG_DEF (phi, g->e->dest_idx); + /* See set_location_for_edge for the rationale. */ + if (g->e->flags & EDGE_EH) + locus = UNKNOWN_LOCATION; + else + locus = gimple_phi_arg_location_from_edge (phi, g->e); + + /* If this argument is a constant, or a SSA_NAME which is being + left in SSA form, just queue a copy to be emitted on this + edge. */ + if (queue_phi_copy_p (g->map, Ti)) + { + /* Save constant copies until all other copies have been emitted + on this edge. */ + g->const_dests.safe_push (p0); + g->const_copies.safe_push (Ti); + g->copy_locus.safe_push (locus); + } + else + { + pi = var_to_partition (g->map, Ti); + if (p0 != pi) + { + eliminate_name (g, p0); + eliminate_name (g, pi); + elim_graph_add_edge (g, p0, pi, locus); + } + } + } +} + + +/* Push successors of T onto the elimination stack for G. */ + +static void +elim_forward (elim_graph *g, int T) +{ + int S; + location_t locus; + + bitmap_set_bit (g->visited, T); + FOR_EACH_ELIM_GRAPH_SUCC (g, T, S, locus, + { + if (!bitmap_bit_p (g->visited, S)) + elim_forward (g, S); + }); + g->stack.safe_push (T); +} + + +/* Return 1 if there unvisited predecessors of T in graph G. */ + +static int +elim_unvisited_predecessor (elim_graph *g, int T) +{ + int P; + location_t locus; + + FOR_EACH_ELIM_GRAPH_PRED (g, T, P, locus, + { + if (!bitmap_bit_p (g->visited, P)) + return 1; + }); + return 0; +} + +/* Process predecessors first, and insert a copy. */ + +static void +elim_backward (elim_graph *g, int T) +{ + int P; + location_t locus; + + bitmap_set_bit (g->visited, T); + FOR_EACH_ELIM_GRAPH_PRED (g, T, P, locus, + { + if (!bitmap_bit_p (g->visited, P)) + { + elim_backward (g, P); + insert_partition_copy_on_edge (g->e, P, T, locus); + } + }); +} + +/* Allocate a new pseudo register usable for storing values sitting + in NAME (a decl or SSA name), i.e. with matching mode and attributes. */ + +static rtx +get_temp_reg (tree name) +{ + tree type = TREE_TYPE (name); + int unsignedp; + machine_mode reg_mode = promote_ssa_mode (name, &unsignedp); + if (reg_mode == BLKmode) + return assign_temp (type, 0, 0); + rtx x = gen_reg_rtx (reg_mode); + if (POINTER_TYPE_P (type)) + mark_reg_pointer (x, TYPE_ALIGN (TREE_TYPE (type))); + return x; +} + +/* Insert required copies for T in graph G. Check for a strongly connected + region, and create a temporary to break the cycle if one is found. */ + +static void +elim_create (elim_graph *g, int T) +{ + int P, S; + location_t locus; + + if (elim_unvisited_predecessor (g, T)) + { + tree var = partition_to_var (g->map, T); + rtx U = get_temp_reg (var); + int unsignedsrcp = TYPE_UNSIGNED (TREE_TYPE (var)); + + insert_part_to_rtx_on_edge (g->e, U, T, UNKNOWN_LOCATION); + FOR_EACH_ELIM_GRAPH_PRED (g, T, P, locus, + { + if (!bitmap_bit_p (g->visited, P)) + { + elim_backward (g, P); + insert_rtx_to_part_on_edge (g->e, P, U, unsignedsrcp, locus); + } + }); + } + else + { + S = elim_graph_remove_succ_edge (g, T, &locus); + if (S != -1) + { + bitmap_set_bit (g->visited, T); + insert_partition_copy_on_edge (g->e, T, S, locus); + } + } +} + + +/* Eliminate all the phi nodes on edge E in graph G. */ + +static void +eliminate_phi (edge e, elim_graph *g) +{ + int x; + + gcc_assert (g->const_copies.length () == 0); + gcc_assert (g->copy_locus.length () == 0); + + /* Abnormal edges already have everything coalesced. */ + if (e->flags & EDGE_ABNORMAL) + return; + + g->e = e; + + eliminate_build (g); + + if (elim_graph_size (g) != 0) + { + int part; + + bitmap_clear (g->visited); + g->stack.truncate (0); + + FOR_EACH_VEC_ELT (g->nodes, x, part) + { + if (!bitmap_bit_p (g->visited, part)) + elim_forward (g, part); + } + + bitmap_clear (g->visited); + while (g->stack.length () > 0) + { + x = g->stack.pop (); + if (!bitmap_bit_p (g->visited, x)) + elim_create (g, x); + } + } + + /* If there are any pending constant copies, issue them now. */ + while (g->const_copies.length () > 0) + { + int dest; + tree src; + location_t locus; + + src = g->const_copies.pop (); + dest = g->const_dests.pop (); + locus = g->copy_locus.pop (); + insert_value_copy_on_edge (e, dest, src, locus); + } +} + + +/* Remove each argument from PHI. If an arg was the last use of an SSA_NAME, + check to see if this allows another PHI node to be removed. */ + +static void +remove_gimple_phi_args (gphi *phi) +{ + use_operand_p arg_p; + ssa_op_iter iter; + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "Removing Dead PHI definition: "); + print_gimple_stmt (dump_file, phi, 0, TDF_SLIM); + } + + FOR_EACH_PHI_ARG (arg_p, phi, iter, SSA_OP_USE) + { + tree arg = USE_FROM_PTR (arg_p); + if (TREE_CODE (arg) == SSA_NAME) + { + /* Remove the reference to the existing argument. */ + SET_USE (arg_p, NULL_TREE); + if (has_zero_uses (arg)) + { + gimple *stmt; + gimple_stmt_iterator gsi; + + stmt = SSA_NAME_DEF_STMT (arg); + + /* Also remove the def if it is a PHI node. */ + if (gimple_code (stmt) == GIMPLE_PHI) + { + remove_gimple_phi_args (as_a <gphi *> (stmt)); + gsi = gsi_for_stmt (stmt); + remove_phi_node (&gsi, true); + } + + } + } + } +} + +/* Remove any PHI node which is a virtual PHI, or a PHI with no uses. */ + +static void +eliminate_useless_phis (void) +{ + basic_block bb; + gphi_iterator gsi; + tree result; + + FOR_EACH_BB_FN (bb, cfun) + { + for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); ) + { + gphi *phi = gsi.phi (); + result = gimple_phi_result (phi); + if (virtual_operand_p (result)) + remove_phi_node (&gsi, true); + else + { + /* Also remove real PHIs with no uses. */ + if (has_zero_uses (result)) + { + remove_gimple_phi_args (phi); + remove_phi_node (&gsi, true); + } + else + gsi_next (&gsi); + } + } + } +} + + +/* This function will rewrite the current program using the variable mapping + found in MAP. If the replacement vector VALUES is provided, any + occurrences of partitions with non-null entries in the vector will be + replaced with the expression in the vector instead of its mapped + variable. */ + +static void +rewrite_trees (var_map map) +{ + if (!flag_checking) + return; + + basic_block bb; + /* Search for PHIs where the destination has no partition, but one + or more arguments has a partition. This should not happen and can + create incorrect code. */ + FOR_EACH_BB_FN (bb, cfun) + { + gphi_iterator gsi; + for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gphi *phi = gsi.phi (); + tree T0 = var_to_partition_to_var (map, gimple_phi_result (phi)); + if (T0 == NULL_TREE) + { + size_t i; + for (i = 0; i < gimple_phi_num_args (phi); i++) + { + tree arg = PHI_ARG_DEF (phi, i); + + if (TREE_CODE (arg) == SSA_NAME + && var_to_partition (map, arg) != NO_PARTITION) + { + fprintf (stderr, "Argument of PHI is in a partition :("); + print_generic_expr (stderr, arg, TDF_SLIM); + fprintf (stderr, "), but the result is not :"); + print_gimple_stmt (stderr, phi, 0, TDF_SLIM); + internal_error ("SSA corruption"); + } + } + } + } + } +} + +/* Create a default def for VAR. */ + +static void +create_default_def (tree var, void *arg ATTRIBUTE_UNUSED) +{ + if (!is_gimple_reg (var)) + return; + + tree ssa = get_or_create_ssa_default_def (cfun, var); + gcc_assert (ssa); +} + +/* Call CALLBACK for all PARM_DECLs and RESULT_DECLs for which + assign_parms may ask for a default partition. */ + +static void +for_all_parms (void (*callback)(tree var, void *arg), void *arg) +{ + for (tree var = DECL_ARGUMENTS (current_function_decl); var; + var = DECL_CHAIN (var)) + callback (var, arg); + if (!VOID_TYPE_P (TREE_TYPE (DECL_RESULT (current_function_decl)))) + callback (DECL_RESULT (current_function_decl), arg); + if (cfun->static_chain_decl) + callback (cfun->static_chain_decl, arg); +} + +/* We need to pass two arguments to set_parm_default_def_partition, + but for_all_parms only supports one. Use a pair. */ + +typedef std::pair<var_map, bitmap> parm_default_def_partition_arg; + +/* Set in ARG's PARTS bitmap the bit corresponding to the partition in + ARG's MAP containing VAR's default def. */ + +static void +set_parm_default_def_partition (tree var, void *arg_) +{ + parm_default_def_partition_arg *arg = (parm_default_def_partition_arg *)arg_; + var_map map = arg->first; + bitmap parts = arg->second; + + if (!is_gimple_reg (var)) + return; + + tree ssa = ssa_default_def (cfun, var); + gcc_assert (ssa); + + int version = var_to_partition (map, ssa); + gcc_assert (version != NO_PARTITION); + + bool changed = bitmap_set_bit (parts, version); + gcc_assert (changed); +} + +/* Allocate and return a bitmap that has a bit set for each partition + that contains a default def for a parameter. */ + +static bitmap +get_parm_default_def_partitions (var_map map) +{ + bitmap parm_default_def_parts = BITMAP_ALLOC (NULL); + + parm_default_def_partition_arg + arg = std::make_pair (map, parm_default_def_parts); + + for_all_parms (set_parm_default_def_partition, &arg); + + return parm_default_def_parts; +} + +/* Allocate and return a bitmap that has a bit set for each partition + that contains an undefined value. */ + +static bitmap +get_undefined_value_partitions (var_map map) +{ + bitmap undefined_value_parts = BITMAP_ALLOC (NULL); + + for (unsigned int i = 1; i < num_ssa_names; i++) + { + tree var = ssa_name (i); + if (var + && !virtual_operand_p (var) + && !has_zero_uses (var) + && ssa_undefined_value_p (var)) + { + const int p = var_to_partition (map, var); + if (p != NO_PARTITION) + bitmap_set_bit (undefined_value_parts, p); + } + } + + return undefined_value_parts; +} + +/* Given the out-of-ssa info object SA (with prepared partitions) + eliminate all phi nodes in all basic blocks. Afterwards no + basic block will have phi nodes anymore and there are possibly + some RTL instructions inserted on edges. */ + +void +expand_phi_nodes (struct ssaexpand *sa) +{ + basic_block bb; + elim_graph g (sa->map); + + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb, + EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb) + if (!gimple_seq_empty_p (phi_nodes (bb))) + { + edge e; + edge_iterator ei; + FOR_EACH_EDGE (e, ei, bb->preds) + eliminate_phi (e, &g); + set_phi_nodes (bb, NULL); + /* We can't redirect EH edges in RTL land, so we need to do this + here. Redirection happens only when splitting is necessary, + which it is only for critical edges, normally. For EH edges + it might also be necessary when the successor has more than + one predecessor. In that case the edge is either required to + be fallthru (which EH edges aren't), or the predecessor needs + to end with a jump (which again, isn't the case with EH edges). + Hence, split all EH edges on which we inserted instructions + and whose successor has multiple predecessors. */ + for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); ) + { + if (e->insns.r && (e->flags & EDGE_EH) + && !single_pred_p (e->dest)) + { + rtx_insn *insns = e->insns.r; + basic_block bb; + e->insns.r = NULL; + bb = split_edge (e); + single_pred_edge (bb)->insns.r = insns; + } + else + ei_next (&ei); + } + } +} + + +/* Remove the ssa-names in the current function and translate them into normal + compiler variables. PERFORM_TER is true if Temporary Expression Replacement + should also be used. */ + +static void +remove_ssa_form (bool perform_ter, struct ssaexpand *sa) +{ + bitmap values = NULL; + var_map map; + + for_all_parms (create_default_def, NULL); + map = init_var_map (num_ssa_names); + coalesce_ssa_name (map); + + /* Return to viewing the variable list as just all reference variables after + coalescing has been performed. */ + partition_view_normal (map); + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "After Coalescing:\n"); + dump_var_map (dump_file, map); + } + + if (perform_ter) + { + values = find_replaceable_exprs (map); + if (values && dump_file && (dump_flags & TDF_DETAILS)) + dump_replaceable_exprs (dump_file, values); + } + + rewrite_trees (map); + + sa->map = map; + sa->values = values; + sa->partitions_for_parm_default_defs = get_parm_default_def_partitions (map); + sa->partitions_for_undefined_values = get_undefined_value_partitions (map); +} + + +/* If not already done so for basic block BB, assign increasing uids + to each of its instructions. */ + +static void +maybe_renumber_stmts_bb (basic_block bb) +{ + unsigned i = 0; + gimple_stmt_iterator gsi; + + if (!bb->aux) + return; + bb->aux = NULL; + for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gimple *stmt = gsi_stmt (gsi); + gimple_set_uid (stmt, i); + i++; + } +} + + +/* Return true if we can determine that the SSA_NAMEs RESULT (a result + of a PHI node) and ARG (one of its arguments) conflict. Return false + otherwise, also when we simply aren't sure. */ + +static bool +trivially_conflicts_p (basic_block bb, tree result, tree arg) +{ + use_operand_p use; + imm_use_iterator imm_iter; + gimple *defa = SSA_NAME_DEF_STMT (arg); + + /* If ARG isn't defined in the same block it's too complicated for + our little mind. */ + if (gimple_bb (defa) != bb) + return false; + + FOR_EACH_IMM_USE_FAST (use, imm_iter, result) + { + gimple *use_stmt = USE_STMT (use); + if (is_gimple_debug (use_stmt)) + continue; + /* Now, if there's a use of RESULT that lies outside this basic block, + then there surely is a conflict with ARG. */ + if (gimple_bb (use_stmt) != bb) + return true; + if (gimple_code (use_stmt) == GIMPLE_PHI) + continue; + /* The use now is in a real stmt of BB, so if ARG was defined + in a PHI node (like RESULT) both conflict. */ + if (gimple_code (defa) == GIMPLE_PHI) + return true; + maybe_renumber_stmts_bb (bb); + /* If the use of RESULT occurs after the definition of ARG, + the two conflict too. */ + if (gimple_uid (defa) < gimple_uid (use_stmt)) + return true; + } + + return false; +} + + +/* Search every PHI node for arguments associated with backedges which + we can trivially determine will need a copy (the argument is either + not an SSA_NAME or the argument has a different underlying variable + than the PHI result). + + Insert a copy from the PHI argument to a new destination at the + end of the block with the backedge to the top of the loop. Update + the PHI argument to reference this new destination. */ + +static void +insert_backedge_copies (void) +{ + basic_block bb; + gphi_iterator gsi; + + mark_dfs_back_edges (); + + FOR_EACH_BB_FN (bb, cfun) + { + /* Mark block as possibly needing calculation of UIDs. */ + bb->aux = &bb->aux; + + for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) + { + gphi *phi = gsi.phi (); + tree result = gimple_phi_result (phi); + size_t i; + + if (virtual_operand_p (result)) + continue; + + for (i = 0; i < gimple_phi_num_args (phi); i++) + { + tree arg = gimple_phi_arg_def (phi, i); + edge e = gimple_phi_arg_edge (phi, i); + /* We are only interested in copies emitted on critical + backedges. */ + if (!(e->flags & EDGE_DFS_BACK) + || !EDGE_CRITICAL_P (e)) + continue; + + /* If the argument is not an SSA_NAME, then we will need a + constant initialization. If the argument is an SSA_NAME then + a copy statement may be needed. First handle the case + where we cannot insert before the argument definition. */ + if (TREE_CODE (arg) != SSA_NAME + || (gimple_code (SSA_NAME_DEF_STMT (arg)) == GIMPLE_PHI + && trivially_conflicts_p (bb, result, arg))) + { + tree name; + gassign *stmt; + gimple *last = NULL; + gimple_stmt_iterator gsi2; + + gsi2 = gsi_last_bb (gimple_phi_arg_edge (phi, i)->src); + if (!gsi_end_p (gsi2)) + last = gsi_stmt (gsi2); + + /* In theory the only way we ought to get back to the + start of a loop should be with a COND_EXPR or GOTO_EXPR. + However, better safe than sorry. + If the block ends with a control statement or + something that might throw, then we have to + insert this assignment before the last + statement. Else insert it after the last statement. */ + if (last && stmt_ends_bb_p (last)) + { + /* If the last statement in the block is the definition + site of the PHI argument, then we can't insert + anything after it. */ + if (TREE_CODE (arg) == SSA_NAME + && SSA_NAME_DEF_STMT (arg) == last) + continue; + } + + /* Create a new instance of the underlying variable of the + PHI result. */ + name = copy_ssa_name (result); + stmt = gimple_build_assign (name, + gimple_phi_arg_def (phi, i)); + + /* copy location if present. */ + if (gimple_phi_arg_has_location (phi, i)) + gimple_set_location (stmt, + gimple_phi_arg_location (phi, i)); + + /* Insert the new statement into the block and update + the PHI node. */ + if (last && stmt_ends_bb_p (last)) + gsi_insert_before (&gsi2, stmt, GSI_NEW_STMT); + else + gsi_insert_after (&gsi2, stmt, GSI_NEW_STMT); + SET_PHI_ARG_DEF (phi, i, name); + } + /* Insert a copy before the definition of the backedge value + and adjust all conflicting uses. */ + else if (trivially_conflicts_p (bb, result, arg)) + { + gimple *def = SSA_NAME_DEF_STMT (arg); + if (gimple_nop_p (def) + || gimple_code (def) == GIMPLE_PHI) + continue; + tree name = copy_ssa_name (result); + gimple *stmt = gimple_build_assign (name, result); + imm_use_iterator imm_iter; + gimple *use_stmt; + /* The following matches trivially_conflicts_p. */ + FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, result) + { + if (gimple_bb (use_stmt) != bb + || (gimple_code (use_stmt) != GIMPLE_PHI + && (maybe_renumber_stmts_bb (bb), true) + && gimple_uid (use_stmt) > gimple_uid (def))) + { + use_operand_p use; + FOR_EACH_IMM_USE_ON_STMT (use, imm_iter) + SET_USE (use, name); + } + } + gimple_stmt_iterator gsi = gsi_for_stmt (def); + gsi_insert_before (&gsi, stmt, GSI_SAME_STMT); + } + } + } + + /* Unmark this block again. */ + bb->aux = NULL; + } +} + +/* Free all memory associated with going out of SSA form. SA is + the outof-SSA info object. */ + +void +finish_out_of_ssa (struct ssaexpand *sa) +{ + free (sa->partition_to_pseudo); + if (sa->values) + BITMAP_FREE (sa->values); + delete_var_map (sa->map); + BITMAP_FREE (sa->partitions_for_parm_default_defs); + BITMAP_FREE (sa->partitions_for_undefined_values); + memset (sa, 0, sizeof *sa); +} + +/* Take the current function out of SSA form, translating PHIs as described in + R. Morgan, ``Building an Optimizing Compiler'', + Butterworth-Heinemann, Boston, MA, 1998. pp 176-186. */ + +unsigned int +rewrite_out_of_ssa (struct ssaexpand *sa) +{ + /* If elimination of a PHI requires inserting a copy on a backedge, + then we will have to split the backedge which has numerous + undesirable performance effects. + + A significant number of such cases can be handled here by inserting + copies into the loop itself. */ + insert_backedge_copies (); + + + /* Eliminate PHIs which are of no use, such as virtual or dead phis. */ + eliminate_useless_phis (); + + if (dump_file && (dump_flags & TDF_DETAILS)) + gimple_dump_cfg (dump_file, dump_flags & ~TDF_DETAILS); + + remove_ssa_form (flag_tree_ter, sa); + + if (dump_file && (dump_flags & TDF_DETAILS)) + gimple_dump_cfg (dump_file, dump_flags & ~TDF_DETAILS); + + return 0; +} |