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[/] [openrisc/] [trunk/] [gnu-src/] [gcc-4.2.2/] [gcc/] [cfgloopanal.c] - Rev 318
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/* Natural loop analysis code for GNU compiler. Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc. 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 "tm.h" #include "rtl.h" #include "hard-reg-set.h" #include "obstack.h" #include "basic-block.h" #include "cfgloop.h" #include "expr.h" #include "output.h" /* Checks whether BB is executed exactly once in each LOOP iteration. */ bool just_once_each_iteration_p (const struct loop *loop, basic_block bb) { /* It must be executed at least once each iteration. */ if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb)) return false; /* And just once. */ if (bb->loop_father != loop) return false; /* But this was not enough. We might have some irreducible loop here. */ if (bb->flags & BB_IRREDUCIBLE_LOOP) return false; return true; } /* Structure representing edge of a graph. */ struct edge { int src, dest; /* Source and destination. */ struct edge *pred_next, *succ_next; /* Next edge in predecessor and successor lists. */ void *data; /* Data attached to the edge. */ }; /* Structure representing vertex of a graph. */ struct vertex { struct edge *pred, *succ; /* Lists of predecessors and successors. */ int component; /* Number of dfs restarts before reaching the vertex. */ int post; /* Postorder number. */ }; /* Structure representing a graph. */ struct graph { int n_vertices; /* Number of vertices. */ struct vertex *vertices; /* The vertices. */ }; /* Dumps graph G into F. */ extern void dump_graph (FILE *, struct graph *); void dump_graph (FILE *f, struct graph *g) { int i; struct edge *e; for (i = 0; i < g->n_vertices; i++) { if (!g->vertices[i].pred && !g->vertices[i].succ) continue; fprintf (f, "%d (%d)\t<-", i, g->vertices[i].component); for (e = g->vertices[i].pred; e; e = e->pred_next) fprintf (f, " %d", e->src); fprintf (f, "\n"); fprintf (f, "\t->"); for (e = g->vertices[i].succ; e; e = e->succ_next) fprintf (f, " %d", e->dest); fprintf (f, "\n"); } } /* Creates a new graph with N_VERTICES vertices. */ static struct graph * new_graph (int n_vertices) { struct graph *g = XNEW (struct graph); g->n_vertices = n_vertices; g->vertices = XCNEWVEC (struct vertex, n_vertices); return g; } /* Adds an edge from F to T to graph G, with DATA attached. */ static void add_edge (struct graph *g, int f, int t, void *data) { struct edge *e = xmalloc (sizeof (struct edge)); e->src = f; e->dest = t; e->data = data; e->pred_next = g->vertices[t].pred; g->vertices[t].pred = e; e->succ_next = g->vertices[f].succ; g->vertices[f].succ = e; } /* Runs dfs search over vertices of G, from NQ vertices in queue QS. The vertices in postorder are stored into QT. If FORWARD is false, backward dfs is run. */ static void dfs (struct graph *g, int *qs, int nq, int *qt, bool forward) { int i, tick = 0, v, comp = 0, top; struct edge *e; struct edge **stack = xmalloc (sizeof (struct edge *) * g->n_vertices); for (i = 0; i < g->n_vertices; i++) { g->vertices[i].component = -1; g->vertices[i].post = -1; } #define FST_EDGE(V) (forward ? g->vertices[(V)].succ : g->vertices[(V)].pred) #define NEXT_EDGE(E) (forward ? (E)->succ_next : (E)->pred_next) #define EDGE_SRC(E) (forward ? (E)->src : (E)->dest) #define EDGE_DEST(E) (forward ? (E)->dest : (E)->src) for (i = 0; i < nq; i++) { v = qs[i]; if (g->vertices[v].post != -1) continue; g->vertices[v].component = comp++; e = FST_EDGE (v); top = 0; while (1) { while (e && g->vertices[EDGE_DEST (e)].component != -1) e = NEXT_EDGE (e); if (!e) { if (qt) qt[tick] = v; g->vertices[v].post = tick++; if (!top) break; e = stack[--top]; v = EDGE_SRC (e); e = NEXT_EDGE (e); continue; } stack[top++] = e; v = EDGE_DEST (e); e = FST_EDGE (v); g->vertices[v].component = comp - 1; } } free (stack); } /* Marks the edge E in graph G irreducible if it connects two vertices in the same scc. */ static void check_irred (struct graph *g, struct edge *e) { edge real = e->data; /* All edges should lead from a component with higher number to the one with lower one. */ gcc_assert (g->vertices[e->src].component >= g->vertices[e->dest].component); if (g->vertices[e->src].component != g->vertices[e->dest].component) return; real->flags |= EDGE_IRREDUCIBLE_LOOP; if (flow_bb_inside_loop_p (real->src->loop_father, real->dest)) real->src->flags |= BB_IRREDUCIBLE_LOOP; } /* Runs CALLBACK for all edges in G. */ static void for_each_edge (struct graph *g, void (callback) (struct graph *, struct edge *)) { struct edge *e; int i; for (i = 0; i < g->n_vertices; i++) for (e = g->vertices[i].succ; e; e = e->succ_next) callback (g, e); } /* Releases the memory occupied by G. */ static void free_graph (struct graph *g) { struct edge *e, *n; int i; for (i = 0; i < g->n_vertices; i++) for (e = g->vertices[i].succ; e; e = n) { n = e->succ_next; free (e); } free (g->vertices); free (g); } /* Marks blocks and edges that are part of non-recognized loops; i.e. we throw away all latch edges and mark blocks inside any remaining cycle. Everything is a bit complicated due to fact we do not want to do this for parts of cycles that only "pass" through some loop -- i.e. for each cycle, we want to mark blocks that belong directly to innermost loop containing the whole cycle. LOOPS is the loop tree. */ #define LOOP_REPR(LOOP) ((LOOP)->num + last_basic_block) #define BB_REPR(BB) ((BB)->index + 1) void mark_irreducible_loops (struct loops *loops) { basic_block act; edge e; edge_iterator ei; int i, src, dest; struct graph *g; int *queue1 = XNEWVEC (int, last_basic_block + loops->num); int *queue2 = XNEWVEC (int, last_basic_block + loops->num); int nq, depth; struct loop *cloop; /* Reset the flags. */ FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) { act->flags &= ~BB_IRREDUCIBLE_LOOP; FOR_EACH_EDGE (e, ei, act->succs) e->flags &= ~EDGE_IRREDUCIBLE_LOOP; } /* Create the edge lists. */ g = new_graph (last_basic_block + loops->num); FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) FOR_EACH_EDGE (e, ei, act->succs) { /* Ignore edges to exit. */ if (e->dest == EXIT_BLOCK_PTR) continue; /* And latch edges. */ if (e->dest->loop_father->header == e->dest && e->dest->loop_father->latch == act) continue; /* Edges inside a single loop should be left where they are. Edges to subloop headers should lead to representative of the subloop, but from the same place. Edges exiting loops should lead from representative of the son of nearest common ancestor of the loops in that act lays. */ src = BB_REPR (act); dest = BB_REPR (e->dest); if (e->dest->loop_father->header == e->dest) dest = LOOP_REPR (e->dest->loop_father); if (!flow_bb_inside_loop_p (act->loop_father, e->dest)) { depth = find_common_loop (act->loop_father, e->dest->loop_father)->depth + 1; if (depth == act->loop_father->depth) cloop = act->loop_father; else cloop = act->loop_father->pred[depth]; src = LOOP_REPR (cloop); } add_edge (g, src, dest, e); } /* Find the strongly connected components. Use the algorithm of Tarjan -- first determine the postorder dfs numbering in reversed graph, then run the dfs on the original graph in the order given by decreasing numbers assigned by the previous pass. */ nq = 0; FOR_BB_BETWEEN (act, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb) { queue1[nq++] = BB_REPR (act); } for (i = 1; i < (int) loops->num; i++) if (loops->parray[i]) queue1[nq++] = LOOP_REPR (loops->parray[i]); dfs (g, queue1, nq, queue2, false); for (i = 0; i < nq; i++) queue1[i] = queue2[nq - i - 1]; dfs (g, queue1, nq, NULL, true); /* Mark the irreducible loops. */ for_each_edge (g, check_irred); free_graph (g); free (queue1); free (queue2); loops->state |= LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS; } /* Counts number of insns inside LOOP. */ int num_loop_insns (struct loop *loop) { basic_block *bbs, bb; unsigned i, ninsns = 0; rtx insn; bbs = get_loop_body (loop); for (i = 0; i < loop->num_nodes; i++) { bb = bbs[i]; ninsns++; for (insn = BB_HEAD (bb); insn != BB_END (bb); insn = NEXT_INSN (insn)) if (INSN_P (insn)) ninsns++; } free(bbs); return ninsns; } /* Counts number of insns executed on average per iteration LOOP. */ int average_num_loop_insns (struct loop *loop) { basic_block *bbs, bb; unsigned i, binsns, ninsns, ratio; rtx insn; ninsns = 0; bbs = get_loop_body (loop); for (i = 0; i < loop->num_nodes; i++) { bb = bbs[i]; binsns = 1; for (insn = BB_HEAD (bb); insn != BB_END (bb); insn = NEXT_INSN (insn)) if (INSN_P (insn)) binsns++; ratio = loop->header->frequency == 0 ? BB_FREQ_MAX : (bb->frequency * BB_FREQ_MAX) / loop->header->frequency; ninsns += binsns * ratio; } free(bbs); ninsns /= BB_FREQ_MAX; if (!ninsns) ninsns = 1; /* To avoid division by zero. */ return ninsns; } /* Returns expected number of LOOP iterations. Compute upper bound on number of iterations in case they do not fit integer to help loop peeling heuristics. Use exact counts if at all possible. */ unsigned expected_loop_iterations (const struct loop *loop) { edge e; edge_iterator ei; if (loop->latch->count || loop->header->count) { gcov_type count_in, count_latch, expected; count_in = 0; count_latch = 0; FOR_EACH_EDGE (e, ei, loop->header->preds) if (e->src == loop->latch) count_latch = e->count; else count_in += e->count; if (count_in == 0) expected = count_latch * 2; else expected = (count_latch + count_in - 1) / count_in; /* Avoid overflows. */ return (expected > REG_BR_PROB_BASE ? REG_BR_PROB_BASE : expected); } else { int freq_in, freq_latch; freq_in = 0; freq_latch = 0; FOR_EACH_EDGE (e, ei, loop->header->preds) if (e->src == loop->latch) freq_latch = EDGE_FREQUENCY (e); else freq_in += EDGE_FREQUENCY (e); if (freq_in == 0) return freq_latch * 2; return (freq_latch + freq_in - 1) / freq_in; } } /* Returns the maximum level of nesting of subloops of LOOP. */ unsigned get_loop_level (const struct loop *loop) { const struct loop *ploop; unsigned mx = 0, l; for (ploop = loop->inner; ploop; ploop = ploop->next) { l = get_loop_level (ploop); if (l >= mx) mx = l + 1; } return mx; } /* Returns estimate on cost of computing SEQ. */ static unsigned seq_cost (rtx seq) { unsigned cost = 0; rtx set; for (; seq; seq = NEXT_INSN (seq)) { set = single_set (seq); if (set) cost += rtx_cost (set, SET); else cost++; } return cost; } /* The properties of the target. */ unsigned target_avail_regs; /* Number of available registers. */ unsigned target_res_regs; /* Number of reserved registers. */ unsigned target_small_cost; /* The cost for register when there is a free one. */ unsigned target_pres_cost; /* The cost for register when there are not too many free ones. */ unsigned target_spill_cost; /* The cost for register when we need to spill. */ /* Initialize the constants for computing set costs. */ void init_set_costs (void) { rtx seq; rtx reg1 = gen_raw_REG (SImode, FIRST_PSEUDO_REGISTER); rtx reg2 = gen_raw_REG (SImode, FIRST_PSEUDO_REGISTER + 1); rtx addr = gen_raw_REG (Pmode, FIRST_PSEUDO_REGISTER + 2); rtx mem = validize_mem (gen_rtx_MEM (SImode, addr)); unsigned i; for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) if (TEST_HARD_REG_BIT (reg_class_contents[GENERAL_REGS], i) && !fixed_regs[i]) target_avail_regs++; target_res_regs = 3; /* These are really just heuristic values. */ start_sequence (); emit_move_insn (reg1, reg2); seq = get_insns (); end_sequence (); target_small_cost = seq_cost (seq); target_pres_cost = 2 * target_small_cost; start_sequence (); emit_move_insn (mem, reg1); emit_move_insn (reg2, mem); seq = get_insns (); end_sequence (); target_spill_cost = seq_cost (seq); } /* Calculates cost for having SIZE new loop global variables. REGS_USED is the number of global registers used in loop. N_USES is the number of relevant variable uses. */ unsigned global_cost_for_size (unsigned size, unsigned regs_used, unsigned n_uses) { unsigned regs_needed = regs_used + size; unsigned cost = 0; if (regs_needed + target_res_regs <= target_avail_regs) cost += target_small_cost * size; else if (regs_needed <= target_avail_regs) cost += target_pres_cost * size; else { cost += target_pres_cost * size; cost += target_spill_cost * n_uses * (regs_needed - target_avail_regs) / regs_needed; } return cost; } /* Sets EDGE_LOOP_EXIT flag for all exits of LOOPS. */ void mark_loop_exit_edges (struct loops *loops) { basic_block bb; edge e; if (loops->num <= 1) return; FOR_EACH_BB (bb) { edge_iterator ei; FOR_EACH_EDGE (e, ei, bb->succs) { if (bb->loop_father->outer && loop_exit_edge_p (bb->loop_father, e)) e->flags |= EDGE_LOOP_EXIT; else e->flags &= ~EDGE_LOOP_EXIT; } } }
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