X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=ir%2Fopt%2Fcfopt.c;h=ac9c7467d79cd0df1d3865a5df3978f7eb350715;hb=5ea61f3166daab45e560f0d7955fd4c72d8c7167;hp=308fe0fb2d9416ba964d1151aee5db0977ac2a3e;hpb=443bd8c8a8ecd8afdc668a878ff4603bb1cb8ffa;p=libfirm diff --git a/ir/opt/cfopt.c b/ir/opt/cfopt.c index 308fe0fb2..ac9c7467d 100644 --- a/ir/opt/cfopt.c +++ b/ir/opt/cfopt.c @@ -79,7 +79,8 @@ static bool is_Block_removable(ir_node *block) } /** checks if a given Cond node is a switch Cond. */ -static bool is_switch_Cond(ir_node *cond) { +static bool is_switch_Cond(ir_node *cond) +{ ir_node *sel = get_Cond_selector(cond); return get_irn_mode(sel) != mode_b; } @@ -283,6 +284,11 @@ static void optimize_blocks(ir_node *b, void *ctx) ir_node **in; merge_env *env = (merge_env*)ctx; + if (get_Block_dom_depth(b) < 0) { + /* ignore unreachable blocks */ + return; + } + /* Count the number of predecessor if this block is merged with pred blocks that are empty. */ max_preds = 0; @@ -597,38 +603,56 @@ typedef enum block_flags_t { BF_IS_UNKNOWN_JUMP_TARGET = 1 << 2, } block_flags_t; -static bool get_phase_flag(ir_phase *block_info, ir_node *block, int flag) { - return ((int)phase_get_irn_data(block_info, block)) & flag; +static bool get_phase_flag(ir_phase *block_info, ir_node *block, int flag) +{ + return PTR_TO_INT(phase_get_irn_data(block_info, block)) & flag; } -static void set_phase_flag(ir_phase *block_info, ir_node *block, block_flags_t flag) { - int data = (int)phase_get_irn_data(block_info, block); + +static void set_phase_flag(ir_phase *block_info, ir_node *block, + block_flags_t flag) +{ + int data = PTR_TO_INT(phase_get_irn_data(block_info, block)); data |= flag; - phase_set_irn_data(block_info, block, (void*)data); + phase_set_irn_data(block_info, block, INT_TO_PTR(data)); +} + +static void clear_phase_flag(ir_phase *block_info, ir_node *block) +{ + phase_set_irn_data(block_info, block, NULL); } -static bool has_operations(ir_phase *block_info, ir_node *block) { +static bool has_operations(ir_phase *block_info, ir_node *block) +{ return get_phase_flag(block_info, block, BF_HAS_OPERATIONS); } -static void set_has_operations(ir_phase *block_info, ir_node *block) { + +static void set_has_operations(ir_phase *block_info, ir_node *block) +{ set_phase_flag(block_info, block, BF_HAS_OPERATIONS); } -static bool has_phis(ir_phase *block_info, ir_node *block) { +static bool has_phis(ir_phase *block_info, ir_node *block) +{ return get_phase_flag(block_info, block, BF_HAS_PHIS); } -static void set_has_phis(ir_phase *block_info, ir_node *block) { + +static void set_has_phis(ir_phase *block_info, ir_node *block) +{ set_phase_flag(block_info, block, BF_HAS_PHIS); } -static bool is_unknown_jump_target(ir_phase *block_info, ir_node *block) { +static bool is_unknown_jump_target(ir_phase *block_info, ir_node *block) +{ return get_phase_flag(block_info, block, BF_IS_UNKNOWN_JUMP_TARGET); } -static void set_is_unknown_jump_target(ir_phase *block_info, ir_node *block) { + +static void set_is_unknown_jump_target(ir_phase *block_info, ir_node *block) +{ set_phase_flag(block_info, block, BF_IS_UNKNOWN_JUMP_TARGET); } /** - * Walker: fill block info information. + * Pre-Walker: fill block info information. */ static void compute_block_info(ir_node *n, void *x) { @@ -653,6 +677,12 @@ static void compute_block_info(ir_node *n, void *x) } } +static void clear_block_info(ir_node *block, void *x) +{ + ir_phase *block_info = (ir_phase *)x; + clear_phase_flag(block_info, block); +} + typedef struct skip_env { bool changed; ir_phase *phase; @@ -681,8 +711,8 @@ static void optimize_ifs(ir_node *block, void *x) } /** - * Pre-Block walker: remove empty blocks that are - * predecessors of the current block. + * Pre-Block walker: remove empty blocks (only contain a Jmp) + * that are control flow predecessors of the current block. */ static void remove_empty_blocks(ir_node *block, void *x) { @@ -692,49 +722,106 @@ static void remove_empty_blocks(ir_node *block, void *x) for (i = 0; i < n_preds; ++i) { ir_node *jmp, *jmp_block, *pred, *pred_block; + int n_jpreds = NULL; jmp = get_Block_cfgpred(block, i); if (!is_Jmp(jmp)) continue; jmp_block = get_nodes_block(jmp); + if (jmp_block == block) + continue; /* this infinite loop cannot be optimized any further */ if (is_unknown_jump_target(env->phase, jmp_block)) - continue; + continue; /* unknown jump target must not be optimized */ if (has_operations(env->phase,jmp_block)) - continue; - /* jmp_block is an empty block! */ + continue; /* this block contains operations and cannot be skipped */ + if (has_phis(env->phase,jmp_block)) + continue; /* this block contains Phis and is not skipped */ - if (get_Block_n_cfgpreds(jmp_block) != 1) - continue; - pred = get_Block_cfgpred(jmp_block, 0); - exchange(jmp, pred); - env->changed = true; + /* jmp_block is an empty block and can be optimized! */ - /* cleanup: jmp_block might have a Keep edge! */ - pred_block = get_nodes_block(pred); - exchange(jmp_block, pred_block); + n_jpreds = get_Block_n_cfgpreds(jmp_block); + /** + * If the jmp block has only one predecessor this is straightforward. + * However, if there are more predecessors, we only handle this, + * if block has no Phis. + */ + if (n_jpreds == 1) { + /* skip jmp block by rerouting its predecessor to block + * + * A A + * | | + * jmp_block => | + * | | + * block block + */ + pred = get_Block_cfgpred(jmp_block, 0); + exchange(jmp, pred); + + /* cleanup: jmp_block might have a Keep edge! */ + pred_block = get_nodes_block(pred); + exchange(jmp_block, pred_block); + env->changed = true; + } else if (! has_phis(env->phase, block)) { + /* all predecessors can skip the jmp block, so block gets some new predecessors + * + * A B A B + * \ / | | + * jmp_block C => Bad C | | + * \ / \ | | / + * block block + */ + ir_node **ins = NULL; + int j; + NEW_ARR_A(ir_node *, ins, n_preds+n_jpreds); + /* first copy the old predecessors, because the outer loop (i) still walks over them */ + for (j = 0; j < n_preds; ++j) { + ins[j] = get_Block_cfgpred(block, j); + } + /* now append the new predecessors */ + for (j = 0; j < n_jpreds; ++j) { + pred = get_Block_cfgpred(jmp_block, j); + ins[n_preds+j] = pred; + } + set_irn_in(block, n_preds+n_jpreds, ins); + /* convert the jmp_block to Bad */ + ir_graph *irg = get_irn_irg(block); + exchange(jmp_block, new_r_Bad(irg, mode_BB)); + exchange(jmp, new_r_Bad(irg, mode_X)); + /* let the outer loop walk over the new predecessors as well */ + n_preds += n_jpreds; + env->changed = true; + // TODO What if jmp_block had a KeepAlive edge? + } else { + /* This would involve Phis ... */ + } } } /* - * Some cfg optimizations, which do not touch Phi nodes + * All cfg optimizations, which do not touch Phi nodes. + * + * Note that this might create critical edges. */ -static void cfgopt_ignoring_phis(ir_graph *irg) { +static void cfgopt_ignoring_phis(ir_graph *irg) +{ ir_phase *block_info = new_phase(irg, NULL); - skip_env env = { false, block_info }; - - irg_walk_graph(irg, compute_block_info, NULL, block_info); + skip_env env = { true, block_info }; - for (;;) { + while (env.changed) { + irg_walk_graph(irg, compute_block_info, NULL, block_info); env.changed = false; - /* optimize useless ifs: will not touch empty blocks */ + /* Remove blocks, which only consist of a Jmp */ + irg_block_walk_graph(irg, remove_empty_blocks, NULL, &env); + + /* Optimize Cond->Jmp, where then- and else-block are the same. */ irg_block_walk_graph(irg, NULL, optimize_ifs, &env); - /* Remove empty blocks */ - irg_block_walk_graph(irg, remove_empty_blocks, NULL, &env); if (env.changed) { set_irg_doms_inconsistent(irg); - /* Removing blocks might enable more useless-if optimizations */ + /* clear block info, because it must be recomputed */ + irg_block_walk_graph(irg, clear_block_info, NULL, block_info); + /* Removing blocks and Conds might enable more optimizations */ continue; } else { break; @@ -762,10 +849,9 @@ void optimize_cf(ir_graph *irg) assert(get_irg_pinned(irg) != op_pin_state_floats && "Control flow optimization need a pinned graph"); - /* FIXME: control flow opt destroys block edges. So edges are deactivated - * here. Fix the edges! */ edges_deactivate(irg); + /* First the "simple" optimizations, which do not touch Phis */ cfgopt_ignoring_phis(irg); /* we use the mark flag to mark removable blocks */