X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=ir%2Fopt%2Fcfopt.c;h=d6f3c0ea715ec200c2023b9ecfce677639c05939;hb=762b472fc81c73cf7a1b0041b8cd286b7206d79d;hp=963a7cddc6c3f5bf054133a4fb3ee95b9551390c;hpb=24f354d5e3d4d2d22ce6fbc2f086f519a78437f8;p=libfirm diff --git a/ir/opt/cfopt.c b/ir/opt/cfopt.c index 963a7cddc..d6f3c0ea7 100644 --- a/ir/opt/cfopt.c +++ b/ir/opt/cfopt.c @@ -56,6 +56,7 @@ #include "irflag_t.h" #include "firmstat.h" #include "irpass.h" +#include "irphase_t.h" #include "iropt_dbg.h" @@ -63,20 +64,29 @@ typedef struct merge_env { bool changed; /**< Set if the graph was changed. */ bool phis_moved; /**< Set if Phi nodes were moved. */ - ir_node **switch_conds; /**< Helper list for all found Switch Conds. */ } merge_env; +/** set or reset the removable property of a block. */ static void set_Block_removable(ir_node *block, bool removable) { set_Block_mark(block, removable); } +/** check if a block has the removable property set. */ static bool is_Block_removable(ir_node *block) { return get_Block_mark(block); } -static void clear_link(ir_node *node, void *ctx) +/** checks if a given Cond node is a switch Cond. */ +static bool is_switch_Cond(ir_node *cond) +{ + ir_node *sel = get_Cond_selector(cond); + return get_irn_mode(sel) != mode_b; +} + +/** Walker: clear link fields and mark all blocks as removable. */ +static void clear_link_and_mark_blocks_removable(ir_node *node, void *ctx) { (void) ctx; set_irn_link(node, NULL); @@ -93,7 +103,7 @@ static void clear_link(ir_node *node, void *ctx) */ static void collect_nodes(ir_node *n, void *ctx) { - merge_env *env = (merge_env*)ctx; + ir_node ***switch_conds = (ir_node***)ctx; if (is_Phi(n)) { /* Collect Phi nodes to compact ins along with block's ins. */ @@ -101,8 +111,10 @@ static void collect_nodes(ir_node *n, void *ctx) set_irn_link(n, get_irn_link(block)); set_irn_link(block, n); } else if (is_Block(n)) { - if (has_Block_entity(n)) + if (has_Block_entity(n)) { + /* block with a jump label attached cannot be removed. */ set_Block_removable(n, false); + } return; } else if (!is_Jmp(n)) { /* Check for non-empty block. */ ir_node *block = get_nodes_block(n); @@ -113,17 +125,14 @@ static void collect_nodes(ir_node *n, void *ctx) ir_node *pred = get_Proj_pred(n); set_irn_link(n, get_irn_link(pred)); set_irn_link(pred, n); - } else if (is_Cond(n)) { - ir_node *sel = get_Cond_selector(n); - if (get_irn_mode(sel) != mode_b) { - /* found a switch-Cond, collect */ - ARR_APP1(ir_node*, env->switch_conds, n); - } + } else if (is_Cond(n) && is_switch_Cond(n)) { + /* found a switch-Cond, collect */ + ARR_APP1(ir_node*, *switch_conds, n); } } } -/** Returns true if pred is predecessor of block. */ +/** Returns true if pred is predecessor of block b. */ static bool is_pred_of(ir_node *pred, ir_node *b) { int i; @@ -275,6 +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; @@ -371,12 +385,19 @@ static void optimize_blocks(ir_node *b, void *ctx) pred = get_Block_cfgpred_block(b, i); if (is_Bad(pred)) { - in[q_preds++] = pred; + ir_graph *irg = get_irn_irg(b); + ir_mode *mode = get_irn_mode(phi); + in[q_preds++] = new_r_Bad(irg, mode); } else if (is_Block_removable(pred) && !Block_block_visited(pred)) { /* It's an empty block and not yet visited. */ for (j = 0; j < get_Block_n_cfgpreds(pred); j++) { - if (! is_Bad(get_Block_cfgpred(pred, j))) + if (! is_Bad(get_Block_cfgpred(pred, j))) { in[q_preds++] = phi; + } else { + ir_graph *irg = get_irn_irg(b); + ir_mode *mode = get_irn_mode(phi); + in[q_preds++] = new_r_Bad(irg, mode); + } } } else { in[q_preds++] = phi; @@ -400,8 +421,13 @@ static void optimize_blocks(ir_node *b, void *ctx) } else if (is_Block_removable(pred) && !Block_block_visited(pred)) { /* It's an empty block and not yet visited. */ for (j = 0; j < get_Block_n_cfgpreds(pred); j++) { - if (! is_Bad(get_Block_cfgpred(pred, j))) + if (! is_Bad(get_Block_cfgpred(pred, j))) { in[q_preds++] = phi; + } else { + ir_graph *irg = get_irn_irg(b); + ir_mode *mode = get_irn_mode(phi); + in[q_preds++] = new_r_Bad(irg, mode); + } } } else { in[q_preds++] = phi; @@ -488,7 +514,7 @@ static bool handle_switch_cond(ir_node *cond) /* handle Cond nodes with constant argument. In this case the localopt rules * should have killed all obviously impossible cases. - * So the only case left to handle here is 1 defaultProj + 1case + * So the only case left to handle here is 1 defaultProj + 1 case * (this one case should be the one taken) */ if (get_irn_link(proj2) == NULL) { ir_tarval *tv = value_of(sel); @@ -535,21 +561,210 @@ static bool handle_switch_cond(ir_node *cond) return false; } -/* Optimizations of the control flow that also require changes of Phi nodes. - * - * This optimization performs two passes over the graph. - * - * The first pass collects all Phi nodes in a link list in the block - * nodes. Further it performs simple control flow optimizations. - * Finally it marks all blocks that do not contain useful - * computations, i.e., these blocks might be removed. - * - * The second pass performs the optimizations intended by this algorithm. - * It walks only over block nodes and adapts these and the Phi nodes in these - * blocks, which it finds in a linked list computed by the first pass. +/** + * Optimize boolean Conds, where true and false jump to the same block into a Jmp + * Block must contain no Phi nodes. * - * We use the mark flag to mark removable blocks in the first phase. + * Cond + * / \ + * projA projB => Jmp Bad + * \ / \ / + * block block + */ +static bool optimize_pred_cond(ir_node *block, int i, int j) +{ + ir_node *projA, *projB, *cond, *pred_block, *jmp, *bad; + assert(i != j); + + projA = get_Block_cfgpred(block, i); + if (!is_Proj(projA)) return false; + projB = get_Block_cfgpred(block, j); + if (!is_Proj(projB)) return false; + cond = get_Proj_pred(projA); + if (!is_Cond(cond)) return false; + + if (cond != get_Proj_pred(projB)) return false; + if (is_switch_Cond(cond)) return false; + + /* cond should actually be a Jmp */ + pred_block = get_nodes_block(cond); + jmp = new_r_Jmp(pred_block); + bad = new_r_Bad(get_irn_irg(block), mode_X); + + assert(projA != projB); + exchange(projA, jmp); + exchange(projB, bad); + return true; +} + +typedef enum block_flags_t { + BF_HAS_OPERATIONS = 1 << 0, + BF_HAS_PHIS = 1 << 1, + 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 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 = PTR_TO_INT(phase_get_irn_data(block_info, block)); + data |= flag; + phase_set_irn_data(block_info, block, INT_TO_PTR(data)); +} + +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) +{ + set_phase_flag(block_info, block, BF_HAS_OPERATIONS); +} + +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) +{ + set_phase_flag(block_info, block, BF_HAS_PHIS); +} + +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) +{ + set_phase_flag(block_info, block, BF_IS_UNKNOWN_JUMP_TARGET); +} + +/** + * Walker: fill block info information. */ +static void compute_block_info(ir_node *n, void *x) +{ + ir_phase *block_info = (ir_phase *)x; + + if (is_Block(n)) { + int i, max = get_Block_n_cfgpreds(n); + for (i=0; iphase, block)) + return; + + /* optimize Cond predecessors (might produce Bad predecessors) */ + for (i = 0; i < n_preds; ++i) { + for (j = i+1; j < n_preds; ++j) { + optimize_pred_cond(block, i, j); + } + } +} + +/** + * Pre-Block walker: remove empty blocks that are + * predecessors of the current block. + */ +static void remove_empty_blocks(ir_node *block, void *x) +{ + skip_env *env = (skip_env*)x; + int i; + int n_preds = get_Block_n_cfgpreds(block); + + for (i = 0; i < n_preds; ++i) { + ir_node *jmp, *jmp_block, *pred, *pred_block; + + jmp = get_Block_cfgpred(block, i); + if (!is_Jmp(jmp)) + continue; + jmp_block = get_nodes_block(jmp); + if (is_unknown_jump_target(env->phase, jmp_block)) + continue; + if (has_operations(env->phase,jmp_block)) + continue; + /* jmp_block is an empty block! */ + + if (get_Block_n_cfgpreds(jmp_block) != 1) + continue; + pred = get_Block_cfgpred(jmp_block, 0); + exchange(jmp, pred); + env->changed = true; + + /* cleanup: jmp_block might have a Keep edge! */ + pred_block = get_nodes_block(pred); + exchange(jmp_block, pred_block); + } +} + +/* + * Some cfg optimizations, which do not touch Phi nodes + */ +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); + + for (;;) { + env.changed = false; + + /* optimize useless ifs: will not touch empty blocks */ + 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 */ + continue; + } else { + break; + } + } + + phase_free(block_info); +} + +/* Optimizations of the control flow that also require changes of Phi nodes. */ void optimize_cf(ir_graph *irg) { int i, j, n; @@ -558,6 +773,9 @@ void optimize_cf(ir_graph *irg) ir_node *new_end; merge_env env; + env.changed = false; + env.phis_moved = false; + assert(get_irg_phase_state(irg) != phase_building); /* if the graph is not pinned, we cannot determine empty blocks */ @@ -568,29 +786,38 @@ void optimize_cf(ir_graph *irg) * here. Fix the edges! */ edges_deactivate(irg); + cfgopt_ignoring_phis(irg); + /* we use the mark flag to mark removable blocks */ ir_reserve_resources(irg, IR_RESOURCE_BLOCK_MARK | IR_RESOURCE_IRN_LINK); - /* The Cond optimization might expose unreachable code, so we loop */ + /* The switch Cond optimization might expose unreachable code, so we loop */ for (;;) { int length; - env.changed = false; - env.phis_moved = false; + ir_node **switch_conds = NULL; + bool changed = false; assure_doms(irg); - env.switch_conds = NEW_ARR_F(ir_node*, 0); - irg_walk(end, clear_link, collect_nodes, &env); + /* + * This pass collects all Phi nodes in a link list in the block + * nodes. Further it performs simple control flow optimizations. + * Finally it marks all blocks that do not contain useful + * computations, i.e., these blocks might be removed. + */ + switch_conds = NEW_ARR_F(ir_node*, 0); + irg_walk(end, clear_link_and_mark_blocks_removable, collect_nodes, &switch_conds); /* handle all collected switch-Conds */ - length = ARR_LEN(env.switch_conds); + length = ARR_LEN(switch_conds); for (i = 0; i < length; ++i) { - ir_node *cond = env.switch_conds[i]; - env.changed |= handle_switch_cond(cond); + ir_node *cond = switch_conds[i]; + changed |= handle_switch_cond(cond); } - DEL_ARR_F(env.switch_conds); + DEL_ARR_F(switch_conds); - if (!env.changed) break; + if (!changed) + break; set_irg_doms_inconsistent(irg); set_irg_extblk_inconsistent(irg); @@ -602,7 +829,10 @@ void optimize_cf(ir_graph *irg) * 2. phi lists are up to date */ - /* Optimize the standard code. */ + /* Optimize the standard code. + * It walks only over block nodes and adapts these and the Phi nodes in these + * blocks, which it finds in a linked list computed before. + * */ assure_doms(irg); irg_block_walk_graph(irg, optimize_blocks, NULL, &env); @@ -618,7 +848,7 @@ void optimize_cf(ir_graph *irg) if (env.phis_moved) { /* Bad: when we moved Phi's, we might produce dead Phi nodes that are kept-alive. - Some other phases cannot copy with this, so will them. + Some other phases cannot copy with this, so kill them. */ n = get_End_n_keepalives(end); if (n > 0) {