/* Liveness for SSA trees. Copyright (C) 2003-2023 Free Software Foundation, Inc. Contributed by Andrew MacLeod 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 . */ #include "config.h" #include "system.h" #include "coretypes.h" #include "backend.h" #include "rtl.h" #include "tree.h" #include "gimple.h" #include "timevar.h" #include "ssa.h" #include "cgraph.h" #include "gimple-pretty-print.h" #include "diagnostic-core.h" #include "gimple-iterator.h" #include "tree-dfa.h" #include "dumpfile.h" #include "tree-ssa-live.h" #include "debug.h" #include "tree-ssa.h" #include "ipa-utils.h" #include "cfgloop.h" #include "stringpool.h" #include "attribs.h" #include "optinfo.h" #include "gimple-walk.h" #include "cfganal.h" #include "tree-cfg.h" static void verify_live_on_entry (tree_live_info_p); /* VARMAP maintains a mapping from SSA version number to real variables. All SSA_NAMES are divided into partitions. Initially each ssa_name is the only member of it's own partition. Coalescing will attempt to group any ssa_names which occur in a copy or in a PHI node into the same partition. At the end of out-of-ssa, each partition becomes a "real" variable and is rewritten as a compiler variable. The var_map data structure is used to manage these partitions. It allows partitions to be combined, and determines which partition belongs to what ssa_name or variable, and vice versa. */ /* Remove the base table in MAP. */ static void var_map_base_fini (var_map map) { /* Free the basevar info if it is present. */ if (map->partition_to_base_index != NULL) { free (map->partition_to_base_index); map->partition_to_base_index = NULL; map->num_basevars = 0; } } /* Create a variable partition map of SIZE for region, initialize and return it. Region is a loop if LOOP is non-NULL, otherwise is the current function. If BITINT is non-NULL, only SSA_NAMEs from that bitmap will be coalesced. */ var_map init_var_map (int size, class loop *loop, bitmap bitint) { var_map map; map = (var_map) xmalloc (sizeof (struct _var_map)); map->var_partition = partition_new (size); map->partition_to_view = NULL; map->view_to_partition = NULL; map->num_partitions = size; map->partition_size = size; map->num_basevars = 0; map->partition_to_base_index = NULL; map->vec_bbs = vNULL; if (loop) { map->bmp_bbs = BITMAP_ALLOC (NULL); map->outofssa_p = false; basic_block *bbs = get_loop_body_in_dom_order (loop); for (unsigned i = 0; i < loop->num_nodes; ++i) { bitmap_set_bit (map->bmp_bbs, bbs[i]->index); map->vec_bbs.safe_push (bbs[i]); } free (bbs); } else { map->bmp_bbs = NULL; map->outofssa_p = bitint == NULL; map->bitint = bitint; basic_block bb; FOR_EACH_BB_FN (bb, cfun) map->vec_bbs.safe_push (bb); } return map; } /* Free memory associated with MAP. */ void delete_var_map (var_map map) { var_map_base_fini (map); partition_delete (map->var_partition); free (map->partition_to_view); free (map->view_to_partition); if (map->bmp_bbs) BITMAP_FREE (map->bmp_bbs); map->vec_bbs.release (); free (map); } /* This function will combine the partitions in MAP for VAR1 and VAR2. It Returns the partition which represents the new partition. If the two partitions cannot be combined, NO_PARTITION is returned. */ int var_union (var_map map, tree var1, tree var2) { int p1, p2, p3; gcc_assert (TREE_CODE (var1) == SSA_NAME); gcc_assert (TREE_CODE (var2) == SSA_NAME); /* This is independent of partition_to_view. If partition_to_view is on, then whichever one of these partitions is absorbed will never have a dereference into the partition_to_view array any more. */ p1 = partition_find (map->var_partition, SSA_NAME_VERSION (var1)); p2 = partition_find (map->var_partition, SSA_NAME_VERSION (var2)); gcc_assert (p1 != NO_PARTITION); gcc_assert (p2 != NO_PARTITION); if (p1 == p2) p3 = p1; else p3 = partition_union (map->var_partition, p1, p2); if (map->partition_to_view) p3 = map->partition_to_view[p3]; return p3; } /* Compress the partition numbers in MAP such that they fall in the range 0..(num_partitions-1) instead of wherever they turned out during the partitioning exercise. This removes any references to unused partitions, thereby allowing bitmaps and other vectors to be much denser. This is implemented such that compaction doesn't affect partitioning. Ie., once partitions are created and possibly merged, running one or more different kind of compaction will not affect the partitions themselves. Their index might change, but all the same variables will still be members of the same partition group. This allows work on reduced sets, and no loss of information when a larger set is later desired. In particular, coalescing can work on partitions which have 2 or more definitions, and then 'recompact' later to include all the single definitions for assignment to program variables. */ /* Set MAP back to the initial state of having no partition view. Return a bitmap which has a bit set for each partition number which is in use in the varmap. */ static bitmap partition_view_init (var_map map) { bitmap used; int tmp; unsigned int x; used = BITMAP_ALLOC (NULL); /* Already in a view? Abandon the old one. */ if (map->partition_to_view) { free (map->partition_to_view); map->partition_to_view = NULL; } if (map->view_to_partition) { free (map->view_to_partition); map->view_to_partition = NULL; } /* Find out which partitions are actually referenced. */ for (x = 0; x < map->partition_size; x++) { tmp = partition_find (map->var_partition, x); if (ssa_name (tmp) != NULL_TREE && !virtual_operand_p (ssa_name (tmp)) && (!has_zero_uses (ssa_name (tmp)) || !SSA_NAME_IS_DEFAULT_DEF (ssa_name (tmp)) || (SSA_NAME_VAR (ssa_name (tmp)) && !VAR_P (SSA_NAME_VAR (ssa_name (tmp)))))) bitmap_set_bit (used, tmp); } map->num_partitions = map->partition_size; return used; } /* This routine will finalize the view data for MAP based on the partitions set in SELECTED. This is either the same bitmap returned from partition_view_init, or a trimmed down version if some of those partitions were not desired in this view. SELECTED is freed before returning. */ static void partition_view_fini (var_map map, bitmap selected) { bitmap_iterator bi; unsigned count, i, x, limit; gcc_assert (selected); count = bitmap_count_bits (selected); limit = map->partition_size; /* If its a one-to-one ratio, we don't need any view compaction. */ if (count < limit) { map->partition_to_view = (int *)xmalloc (limit * sizeof (int)); memset (map->partition_to_view, 0xff, (limit * sizeof (int))); map->view_to_partition = (int *)xmalloc (count * sizeof (int)); i = 0; /* Give each selected partition an index. */ EXECUTE_IF_SET_IN_BITMAP (selected, 0, x, bi) { map->partition_to_view[x] = i; map->view_to_partition[i] = x; i++; } gcc_assert (i == count); map->num_partitions = i; } BITMAP_FREE (selected); } /* Create a partition view which includes all the used partitions in MAP. */ void partition_view_normal (var_map map) { bitmap used; used = partition_view_init (map); partition_view_fini (map, used); var_map_base_fini (map); } /* Create a partition view in MAP which includes just partitions which occur in the bitmap ONLY. If WANT_BASES is true, create the base variable map as well. */ void partition_view_bitmap (var_map map, bitmap only) { bitmap used; bitmap new_partitions = BITMAP_ALLOC (NULL); unsigned x, p; bitmap_iterator bi; used = partition_view_init (map); EXECUTE_IF_SET_IN_BITMAP (only, 0, x, bi) { p = partition_find (map->var_partition, x); gcc_assert (bitmap_bit_p (used, p)); bitmap_set_bit (new_partitions, p); } partition_view_fini (map, new_partitions); var_map_base_fini (map); } static bitmap usedvars; /* Mark VAR as used, so that it'll be preserved during rtl expansion. Returns true if VAR wasn't marked before. */ static inline bool set_is_used (tree var) { return bitmap_set_bit (usedvars, DECL_UID (var)); } /* Return true if VAR is marked as used. */ static inline bool is_used_p (tree var) { return bitmap_bit_p (usedvars, DECL_UID (var)); } static inline void mark_all_vars_used (tree *); /* Helper function for mark_all_vars_used, called via walk_tree. */ static tree mark_all_vars_used_1 (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED) { tree t = *tp; enum tree_code_class c = TREE_CODE_CLASS (TREE_CODE (t)); tree b; if (TREE_CODE (t) == SSA_NAME) { *walk_subtrees = 0; t = SSA_NAME_VAR (t); if (!t) return NULL; } if (IS_EXPR_CODE_CLASS (c) && (b = TREE_BLOCK (t)) != NULL) TREE_USED (b) = true; /* Ignore TMR_OFFSET and TMR_STEP for TARGET_MEM_REFS, as those fields do not contain vars. */ if (TREE_CODE (t) == TARGET_MEM_REF) { mark_all_vars_used (&TMR_BASE (t)); mark_all_vars_used (&TMR_INDEX (t)); mark_all_vars_used (&TMR_INDEX2 (t)); *walk_subtrees = 0; return NULL; } /* Only need to mark VAR_DECLS; parameters and return results are not eliminated as unused. */ if (VAR_P (t)) { /* When a global var becomes used for the first time also walk its initializer (non global ones don't have any). */ if (set_is_used (t) && is_global_var (t) && DECL_CONTEXT (t) == current_function_decl) mark_all_vars_used (&DECL_INITIAL (t)); } /* remove_unused_scope_block_p requires information about labels which are not DECL_IGNORED_P to tell if they might be used in the IL. */ else if (TREE_CODE (t) == LABEL_DECL) /* Although the TREE_USED values that the frontend uses would be acceptable (albeit slightly over-conservative) for our purposes, init_vars_expansion clears TREE_USED for LABEL_DECLs too, so we must re-compute it here. */ TREE_USED (t) = 1; if (IS_TYPE_OR_DECL_P (t)) *walk_subtrees = 0; return NULL; } /* Mark the scope block SCOPE and its subblocks unused when they can be possibly eliminated if dead. */ static void mark_scope_block_unused (tree scope) { tree t; TREE_USED (scope) = false; if (!(*debug_hooks->ignore_block) (scope)) TREE_USED (scope) = true; for (t = BLOCK_SUBBLOCKS (scope); t ; t = BLOCK_CHAIN (t)) mark_scope_block_unused (t); } /* Look if the block is dead (by possibly eliminating its dead subblocks) and return true if so. Block is declared dead if: 1) No statements are associated with it. 2) Declares no live variables 3) All subblocks are dead or there is precisely one subblocks and the block has same abstract origin as outer block and declares no variables, so it is pure wrapper. When we are not outputting full debug info, we also eliminate dead variables out of scope blocks to let them to be recycled by GGC and to save copying work done by the inliner. */ static bool remove_unused_scope_block_p (tree scope, bool in_ctor_dtor_block) { tree *t, *next; bool unused = !TREE_USED (scope); int nsubblocks = 0; /* For ipa-polymorphic-call.cc purposes, preserve blocks: 1) with BLOCK_ABSTRACT_ORIGIN of a ctor/dtor or their clones */ if (inlined_polymorphic_ctor_dtor_block_p (scope, true)) { in_ctor_dtor_block = true; unused = false; } /* 2) inside such blocks, the outermost block with block_ultimate_origin being a FUNCTION_DECL. */ else if (in_ctor_dtor_block) { tree fn = block_ultimate_origin (scope); if (fn && TREE_CODE (fn) == FUNCTION_DECL) { in_ctor_dtor_block = false; unused = false; } } for (t = &BLOCK_VARS (scope); *t; t = next) { next = &DECL_CHAIN (*t); /* Debug info of nested function refers to the block of the function. We might stil call it even if all statements of function it was nested into was elliminated. TODO: We can actually look into cgraph to see if function will be output to file. */ if (TREE_CODE (*t) == FUNCTION_DECL) unused = false; /* If a decl has a value expr, we need to instantiate it regardless of debug info generation, to avoid codegen differences in memory overlap tests. update_equiv_regs() may indirectly call validate_equiv_mem() to test whether a SET_DEST overlaps with others, and if the value expr changes by virtual register instantiation, we may get end up with different results. */ else if (VAR_P (*t) && DECL_HAS_VALUE_EXPR_P (*t)) unused = false; /* Remove everything we don't generate debug info for. */ else if (DECL_IGNORED_P (*t)) { *t = DECL_CHAIN (*t); next = t; } /* When we are outputting debug info, we usually want to output info about optimized-out variables in the scope blocks. Exception are the scope blocks not containing any instructions at all so user can't get into the scopes at first place. */ else if (is_used_p (*t)) unused = false; else if (TREE_CODE (*t) == LABEL_DECL && TREE_USED (*t)) /* For labels that are still used in the IL, the decision to preserve them must not depend DEBUG_INFO_LEVEL, otherwise we risk having different ordering in debug vs. non-debug builds during inlining or versioning. A label appearing here (we have already checked DECL_IGNORED_P) should not be used in the IL unless it has been explicitly used before, so we use TREE_USED as an approximation. */ /* In principle, we should do the same here as for the debug case below, however, when debugging, there might be additional nested levels that keep an upper level with a label live, so we have to force this block to be considered used, too. */ unused = false; /* When we are not doing full debug info, we however can keep around only the used variables for cfgexpand's memory packing saving quite a lot of memory. For sake of -g3, we keep around those vars but we don't count this as use of block, so innermost block with no used vars and no instructions can be considered dead. We only want to keep around blocks user can breakpoint into and ask about value of optimized out variables. Similarly we need to keep around types at least until all variables of all nested blocks are gone. We track no information on whether given type is used or not, so we have to keep them even when not emitting debug information, otherwise we may end up remapping variables and their (local) types in different orders depending on whether debug information is being generated. */ else if (TREE_CODE (*t) == TYPE_DECL || debug_info_level == DINFO_LEVEL_NORMAL || debug_info_level == DINFO_LEVEL_VERBOSE) ; else { *t = DECL_CHAIN (*t); next = t; } } for (t = &BLOCK_SUBBLOCKS (scope); *t ;) if (remove_unused_scope_block_p (*t, in_ctor_dtor_block)) { if (BLOCK_SUBBLOCKS (*t)) { tree next = BLOCK_CHAIN (*t); tree supercontext = BLOCK_SUPERCONTEXT (*t); *t = BLOCK_SUBBLOCKS (*t); while (BLOCK_CHAIN (*t)) { BLOCK_SUPERCONTEXT (*t) = supercontext; t = &BLOCK_CHAIN (*t); } BLOCK_CHAIN (*t) = next; BLOCK_SUPERCONTEXT (*t) = supercontext; t = &BLOCK_CHAIN (*t); nsubblocks ++; } else *t = BLOCK_CHAIN (*t); } else { t = &BLOCK_CHAIN (*t); nsubblocks ++; } if (!unused) ; /* Outer scope is always used. */ else if (!BLOCK_SUPERCONTEXT (scope) || TREE_CODE (BLOCK_SUPERCONTEXT (scope)) == FUNCTION_DECL) unused = false; /* Innermost blocks with no live variables nor statements can be always eliminated. */ else if (!nsubblocks) ; /* When not generating debug info we can eliminate info on unused variables. */ else if (!flag_auto_profile && debug_info_level == DINFO_LEVEL_NONE && !optinfo_wants_inlining_info_p ()) { /* Even for -g0 don't prune outer scopes from inlined functions, otherwise late diagnostics from such functions will not be emitted or suppressed properly. */ if (inlined_function_outer_scope_p (scope)) { gcc_assert (TREE_CODE (BLOCK_ORIGIN (scope)) == FUNCTION_DECL); unused = false; } } else if (BLOCK_VARS (scope) || BLOCK_NUM_NONLOCALIZED_VARS (scope)) unused = false; /* See if this block is important for representation of inlined function. Inlined functions are always represented by block with block_ultimate_origin being set to FUNCTION_DECL and DECL_SOURCE_LOCATION set, unless they expand to nothing... */ else if (inlined_function_outer_scope_p (scope)) unused = false; else /* Verfify that only blocks with source location set are entry points to the inlined functions. */ gcc_assert (LOCATION_LOCUS (BLOCK_SOURCE_LOCATION (scope)) == UNKNOWN_LOCATION); TREE_USED (scope) = !unused; return unused; } /* Mark all VAR_DECLS under *EXPR_P as used, so that they won't be eliminated during the tree->rtl conversion process. */ static inline void mark_all_vars_used (tree *expr_p) { walk_tree (expr_p, mark_all_vars_used_1, NULL, NULL); } /* Helper function for clear_unused_block_pointer, called via walk_tree. */ static tree clear_unused_block_pointer_1 (tree *tp, int *, void *) { if (EXPR_P (*tp) && TREE_BLOCK (*tp) && !TREE_USED (TREE_BLOCK (*tp))) TREE_SET_BLOCK (*tp, NULL); return NULL_TREE; } /* Set all block pointer in debug or clobber stmt to NULL if the block is unused, so that they will not be streamed out. */ static void clear_unused_block_pointer (void) { basic_block bb; gimple_stmt_iterator gsi; FOR_EACH_BB_FN (bb, cfun) for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) { unsigned i; tree b; gimple *stmt; next: stmt = gsi_stmt (gsi); if (!is_gimple_debug (stmt) && !gimple_clobber_p (stmt)) continue; b = gimple_block (stmt); if (b && !TREE_USED (b)) { /* Elide debug marker stmts that have an associated BLOCK from an inline instance removed with also the outermost scope BLOCK of said inline instance removed. If the outermost scope BLOCK of said inline instance is preserved use that in place of the removed BLOCK. That keeps the marker associated to the correct inline instance (or no inline instance in case it was not from an inline instance). */ if (gimple_debug_nonbind_marker_p (stmt) && BLOCK_ABSTRACT_ORIGIN (b)) { while (TREE_CODE (b) == BLOCK && !inlined_function_outer_scope_p (b)) b = BLOCK_SUPERCONTEXT (b); if (TREE_CODE (b) == BLOCK) { if (TREE_USED (b)) { gimple_set_block (stmt, b); continue; } gsi_remove (&gsi, true); if (gsi_end_p (gsi)) break; goto next; } } gimple_set_block (stmt, NULL); } for (i = 0; i < gimple_num_ops (stmt); i++) walk_tree (gimple_op_ptr (stmt, i), clear_unused_block_pointer_1, NULL, NULL); } } /* Dump scope blocks starting at SCOPE to FILE. INDENT is the indentation level and FLAGS is as in print_generic_expr. */ static void dump_scope_block (FILE *file, int indent, tree scope, dump_flags_t flags) { tree var, t; unsigned int i; fprintf (file, "\n%*s{ Scope block #%i%s",indent, "" , BLOCK_NUMBER (scope), TREE_USED (scope) ? "" : " (unused)"); if (LOCATION_LOCUS (BLOCK_SOURCE_LOCATION (scope)) != UNKNOWN_LOCATION) { expanded_location s = expand_location (BLOCK_SOURCE_LOCATION (scope)); fprintf (file, " %s:%i", s.file, s.line); } if (BLOCK_ABSTRACT_ORIGIN (scope)) { tree origin = block_ultimate_origin (scope); if (origin) { fprintf (file, " Originating from :"); if (DECL_P (origin)) print_generic_decl (file, origin, flags); else fprintf (file, "#%i", BLOCK_NUMBER (origin)); } } if (BLOCK_FRAGMENT_ORIGIN (scope)) fprintf (file, " Fragment of : #%i", BLOCK_NUMBER (BLOCK_FRAGMENT_ORIGIN (scope))); else if (BLOCK_FRAGMENT_CHAIN (scope)) { fprintf (file, " Fragment chain :"); for (t = BLOCK_FRAGMENT_CHAIN (scope); t ; t = BLOCK_FRAGMENT_CHAIN (t)) fprintf (file, " #%i", BLOCK_NUMBER (t)); } fprintf (file, " \n"); for (var = BLOCK_VARS (scope); var; var = DECL_CHAIN (var)) { fprintf (file, "%*s", indent, ""); print_generic_decl (file, var, flags); fprintf (file, "\n"); } for (i = 0; i < BLOCK_NUM_NONLOCALIZED_VARS (scope); i++) { fprintf (file, "%*s",indent, ""); print_generic_decl (file, BLOCK_NONLOCALIZED_VAR (scope, i), flags); fprintf (file, " (nonlocalized)\n"); } for (t = BLOCK_SUBBLOCKS (scope); t ; t = BLOCK_CHAIN (t)) dump_scope_block (file, indent + 2, t, flags); fprintf (file, "\n%*s}\n",indent, ""); } /* Dump the tree of lexical scopes starting at SCOPE to stderr. FLAGS is as in print_generic_expr. */ DEBUG_FUNCTION void debug_scope_block (tree scope, dump_flags_t flags) { dump_scope_block (stderr, 0, scope, flags); } /* Dump the tree of lexical scopes of current_function_decl to FILE. FLAGS is as in print_generic_expr. */ void dump_scope_blocks (FILE *file, dump_flags_t flags) { dump_scope_block (file, 0, DECL_INITIAL (current_function_decl), flags); } /* Dump the tree of lexical scopes of current_function_decl to stderr. FLAGS is as in print_generic_expr. */ DEBUG_FUNCTION void debug_scope_blocks (dump_flags_t flags) { dump_scope_blocks (stderr, flags); } /* Remove local variables that are not referenced in the IL. */ void remove_unused_locals (void) { basic_block bb; tree var; unsigned srcidx, dstidx, num; bool have_local_clobbers = false; /* Removing declarations from lexical blocks when not optimizing is not only a waste of time, it actually causes differences in stack layout. */ if (!optimize) return; timevar_push (TV_REMOVE_UNUSED); mark_scope_block_unused (DECL_INITIAL (current_function_decl)); usedvars = BITMAP_ALLOC (NULL); auto_bitmap useddebug; /* Walk the CFG marking all referenced symbols. */ FOR_EACH_BB_FN (bb, cfun) { gimple_stmt_iterator gsi; size_t i; edge_iterator ei; edge e; /* Walk the statements. */ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) { gimple *stmt = gsi_stmt (gsi); tree b = gimple_block (stmt); /* If we wanted to mark the block referenced by the inline entry point marker as used, this would be a good spot to do it. If the block is not otherwise used, the stmt will be cleaned up in clean_unused_block_pointer. */ if (is_gimple_debug (stmt)) { if (gimple_debug_bind_p (stmt)) { tree var = gimple_debug_bind_get_var (stmt); if (VAR_P (var)) { if (!gimple_debug_bind_get_value (stmt)) /* Run the 2nd phase. */ have_local_clobbers = true; else bitmap_set_bit (useddebug, DECL_UID (var)); } } continue; } if (gimple_clobber_p (stmt)) { have_local_clobbers = true; continue; } if (gimple_call_internal_p (stmt, IFN_DEFERRED_INIT)) { have_local_clobbers = true; continue; } if (b) TREE_USED (b) = true; for (i = 0; i < gimple_num_ops (stmt); i++) mark_all_vars_used (gimple_op_ptr (gsi_stmt (gsi), i)); } for (gphi_iterator gpi = gsi_start_phis (bb); !gsi_end_p (gpi); gsi_next (&gpi)) { use_operand_p arg_p; ssa_op_iter i; tree def; gphi *phi = gpi.phi (); if (virtual_operand_p (gimple_phi_result (phi))) continue; def = gimple_phi_result (phi); mark_all_vars_used (&def); FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_ALL_USES) { tree arg = USE_FROM_PTR (arg_p); int index = PHI_ARG_INDEX_FROM_USE (arg_p); tree block = LOCATION_BLOCK (gimple_phi_arg_location (phi, index)); if (block != NULL) TREE_USED (block) = true; mark_all_vars_used (&arg); } } FOR_EACH_EDGE (e, ei, bb->succs) if (LOCATION_BLOCK (e->goto_locus) != NULL) TREE_USED (LOCATION_BLOCK (e->goto_locus)) = true; } /* We do a two-pass approach about the out-of-scope clobbers. We want to remove them if they are the only references to a local variable, but we want to retain them when there's any other. So the first pass ignores them, and the second pass (if there were any) tries to remove them. We do the same for .DEFERRED_INIT. */ if (have_local_clobbers) FOR_EACH_BB_FN (bb, cfun) { gimple_stmt_iterator gsi; for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi);) { gimple *stmt = gsi_stmt (gsi); tree b = gimple_block (stmt); if (gimple_clobber_p (stmt)) { tree lhs = gimple_assign_lhs (stmt); tree base = get_base_address (lhs); /* Remove clobbers referencing unused vars, or clobbers with MEM_REF lhs referencing uninitialized pointers. */ if ((VAR_P (base) && !is_used_p (base)) || (TREE_CODE (lhs) == MEM_REF && TREE_CODE (TREE_OPERAND (lhs, 0)) == SSA_NAME && SSA_NAME_IS_DEFAULT_DEF (TREE_OPERAND (lhs, 0)) && (TREE_CODE (SSA_NAME_VAR (TREE_OPERAND (lhs, 0))) != PARM_DECL))) { unlink_stmt_vdef (stmt); gsi_remove (&gsi, true); release_defs (stmt); continue; } if (b) TREE_USED (b) = true; } else if (gimple_call_internal_p (stmt, IFN_DEFERRED_INIT)) { tree lhs = gimple_call_lhs (stmt); tree base = get_base_address (lhs); if (DECL_P (base) && !is_used_p (base)) { unlink_stmt_vdef (stmt); gsi_remove (&gsi, true); release_defs (stmt); continue; } if (b) TREE_USED (b) = true; } else if (gimple_debug_bind_p (stmt)) { tree var = gimple_debug_bind_get_var (stmt); if (VAR_P (var) && !bitmap_bit_p (useddebug, DECL_UID (var)) && !is_used_p (var)) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Dead debug bind reset to %u\n", DECL_UID (var)); gsi_remove (&gsi, true); continue; } } gsi_next (&gsi); } } if (cfun->has_simduid_loops) { for (auto loop : loops_list (cfun, 0)) if (loop->simduid && !is_used_p (loop->simduid)) loop->simduid = NULL_TREE; } cfun->has_local_explicit_reg_vars = false; /* Remove unmarked local and global vars from local_decls. */ num = vec_safe_length (cfun->local_decls); for (srcidx = 0, dstidx = 0; srcidx < num; srcidx++) { var = (*cfun->local_decls)[srcidx]; if (VAR_P (var)) { if (!is_used_p (var)) { tree def; if (cfun->nonlocal_goto_save_area && TREE_OPERAND (cfun->nonlocal_goto_save_area, 0) == var) cfun->nonlocal_goto_save_area = NULL; /* Release any default def associated with var. */ if ((def = ssa_default_def (cfun, var)) != NULL_TREE) { set_ssa_default_def (cfun, var, NULL_TREE); release_ssa_name (def); } continue; } } if (VAR_P (var) && DECL_HARD_REGISTER (var) && !is_global_var (var)) cfun->has_local_explicit_reg_vars = true; if (srcidx != dstidx) (*cfun->local_decls)[dstidx] = var; dstidx++; } if (dstidx != num) { statistics_counter_event (cfun, "unused VAR_DECLs removed", num - dstidx); cfun->local_decls->truncate (dstidx); } remove_unused_scope_block_p (DECL_INITIAL (current_function_decl), polymorphic_ctor_dtor_p (current_function_decl, true) != NULL_TREE); clear_unused_block_pointer (); BITMAP_FREE (usedvars); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, "Scope blocks after cleanups:\n"); dump_scope_blocks (dump_file, dump_flags); } timevar_pop (TV_REMOVE_UNUSED); } /* Allocate and return a new live range information object base on MAP. */ static tree_live_info_p new_tree_live_info (var_map map) { tree_live_info_p live; basic_block bb; live = XNEW (struct tree_live_info_d); live->map = map; live->num_blocks = last_basic_block_for_fn (cfun); bitmap_obstack_initialize (&live->livein_obstack); bitmap_obstack_initialize (&live->liveout_obstack); live->livein = XCNEWVEC (bitmap_head, last_basic_block_for_fn (cfun)); live->liveout = XCNEWVEC (bitmap_head, last_basic_block_for_fn (cfun)); for (unsigned i = 0; map->vec_bbs.iterate (i, &bb); ++i) { bitmap_initialize (&live->livein[bb->index], &live->livein_obstack); bitmap_initialize (&live->liveout[bb->index], &live->liveout_obstack); } live->work_stack = XNEWVEC (int, last_basic_block_for_fn (cfun)); live->stack_top = live->work_stack; live->global = BITMAP_ALLOC (NULL); return live; } /* Free storage for live range info object LIVE. */ void delete_tree_live_info (tree_live_info_p live) { if (live->livein) { bitmap_obstack_release (&live->livein_obstack); free (live->livein); } if (live->liveout) { bitmap_obstack_release (&live->liveout_obstack); free (live->liveout); } BITMAP_FREE (live->global); free (live->work_stack); free (live); } /* Visit basic block BB and propagate any required live on entry bits from LIVE into the predecessors. VISITED is the bitmap of visited blocks. TMP is a temporary work bitmap which is passed in to avoid reallocating it each time. */ static void loe_visit_block (tree_live_info_p live, basic_block bb, sbitmap visited) { edge e; bool change; edge_iterator ei; basic_block pred_bb; bitmap loe; gcc_checking_assert (!bitmap_bit_p (visited, bb->index)); bitmap_set_bit (visited, bb->index); loe = live_on_entry (live, bb); FOR_EACH_EDGE (e, ei, bb->preds) { pred_bb = e->src; if (!region_contains_p (live->map, pred_bb)) continue; /* Variables live-on-entry from BB that aren't defined in the predecessor block. This should be the live on entry vars to pred. Note that liveout is the DEFs in a block while live on entry is being calculated. Add these bits to live-on-entry for the pred. if there are any changes, and pred_bb has been visited already, add it to the revisit stack. */ change = bitmap_ior_and_compl_into (live_on_entry (live, pred_bb), loe, &live->liveout[pred_bb->index]); if (change && bitmap_bit_p (visited, pred_bb->index)) { bitmap_clear_bit (visited, pred_bb->index); *(live->stack_top)++ = pred_bb->index; } } } /* Using LIVE, fill in all the live-on-entry blocks between the defs and uses of all the variables. */ static void live_worklist (tree_live_info_p live) { unsigned b; basic_block bb; auto_sbitmap visited (last_basic_block_for_fn (cfun) + 1); bitmap_clear (visited); /* Visit region's blocks in reverse order and propagate live on entry values into the predecessors blocks. */ for (unsigned i = live->map->vec_bbs.length () - 1; live->map->vec_bbs.iterate (i, &bb); --i) loe_visit_block (live, bb, visited); /* Process any blocks which require further iteration. */ while (live->stack_top != live->work_stack) { b = *--(live->stack_top); loe_visit_block (live, BASIC_BLOCK_FOR_FN (cfun, b), visited); } } /* Calculate the initial live on entry vector for SSA_NAME using immediate_use links. Set the live on entry fields in LIVE. Def's are marked temporarily in the liveout vector. */ static void set_var_live_on_entry (tree ssa_name, tree_live_info_p live) { int p; gimple *stmt; use_operand_p use; basic_block def_bb = NULL; imm_use_iterator imm_iter; bool global = false; p = var_to_partition (live->map, ssa_name); if (p == NO_PARTITION) return; stmt = SSA_NAME_DEF_STMT (ssa_name); if (stmt) { def_bb = gimple_bb (stmt); /* Mark defs in liveout bitmap temporarily. */ if (def_bb && region_contains_p (live->map, def_bb)) bitmap_set_bit (&live->liveout[def_bb->index], p); } else def_bb = ENTRY_BLOCK_PTR_FOR_FN (cfun); /* An undefined local variable does not need to be very alive. */ if (ssa_undefined_value_p (ssa_name, false)) return; /* Visit each use of SSA_NAME and if it isn't in the same block as the def, add it to the list of live on entry blocks. */ FOR_EACH_IMM_USE_FAST (use, imm_iter, ssa_name) { gimple *use_stmt = USE_STMT (use); basic_block add_block = NULL; if (gimple_code (use_stmt) == GIMPLE_PHI) { /* Uses in PHI's are considered to be live at exit of the SRC block as this is where a copy would be inserted. Check to see if it is defined in that block, or whether its live on entry. */ int index = PHI_ARG_INDEX_FROM_USE (use); edge e = gimple_phi_arg_edge (as_a (use_stmt), index); if (e->src != def_bb && region_contains_p (live->map, e->src)) add_block = e->src; } else if (is_gimple_debug (use_stmt)) continue; else { /* If its not defined in this block, its live on entry. */ basic_block use_bb = gimple_bb (use_stmt); if (use_bb != def_bb && region_contains_p (live->map, use_bb)) add_block = use_bb; } /* If there was a live on entry use, set the bit. */ if (add_block) { global = true; bitmap_set_bit (&live->livein[add_block->index], p); } } /* If SSA_NAME is live on entry to at least one block, fill in all the live on entry blocks between the def and all the uses. */ if (global) bitmap_set_bit (live->global, p); } /* Calculate the live on exit vectors based on the entry info in LIVEINFO. */ static void calculate_live_on_exit (tree_live_info_p liveinfo) { basic_block bb; edge e; edge_iterator ei; /* live on entry calculations used liveout vectors for defs, clear them. */ for (unsigned i = 0; liveinfo->map->vec_bbs.iterate (i, &bb); ++i) bitmap_clear (&liveinfo->liveout[bb->index]); /* Set all the live-on-exit bits for uses in PHIs. */ FOR_EACH_BB_FN (bb, cfun) { gphi_iterator gsi; size_t i; /* Mark the PHI arguments which are live on exit to the pred block. */ for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) { gphi *phi = gsi.phi (); if (virtual_operand_p (gimple_phi_result (phi))) continue; for (i = 0; i < gimple_phi_num_args (phi); i++) { tree t = PHI_ARG_DEF (phi, i); int p; if (TREE_CODE (t) != SSA_NAME) continue; p = var_to_partition (liveinfo->map, t); if (p == NO_PARTITION) continue; e = gimple_phi_arg_edge (phi, i); if (region_contains_p (liveinfo->map, e->src)) bitmap_set_bit (&liveinfo->liveout[e->src->index], p); } } if (!region_contains_p (liveinfo->map, bb)) continue; /* Add each successors live on entry to this bock live on exit. */ FOR_EACH_EDGE (e, ei, bb->succs) if (region_contains_p (liveinfo->map, e->dest)) bitmap_ior_into (&liveinfo->liveout[bb->index], live_on_entry (liveinfo, e->dest)); } } /* Given partition map MAP, calculate all the live on entry bitmaps for each partition. Return a new live info object. */ tree_live_info_p calculate_live_ranges (var_map map, bool want_livein) { tree var; unsigned i; tree_live_info_p live; live = new_tree_live_info (map); for (i = 0; i < num_var_partitions (map); i++) { var = partition_to_var (map, i); if (var != NULL_TREE) set_var_live_on_entry (var, live); } live_worklist (live); if (flag_checking) verify_live_on_entry (live); calculate_live_on_exit (live); if (!want_livein) { bitmap_obstack_release (&live->livein_obstack); free (live->livein); live->livein = NULL; } return live; } /* Data structure for compute_live_vars* functions. */ struct compute_live_vars_data { /* Vector of bitmaps for live vars indices at the end of basic blocks, indexed by bb->index. ACTIVE[ENTRY_BLOCK] must be empty bitmap, ACTIVE[EXIT_BLOCK] is used for STOP_AFTER. */ vec active; /* Work bitmap of currently live variables. */ bitmap work; /* Set of interesting variables. Variables with uids not in this hash_map are not tracked. */ live_vars_map *vars; }; /* Callback for walk_stmt_load_store_addr_ops. If OP is a VAR_DECL with uid set in DATA->vars, enter its corresponding index into bitmap DATA->work. */ static bool compute_live_vars_visit (gimple *, tree op, tree, void *pdata) { compute_live_vars_data *data = (compute_live_vars_data *) pdata; op = get_base_address (op); if (op && VAR_P (op)) if (unsigned int *v = data->vars->get (DECL_UID (op))) bitmap_set_bit (data->work, *v); return false; } /* Helper routine for compute_live_vars, calculating the sets of live variables at the end of BB, leaving the result in DATA->work. If STOP_AFTER is non-NULL, stop processing after that stmt. */ static void compute_live_vars_1 (basic_block bb, compute_live_vars_data *data, gimple *stop_after) { edge e; edge_iterator ei; gimple_stmt_iterator gsi; walk_stmt_load_store_addr_fn visit = compute_live_vars_visit; bitmap_clear (data->work); FOR_EACH_EDGE (e, ei, bb->preds) bitmap_ior_into (data->work, &data->active[e->src->index]); for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) walk_stmt_load_store_addr_ops (gsi_stmt (gsi), data, NULL, NULL, visit); for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi); gsi_next (&gsi)) { gimple *stmt = gsi_stmt (gsi); if (gimple_clobber_p (stmt)) { tree lhs = gimple_assign_lhs (stmt); if (VAR_P (lhs)) if (unsigned int *v = data->vars->get (DECL_UID (lhs))) bitmap_clear_bit (data->work, *v); } else if (!is_gimple_debug (stmt)) walk_stmt_load_store_addr_ops (stmt, data, visit, visit, visit); if (stmt == stop_after) break; } } /* For function FN and live_vars_map (hash map from DECL_UIDs to a dense set of indexes of automatic variables VARS, compute which of those variables are (might be) live at the end of each basic block. */ vec compute_live_vars (struct function *fn, live_vars_map *vars) { vec active; /* We approximate the live range of a stack variable by taking the first mention of its name as starting point(s), and by the end-of-scope death clobber added by gimplify as ending point(s) of the range. This overapproximates in the case we for instance moved an address-taken operation upward, without also moving a dereference to it upwards. But it's conservatively correct as a variable never can hold values before its name is mentioned at least once. We then do a mostly classical bitmap liveness algorithm. */ active.create (last_basic_block_for_fn (fn)); active.quick_grow_cleared (last_basic_block_for_fn (fn)); for (int i = 0; i < last_basic_block_for_fn (fn); i++) bitmap_initialize (&active[i], &bitmap_default_obstack); bitmap work = BITMAP_ALLOC (NULL); int *rpo = XNEWVEC (int, last_basic_block_for_fn (fn)); int n_bbs = pre_and_rev_post_order_compute_fn (fn, NULL, rpo, false); bool changed = true; compute_live_vars_data data = { active, work, vars }; while (changed) { int i; changed = false; for (i = 0; i < n_bbs; i++) { basic_block bb = BASIC_BLOCK_FOR_FN (fn, rpo[i]); compute_live_vars_1 (bb, &data, NULL); if (bitmap_ior_into (&active[bb->index], work)) changed = true; } } free (rpo); BITMAP_FREE (work); return active; } /* For ACTIVE computed by compute_live_vars, compute a bitmap of variables live after the STOP_AFTER statement and return that bitmap. */ bitmap live_vars_at_stmt (vec &active, live_vars_map *vars, gimple *stop_after) { bitmap work = BITMAP_ALLOC (NULL); compute_live_vars_data data = { active, work, vars }; basic_block bb = gimple_bb (stop_after); compute_live_vars_1 (bb, &data, stop_after); return work; } /* Destroy what compute_live_vars has returned when it is no longer needed. */ void destroy_live_vars (vec &active) { unsigned len = active.length (); for (unsigned i = 0; i < len; i++) bitmap_clear (&active[i]); active.release (); } /* Output partition map MAP to file F. */ void dump_var_map (FILE *f, var_map map) { int t; unsigned x, y; int p; fprintf (f, "\nPartition map \n\n"); for (x = 0; x < map->num_partitions; x++) { if (map->view_to_partition != NULL) p = map->view_to_partition[x]; else p = x; if (ssa_name (p) == NULL_TREE || virtual_operand_p (ssa_name (p))) continue; t = 0; for (y = 1; y < num_ssa_names; y++) { p = partition_find (map->var_partition, y); if (map->partition_to_view) p = map->partition_to_view[p]; if (p == (int)x) { if (t++ == 0) { fprintf (f, "Partition %d (", x); print_generic_expr (f, partition_to_var (map, p), TDF_SLIM); fprintf (f, " - "); } fprintf (f, "%d ", y); } } if (t != 0) fprintf (f, ")\n"); } fprintf (f, "\n"); } /* Generic dump for the above. */ DEBUG_FUNCTION void debug (_var_map &ref) { dump_var_map (stderr, &ref); } DEBUG_FUNCTION void debug (_var_map *ptr) { if (ptr) debug (*ptr); else fprintf (stderr, "\n"); } /* Output live range info LIVE to file F, controlled by FLAG. */ void dump_live_info (FILE *f, tree_live_info_p live, int flag) { basic_block bb; unsigned i; var_map map = live->map; bitmap_iterator bi; if ((flag & LIVEDUMP_ENTRY) && live->livein) { FOR_EACH_BB_FN (bb, cfun) { fprintf (f, "\nLive on entry to BB%d : ", bb->index); EXECUTE_IF_SET_IN_BITMAP (&live->livein[bb->index], 0, i, bi) { print_generic_expr (f, partition_to_var (map, i), TDF_SLIM); fprintf (f, " "); } fprintf (f, "\n"); } } if ((flag & LIVEDUMP_EXIT) && live->liveout) { FOR_EACH_BB_FN (bb, cfun) { fprintf (f, "\nLive on exit from BB%d : ", bb->index); EXECUTE_IF_SET_IN_BITMAP (&live->liveout[bb->index], 0, i, bi) { print_generic_expr (f, partition_to_var (map, i), TDF_SLIM); fprintf (f, " "); } fprintf (f, "\n"); } } } /* Generic dump for the above. */ DEBUG_FUNCTION void debug (tree_live_info_d &ref) { dump_live_info (stderr, &ref, 0); } DEBUG_FUNCTION void debug (tree_live_info_d *ptr) { if (ptr) debug (*ptr); else fprintf (stderr, "\n"); } /* Verify that the info in LIVE matches the current cfg. */ static void verify_live_on_entry (tree_live_info_p live) { unsigned i; tree var; gimple *stmt; basic_block bb; edge e; int num; edge_iterator ei; var_map map = live->map; /* Check for live on entry partitions and report those with a DEF in the program. This will typically mean an optimization has done something wrong. */ bb = ENTRY_BLOCK_PTR_FOR_FN (cfun); num = 0; FOR_EACH_EDGE (e, ei, bb->succs) { int entry_block = e->dest->index; if (!region_contains_p (live->map, e->dest)) continue; for (i = 0; i < (unsigned)num_var_partitions (map); i++) { basic_block tmp; tree d = NULL_TREE; bitmap loe; var = partition_to_var (map, i); stmt = SSA_NAME_DEF_STMT (var); tmp = gimple_bb (stmt); if (SSA_NAME_VAR (var)) d = ssa_default_def (cfun, SSA_NAME_VAR (var)); loe = live_on_entry (live, e->dest); if (loe && bitmap_bit_p (loe, i)) { if (!gimple_nop_p (stmt)) { num++; print_generic_expr (stderr, var, TDF_SLIM); fprintf (stderr, " is defined "); if (tmp) fprintf (stderr, " in BB%d, ", tmp->index); fprintf (stderr, "by:\n"); print_gimple_stmt (stderr, stmt, 0, TDF_SLIM); fprintf (stderr, "\nIt is also live-on-entry to entry BB %d", entry_block); fprintf (stderr, " So it appears to have multiple defs.\n"); } else { if (d != var) { num++; print_generic_expr (stderr, var, TDF_SLIM); fprintf (stderr, " is live-on-entry to BB%d ", entry_block); if (d) { fprintf (stderr, " but is not the default def of "); print_generic_expr (stderr, d, TDF_SLIM); fprintf (stderr, "\n"); } else fprintf (stderr, " and there is no default def.\n"); } } } else if (d == var) { /* An undefined local variable does not need to be very alive. */ if (ssa_undefined_value_p (var, false)) continue; /* The only way this var shouldn't be marked live on entry is if it occurs in a PHI argument of the block. */ size_t z; bool ok = false; gphi_iterator gsi; for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi) && !ok; gsi_next (&gsi)) { gphi *phi = gsi.phi (); if (virtual_operand_p (gimple_phi_result (phi))) continue; for (z = 0; z < gimple_phi_num_args (phi); z++) if (var == gimple_phi_arg_def (phi, z)) { ok = true; break; } } if (ok) continue; /* Expand adds unused default defs for PARM_DECLs and RESULT_DECLs. They're ok. */ if (has_zero_uses (var) && SSA_NAME_VAR (var) && !VAR_P (SSA_NAME_VAR (var))) continue; num++; print_generic_expr (stderr, var, TDF_SLIM); fprintf (stderr, " is not marked live-on-entry to entry BB%d ", entry_block); fprintf (stderr, "but it is a default def so it should be.\n"); } } } gcc_assert (num <= 0); } /* Virtual operand liveness analysis data init. */ void virtual_operand_live::init () { liveout = XCNEWVEC (tree, last_basic_block_for_fn (cfun) + 1); liveout[ENTRY_BLOCK] = ssa_default_def (cfun, gimple_vop (cfun)); } /* Compute live-in of BB from cached live-out. */ tree virtual_operand_live::get_live_in (basic_block bb) { /* A virtual PHI is a convenient cache for live-in. */ gphi *phi = get_virtual_phi (bb); if (phi) return gimple_phi_result (phi); if (!liveout) init (); /* Since we don't have a virtual PHI and we don't know whether there's a downstream virtual use (and thus PHIs are inserted where necessary) we now have to check each incoming edge live-out. */ edge_iterator ei; edge e; tree livein = NULL_TREE; FOR_EACH_EDGE (e, ei, bb->preds) if (e->flags & EDGE_DFS_BACK) /* We can ignore backedges since if there's a def there it would have forced a PHI in the source because it also acts as use downstream. */ continue; else if (!livein) livein = get_live_out (e->src); else if (get_live_out (e->src) != livein) /* When there's no virtual use downstream this indicates a point where we'd insert a PHI merging the different live virtual operands. */ return NULL_TREE; return livein; } /* Compute live-out of BB. */ tree virtual_operand_live::get_live_out (basic_block bb) { if (!liveout) init (); if (liveout[bb->index]) return liveout[bb->index]; tree lo = NULL_TREE; for (auto gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi)) { gimple *stmt = gsi_stmt (gsi); if (gimple_vdef (stmt)) { lo = gimple_vdef (stmt); break; } if (gimple_vuse (stmt)) { lo = gimple_vuse (stmt); break; } } if (!lo) lo = get_live_in (bb); liveout[bb->index] = lo; return lo; }