| /* Alias analysis for trees. |
| Copyright (C) 2004, 2005 Free Software Foundation, Inc. |
| Contributed by Diego Novillo <dnovillo@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 2, 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 COPYING. If not, write to |
| the Free Software Foundation, 59 Temple Place - Suite 330, |
| Boston, MA 02111-1307, USA. */ |
| |
| #include "config.h" |
| #include "system.h" |
| #include "coretypes.h" |
| #include "tm.h" |
| #include "tree.h" |
| #include "rtl.h" |
| #include "tm_p.h" |
| #include "hard-reg-set.h" |
| #include "basic-block.h" |
| #include "timevar.h" |
| #include "expr.h" |
| #include "ggc.h" |
| #include "langhooks.h" |
| #include "flags.h" |
| #include "function.h" |
| #include "diagnostic.h" |
| #include "tree-dump.h" |
| #include "tree-gimple.h" |
| #include "tree-flow.h" |
| #include "tree-inline.h" |
| #include "tree-pass.h" |
| #include "convert.h" |
| #include "params.h" |
| |
| /* 'true' after aliases have been computed (see compute_may_aliases). */ |
| bool aliases_computed_p; |
| |
| /* Structure to map a variable to its alias set and keep track of the |
| virtual operands that will be needed to represent it. */ |
| struct alias_map_d |
| { |
| /* Variable and its alias set. */ |
| tree var; |
| HOST_WIDE_INT set; |
| |
| /* Total number of virtual operands that will be needed to represent |
| all the aliases of VAR. */ |
| long total_alias_vops; |
| |
| /* Nonzero if the aliases for this memory tag have been grouped |
| already. Used in group_aliases. */ |
| unsigned int grouped_p : 1; |
| |
| /* Set of variables aliased with VAR. This is the exact same |
| information contained in VAR_ANN (VAR)->MAY_ALIASES, but in |
| bitmap form to speed up alias grouping. */ |
| sbitmap may_aliases; |
| }; |
| |
| |
| /* Alias information used by compute_may_aliases and its helpers. */ |
| struct alias_info |
| { |
| /* SSA names visited while collecting points-to information. If bit I |
| is set, it means that SSA variable with version I has already been |
| visited. */ |
| sbitmap ssa_names_visited; |
| |
| /* Array of SSA_NAME pointers processed by the points-to collector. */ |
| varray_type processed_ptrs; |
| |
| /* Variables whose address is still needed. */ |
| bitmap addresses_needed; |
| |
| /* ADDRESSABLE_VARS contains all the global variables and locals that |
| have had their address taken. */ |
| struct alias_map_d **addressable_vars; |
| size_t num_addressable_vars; |
| |
| /* POINTERS contains all the _DECL pointers with unique memory tags |
| that have been referenced in the program. */ |
| struct alias_map_d **pointers; |
| size_t num_pointers; |
| |
| /* Number of function calls found in the program. */ |
| size_t num_calls_found; |
| |
| /* Number of const/pure function calls found in the program. */ |
| size_t num_pure_const_calls_found; |
| |
| /* Array of counters to keep track of how many times each pointer has |
| been dereferenced in the program. This is used by the alias grouping |
| heuristic in compute_flow_insensitive_aliasing. */ |
| varray_type num_references; |
| |
| /* Total number of virtual operands that will be needed to represent |
| all the aliases of all the pointers found in the program. */ |
| long total_alias_vops; |
| |
| /* Variables that have been written to. */ |
| bitmap written_vars; |
| |
| /* Pointers that have been used in an indirect store operation. */ |
| bitmap dereferenced_ptrs_store; |
| |
| /* Pointers that have been used in an indirect load operation. */ |
| bitmap dereferenced_ptrs_load; |
| }; |
| |
| |
| /* Counters used to display statistics on alias analysis. */ |
| struct alias_stats_d |
| { |
| unsigned int alias_queries; |
| unsigned int alias_mayalias; |
| unsigned int alias_noalias; |
| unsigned int simple_queries; |
| unsigned int simple_resolved; |
| unsigned int tbaa_queries; |
| unsigned int tbaa_resolved; |
| }; |
| |
| |
| /* Local variables. */ |
| static struct alias_stats_d alias_stats; |
| |
| /* Local functions. */ |
| static void compute_flow_insensitive_aliasing (struct alias_info *); |
| static void dump_alias_stats (FILE *); |
| static bool may_alias_p (tree, HOST_WIDE_INT, tree, HOST_WIDE_INT); |
| static tree create_memory_tag (tree type, bool is_type_tag); |
| static tree get_tmt_for (tree, struct alias_info *); |
| static tree get_nmt_for (tree); |
| static void add_may_alias (tree, tree); |
| static void replace_may_alias (tree, size_t, tree); |
| static struct alias_info *init_alias_info (void); |
| static void delete_alias_info (struct alias_info *); |
| static void compute_points_to_and_addr_escape (struct alias_info *); |
| static void compute_flow_sensitive_aliasing (struct alias_info *); |
| static void setup_pointers_and_addressables (struct alias_info *); |
| static bool collect_points_to_info_r (tree, tree, void *); |
| static bool is_escape_site (tree, struct alias_info *); |
| static void add_pointed_to_var (struct alias_info *, tree, tree); |
| static void create_global_var (void); |
| static void collect_points_to_info_for (struct alias_info *, tree); |
| static void maybe_create_global_var (struct alias_info *ai); |
| static void group_aliases (struct alias_info *); |
| static void set_pt_anything (tree ptr); |
| static void set_pt_malloc (tree ptr); |
| |
| /* Global declarations. */ |
| |
| /* Call clobbered variables in the function. If bit I is set, then |
| REFERENCED_VARS (I) is call-clobbered. */ |
| bitmap call_clobbered_vars; |
| |
| /* Addressable variables in the function. If bit I is set, then |
| REFERENCED_VARS (I) has had its address taken. Note that |
| CALL_CLOBBERED_VARS and ADDRESSABLE_VARS are not related. An |
| addressable variable is not necessarily call-clobbered (e.g., a |
| local addressable whose address does not escape) and not all |
| call-clobbered variables are addressable (e.g., a local static |
| variable). */ |
| bitmap addressable_vars; |
| |
| /* When the program has too many call-clobbered variables and call-sites, |
| this variable is used to represent the clobbering effects of function |
| calls. In these cases, all the call clobbered variables in the program |
| are forced to alias this variable. This reduces compile times by not |
| having to keep track of too many V_MAY_DEF expressions at call sites. */ |
| tree global_var; |
| |
| |
| /* Compute may-alias information for every variable referenced in function |
| FNDECL. |
| |
| Alias analysis proceeds in 3 main phases: |
| |
| 1- Points-to and escape analysis. |
| |
| This phase walks the use-def chains in the SSA web looking for three |
| things: |
| |
| * Assignments of the form P_i = &VAR |
| * Assignments of the form P_i = malloc() |
| * Pointers and ADDR_EXPR that escape the current function. |
| |
| The concept of 'escaping' is the same one used in the Java world. When |
| a pointer or an ADDR_EXPR escapes, it means that it has been exposed |
| outside of the current function. So, assignment to global variables, |
| function arguments and returning a pointer are all escape sites, as are |
| conversions between pointers and integers. |
| |
| This is where we are currently limited. Since not everything is renamed |
| into SSA, we lose track of escape properties when a pointer is stashed |
| inside a field in a structure, for instance. In those cases, we are |
| assuming that the pointer does escape. |
| |
| We use escape analysis to determine whether a variable is |
| call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable |
| is call-clobbered. If a pointer P_i escapes, then all the variables |
| pointed-to by P_i (and its memory tag) also escape. |
| |
| 2- Compute flow-sensitive aliases |
| |
| We have two classes of memory tags. Memory tags associated with the |
| pointed-to data type of the pointers in the program. These tags are |
| called "type memory tag" (TMT). The other class are those associated |
| with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that |
| when adding operands for an INDIRECT_REF *P_i, we will first check |
| whether P_i has a name tag, if it does we use it, because that will have |
| more precise aliasing information. Otherwise, we use the standard type |
| tag. |
| |
| In this phase, we go through all the pointers we found in points-to |
| analysis and create alias sets for the name memory tags associated with |
| each pointer P_i. If P_i escapes, we mark call-clobbered the variables |
| it points to and its tag. |
| |
| |
| 3- Compute flow-insensitive aliases |
| |
| This pass will compare the alias set of every type memory tag and every |
| addressable variable found in the program. Given a type memory tag TMT |
| and an addressable variable V. If the alias sets of TMT and V conflict |
| (as computed by may_alias_p), then V is marked as an alias tag and added |
| to the alias set of TMT. |
| |
| For instance, consider the following function: |
| |
| foo (int i) |
| { |
| int *p, a, b; |
| |
| if (i > 10) |
| p = &a; |
| else |
| p = &b; |
| |
| *p = 3; |
| a = b + 2; |
| return *p; |
| } |
| |
| After aliasing analysis has finished, the type memory tag for pointer |
| 'p' will have two aliases, namely variables 'a' and 'b'. Every time |
| pointer 'p' is dereferenced, we want to mark the operation as a |
| potential reference to 'a' and 'b'. |
| |
| foo (int i) |
| { |
| int *p, a, b; |
| |
| if (i_2 > 10) |
| p_4 = &a; |
| else |
| p_6 = &b; |
| # p_1 = PHI <p_4(1), p_6(2)>; |
| |
| # a_7 = V_MAY_DEF <a_3>; |
| # b_8 = V_MAY_DEF <b_5>; |
| *p_1 = 3; |
| |
| # a_9 = V_MAY_DEF <a_7> |
| # VUSE <b_8> |
| a_9 = b_8 + 2; |
| |
| # VUSE <a_9>; |
| # VUSE <b_8>; |
| return *p_1; |
| } |
| |
| In certain cases, the list of may aliases for a pointer may grow too |
| large. This may cause an explosion in the number of virtual operands |
| inserted in the code. Resulting in increased memory consumption and |
| compilation time. |
| |
| When the number of virtual operands needed to represent aliased |
| loads and stores grows too large (configurable with @option{--param |
| max-aliased-vops}), alias sets are grouped to avoid severe |
| compile-time slow downs and memory consumption. See group_aliases. */ |
| |
| static void |
| compute_may_aliases (void) |
| { |
| struct alias_info *ai; |
| |
| memset (&alias_stats, 0, sizeof (alias_stats)); |
| |
| /* Initialize aliasing information. */ |
| ai = init_alias_info (); |
| |
| /* For each pointer P_i, determine the sets of variables that P_i may |
| point-to. For every addressable variable V, determine whether the |
| address of V escapes the current function, making V call-clobbered |
| (i.e., whether &V is stored in a global variable or if its passed as a |
| function call argument). */ |
| compute_points_to_and_addr_escape (ai); |
| |
| /* Collect all pointers and addressable variables, compute alias sets, |
| create memory tags for pointers and promote variables whose address is |
| not needed anymore. */ |
| setup_pointers_and_addressables (ai); |
| |
| /* Compute flow-sensitive, points-to based aliasing for all the name |
| memory tags. Note that this pass needs to be done before flow |
| insensitive analysis because it uses the points-to information |
| gathered before to mark call-clobbered type tags. */ |
| compute_flow_sensitive_aliasing (ai); |
| |
| /* Compute type-based flow-insensitive aliasing for all the type |
| memory tags. */ |
| compute_flow_insensitive_aliasing (ai); |
| |
| /* If the program has too many call-clobbered variables and/or function |
| calls, create .GLOBAL_VAR and use it to model call-clobbering |
| semantics at call sites. This reduces the number of virtual operands |
| considerably, improving compile times at the expense of lost |
| aliasing precision. */ |
| maybe_create_global_var (ai); |
| |
| /* Debugging dumps. */ |
| if (dump_file) |
| { |
| dump_referenced_vars (dump_file); |
| if (dump_flags & TDF_STATS) |
| dump_alias_stats (dump_file); |
| dump_points_to_info (dump_file); |
| dump_alias_info (dump_file); |
| } |
| |
| /* Deallocate memory used by aliasing data structures. */ |
| delete_alias_info (ai); |
| } |
| |
| struct tree_opt_pass pass_may_alias = |
| { |
| "alias", /* name */ |
| NULL, /* gate */ |
| compute_may_aliases, /* execute */ |
| NULL, /* sub */ |
| NULL, /* next */ |
| 0, /* static_pass_number */ |
| TV_TREE_MAY_ALIAS, /* tv_id */ |
| PROP_cfg | PROP_ssa, /* properties_required */ |
| PROP_alias, /* properties_provided */ |
| 0, /* properties_destroyed */ |
| 0, /* todo_flags_start */ |
| TODO_dump_func | TODO_rename_vars |
| | TODO_ggc_collect | TODO_verify_ssa |
| | TODO_verify_stmts, /* todo_flags_finish */ |
| 0 /* letter */ |
| }; |
| |
| |
| /* Data structure used to count the number of dereferences to PTR |
| inside an expression. */ |
| struct count_ptr_d |
| { |
| tree ptr; |
| unsigned count; |
| }; |
| |
| |
| /* Helper for count_uses_and_derefs. Called by walk_tree to look for |
| (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */ |
| |
| static tree |
| count_ptr_derefs (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data) |
| { |
| struct count_ptr_d *count_p = (struct count_ptr_d *) data; |
| |
| if (INDIRECT_REF_P (*tp) && TREE_OPERAND (*tp, 0) == count_p->ptr) |
| count_p->count++; |
| |
| return NULL_TREE; |
| } |
| |
| |
| /* Count the number of direct and indirect uses for pointer PTR in |
| statement STMT. The two counts are stored in *NUM_USES_P and |
| *NUM_DEREFS_P respectively. *IS_STORE_P is set to 'true' if at |
| least one of those dereferences is a store operation. */ |
| |
| static void |
| count_uses_and_derefs (tree ptr, tree stmt, unsigned *num_uses_p, |
| unsigned *num_derefs_p, bool *is_store) |
| { |
| ssa_op_iter i; |
| tree use; |
| |
| *num_uses_p = 0; |
| *num_derefs_p = 0; |
| *is_store = false; |
| |
| /* Find out the total number of uses of PTR in STMT. */ |
| FOR_EACH_SSA_TREE_OPERAND (use, stmt, i, SSA_OP_USE) |
| if (use == ptr) |
| (*num_uses_p)++; |
| |
| /* Now count the number of indirect references to PTR. This is |
| truly awful, but we don't have much choice. There are no parent |
| pointers inside INDIRECT_REFs, so an expression like |
| '*x_1 = foo (x_1, *x_1)' needs to be traversed piece by piece to |
| find all the indirect and direct uses of x_1 inside. The only |
| shortcut we can take is the fact that GIMPLE only allows |
| INDIRECT_REFs inside the expressions below. */ |
| if (TREE_CODE (stmt) == MODIFY_EXPR |
| || (TREE_CODE (stmt) == RETURN_EXPR |
| && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR) |
| || TREE_CODE (stmt) == ASM_EXPR |
| || TREE_CODE (stmt) == CALL_EXPR) |
| { |
| tree lhs, rhs; |
| |
| if (TREE_CODE (stmt) == MODIFY_EXPR) |
| { |
| lhs = TREE_OPERAND (stmt, 0); |
| rhs = TREE_OPERAND (stmt, 1); |
| } |
| else if (TREE_CODE (stmt) == RETURN_EXPR) |
| { |
| tree e = TREE_OPERAND (stmt, 0); |
| lhs = TREE_OPERAND (e, 0); |
| rhs = TREE_OPERAND (e, 1); |
| } |
| else if (TREE_CODE (stmt) == ASM_EXPR) |
| { |
| lhs = ASM_OUTPUTS (stmt); |
| rhs = ASM_INPUTS (stmt); |
| } |
| else |
| { |
| lhs = NULL_TREE; |
| rhs = stmt; |
| } |
| |
| if (lhs && (TREE_CODE (lhs) == TREE_LIST || EXPR_P (lhs))) |
| { |
| struct count_ptr_d count; |
| count.ptr = ptr; |
| count.count = 0; |
| walk_tree (&lhs, count_ptr_derefs, &count, NULL); |
| *is_store = true; |
| *num_derefs_p = count.count; |
| } |
| |
| if (rhs && (TREE_CODE (rhs) == TREE_LIST || EXPR_P (rhs))) |
| { |
| struct count_ptr_d count; |
| count.ptr = ptr; |
| count.count = 0; |
| walk_tree (&rhs, count_ptr_derefs, &count, NULL); |
| *num_derefs_p += count.count; |
| } |
| } |
| |
| gcc_assert (*num_uses_p >= *num_derefs_p); |
| } |
| |
| |
| /* Initialize the data structures used for alias analysis. */ |
| |
| static struct alias_info * |
| init_alias_info (void) |
| { |
| struct alias_info *ai; |
| |
| ai = xcalloc (1, sizeof (struct alias_info)); |
| ai->ssa_names_visited = sbitmap_alloc (num_ssa_names); |
| sbitmap_zero (ai->ssa_names_visited); |
| VARRAY_TREE_INIT (ai->processed_ptrs, 50, "processed_ptrs"); |
| ai->addresses_needed = BITMAP_ALLOC (NULL); |
| VARRAY_UINT_INIT (ai->num_references, num_referenced_vars, "num_references"); |
| ai->written_vars = BITMAP_ALLOC (NULL); |
| ai->dereferenced_ptrs_store = BITMAP_ALLOC (NULL); |
| ai->dereferenced_ptrs_load = BITMAP_ALLOC (NULL); |
| |
| /* If aliases have been computed before, clear existing information. */ |
| if (aliases_computed_p) |
| { |
| unsigned i; |
| basic_block bb; |
| |
| /* Make sure that every statement has a valid set of operands. |
| If a statement needs to be scanned for operands while we |
| compute aliases, it may get erroneous operands because all |
| the alias relations are not built at that point. |
| FIXME: This code will become obsolete when operands are not |
| lazily updated. */ |
| FOR_EACH_BB (bb) |
| { |
| block_stmt_iterator si; |
| for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si)) |
| get_stmt_operands (bsi_stmt (si)); |
| } |
| |
| /* Similarly, clear the set of addressable variables. In this |
| case, we can just clear the set because addressability is |
| only computed here. */ |
| bitmap_clear (addressable_vars); |
| |
| /* Clear flow-insensitive alias information from each symbol. */ |
| for (i = 0; i < num_referenced_vars; i++) |
| { |
| tree var = referenced_var (i); |
| var_ann_t ann = var_ann (var); |
| |
| ann->is_alias_tag = 0; |
| ann->may_aliases = NULL; |
| |
| /* Since we are about to re-discover call-clobbered |
| variables, clear the call-clobbered flag. Variables that |
| are intrinsically call-clobbered (globals, local statics, |
| etc) will not be marked by the aliasing code, so we can't |
| remove them from CALL_CLOBBERED_VARS. */ |
| if (ann->mem_tag_kind != NOT_A_TAG || !is_global_var (var)) |
| clear_call_clobbered (var); |
| } |
| |
| /* Clear flow-sensitive points-to information from each SSA name. */ |
| for (i = 1; i < num_ssa_names; i++) |
| { |
| tree name = ssa_name (i); |
| |
| if (!name || !POINTER_TYPE_P (TREE_TYPE (name))) |
| continue; |
| |
| if (SSA_NAME_PTR_INFO (name)) |
| { |
| struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name); |
| |
| /* Clear all the flags but keep the name tag to |
| avoid creating new temporaries unnecessarily. If |
| this pointer is found to point to a subset or |
| superset of its former points-to set, then a new |
| tag will need to be created in create_name_tags. */ |
| pi->pt_anything = 0; |
| pi->pt_malloc = 0; |
| pi->pt_null = 0; |
| pi->value_escapes_p = 0; |
| pi->is_dereferenced = 0; |
| if (pi->pt_vars) |
| bitmap_clear (pi->pt_vars); |
| } |
| } |
| } |
| |
| /* Next time, we will need to reset alias information. */ |
| aliases_computed_p = true; |
| |
| return ai; |
| } |
| |
| |
| /* Deallocate memory used by alias analysis. */ |
| |
| static void |
| delete_alias_info (struct alias_info *ai) |
| { |
| size_t i; |
| |
| sbitmap_free (ai->ssa_names_visited); |
| ai->processed_ptrs = NULL; |
| BITMAP_FREE (ai->addresses_needed); |
| |
| for (i = 0; i < ai->num_addressable_vars; i++) |
| { |
| sbitmap_free (ai->addressable_vars[i]->may_aliases); |
| free (ai->addressable_vars[i]); |
| } |
| free (ai->addressable_vars); |
| |
| for (i = 0; i < ai->num_pointers; i++) |
| { |
| sbitmap_free (ai->pointers[i]->may_aliases); |
| free (ai->pointers[i]); |
| } |
| free (ai->pointers); |
| |
| ai->num_references = NULL; |
| BITMAP_FREE (ai->written_vars); |
| BITMAP_FREE (ai->dereferenced_ptrs_store); |
| BITMAP_FREE (ai->dereferenced_ptrs_load); |
| |
| free (ai); |
| } |
| |
| |
| /* Walk use-def chains for pointer PTR to determine what variables is PTR |
| pointing to. */ |
| |
| static void |
| collect_points_to_info_for (struct alias_info *ai, tree ptr) |
| { |
| gcc_assert (POINTER_TYPE_P (TREE_TYPE (ptr))); |
| |
| if (!TEST_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (ptr))) |
| { |
| SET_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (ptr)); |
| walk_use_def_chains (ptr, collect_points_to_info_r, ai, true); |
| VARRAY_PUSH_TREE (ai->processed_ptrs, ptr); |
| } |
| } |
| |
| |
| /* Traverse use-def links for all the pointers in the program to collect |
| address escape and points-to information. |
| |
| This is loosely based on the same idea described in R. Hasti and S. |
| Horwitz, ``Using static single assignment form to improve |
| flow-insensitive pointer analysis,'' in SIGPLAN Conference on |
| Programming Language Design and Implementation, pp. 97-105, 1998. */ |
| |
| static void |
| compute_points_to_and_addr_escape (struct alias_info *ai) |
| { |
| basic_block bb; |
| unsigned i; |
| tree op; |
| ssa_op_iter iter; |
| |
| timevar_push (TV_TREE_PTA); |
| |
| FOR_EACH_BB (bb) |
| { |
| bb_ann_t block_ann = bb_ann (bb); |
| block_stmt_iterator si; |
| |
| for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si)) |
| { |
| bitmap addr_taken; |
| tree stmt = bsi_stmt (si); |
| bool stmt_escapes_p = is_escape_site (stmt, ai); |
| bitmap_iterator bi; |
| |
| /* Mark all the variables whose address are taken by the |
| statement. Note that this will miss all the addresses taken |
| in PHI nodes (those are discovered while following the use-def |
| chains). */ |
| get_stmt_operands (stmt); |
| addr_taken = addresses_taken (stmt); |
| if (addr_taken) |
| EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i, bi) |
| { |
| tree var = referenced_var (i); |
| bitmap_set_bit (ai->addresses_needed, var_ann (var)->uid); |
| if (stmt_escapes_p) |
| mark_call_clobbered (var); |
| } |
| |
| if (stmt_escapes_p) |
| block_ann->has_escape_site = 1; |
| |
| FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE) |
| { |
| var_ann_t v_ann = var_ann (SSA_NAME_VAR (op)); |
| struct ptr_info_def *pi; |
| bool is_store; |
| unsigned num_uses, num_derefs; |
| |
| /* If the operand's variable may be aliased, keep track |
| of how many times we've referenced it. This is used |
| for alias grouping in compute_flow_sensitive_aliasing. |
| Note that we don't need to grow AI->NUM_REFERENCES |
| because we are processing regular variables, not |
| memory tags (the array's initial size is set to |
| NUM_REFERENCED_VARS). */ |
| if (may_be_aliased (SSA_NAME_VAR (op))) |
| (VARRAY_UINT (ai->num_references, v_ann->uid))++; |
| |
| if (!POINTER_TYPE_P (TREE_TYPE (op))) |
| continue; |
| |
| collect_points_to_info_for (ai, op); |
| |
| pi = SSA_NAME_PTR_INFO (op); |
| count_uses_and_derefs (op, stmt, &num_uses, &num_derefs, |
| &is_store); |
| |
| if (num_derefs > 0) |
| { |
| /* Mark OP as dereferenced. In a subsequent pass, |
| dereferenced pointers that point to a set of |
| variables will be assigned a name tag to alias |
| all the variables OP points to. */ |
| pi->is_dereferenced = 1; |
| |
| /* Keep track of how many time we've dereferenced each |
| pointer. Again, we don't need to grow |
| AI->NUM_REFERENCES because we're processing |
| existing program variables. */ |
| (VARRAY_UINT (ai->num_references, v_ann->uid))++; |
| |
| /* If this is a store operation, mark OP as being |
| dereferenced to store, otherwise mark it as being |
| dereferenced to load. */ |
| if (is_store) |
| bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid); |
| else |
| bitmap_set_bit (ai->dereferenced_ptrs_load, v_ann->uid); |
| } |
| |
| if (stmt_escapes_p && num_derefs < num_uses) |
| { |
| /* If STMT is an escape point and STMT contains at |
| least one direct use of OP, then the value of OP |
| escapes and so the pointed-to variables need to |
| be marked call-clobbered. */ |
| pi->value_escapes_p = 1; |
| |
| /* If the statement makes a function call, assume |
| that pointer OP will be dereferenced in a store |
| operation inside the called function. */ |
| if (get_call_expr_in (stmt)) |
| { |
| bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid); |
| pi->is_dereferenced = 1; |
| } |
| } |
| } |
| |
| /* Update reference counter for definitions to any |
| potentially aliased variable. This is used in the alias |
| grouping heuristics. */ |
| FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF) |
| { |
| tree var = SSA_NAME_VAR (op); |
| var_ann_t ann = var_ann (var); |
| bitmap_set_bit (ai->written_vars, ann->uid); |
| if (may_be_aliased (var)) |
| (VARRAY_UINT (ai->num_references, ann->uid))++; |
| |
| if (POINTER_TYPE_P (TREE_TYPE (op))) |
| collect_points_to_info_for (ai, op); |
| } |
| |
| /* Mark variables in V_MAY_DEF operands as being written to. */ |
| FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_DEFS) |
| { |
| tree var = SSA_NAME_VAR (op); |
| var_ann_t ann = var_ann (var); |
| bitmap_set_bit (ai->written_vars, ann->uid); |
| } |
| |
| /* After promoting variables and computing aliasing we will |
| need to re-scan most statements. FIXME: Try to minimize the |
| number of statements re-scanned. It's not really necessary to |
| re-scan *all* statements. */ |
| modify_stmt (stmt); |
| } |
| } |
| |
| timevar_pop (TV_TREE_PTA); |
| } |
| |
| |
| /* Create name tags for all the pointers that have been dereferenced. |
| We only create a name tag for a pointer P if P is found to point to |
| a set of variables (so that we can alias them to *P) or if it is |
| the result of a call to malloc (which means that P cannot point to |
| anything else nor alias any other variable). |
| |
| If two pointers P and Q point to the same set of variables, they |
| are assigned the same name tag. */ |
| |
| static void |
| create_name_tags (struct alias_info *ai) |
| { |
| size_t i; |
| |
| for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++) |
| { |
| tree ptr = VARRAY_TREE (ai->processed_ptrs, i); |
| struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr); |
| |
| if (pi->pt_anything || !pi->is_dereferenced) |
| { |
| /* No name tags for pointers that have not been |
| dereferenced or point to an arbitrary location. */ |
| pi->name_mem_tag = NULL_TREE; |
| continue; |
| } |
| |
| if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars)) |
| { |
| size_t j; |
| tree old_name_tag = pi->name_mem_tag; |
| |
| /* If PTR points to a set of variables, check if we don't |
| have another pointer Q with the same points-to set before |
| creating a tag. If so, use Q's tag instead of creating a |
| new one. |
| |
| This is important for not creating unnecessary symbols |
| and also for copy propagation. If we ever need to |
| propagate PTR into Q or vice-versa, we would run into |
| problems if they both had different name tags because |
| they would have different SSA version numbers (which |
| would force us to take the name tags in and out of SSA). */ |
| for (j = 0; j < i; j++) |
| { |
| tree q = VARRAY_TREE (ai->processed_ptrs, j); |
| struct ptr_info_def *qi = SSA_NAME_PTR_INFO (q); |
| |
| if (qi |
| && qi->pt_vars |
| && qi->name_mem_tag |
| && bitmap_equal_p (pi->pt_vars, qi->pt_vars)) |
| { |
| pi->name_mem_tag = qi->name_mem_tag; |
| break; |
| } |
| } |
| |
| /* If we didn't find a pointer with the same points-to set |
| as PTR, create a new name tag if needed. */ |
| if (pi->name_mem_tag == NULL_TREE) |
| pi->name_mem_tag = get_nmt_for (ptr); |
| |
| /* If the new name tag computed for PTR is different than |
| the old name tag that it used to have, then the old tag |
| needs to be removed from the IL, so we mark it for |
| renaming. */ |
| if (old_name_tag && old_name_tag != pi->name_mem_tag) |
| bitmap_set_bit (vars_to_rename, var_ann (old_name_tag)->uid); |
| } |
| else if (pi->pt_malloc) |
| { |
| /* Otherwise, create a unique name tag for this pointer. */ |
| pi->name_mem_tag = get_nmt_for (ptr); |
| } |
| else |
| { |
| /* Only pointers that may point to malloc or other variables |
| may receive a name tag. If the pointer does not point to |
| a known spot, we should use type tags. */ |
| set_pt_anything (ptr); |
| continue; |
| } |
| |
| TREE_THIS_VOLATILE (pi->name_mem_tag) |
| |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr))); |
| |
| /* Mark the new name tag for renaming. */ |
| bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid); |
| } |
| } |
| |
| |
| |
| /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for |
| the name memory tag (NMT) associated with P_i. If P_i escapes, then its |
| name tag and the variables it points-to are call-clobbered. Finally, if |
| P_i escapes and we could not determine where it points to, then all the |
| variables in the same alias set as *P_i are marked call-clobbered. This |
| is necessary because we must assume that P_i may take the address of any |
| variable in the same alias set. */ |
| |
| static void |
| compute_flow_sensitive_aliasing (struct alias_info *ai) |
| { |
| size_t i; |
| |
| create_name_tags (ai); |
| |
| for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++) |
| { |
| unsigned j; |
| tree ptr = VARRAY_TREE (ai->processed_ptrs, i); |
| struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr); |
| var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr)); |
| bitmap_iterator bi; |
| |
| if (pi->value_escapes_p || pi->pt_anything) |
| { |
| /* If PTR escapes or may point to anything, then its associated |
| memory tags and pointed-to variables are call-clobbered. */ |
| if (pi->name_mem_tag) |
| mark_call_clobbered (pi->name_mem_tag); |
| |
| if (v_ann->type_mem_tag) |
| mark_call_clobbered (v_ann->type_mem_tag); |
| |
| if (pi->pt_vars) |
| EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi) |
| { |
| mark_call_clobbered (referenced_var (j)); |
| } |
| } |
| |
| /* Set up aliasing information for PTR's name memory tag (if it has |
| one). Note that only pointers that have been dereferenced will |
| have a name memory tag. */ |
| if (pi->name_mem_tag && pi->pt_vars) |
| EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi) |
| { |
| add_may_alias (pi->name_mem_tag, referenced_var (j)); |
| add_may_alias (v_ann->type_mem_tag, referenced_var (j)); |
| } |
| |
| /* If the name tag is call clobbered, so is the type tag |
| associated with the base VAR_DECL. */ |
| if (pi->name_mem_tag |
| && v_ann->type_mem_tag |
| && is_call_clobbered (pi->name_mem_tag)) |
| mark_call_clobbered (v_ann->type_mem_tag); |
| } |
| } |
| |
| |
| /* Compute type-based alias sets. Traverse all the pointers and |
| addressable variables found in setup_pointers_and_addressables. |
| |
| For every pointer P in AI->POINTERS and addressable variable V in |
| AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type |
| memory tag (TMT) if their alias sets conflict. V is then marked as |
| an alias tag so that the operand scanner knows that statements |
| containing V have aliased operands. */ |
| |
| static void |
| compute_flow_insensitive_aliasing (struct alias_info *ai) |
| { |
| size_t i; |
| |
| /* Initialize counter for the total number of virtual operands that |
| aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the |
| threshold set by --params max-alias-vops, we enable alias |
| grouping. */ |
| ai->total_alias_vops = 0; |
| |
| /* For every pointer P, determine which addressable variables may alias |
| with P's type memory tag. */ |
| for (i = 0; i < ai->num_pointers; i++) |
| { |
| size_t j; |
| struct alias_map_d *p_map = ai->pointers[i]; |
| tree tag = var_ann (p_map->var)->type_mem_tag; |
| var_ann_t tag_ann = var_ann (tag); |
| |
| p_map->total_alias_vops = 0; |
| p_map->may_aliases = sbitmap_alloc (num_referenced_vars); |
| sbitmap_zero (p_map->may_aliases); |
| |
| for (j = 0; j < ai->num_addressable_vars; j++) |
| { |
| struct alias_map_d *v_map; |
| var_ann_t v_ann; |
| tree var; |
| bool tag_stored_p, var_stored_p; |
| |
| v_map = ai->addressable_vars[j]; |
| var = v_map->var; |
| v_ann = var_ann (var); |
| |
| /* Skip memory tags and variables that have never been |
| written to. We also need to check if the variables are |
| call-clobbered because they may be overwritten by |
| function calls. |
| |
| Note this is effectively random accessing elements in |
| the sparse bitset, which can be highly inefficient. |
| So we first check the call_clobbered status of the |
| tag and variable before querying the bitmap. */ |
| tag_stored_p = is_call_clobbered (tag) |
| || bitmap_bit_p (ai->written_vars, tag_ann->uid); |
| var_stored_p = is_call_clobbered (var) |
| || bitmap_bit_p (ai->written_vars, v_ann->uid); |
| if (!tag_stored_p && !var_stored_p) |
| continue; |
| |
| if (may_alias_p (p_map->var, p_map->set, var, v_map->set)) |
| { |
| size_t num_tag_refs, num_var_refs; |
| |
| num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid); |
| num_var_refs = VARRAY_UINT (ai->num_references, v_ann->uid); |
| |
| /* Add VAR to TAG's may-aliases set. */ |
| add_may_alias (tag, var); |
| |
| /* Update the total number of virtual operands due to |
| aliasing. Since we are adding one more alias to TAG's |
| may-aliases set, the total number of virtual operands due |
| to aliasing will be increased by the number of references |
| made to VAR and TAG (every reference to TAG will also |
| count as a reference to VAR). */ |
| ai->total_alias_vops += (num_var_refs + num_tag_refs); |
| p_map->total_alias_vops += (num_var_refs + num_tag_refs); |
| |
| /* Update the bitmap used to represent TAG's alias set |
| in case we need to group aliases. */ |
| SET_BIT (p_map->may_aliases, var_ann (var)->uid); |
| } |
| } |
| } |
| |
| /* Since this analysis is based exclusively on symbols, it fails to |
| handle cases where two pointers P and Q have different memory |
| tags with conflicting alias set numbers but no aliased symbols in |
| common. |
| |
| For example, suppose that we have two memory tags TMT.1 and TMT.2 |
| such that |
| |
| may-aliases (TMT.1) = { a } |
| may-aliases (TMT.2) = { b } |
| |
| and the alias set number of TMT.1 conflicts with that of TMT.2. |
| Since they don't have symbols in common, loads and stores from |
| TMT.1 and TMT.2 will seem independent of each other, which will |
| lead to the optimizers making invalid transformations (see |
| testsuite/gcc.c-torture/execute/pr15262-[12].c). |
| |
| To avoid this problem, we do a final traversal of AI->POINTERS |
| looking for pairs of pointers that have no aliased symbols in |
| common and yet have conflicting alias set numbers. */ |
| for (i = 0; i < ai->num_pointers; i++) |
| { |
| size_t j; |
| struct alias_map_d *p_map1 = ai->pointers[i]; |
| tree tag1 = var_ann (p_map1->var)->type_mem_tag; |
| sbitmap may_aliases1 = p_map1->may_aliases; |
| |
| for (j = i + 1; j < ai->num_pointers; j++) |
| { |
| struct alias_map_d *p_map2 = ai->pointers[j]; |
| tree tag2 = var_ann (p_map2->var)->type_mem_tag; |
| sbitmap may_aliases2 = p_map2->may_aliases; |
| |
| /* If the pointers may not point to each other, do nothing. */ |
| if (!may_alias_p (p_map1->var, p_map1->set, p_map2->var, p_map2->set)) |
| continue; |
| |
| /* The two pointers may alias each other. If they already have |
| symbols in common, do nothing. */ |
| if (sbitmap_any_common_bits (may_aliases1, may_aliases2)) |
| continue; |
| |
| if (sbitmap_first_set_bit (may_aliases2) >= 0) |
| { |
| size_t k; |
| |
| /* Add all the aliases for TAG2 into TAG1's alias set. |
| FIXME, update grouping heuristic counters. */ |
| EXECUTE_IF_SET_IN_SBITMAP (may_aliases2, 0, k, |
| add_may_alias (tag1, referenced_var (k))); |
| sbitmap_a_or_b (may_aliases1, may_aliases1, may_aliases2); |
| } |
| else |
| { |
| /* Since TAG2 does not have any aliases of its own, add |
| TAG2 itself to the alias set of TAG1. */ |
| add_may_alias (tag1, tag2); |
| SET_BIT (may_aliases1, var_ann (tag2)->uid); |
| } |
| } |
| } |
| |
| if (dump_file) |
| fprintf (dump_file, "%s: Total number of aliased vops: %ld\n", |
| get_name (current_function_decl), |
| ai->total_alias_vops); |
| |
| /* Determine if we need to enable alias grouping. */ |
| if (ai->total_alias_vops >= MAX_ALIASED_VOPS) |
| group_aliases (ai); |
| } |
| |
| |
| /* Comparison function for qsort used in group_aliases. */ |
| |
| static int |
| total_alias_vops_cmp (const void *p, const void *q) |
| { |
| const struct alias_map_d **p1 = (const struct alias_map_d **)p; |
| const struct alias_map_d **p2 = (const struct alias_map_d **)q; |
| long n1 = (*p1)->total_alias_vops; |
| long n2 = (*p2)->total_alias_vops; |
| |
| /* We want to sort in descending order. */ |
| return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1); |
| } |
| |
| /* Group all the aliases for TAG to make TAG represent all the |
| variables in its alias set. Update the total number |
| of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This |
| function will make TAG be the unique alias tag for all the |
| variables in its may-aliases. So, given: |
| |
| may-aliases(TAG) = { V1, V2, V3 } |
| |
| This function will group the variables into: |
| |
| may-aliases(V1) = { TAG } |
| may-aliases(V2) = { TAG } |
| may-aliases(V2) = { TAG } */ |
| |
| static void |
| group_aliases_into (tree tag, sbitmap tag_aliases, struct alias_info *ai) |
| { |
| size_t i; |
| var_ann_t tag_ann = var_ann (tag); |
| size_t num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid); |
| |
| EXECUTE_IF_SET_IN_SBITMAP (tag_aliases, 0, i, |
| { |
| tree var = referenced_var (i); |
| var_ann_t ann = var_ann (var); |
| |
| /* Make TAG the unique alias of VAR. */ |
| ann->is_alias_tag = 0; |
| ann->may_aliases = NULL; |
| |
| /* Note that VAR and TAG may be the same if the function has no |
| addressable variables (see the discussion at the end of |
| setup_pointers_and_addressables). */ |
| if (var != tag) |
| add_may_alias (var, tag); |
| |
| /* Reduce total number of virtual operands contributed |
| by TAG on behalf of VAR. Notice that the references to VAR |
| itself won't be removed. We will merely replace them with |
| references to TAG. */ |
| ai->total_alias_vops -= num_tag_refs; |
| }); |
| |
| /* We have reduced the number of virtual operands that TAG makes on |
| behalf of all the variables formerly aliased with it. However, |
| we have also "removed" all the virtual operands for TAG itself, |
| so we add them back. */ |
| ai->total_alias_vops += num_tag_refs; |
| |
| /* TAG no longer has any aliases. */ |
| tag_ann->may_aliases = NULL; |
| } |
| |
| |
| /* Group may-aliases sets to reduce the number of virtual operands due |
| to aliasing. |
| |
| 1- Sort the list of pointers in decreasing number of contributed |
| virtual operands. |
| |
| 2- Take the first entry in AI->POINTERS and revert the role of |
| the memory tag and its aliases. Usually, whenever an aliased |
| variable Vi is found to alias with a memory tag T, we add Vi |
| to the may-aliases set for T. Meaning that after alias |
| analysis, we will have: |
| |
| may-aliases(T) = { V1, V2, V3, ..., Vn } |
| |
| This means that every statement that references T, will get 'n' |
| virtual operands for each of the Vi tags. But, when alias |
| grouping is enabled, we make T an alias tag and add it to the |
| alias set of all the Vi variables: |
| |
| may-aliases(V1) = { T } |
| may-aliases(V2) = { T } |
| ... |
| may-aliases(Vn) = { T } |
| |
| This has two effects: (a) statements referencing T will only get |
| a single virtual operand, and, (b) all the variables Vi will now |
| appear to alias each other. So, we lose alias precision to |
| improve compile time. But, in theory, a program with such a high |
| level of aliasing should not be very optimizable in the first |
| place. |
| |
| 3- Since variables may be in the alias set of more than one |
| memory tag, the grouping done in step (2) needs to be extended |
| to all the memory tags that have a non-empty intersection with |
| the may-aliases set of tag T. For instance, if we originally |
| had these may-aliases sets: |
| |
| may-aliases(T) = { V1, V2, V3 } |
| may-aliases(R) = { V2, V4 } |
| |
| In step (2) we would have reverted the aliases for T as: |
| |
| may-aliases(V1) = { T } |
| may-aliases(V2) = { T } |
| may-aliases(V3) = { T } |
| |
| But note that now V2 is no longer aliased with R. We could |
| add R to may-aliases(V2), but we are in the process of |
| grouping aliases to reduce virtual operands so what we do is |
| add V4 to the grouping to obtain: |
| |
| may-aliases(V1) = { T } |
| may-aliases(V2) = { T } |
| may-aliases(V3) = { T } |
| may-aliases(V4) = { T } |
| |
| 4- If the total number of virtual operands due to aliasing is |
| still above the threshold set by max-alias-vops, go back to (2). */ |
| |
| static void |
| group_aliases (struct alias_info *ai) |
| { |
| size_t i; |
| |
| /* Sort the POINTERS array in descending order of contributed |
| virtual operands. */ |
| qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *), |
| total_alias_vops_cmp); |
| |
| /* For every pointer in AI->POINTERS, reverse the roles of its tag |
| and the tag's may-aliases set. */ |
| for (i = 0; i < ai->num_pointers; i++) |
| { |
| size_t j; |
| tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag; |
| sbitmap tag1_aliases = ai->pointers[i]->may_aliases; |
| |
| /* Skip tags that have been grouped already. */ |
| if (ai->pointers[i]->grouped_p) |
| continue; |
| |
| /* See if TAG1 had any aliases in common with other type tags. |
| If we find a TAG2 with common aliases with TAG1, add TAG2's |
| aliases into TAG1. */ |
| for (j = i + 1; j < ai->num_pointers; j++) |
| { |
| sbitmap tag2_aliases = ai->pointers[j]->may_aliases; |
| |
| if (sbitmap_any_common_bits (tag1_aliases, tag2_aliases)) |
| { |
| tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag; |
| |
| sbitmap_a_or_b (tag1_aliases, tag1_aliases, tag2_aliases); |
| |
| /* TAG2 does not need its aliases anymore. */ |
| sbitmap_zero (tag2_aliases); |
| var_ann (tag2)->may_aliases = NULL; |
| |
| /* TAG1 is the unique alias of TAG2. */ |
| add_may_alias (tag2, tag1); |
| |
| ai->pointers[j]->grouped_p = true; |
| } |
| } |
| |
| /* Now group all the aliases we collected into TAG1. */ |
| group_aliases_into (tag1, tag1_aliases, ai); |
| |
| /* If we've reduced total number of virtual operands below the |
| threshold, stop. */ |
| if (ai->total_alias_vops < MAX_ALIASED_VOPS) |
| break; |
| } |
| |
| /* Finally, all the variables that have been grouped cannot be in |
| the may-alias set of name memory tags. Suppose that we have |
| grouped the aliases in this code so that may-aliases(a) = TMT.20 |
| |
| p_5 = &a; |
| ... |
| # a_9 = V_MAY_DEF <a_8> |
| p_5->field = 0 |
| ... Several modifications to TMT.20 ... |
| # VUSE <a_9> |
| x_30 = p_5->field |
| |
| Since p_5 points to 'a', the optimizers will try to propagate 0 |
| into p_5->field, but that is wrong because there have been |
| modifications to 'TMT.20' in between. To prevent this we have to |
| replace 'a' with 'TMT.20' in the name tag of p_5. */ |
| for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++) |
| { |
| size_t j; |
| tree ptr = VARRAY_TREE (ai->processed_ptrs, i); |
| tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag; |
| varray_type aliases; |
| |
| if (name_tag == NULL_TREE) |
| continue; |
| |
| aliases = var_ann (name_tag)->may_aliases; |
| for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++) |
| { |
| tree alias = VARRAY_TREE (aliases, j); |
| var_ann_t ann = var_ann (alias); |
| |
| if (ann->mem_tag_kind == NOT_A_TAG && ann->may_aliases) |
| { |
| tree new_alias; |
| |
| gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1); |
| |
| new_alias = VARRAY_TREE (ann->may_aliases, 0); |
| replace_may_alias (name_tag, j, new_alias); |
| } |
| } |
| } |
| |
| if (dump_file) |
| fprintf (dump_file, |
| "%s: Total number of aliased vops after grouping: %ld%s\n", |
| get_name (current_function_decl), |
| ai->total_alias_vops, |
| (ai->total_alias_vops < 0) ? " (negative values are OK)" : ""); |
| } |
| |
| |
| /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */ |
| |
| static void |
| create_alias_map_for (tree var, struct alias_info *ai) |
| { |
| struct alias_map_d *alias_map; |
| alias_map = xcalloc (1, sizeof (*alias_map)); |
| alias_map->var = var; |
| alias_map->set = get_alias_set (var); |
| ai->addressable_vars[ai->num_addressable_vars++] = alias_map; |
| } |
| |
| |
| /* Create memory tags for all the dereferenced pointers and build the |
| ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias |
| sets. Based on the address escape and points-to information collected |
| earlier, this pass will also clear the TREE_ADDRESSABLE flag from those |
| variables whose address is not needed anymore. */ |
| |
| static void |
| setup_pointers_and_addressables (struct alias_info *ai) |
| { |
| size_t i, n_vars, num_addressable_vars, num_pointers; |
| |
| /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */ |
| num_addressable_vars = num_pointers = 0; |
| for (i = 0; i < num_referenced_vars; i++) |
| { |
| tree var = referenced_var (i); |
| |
| if (may_be_aliased (var)) |
| num_addressable_vars++; |
| |
| if (POINTER_TYPE_P (TREE_TYPE (var))) |
| { |
| /* Since we don't keep track of volatile variables, assume that |
| these pointers are used in indirect store operations. */ |
| if (TREE_THIS_VOLATILE (var)) |
| bitmap_set_bit (ai->dereferenced_ptrs_store, var_ann (var)->uid); |
| |
| num_pointers++; |
| } |
| } |
| |
| /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are |
| always going to be slightly bigger than we actually need them |
| because some TREE_ADDRESSABLE variables will be marked |
| non-addressable below and only pointers with unique type tags are |
| going to be added to POINTERS. */ |
| ai->addressable_vars = xcalloc (num_addressable_vars, |
| sizeof (struct alias_map_d *)); |
| ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *)); |
| ai->num_addressable_vars = 0; |
| ai->num_pointers = 0; |
| |
| /* Since we will be creating type memory tags within this loop, cache the |
| value of NUM_REFERENCED_VARS to avoid processing the additional tags |
| unnecessarily. */ |
| n_vars = num_referenced_vars; |
| |
| for (i = 0; i < n_vars; i++) |
| { |
| tree var = referenced_var (i); |
| var_ann_t v_ann = var_ann (var); |
| |
| /* Name memory tags already have flow-sensitive aliasing |
| information, so they need not be processed by |
| compute_flow_insensitive_aliasing. Similarly, type memory |
| tags are already accounted for when we process their |
| associated pointer. */ |
| if (v_ann->mem_tag_kind != NOT_A_TAG) |
| continue; |
| |
| /* Remove the ADDRESSABLE flag from every addressable variable whose |
| address is not needed anymore. This is caused by the propagation |
| of ADDR_EXPR constants into INDIRECT_REF expressions and the |
| removal of dead pointer assignments done by the early scalar |
| cleanup passes. */ |
| if (TREE_ADDRESSABLE (var)) |
| { |
| if (!bitmap_bit_p (ai->addresses_needed, v_ann->uid) |
| && TREE_CODE (var) != RESULT_DECL |
| && !is_global_var (var)) |
| { |
| /* The address of VAR is not needed, remove the |
| addressable bit, so that it can be optimized as a |
| regular variable. */ |
| mark_non_addressable (var); |
| |
| /* Since VAR is now a regular GIMPLE register, we will need |
| to rename VAR into SSA afterwards. */ |
| bitmap_set_bit (vars_to_rename, v_ann->uid); |
| } |
| else |
| { |
| /* Add the variable to the set of addressables. Mostly |
| used when scanning operands for ASM_EXPRs that |
| clobber memory. In those cases, we need to clobber |
| all call-clobbered variables and all addressables. */ |
| bitmap_set_bit (addressable_vars, v_ann->uid); |
| } |
| } |
| |
| /* Global variables and addressable locals may be aliased. Create an |
| entry in ADDRESSABLE_VARS for VAR. */ |
| if (may_be_aliased (var)) |
| { |
| create_alias_map_for (var, ai); |
| bitmap_set_bit (vars_to_rename, var_ann (var)->uid); |
| } |
| |
| /* Add pointer variables that have been dereferenced to the POINTERS |
| array and create a type memory tag for them. */ |
| if (POINTER_TYPE_P (TREE_TYPE (var))) |
| { |
| if ((bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid) |
| || bitmap_bit_p (ai->dereferenced_ptrs_load, v_ann->uid))) |
| { |
| tree tag; |
| var_ann_t t_ann; |
| |
| /* If pointer VAR still doesn't have a memory tag |
| associated with it, create it now or re-use an |
| existing one. */ |
| tag = get_tmt_for (var, ai); |
| t_ann = var_ann (tag); |
| |
| /* The type tag will need to be renamed into SSA |
| afterwards. Note that we cannot do this inside |
| get_tmt_for because aliasing may run multiple times |
| and we only create type tags the first time. */ |
| bitmap_set_bit (vars_to_rename, t_ann->uid); |
| |
| /* Associate the tag with pointer VAR. */ |
| v_ann->type_mem_tag = tag; |
| |
| /* If pointer VAR has been used in a store operation, |
| then its memory tag must be marked as written-to. */ |
| if (bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid)) |
| bitmap_set_bit (ai->written_vars, t_ann->uid); |
| |
| /* If pointer VAR is a global variable or a PARM_DECL, |
| then its memory tag should be considered a global |
| variable. */ |
| if (TREE_CODE (var) == PARM_DECL || is_global_var (var)) |
| mark_call_clobbered (tag); |
| |
| /* All the dereferences of pointer VAR count as |
| references of TAG. Since TAG can be associated with |
| several pointers, add the dereferences of VAR to the |
| TAG. We may need to grow AI->NUM_REFERENCES because |
| we have been adding name and type tags. */ |
| if (t_ann->uid >= VARRAY_SIZE (ai->num_references)) |
| VARRAY_GROW (ai->num_references, t_ann->uid + 10); |
| |
| VARRAY_UINT (ai->num_references, t_ann->uid) |
| += VARRAY_UINT (ai->num_references, v_ann->uid); |
| } |
| else |
| { |
| /* The pointer has not been dereferenced. If it had a |
| type memory tag, remove it and mark the old tag for |
| renaming to remove it out of the IL. */ |
| var_ann_t ann = var_ann (var); |
| tree tag = ann->type_mem_tag; |
| if (tag) |
| { |
| bitmap_set_bit (vars_to_rename, var_ann (tag)->uid); |
| ann->type_mem_tag = NULL_TREE; |
| } |
| } |
| } |
| } |
| } |
| |
| |
| /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At |
| every call site, we need to emit V_MAY_DEF expressions to represent the |
| clobbering effects of the call for variables whose address escapes the |
| current function. |
| |
| One approach is to group all call-clobbered variables into a single |
| representative that is used as an alias of every call-clobbered variable |
| (.GLOBAL_VAR). This works well, but it ties the optimizer hands because |
| references to any call clobbered variable is a reference to .GLOBAL_VAR. |
| |
| The second approach is to emit a clobbering V_MAY_DEF for every |
| call-clobbered variable at call sites. This is the preferred way in terms |
| of optimization opportunities but it may create too many V_MAY_DEF operands |
| if there are many call clobbered variables and function calls in the |
| function. |
| |
| To decide whether or not to use .GLOBAL_VAR we multiply the number of |
| function calls found by the number of call-clobbered variables. If that |
| product is beyond a certain threshold, as determined by the parameterized |
| values shown below, we use .GLOBAL_VAR. |
| |
| FIXME. This heuristic should be improved. One idea is to use several |
| .GLOBAL_VARs of different types instead of a single one. The thresholds |
| have been derived from a typical bootstrap cycle, including all target |
| libraries. Compile times were found increase by ~1% compared to using |
| .GLOBAL_VAR. */ |
| |
| static void |
| maybe_create_global_var (struct alias_info *ai) |
| { |
| unsigned i, n_clobbered; |
| bitmap_iterator bi; |
| |
| /* No need to create it, if we have one already. */ |
| if (global_var == NULL_TREE) |
| { |
| /* Count all the call-clobbered variables. */ |
| n_clobbered = 0; |
| EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi) |
| { |
| n_clobbered++; |
| } |
| |
| /* If the number of virtual operands that would be needed to |
| model all the call-clobbered variables is larger than |
| GLOBAL_VAR_THRESHOLD, create .GLOBAL_VAR. |
| |
| Also create .GLOBAL_VAR if there are no call-clobbered |
| variables and the program contains a mixture of pure/const |
| and regular function calls. This is to avoid the problem |
| described in PR 20115: |
| |
| int X; |
| int func_pure (void) { return X; } |
| int func_non_pure (int a) { X += a; } |
| int foo () |
| { |
| int a = func_pure (); |
| func_non_pure (a); |
| a = func_pure (); |
| return a; |
| } |
| |
| Since foo() has no call-clobbered variables, there is |
| no relationship between the calls to func_pure and |
| func_non_pure. Since func_pure has no side-effects, value |
| numbering optimizations elide the second call to func_pure. |
| So, if we have some pure/const and some regular calls in the |
| program we create .GLOBAL_VAR to avoid missing these |
| relations. */ |
| if (ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD |
| || (n_clobbered == 0 |
| && ai->num_calls_found > 0 |
| && ai->num_pure_const_calls_found > 0 |
| && ai->num_calls_found > ai->num_pure_const_calls_found)) |
| create_global_var (); |
| } |
| |
| /* Mark all call-clobbered symbols for renaming. Since the initial |
| rewrite into SSA ignored all call sites, we may need to rename |
| .GLOBAL_VAR and the call-clobbered variables. */ |
| EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi) |
| { |
| tree var = referenced_var (i); |
| |
| /* If the function has calls to clobbering functions and |
| .GLOBAL_VAR has been created, make it an alias for all |
| call-clobbered variables. */ |
| if (global_var && var != global_var) |
| add_may_alias (var, global_var); |
| |
| bitmap_set_bit (vars_to_rename, var_ann (var)->uid); |
| } |
| } |
| |
| |
| /* Return TRUE if pointer PTR may point to variable VAR. |
| |
| MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR |
| This is needed because when checking for type conflicts we are |
| interested in the alias set of the memory location pointed-to by |
| PTR. The alias set of PTR itself is irrelevant. |
| |
| VAR_ALIAS_SET is the alias set for VAR. */ |
| |
| static bool |
| may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set, |
| tree var, HOST_WIDE_INT var_alias_set) |
| { |
| tree mem; |
| var_ann_t v_ann, m_ann; |
| |
| alias_stats.alias_queries++; |
| alias_stats.simple_queries++; |
| |
| /* By convention, a variable cannot alias itself. */ |
| mem = var_ann (ptr)->type_mem_tag; |
| if (mem == var) |
| { |
| alias_stats.alias_noalias++; |
| alias_stats.simple_resolved++; |
| return false; |
| } |
| |
| v_ann = var_ann (var); |
| m_ann = var_ann (mem); |
| |
| gcc_assert (m_ann->mem_tag_kind == TYPE_TAG); |
| |
| alias_stats.tbaa_queries++; |
| |
| /* If the alias sets don't conflict then MEM cannot alias VAR. */ |
| if (!alias_sets_conflict_p (mem_alias_set, var_alias_set)) |
| { |
| alias_stats.alias_noalias++; |
| alias_stats.tbaa_resolved++; |
| return false; |
| } |
| |
| alias_stats.alias_mayalias++; |
| return true; |
| } |
| |
| |
| /* Add ALIAS to the set of variables that may alias VAR. */ |
| |
| static void |
| add_may_alias (tree var, tree alias) |
| { |
| size_t i; |
| var_ann_t v_ann = get_var_ann (var); |
| var_ann_t a_ann = get_var_ann (alias); |
| |
| gcc_assert (var != alias); |
| |
| if (v_ann->may_aliases == NULL) |
| VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases"); |
| |
| /* Avoid adding duplicates. */ |
| for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++) |
| if (alias == VARRAY_TREE (v_ann->may_aliases, i)) |
| return; |
| |
| /* If VAR is a call-clobbered variable, so is its new ALIAS. |
| FIXME, call-clobbering should only depend on whether an address |
| escapes. It should be independent of aliasing. */ |
| if (is_call_clobbered (var)) |
| mark_call_clobbered (alias); |
| |
| /* Likewise. If ALIAS is call-clobbered, so is VAR. */ |
| else if (is_call_clobbered (alias)) |
| mark_call_clobbered (var); |
| |
| VARRAY_PUSH_TREE (v_ann->may_aliases, alias); |
| a_ann->is_alias_tag = 1; |
| } |
| |
| |
| /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */ |
| |
| static void |
| replace_may_alias (tree var, size_t i, tree new_alias) |
| { |
| var_ann_t v_ann = var_ann (var); |
| VARRAY_TREE (v_ann->may_aliases, i) = new_alias; |
| |
| /* If VAR is a call-clobbered variable, so is NEW_ALIAS. |
| FIXME, call-clobbering should only depend on whether an address |
| escapes. It should be independent of aliasing. */ |
| if (is_call_clobbered (var)) |
| mark_call_clobbered (new_alias); |
| |
| /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */ |
| else if (is_call_clobbered (new_alias)) |
| mark_call_clobbered (var); |
| } |
| |
| |
| /* Mark pointer PTR as pointing to an arbitrary memory location. */ |
| |
| static void |
| set_pt_anything (tree ptr) |
| { |
| struct ptr_info_def *pi = get_ptr_info (ptr); |
| |
| pi->pt_anything = 1; |
| pi->pt_malloc = 0; |
| |
| /* The pointer used to have a name tag, but we now found it pointing |
| to an arbitrary location. The name tag needs to be renamed and |
| disassociated from PTR. */ |
| if (pi->name_mem_tag) |
| { |
| bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid); |
| pi->name_mem_tag = NULL_TREE; |
| } |
| } |
| |
| |
| /* Mark pointer PTR as pointing to a malloc'd memory area. */ |
| |
| static void |
| set_pt_malloc (tree ptr) |
| { |
| struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr); |
| |
| /* If the pointer has already been found to point to arbitrary |
| memory locations, it is unsafe to mark it as pointing to malloc. */ |
| if (pi->pt_anything) |
| return; |
| |
| pi->pt_malloc = 1; |
| } |
| |
| |
| /* Given two different pointers DEST and ORIG. Merge the points-to |
| information in ORIG into DEST. AI contains all the alias |
| information collected up to this point. */ |
| |
| static void |
| merge_pointed_to_info (struct alias_info *ai, tree dest, tree orig) |
| { |
| struct ptr_info_def *dest_pi, *orig_pi; |
| |
| gcc_assert (dest != orig); |
| |
| /* Make sure we have points-to information for ORIG. */ |
| collect_points_to_info_for (ai, orig); |
| |
| dest_pi = get_ptr_info (dest); |
| orig_pi = SSA_NAME_PTR_INFO (orig); |
| |
| if (orig_pi) |
| { |
| gcc_assert (orig_pi != dest_pi); |
| |
| /* Notice that we never merge PT_MALLOC. This attribute is only |
| true if the pointer is the result of a malloc() call. |
| Otherwise, we can end up in this situation: |
| |
| P_i = malloc (); |
| ... |
| P_j = P_i + X; |
| |
| P_j would be marked as PT_MALLOC, however we currently do not |
| handle cases of more than one pointer pointing to the same |
| malloc'd area. |
| |
| FIXME: If the merging comes from an expression that preserves |
| the PT_MALLOC attribute (copy assignment, address |
| arithmetic), we ought to merge PT_MALLOC, but then both |
| pointers would end up getting different name tags because |
| create_name_tags is not smart enough to determine that the |
| two come from the same malloc call. Copy propagation before |
| aliasing should cure this. */ |
| dest_pi->pt_malloc = 0; |
| if (orig_pi->pt_malloc || orig_pi->pt_anything) |
| set_pt_anything (dest); |
| |
| dest_pi->pt_null |= orig_pi->pt_null; |
| |
| if (!dest_pi->pt_anything |
| && orig_pi->pt_vars |
| && !bitmap_empty_p (orig_pi->pt_vars)) |
| { |
| if (dest_pi->pt_vars == NULL) |
| { |
| dest_pi->pt_vars = BITMAP_GGC_ALLOC (); |
| bitmap_copy (dest_pi->pt_vars, orig_pi->pt_vars); |
| } |
| else |
| bitmap_ior_into (dest_pi->pt_vars, orig_pi->pt_vars); |
| } |
| } |
| else |
| set_pt_anything (dest); |
| } |
| |
| |
| /* Add EXPR to the list of expressions pointed-to by PTR. */ |
| |
| static void |
| add_pointed_to_expr (struct alias_info *ai, tree ptr, tree expr) |
| { |
| if (TREE_CODE (expr) == WITH_SIZE_EXPR) |
| expr = TREE_OPERAND (expr, 0); |
| |
| get_ptr_info (ptr); |
| |
| if (TREE_CODE (expr) == CALL_EXPR |
| && (call_expr_flags (expr) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA))) |
| { |
| /* If EXPR is a malloc-like call, then the area pointed to PTR |
| is guaranteed to not alias with anything else. */ |
| set_pt_malloc (ptr); |
| } |
| else if (TREE_CODE (expr) == ADDR_EXPR) |
| { |
| /* Found P_i = ADDR_EXPR */ |
| add_pointed_to_var (ai, ptr, expr); |
| } |
| else if (TREE_CODE (expr) == SSA_NAME && POINTER_TYPE_P (TREE_TYPE (expr))) |
| { |
| /* Found P_i = Q_j. */ |
| merge_pointed_to_info (ai, ptr, expr); |
| } |
| else if (TREE_CODE (expr) == PLUS_EXPR || TREE_CODE (expr) == MINUS_EXPR) |
| { |
| /* Found P_i = PLUS_EXPR or P_i = MINUS_EXPR */ |
| tree op0 = TREE_OPERAND (expr, 0); |
| tree op1 = TREE_OPERAND (expr, 1); |
| |
| /* Both operands may be of pointer type. FIXME: Shouldn't |
| we just expect PTR + OFFSET always? */ |
| if (POINTER_TYPE_P (TREE_TYPE (op0)) |
| && TREE_CODE (op0) != INTEGER_CST) |
| { |
| if (TREE_CODE (op0) == SSA_NAME) |
| merge_pointed_to_info (ai, ptr, op0); |
| else if (TREE_CODE (op0) == ADDR_EXPR) |
| add_pointed_to_var (ai, ptr, op0); |
| else |
| set_pt_anything (ptr); |
| } |
| |
| if (POINTER_TYPE_P (TREE_TYPE (op1)) |
| && TREE_CODE (op1) != INTEGER_CST) |
| { |
| if (TREE_CODE (op1) == SSA_NAME) |
| merge_pointed_to_info (ai, ptr, op1); |
| else if (TREE_CODE (op1) == ADDR_EXPR) |
| add_pointed_to_var (ai, ptr, op1); |
| else |
| set_pt_anything (ptr); |
| } |
| |
| /* Neither operand is a pointer? VAR can be pointing anywhere. |
| FIXME: Shouldn't we abort here? If we get here, we found |
| PTR = INT_CST + INT_CST, which should not be a valid pointer |
| expression. */ |
| if (!(POINTER_TYPE_P (TREE_TYPE (op0)) |
| && TREE_CODE (op0) != INTEGER_CST) |
| && !(POINTER_TYPE_P (TREE_TYPE (op1)) |
| && TREE_CODE (op1) != INTEGER_CST)) |
| set_pt_anything (ptr); |
| } |
| else if (integer_zerop (expr)) |
| { |
| /* EXPR is the NULL pointer. Mark PTR as pointing to NULL. */ |
| SSA_NAME_PTR_INFO (ptr)->pt_null = 1; |
| } |
| else |
| { |
| /* If we can't recognize the expression, assume that PTR may |
| point anywhere. */ |
| set_pt_anything (ptr); |
| } |
| } |
| |
| |
| /* If VALUE is of the form &DECL, add DECL to the set of variables |
| pointed-to by PTR. Otherwise, add VALUE as a pointed-to expression by |
| PTR. AI points to the collected alias information. */ |
| |
| static void |
| add_pointed_to_var (struct alias_info *ai, tree ptr, tree value) |
| { |
| struct ptr_info_def *pi = get_ptr_info (ptr); |
| tree pt_var; |
| size_t uid; |
| |
| gcc_assert (TREE_CODE (value) == ADDR_EXPR); |
| |
| pt_var = TREE_OPERAND (value, 0); |
| if (REFERENCE_CLASS_P (pt_var)) |
| pt_var = get_base_address (pt_var); |
| |
| if (pt_var == NULL) |
| { |
| pi->pt_anything = 1; |
| } |
| else if (SSA_VAR_P (pt_var)) |
| { |
| uid = var_ann (pt_var)->uid; |
| bitmap_set_bit (ai->addresses_needed, uid); |
| |
| if (pi->pt_vars == NULL) |
| pi->pt_vars = BITMAP_GGC_ALLOC (); |
| bitmap_set_bit (pi->pt_vars, uid); |
| |
| /* If the variable is a global, mark the pointer as pointing to |
| global memory (which will make its tag a global variable). */ |
| if (is_global_var (pt_var)) |
| pi->pt_global_mem = 1; |
| } |
| else if (TREE_CODE (pt_var) == INDIRECT_REF |
| && TREE_CODE (TREE_OPERAND (pt_var, 0)) == SSA_NAME) |
| { |
| /* If VALUE is of the form &(*P_j), then PTR will have the same |
| points-to information as P_j. */ |
| add_pointed_to_expr (ai, ptr, TREE_OPERAND (pt_var, 0)); |
| } |
| else |
| { |
| /* Give up. PTR points anywhere. */ |
| set_pt_anything (ptr); |
| } |
| } |
| |
| |
| /* Callback for walk_use_def_chains to gather points-to information from the |
| SSA web. |
| |
| VAR is an SSA variable or a GIMPLE expression. |
| |
| STMT is the statement that generates the SSA variable or, if STMT is a |
| PHI_NODE, VAR is one of the PHI arguments. |
| |
| DATA is a pointer to a structure of type ALIAS_INFO. */ |
| |
| static bool |
| collect_points_to_info_r (tree var, tree stmt, void *data) |
| { |
| struct alias_info *ai = (struct alias_info *) data; |
| |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "Visiting use-def links for "); |
| print_generic_expr (dump_file, var, dump_flags); |
| fprintf (dump_file, "\n"); |
| } |
| |
| switch (TREE_CODE (stmt)) |
| { |
| case RETURN_EXPR: |
| if (TREE_CODE (TREE_OPERAND (stmt, 0)) != MODIFY_EXPR) |
| abort (); |
| stmt = TREE_OPERAND (stmt, 0); |
| /* FALLTHRU */ |
| |
| case MODIFY_EXPR: |
| { |
| tree rhs = TREE_OPERAND (stmt, 1); |
| STRIP_NOPS (rhs); |
| add_pointed_to_expr (ai, var, rhs); |
| break; |
| } |
| |
| case ASM_EXPR: |
| /* Pointers defined by __asm__ statements can point anywhere. */ |
| set_pt_anything (var); |
| break; |
| |
| case NOP_EXPR: |
| if (IS_EMPTY_STMT (stmt)) |
| { |
| tree decl = SSA_NAME_VAR (var); |
| |
| if (TREE_CODE (decl) == PARM_DECL) |
| add_pointed_to_expr (ai, var, decl); |
| else if (DECL_INITIAL (decl)) |
| add_pointed_to_expr (ai, var, DECL_INITIAL (decl)); |
| else |
| add_pointed_to_expr (ai, var, decl); |
| } |
| break; |
| |
| case PHI_NODE: |
| { |
| /* It STMT is a PHI node, then VAR is one of its arguments. The |
| variable that we are analyzing is the LHS of the PHI node. */ |
| tree lhs = PHI_RESULT (stmt); |
| |
| switch (TREE_CODE (var)) |
| { |
| case ADDR_EXPR: |
| add_pointed_to_var (ai, lhs, var); |
| break; |
| |
| case SSA_NAME: |
| /* Avoid unnecessary merges. */ |
| if (lhs != var) |
| merge_pointed_to_info (ai, lhs, var); |
| break; |
| |
| default: |
| gcc_assert (is_gimple_min_invariant (var)); |
| add_pointed_to_expr (ai, lhs, var); |
| break; |
| } |
| break; |
| } |
| |
| default: |
| gcc_unreachable (); |
| } |
| |
| return false; |
| } |
| |
| |
| /* Return true if STMT is an "escape" site from the current function. Escape |
| sites those statements which might expose the address of a variable |
| outside the current function. STMT is an escape site iff: |
| |
| 1- STMT is a function call, or |
| 2- STMT is an __asm__ expression, or |
| 3- STMT is an assignment to a non-local variable, or |
| 4- STMT is a return statement. |
| |
| AI points to the alias information collected so far. */ |
| |
| static bool |
| is_escape_site (tree stmt, struct alias_info *ai) |
| { |
| tree call = get_call_expr_in (stmt); |
| if (call != NULL_TREE) |
| { |
| ai->num_calls_found++; |
| |
| if (!TREE_SIDE_EFFECTS (call)) |
| ai->num_pure_const_calls_found++; |
| |
| return true; |
| } |
| else if (TREE_CODE (stmt) == ASM_EXPR) |
| return true; |
| else if (TREE_CODE (stmt) == MODIFY_EXPR) |
| { |
| tree lhs = TREE_OPERAND (stmt, 0); |
| |
| /* Get to the base of _REF nodes. */ |
| if (TREE_CODE (lhs) != SSA_NAME) |
| lhs = get_base_address (lhs); |
| |
| /* If we couldn't recognize the LHS of the assignment, assume that it |
| is a non-local store. */ |
| if (lhs == NULL_TREE) |
| return true; |
| |
| /* If the RHS is a conversion between a pointer and an integer, the |
| pointer escapes since we can't track the integer. */ |
| if ((TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR |
| || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR |
| || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR) |
| && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND |
| (TREE_OPERAND (stmt, 1), 0))) |
| && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1)))) |
| return true; |
| |
| /* If the LHS is an SSA name, it can't possibly represent a non-local |
| memory store. */ |
| if (TREE_CODE (lhs) == SSA_NAME) |
| return false; |
| |
| /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a |
| local variables we cannot be sure if it will escape, because we |
| don't have information about objects not in SSA form. Need to |
| implement something along the lines of |
| |
| J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P. |
| Midkiff, ``Escape analysis for java,'' in Proceedings of the |
| Conference on Object-Oriented Programming Systems, Languages, and |
| Applications (OOPSLA), pp. 1-19, 1999. */ |
| return true; |
| } |
| else if (TREE_CODE (stmt) == RETURN_EXPR) |
| return true; |
| |
| return false; |
| } |
| |
| |
| /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag |
| is considered to represent all the pointers whose pointed-to types are |
| in the same alias set class. Otherwise, the tag represents a single |
| SSA_NAME pointer variable. */ |
| |
| static tree |
| create_memory_tag (tree type, bool is_type_tag) |
| { |
| var_ann_t ann; |
| tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT"); |
| |
| /* By default, memory tags are local variables. Alias analysis will |
| determine whether they should be considered globals. */ |
| DECL_CONTEXT (tag) = current_function_decl; |
| |
| /* Memory tags are by definition addressable. This also prevents |
| is_gimple_ref frome confusing memory tags with optimizable |
| variables. */ |
| TREE_ADDRESSABLE (tag) = 1; |
| |
| ann = get_var_ann (tag); |
| ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG; |
| ann->type_mem_tag = NULL_TREE; |
| |
| /* Add the tag to the symbol table. */ |
| add_referenced_tmp_var (tag); |
| |
| return tag; |
| } |
| |
| |
| /* Create a name memory tag to represent a specific SSA_NAME pointer P_i. |
| This is used if P_i has been found to point to a specific set of |
| variables or to a non-aliased memory location like the address returned |
| by malloc functions. */ |
| |
| static tree |
| get_nmt_for (tree ptr) |
| { |
| struct ptr_info_def *pi = get_ptr_info (ptr); |
| tree tag = pi->name_mem_tag; |
| |
| if (tag == NULL_TREE) |
| tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false); |
| |
| /* If PTR is a PARM_DECL, it points to a global variable or malloc, |
| then its name tag should be considered a global variable. */ |
| if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL |
| || pi->pt_malloc |
| || pi->pt_global_mem) |
| mark_call_clobbered (tag); |
| |
| return tag; |
| } |
| |
| |
| /* Return the type memory tag associated to pointer PTR. A memory tag is an |
| artificial variable that represents the memory location pointed-to by |
| PTR. It is used to model the effects of pointer de-references on |
| addressable variables. |
| |
| AI points to the data gathered during alias analysis. This function |
| populates the array AI->POINTERS. */ |
| |
| static tree |
| get_tmt_for (tree ptr, struct alias_info *ai) |
| { |
| size_t i; |
| tree tag; |
| tree tag_type = TREE_TYPE (TREE_TYPE (ptr)); |
| HOST_WIDE_INT tag_set = get_alias_set (tag_type); |
| |
| /* To avoid creating unnecessary memory tags, only create one memory tag |
| per alias set class. Note that it may be tempting to group |
| memory tags based on conflicting alias sets instead of |
| equivalence. That would be wrong because alias sets are not |
| necessarily transitive (as demonstrated by the libstdc++ test |
| 23_containers/vector/cons/4.cc). Given three alias sets A, B, C |
| such that conflicts (A, B) == true and conflicts (A, C) == true, |
| it does not necessarily follow that conflicts (B, C) == true. */ |
| for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++) |
| { |
| struct alias_map_d *curr = ai->pointers[i]; |
| if (tag_set == curr->set) |
| { |
| tag = var_ann (curr->var)->type_mem_tag; |
| break; |
| } |
| } |
| |
| /* If VAR cannot alias with any of the existing memory tags, create a new |
| tag for PTR and add it to the POINTERS array. */ |
| if (tag == NULL_TREE) |
| { |
| struct alias_map_d *alias_map; |
| |
| /* If PTR did not have a type tag already, create a new TMT.* |
| artificial variable representing the memory location |
| pointed-to by PTR. */ |
| if (var_ann (ptr)->type_mem_tag == NULL_TREE) |
| tag = create_memory_tag (tag_type, true); |
| else |
| tag = var_ann (ptr)->type_mem_tag; |
| |
| /* Add PTR to the POINTERS array. Note that we are not interested in |
| PTR's alias set. Instead, we cache the alias set for the memory that |
| PTR points to. */ |
| alias_map = xcalloc (1, sizeof (*alias_map)); |
| alias_map->var = ptr; |
| alias_map->set = tag_set; |
| ai->pointers[ai->num_pointers++] = alias_map; |
| } |
| |
| /* If the pointed-to type is volatile, so is the tag. */ |
| TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type); |
| |
| /* Make sure that the type tag has the same alias set as the |
| pointed-to type. */ |
| gcc_assert (tag_set == get_alias_set (tag)); |
| |
| return tag; |
| } |
| |
| |
| /* Create GLOBAL_VAR, an artificial global variable to act as a |
| representative of all the variables that may be clobbered by function |
| calls. */ |
| |
| static void |
| create_global_var (void) |
| { |
| global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"), |
| void_type_node); |
| DECL_ARTIFICIAL (global_var) = 1; |
| TREE_READONLY (global_var) = 0; |
| DECL_EXTERNAL (global_var) = 1; |
| TREE_STATIC (global_var) = 1; |
| TREE_USED (global_var) = 1; |
| DECL_CONTEXT (global_var) = NULL_TREE; |
| TREE_THIS_VOLATILE (global_var) = 0; |
| TREE_ADDRESSABLE (global_var) = 0; |
| |
| add_referenced_tmp_var (global_var); |
| bitmap_set_bit (vars_to_rename, var_ann (global_var)->uid); |
| } |
| |
| |
| /* Dump alias statistics on FILE. */ |
| |
| static void |
| dump_alias_stats (FILE *file) |
| { |
| const char *funcname |
| = lang_hooks.decl_printable_name (current_function_decl, 2); |
| fprintf (file, "\nAlias statistics for %s\n\n", funcname); |
| fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries); |
| fprintf (file, "Total alias mayalias results:\t%u\n", |
| alias_stats.alias_mayalias); |
| fprintf (file, "Total alias noalias results:\t%u\n", |
| alias_stats.alias_noalias); |
| fprintf (file, "Total simple queries:\t%u\n", |
| alias_stats.simple_queries); |
| fprintf (file, "Total simple resolved:\t%u\n", |
| alias_stats.simple_resolved); |
| fprintf (file, "Total TBAA queries:\t%u\n", |
| alias_stats.tbaa_queries); |
| fprintf (file, "Total TBAA resolved:\t%u\n", |
| alias_stats.tbaa_resolved); |
| } |
| |
| |
| /* Dump alias information on FILE. */ |
| |
| void |
| dump_alias_info (FILE *file) |
| { |
| size_t i; |
| const char *funcname |
| = lang_hooks.decl_printable_name (current_function_decl, 2); |
| |
| fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname); |
| |
| fprintf (file, "Aliased symbols\n\n"); |
| for (i = 0; i < num_referenced_vars; i++) |
| { |
| tree var = referenced_var (i); |
| if (may_be_aliased (var)) |
| dump_variable (file, var); |
| } |
| |
| fprintf (file, "\nDereferenced pointers\n\n"); |
| for (i = 0; i < num_referenced_vars; i++) |
| { |
| tree var = referenced_var (i); |
| var_ann_t ann = var_ann (var); |
| if (ann->type_mem_tag) |
| dump_variable (file, var); |
| } |
| |
| fprintf (file, "\nType memory tags\n\n"); |
| for (i = 0; i < num_referenced_vars; i++) |
| { |
| tree var = referenced_var (i); |
| var_ann_t ann = var_ann (var); |
| if (ann->mem_tag_kind == TYPE_TAG) |
| dump_variable (file, var); |
| } |
| |
| fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname); |
| |
| fprintf (file, "SSA_NAME pointers\n\n"); |
| for (i = 1; i < num_ssa_names; i++) |
| { |
| tree ptr = ssa_name (i); |
| struct ptr_info_def *pi; |
| |
| if (ptr == NULL_TREE) |
| continue; |
| |
| pi = SSA_NAME_PTR_INFO (ptr); |
| if (!SSA_NAME_IN_FREE_LIST (ptr) |
| && pi |
| && pi->name_mem_tag) |
| dump_points_to_info_for (file, ptr); |
| } |
| |
| fprintf (file, "\nName memory tags\n\n"); |
| for (i = 0; i < num_referenced_vars; i++) |
| { |
| tree var = referenced_var (i); |
| var_ann_t ann = var_ann (var); |
| if (ann->mem_tag_kind == NAME_TAG) |
| dump_variable (file, var); |
| } |
| |
| fprintf (file, "\n"); |
| } |
| |
| |
| /* Dump alias information on stderr. */ |
| |
| void |
| debug_alias_info (void) |
| { |
| dump_alias_info (stderr); |
| } |
| |
| |
| /* Return the alias information associated with pointer T. It creates a |
| new instance if none existed. */ |
| |
| struct ptr_info_def * |
| get_ptr_info (tree t) |
| { |
| struct ptr_info_def *pi; |
| |
| gcc_assert (POINTER_TYPE_P (TREE_TYPE (t))); |
| |
| pi = SSA_NAME_PTR_INFO (t); |
| if (pi == NULL) |
| { |
| pi = ggc_alloc (sizeof (*pi)); |
| memset ((void *)pi, 0, sizeof (*pi)); |
| SSA_NAME_PTR_INFO (t) = pi; |
| } |
| |
| return pi; |
| } |
| |
| |
| /* Dump points-to information for SSA_NAME PTR into FILE. */ |
| |
| void |
| dump_points_to_info_for (FILE *file, tree ptr) |
| { |
| struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr); |
| |
| print_generic_expr (file, ptr, dump_flags); |
| |
| if (pi) |
| { |
| if (pi->name_mem_tag) |
| { |
| fprintf (file, ", name memory tag: "); |
| print_generic_expr (file, pi->name_mem_tag, dump_flags); |
| } |
| |
| if (pi->is_dereferenced) |
| fprintf (file, ", is dereferenced"); |
| |
| if (pi->value_escapes_p) |
| fprintf (file, ", its value escapes"); |
| |
| if (pi->pt_anything) |
| fprintf (file, ", points-to anything"); |
| |
| if (pi->pt_malloc) |
| fprintf (file, ", points-to malloc"); |
| |
| if (pi->pt_null) |
| fprintf (file, ", points-to NULL"); |
| |
| if (pi->pt_vars) |
| { |
| unsigned ix; |
| bitmap_iterator bi; |
| |
| fprintf (file, ", points-to vars: { "); |
| EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi) |
| { |
| print_generic_expr (file, referenced_var (ix), dump_flags); |
| fprintf (file, " "); |
| } |
| fprintf (file, "}"); |
| } |
| } |
| |
| fprintf (file, "\n"); |
| } |
| |
| |
| /* Dump points-to information for VAR into stderr. */ |
| |
| void |
| debug_points_to_info_for (tree var) |
| { |
| dump_points_to_info_for (stderr, var); |
| } |
| |
| |
| /* Dump points-to information into FILE. NOTE: This function is slow, as |
| it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */ |
| |
| void |
| dump_points_to_info (FILE *file) |
| { |
| basic_block bb; |
| block_stmt_iterator si; |
| size_t i; |
| ssa_op_iter iter; |
| const char *fname = |
| lang_hooks.decl_printable_name (current_function_decl, 2); |
| |
| fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname); |
| |
| /* First dump points-to information for the default definitions of |
| pointer variables. This is necessary because default definitions are |
| not part of the code. */ |
| for (i = 0; i < num_referenced_vars; i++) |
| { |
| tree var = referenced_var (i); |
| if (POINTER_TYPE_P (TREE_TYPE (var))) |
| { |
| var_ann_t ann = var_ann (var); |
| if (ann->default_def) |
| dump_points_to_info_for (file, ann->default_def); |
| } |
| } |
| |
| /* Dump points-to information for every pointer defined in the program. */ |
| FOR_EACH_BB (bb) |
| { |
| tree phi; |
| |
| for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) |
| { |
| tree ptr = PHI_RESULT (phi); |
| if (POINTER_TYPE_P (TREE_TYPE (ptr))) |
| dump_points_to_info_for (file, ptr); |
| } |
| |
| for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si)) |
| { |
| tree stmt = bsi_stmt (si); |
| tree def; |
| FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF) |
| if (POINTER_TYPE_P (TREE_TYPE (def))) |
| dump_points_to_info_for (file, def); |
| } |
| } |
| |
| fprintf (file, "\n"); |
| } |
| |
| |
| /* Dump points-to info pointed by PTO into STDERR. */ |
| |
| void |
| debug_points_to_info (void) |
| { |
| dump_points_to_info (stderr); |
| } |
| |
| /* Dump to FILE the list of variables that may be aliasing VAR. */ |
| |
| void |
| dump_may_aliases_for (FILE *file, tree var) |
| { |
| varray_type aliases; |
| |
| if (TREE_CODE (var) == SSA_NAME) |
| var = SSA_NAME_VAR (var); |
| |
| aliases = var_ann (var)->may_aliases; |
| if (aliases) |
| { |
| size_t i; |
| fprintf (file, "{ "); |
| for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++) |
| { |
| print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags); |
| fprintf (file, " "); |
| } |
| fprintf (file, "}"); |
| } |
| } |
| |
| |
| /* Dump to stderr the list of variables that may be aliasing VAR. */ |
| |
| void |
| debug_may_aliases_for (tree var) |
| { |
| dump_may_aliases_for (stderr, var); |
| } |
| |
| /* Return true if VAR may be aliased. */ |
| |
| bool |
| may_be_aliased (tree var) |
| { |
| /* Obviously. */ |
| if (TREE_ADDRESSABLE (var)) |
| return true; |
| |
| /* Globally visible variables can have their addresses taken by other |
| translation units. */ |
| if (DECL_EXTERNAL (var) || TREE_PUBLIC (var)) |
| return true; |
| |
| /* Automatic variables can't have their addresses escape any other way. |
| This must be after the check for global variables, as extern declarations |
| do not have TREE_STATIC set. */ |
| if (!TREE_STATIC (var)) |
| return false; |
| |
| /* If we're in unit-at-a-time mode, then we must have seen all occurrences |
| of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise |
| we can only be sure the variable isn't addressable if it's local to the |
| current function. */ |
| if (flag_unit_at_a_time) |
| return false; |
| if (decl_function_context (var) == current_function_decl) |
| return false; |
| |
| return true; |
| } |