+/* Given a tree for an expression for which we might want to emit
+ locations or values in debug information (generally a variable, but
+ we might deal with other kinds of trees in the future), return the
+ tree that should be used as the variable of a DEBUG_BIND STMT or
+ VAR_LOCATION INSN or NOTE. Return NULL if VAR is not to be tracked. */
+
+tree
+target_for_debug_bind (tree var)
+{
+ if (!MAY_HAVE_DEBUG_STMTS)
+ return NULL_TREE;
+
+ if (TREE_CODE (var) != VAR_DECL
+ && TREE_CODE (var) != PARM_DECL)
+ return NULL_TREE;
+
+ if (DECL_HAS_VALUE_EXPR_P (var))
+ return target_for_debug_bind (DECL_VALUE_EXPR (var));
+
+ if (DECL_IGNORED_P (var))
+ return NULL_TREE;
+
+ if (!is_gimple_reg (var))
+ {
+ if (is_gimple_reg_type (TREE_TYPE (var))
+ && referenced_var_lookup (cfun, DECL_UID (var)) == NULL_TREE)
+ return var;
+ return NULL_TREE;
+ }
+
+ return var;
+}
+
+/* Called via walk_tree, look for SSA_NAMEs that have already been
+ released. */
+
+static tree
+find_released_ssa_name (tree *tp, int *walk_subtrees, void *data_)
+{
+ struct walk_stmt_info *wi = (struct walk_stmt_info *) data_;
+
+ if (wi && wi->is_lhs)
+ return NULL_TREE;
+
+ if (TREE_CODE (*tp) == SSA_NAME)
+ {
+ if (SSA_NAME_IN_FREE_LIST (*tp))
+ return *tp;
+
+ *walk_subtrees = 0;
+ }
+ else if (IS_TYPE_OR_DECL_P (*tp))
+ *walk_subtrees = 0;
+
+ return NULL_TREE;
+}
+
+/* Insert a DEBUG BIND stmt before the DEF of VAR if VAR is referenced
+ by other DEBUG stmts, and replace uses of the DEF with the
+ newly-created debug temp. */
+
+void
+insert_debug_temp_for_var_def (gimple_stmt_iterator *gsi, tree var)
+{
+ imm_use_iterator imm_iter;
+ use_operand_p use_p;
+ gimple stmt;
+ gimple def_stmt = NULL;
+ int usecount = 0;
+ tree value = NULL;
+
+ if (!MAY_HAVE_DEBUG_STMTS)
+ return;
+
+ /* If this name has already been registered for replacement, do nothing
+ as anything that uses this name isn't in SSA form. */
+ if (name_registered_for_update_p (var))
+ return;
+
+ /* Check whether there are debug stmts that reference this variable and,
+ if there are, decide whether we should use a debug temp. */
+ FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var)
+ {
+ stmt = USE_STMT (use_p);
+
+ if (!gimple_debug_bind_p (stmt))
+ continue;
+
+ if (usecount++)
+ break;
+
+ if (gimple_debug_bind_get_value (stmt) != var)
+ {
+ /* Count this as an additional use, so as to make sure we
+ use a temp unless VAR's definition has a SINGLE_RHS that
+ can be shared. */
+ usecount++;
+ break;
+ }
+ }
+
+ if (!usecount)
+ return;
+
+ if (gsi)
+ def_stmt = gsi_stmt (*gsi);
+ else
+ def_stmt = SSA_NAME_DEF_STMT (var);
+
+ /* If we didn't get an insertion point, and the stmt has already
+ been removed, we won't be able to insert the debug bind stmt, so
+ we'll have to drop debug information. */
+ if (gimple_code (def_stmt) == GIMPLE_PHI)
+ {
+ value = degenerate_phi_result (def_stmt);
+ if (value && walk_tree (&value, find_released_ssa_name, NULL, NULL))
+ value = NULL;
+ /* error_mark_node is what fixup_noreturn_call changes PHI arguments
+ to. */
+ else if (value == error_mark_node)
+ value = NULL;
+ }
+ else if (is_gimple_assign (def_stmt))
+ {
+ bool no_value = false;
+
+ if (!dom_info_available_p (CDI_DOMINATORS))
+ {
+ struct walk_stmt_info wi;
+
+ memset (&wi, 0, sizeof (wi));
+
+ /* When removing blocks without following reverse dominance
+ order, we may sometimes encounter SSA_NAMEs that have
+ already been released, referenced in other SSA_DEFs that
+ we're about to release. Consider:
+
+ <bb X>:
+ v_1 = foo;
+
+ <bb Y>:
+ w_2 = v_1 + bar;
+ # DEBUG w => w_2
+
+ If we deleted BB X first, propagating the value of w_2
+ won't do us any good. It's too late to recover their
+ original definition of v_1: when it was deleted, it was
+ only referenced in other DEFs, it couldn't possibly know
+ it should have been retained, and propagating every
+ single DEF just in case it might have to be propagated
+ into a DEBUG STMT would probably be too wasteful.
+
+ When dominator information is not readily available, we
+ check for and accept some loss of debug information. But
+ if it is available, there's no excuse for us to remove
+ blocks in the wrong order, so we don't even check for
+ dead SSA NAMEs. SSA verification shall catch any
+ errors. */
+ if ((!gsi && !gimple_bb (def_stmt))
+ || walk_gimple_op (def_stmt, find_released_ssa_name, &wi))
+ no_value = true;
+ }
+
+ if (!no_value)
+ value = gimple_assign_rhs_to_tree (def_stmt);
+ }
+
+ if (value)
+ {
+ /* If there's a single use of VAR, and VAR is the entire debug
+ expression (usecount would have been incremented again
+ otherwise), and the definition involves only constants and
+ SSA names, then we can propagate VALUE into this single use,
+ avoiding the temp.
+
+ We can also avoid using a temp if VALUE can be shared and
+ propagated into all uses, without generating expressions that
+ wouldn't be valid gimple RHSs.
+
+ Other cases that would require unsharing or non-gimple RHSs
+ are deferred to a debug temp, although we could avoid temps
+ at the expense of duplication of expressions. */
+
+ if (CONSTANT_CLASS_P (value)
+ || gimple_code (def_stmt) == GIMPLE_PHI
+ || (usecount == 1
+ && (!gimple_assign_single_p (def_stmt)
+ || is_gimple_min_invariant (value)))
+ || is_gimple_reg (value))
+ value = unshare_expr (value);
+ else
+ {
+ gimple def_temp;
+ tree vexpr = make_node (DEBUG_EXPR_DECL);
+
+ def_temp = gimple_build_debug_bind (vexpr,
+ unshare_expr (value),
+ def_stmt);
+
+ DECL_ARTIFICIAL (vexpr) = 1;
+ TREE_TYPE (vexpr) = TREE_TYPE (value);
+ if (DECL_P (value))
+ DECL_MODE (vexpr) = DECL_MODE (value);
+ else
+ DECL_MODE (vexpr) = TYPE_MODE (TREE_TYPE (value));
+
+ if (gsi)
+ gsi_insert_before (gsi, def_temp, GSI_SAME_STMT);
+ else
+ {
+ gimple_stmt_iterator ngsi = gsi_for_stmt (def_stmt);
+ gsi_insert_before (&ngsi, def_temp, GSI_SAME_STMT);
+ }
+
+ value = vexpr;
+ }
+ }
+
+ FOR_EACH_IMM_USE_STMT (stmt, imm_iter, var)
+ {
+ if (!gimple_debug_bind_p (stmt))
+ continue;
+
+ if (value)
+ {
+ FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
+ /* unshare_expr is not needed here. vexpr is either a
+ SINGLE_RHS, that can be safely shared, some other RHS
+ that was unshared when we found it had a single debug
+ use, or a DEBUG_EXPR_DECL, that can be safely
+ shared. */
+ SET_USE (use_p, value);
+ /* If we didn't replace uses with a debug decl fold the
+ resulting expression. Otherwise we end up with invalid IL. */
+ if (TREE_CODE (value) != DEBUG_EXPR_DECL)
+ {
+ gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
+ fold_stmt_inplace (&gsi);
+ }
+ }
+ else
+ gimple_debug_bind_reset_value (stmt);
+
+ update_stmt (stmt);
+ }
+}
+
+
+/* Insert a DEBUG BIND stmt before STMT for each DEF referenced by
+ other DEBUG stmts, and replace uses of the DEF with the
+ newly-created debug temp. */
+
+void
+insert_debug_temps_for_defs (gimple_stmt_iterator *gsi)
+{
+ gimple stmt;
+ ssa_op_iter op_iter;
+ def_operand_p def_p;
+
+ if (!MAY_HAVE_DEBUG_STMTS)
+ return;
+
+ stmt = gsi_stmt (*gsi);
+
+ FOR_EACH_PHI_OR_STMT_DEF (def_p, stmt, op_iter, SSA_OP_DEF)
+ {
+ tree var = DEF_FROM_PTR (def_p);
+
+ if (TREE_CODE (var) != SSA_NAME)
+ continue;
+
+ insert_debug_temp_for_var_def (gsi, var);
+ }
+}
+
+/* Reset all debug stmts that use SSA_NAME(s) defined in STMT. */
+
+void
+reset_debug_uses (gimple stmt)
+{
+ ssa_op_iter op_iter;
+ def_operand_p def_p;
+ imm_use_iterator imm_iter;
+ gimple use_stmt;
+
+ if (!MAY_HAVE_DEBUG_STMTS)
+ return;
+
+ FOR_EACH_PHI_OR_STMT_DEF (def_p, stmt, op_iter, SSA_OP_DEF)
+ {
+ tree var = DEF_FROM_PTR (def_p);
+
+ if (TREE_CODE (var) != SSA_NAME)
+ continue;
+
+ FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, var)
+ {
+ if (!gimple_debug_bind_p (use_stmt))
+ continue;
+
+ gimple_debug_bind_reset_value (use_stmt);
+ update_stmt (use_stmt);
+ }
+ }
+}
+
+/* Delete SSA DEFs for SSA versions in the TOREMOVE bitmap, removing
+ dominated stmts before their dominators, so that release_ssa_defs
+ stands a chance of propagating DEFs into debug bind stmts. */
+
+void
+release_defs_bitset (bitmap toremove)
+{
+ unsigned j;
+ bitmap_iterator bi;
+
+ /* Performing a topological sort is probably overkill, this will
+ most likely run in slightly superlinear time, rather than the
+ pathological quadratic worst case. */
+ while (!bitmap_empty_p (toremove))
+ EXECUTE_IF_SET_IN_BITMAP (toremove, 0, j, bi)
+ {
+ bool remove_now = true;
+ tree var = ssa_name (j);
+ gimple stmt;
+ imm_use_iterator uit;
+
+ FOR_EACH_IMM_USE_STMT (stmt, uit, var)
+ {
+ ssa_op_iter dit;
+ def_operand_p def_p;
+
+ /* We can't propagate PHI nodes into debug stmts. */
+ if (gimple_code (stmt) == GIMPLE_PHI
+ || is_gimple_debug (stmt))
+ continue;
+
+ /* If we find another definition to remove that uses
+ the one we're looking at, defer the removal of this
+ one, so that it can be propagated into debug stmts
+ after the other is. */
+ FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, dit, SSA_OP_DEF)
+ {
+ tree odef = DEF_FROM_PTR (def_p);
+
+ if (bitmap_bit_p (toremove, SSA_NAME_VERSION (odef)))
+ {
+ remove_now = false;
+ break;
+ }
+ }
+
+ if (!remove_now)
+ BREAK_FROM_IMM_USE_STMT (uit);
+ }
+
+ if (remove_now)
+ {
+ gimple def = SSA_NAME_DEF_STMT (var);
+ gimple_stmt_iterator gsi = gsi_for_stmt (def);
+
+ if (gimple_code (def) == GIMPLE_PHI)
+ remove_phi_node (&gsi, true);
+ else
+ {
+ gsi_remove (&gsi, true);
+ release_defs (def);
+ }
+
+ bitmap_clear_bit (toremove, j);
+ }
+ }
+}
+
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