| /* Support routines for Value Range Propagation (VRP). |
| Copyright (C) 2005-2021 Free Software Foundation, Inc. |
| |
| 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 |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include "config.h" |
| #include "system.h" |
| #include "coretypes.h" |
| #include "backend.h" |
| #include "tree.h" |
| #include "gimple.h" |
| #include "tree-pass.h" |
| #include "ssa.h" |
| #include "gimple-pretty-print.h" |
| #include "cfganal.h" |
| #include "gimple-fold.h" |
| #include "tree-eh.h" |
| #include "gimple-iterator.h" |
| #include "tree-cfg.h" |
| #include "tree-ssa-loop-manip.h" |
| #include "tree-ssa-loop.h" |
| #include "cfgloop.h" |
| #include "tree-scalar-evolution.h" |
| #include "tree-ssa-propagate.h" |
| #include "alloc-pool.h" |
| #include "domwalk.h" |
| #include "tree-cfgcleanup.h" |
| #include "vr-values.h" |
| #include "gimple-ssa-evrp-analyze.h" |
| |
| evrp_range_analyzer::evrp_range_analyzer (bool update_global_ranges) |
| : stack (10), m_update_global_ranges (update_global_ranges) |
| { |
| edge e; |
| edge_iterator ei; |
| basic_block bb; |
| FOR_EACH_BB_FN (bb, cfun) |
| { |
| bb->flags &= ~BB_VISITED; |
| FOR_EACH_EDGE (e, ei, bb->preds) |
| e->flags |= EDGE_EXECUTABLE; |
| } |
| } |
| |
| /* Push an unwinding marker onto the unwinding stack. */ |
| |
| void |
| evrp_range_analyzer::push_marker () |
| { |
| stack.safe_push (std::make_pair (NULL_TREE, (value_range_equiv *)NULL)); |
| } |
| |
| /* Analyze ranges as we enter basic block BB. */ |
| |
| void |
| evrp_range_analyzer::enter (basic_block bb) |
| { |
| if (!optimize) |
| return; |
| push_marker (); |
| record_ranges_from_incoming_edge (bb); |
| record_ranges_from_phis (bb); |
| bb->flags |= BB_VISITED; |
| } |
| |
| /* Find new range for NAME such that (OP CODE LIMIT) is true. */ |
| value_range_equiv * |
| evrp_range_analyzer::try_find_new_range (tree name, |
| tree op, tree_code code, tree limit) |
| { |
| value_range_equiv vr; |
| const value_range_equiv *old_vr = get_value_range (name); |
| |
| /* Discover VR when condition is true. */ |
| extract_range_for_var_from_comparison_expr (name, code, op, limit, &vr); |
| /* If we found any usable VR, set the VR to ssa_name and create a |
| PUSH old value in the stack with the old VR. */ |
| if (!vr.undefined_p () && !vr.varying_p ()) |
| { |
| if (old_vr->equal_p (vr, /*ignore_equivs=*/true)) |
| return NULL; |
| value_range_equiv *new_vr = allocate_value_range_equiv (); |
| new_vr->move (&vr); |
| return new_vr; |
| } |
| return NULL; |
| } |
| |
| /* For LHS record VR in the SSA info. */ |
| void |
| evrp_range_analyzer::set_ssa_range_info (tree lhs, value_range_equiv *vr) |
| { |
| gcc_assert (m_update_global_ranges); |
| |
| /* Set the SSA with the value range. */ |
| if (INTEGRAL_TYPE_P (TREE_TYPE (lhs))) |
| { |
| if (vr->constant_p ()) |
| set_range_info (lhs, vr->kind (), |
| wi::to_wide (vr->min ()), |
| wi::to_wide (vr->max ())); |
| } |
| else if (POINTER_TYPE_P (TREE_TYPE (lhs)) |
| && range_includes_zero_p (vr) == 0) |
| set_ptr_nonnull (lhs); |
| } |
| |
| /* Return true if all uses of NAME are dominated by STMT or feed STMT |
| via a chain of single immediate uses. */ |
| |
| static bool |
| all_uses_feed_or_dominated_by_stmt (tree name, gimple *stmt) |
| { |
| use_operand_p use_p, use2_p; |
| imm_use_iterator iter; |
| basic_block stmt_bb = gimple_bb (stmt); |
| |
| FOR_EACH_IMM_USE_FAST (use_p, iter, name) |
| { |
| gimple *use_stmt = USE_STMT (use_p), *use_stmt2; |
| if (use_stmt == stmt |
| || is_gimple_debug (use_stmt) |
| || (gimple_bb (use_stmt) != stmt_bb |
| && dominated_by_p (CDI_DOMINATORS, |
| gimple_bb (use_stmt), stmt_bb))) |
| continue; |
| while (use_stmt != stmt |
| && is_gimple_assign (use_stmt) |
| && TREE_CODE (gimple_assign_lhs (use_stmt)) == SSA_NAME |
| && single_imm_use (gimple_assign_lhs (use_stmt), |
| &use2_p, &use_stmt2)) |
| use_stmt = use_stmt2; |
| if (use_stmt != stmt) |
| return false; |
| } |
| return true; |
| } |
| |
| void |
| evrp_range_analyzer::record_ranges_from_incoming_edge (basic_block bb) |
| { |
| edge pred_e = single_pred_edge_ignoring_loop_edges (bb, false); |
| if (pred_e) |
| { |
| gimple *stmt = last_stmt (pred_e->src); |
| tree op0 = NULL_TREE; |
| |
| if (stmt |
| && gimple_code (stmt) == GIMPLE_COND |
| && (op0 = gimple_cond_lhs (stmt)) |
| && TREE_CODE (op0) == SSA_NAME |
| && (INTEGRAL_TYPE_P (TREE_TYPE (gimple_cond_lhs (stmt))) |
| || POINTER_TYPE_P (TREE_TYPE (gimple_cond_lhs (stmt))))) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "Visiting controlling predicate "); |
| print_gimple_stmt (dump_file, stmt, 0); |
| } |
| /* Entering a new scope. Try to see if we can find a VR |
| here. */ |
| tree op1 = gimple_cond_rhs (stmt); |
| if (TREE_OVERFLOW_P (op1)) |
| op1 = drop_tree_overflow (op1); |
| tree_code code = gimple_cond_code (stmt); |
| |
| auto_vec<assert_info, 8> asserts; |
| register_edge_assert_for (op0, pred_e, code, op0, op1, asserts); |
| if (TREE_CODE (op1) == SSA_NAME) |
| register_edge_assert_for (op1, pred_e, code, op0, op1, asserts); |
| |
| auto_vec<std::pair<tree, value_range_equiv *>, 8> vrs; |
| for (unsigned i = 0; i < asserts.length (); ++i) |
| { |
| value_range_equiv *vr |
| = try_find_new_range (asserts[i].name, |
| asserts[i].expr, |
| asserts[i].comp_code, |
| asserts[i].val); |
| if (vr) |
| vrs.safe_push (std::make_pair (asserts[i].name, vr)); |
| } |
| |
| /* If pred_e is really a fallthru we can record value ranges |
| in SSA names as well. */ |
| bool is_fallthru = assert_unreachable_fallthru_edge_p (pred_e); |
| |
| /* Push updated ranges only after finding all of them to avoid |
| ordering issues that can lead to worse ranges. */ |
| for (unsigned i = 0; i < vrs.length (); ++i) |
| { |
| /* But make sure we do not weaken ranges like when |
| getting first [64, +INF] and then ~[0, 0] from |
| conditions like (s & 0x3cc0) == 0). */ |
| const value_range_equiv *old_vr |
| = get_value_range (vrs[i].first); |
| value_range tem (*old_vr); |
| tem.intersect (vrs[i].second); |
| if (tem.equal_p (*old_vr)) |
| { |
| free_value_range (vrs[i].second); |
| continue; |
| } |
| push_value_range (vrs[i].first, vrs[i].second); |
| if (is_fallthru |
| && m_update_global_ranges |
| && all_uses_feed_or_dominated_by_stmt (vrs[i].first, stmt) |
| /* The condition must post-dominate the definition point. */ |
| && (SSA_NAME_IS_DEFAULT_DEF (vrs[i].first) |
| || (gimple_bb (SSA_NAME_DEF_STMT (vrs[i].first)) |
| == pred_e->src))) |
| { |
| set_ssa_range_info (vrs[i].first, vrs[i].second); |
| maybe_set_nonzero_bits (pred_e, vrs[i].first); |
| } |
| } |
| } |
| } |
| } |
| |
| void |
| evrp_range_analyzer::record_ranges_from_phis (basic_block bb) |
| { |
| /* Visit PHI stmts and discover any new VRs possible. */ |
| bool has_unvisited_preds = false; |
| edge_iterator ei; |
| edge e; |
| FOR_EACH_EDGE (e, ei, bb->preds) |
| if (e->flags & EDGE_EXECUTABLE |
| && !(e->src->flags & BB_VISITED)) |
| { |
| has_unvisited_preds = true; |
| break; |
| } |
| |
| for (gphi_iterator gpi = gsi_start_phis (bb); |
| !gsi_end_p (gpi); gsi_next (&gpi)) |
| { |
| gphi *phi = gpi.phi (); |
| tree lhs = PHI_RESULT (phi); |
| if (virtual_operand_p (lhs)) |
| continue; |
| |
| /* Skips floats and other things we can't represent in a |
| range. */ |
| if (!value_range::supports_type_p (TREE_TYPE (lhs))) |
| continue; |
| |
| value_range_equiv vr_result; |
| bool interesting = stmt_interesting_for_vrp (phi); |
| if (!has_unvisited_preds && interesting) |
| extract_range_from_phi_node (phi, &vr_result); |
| else |
| { |
| vr_result.set_varying (TREE_TYPE (lhs)); |
| /* When we have an unvisited executable predecessor we can't |
| use PHI arg ranges which may be still UNDEFINED but have |
| to use VARYING for them. But we can still resort to |
| SCEV for loop header PHIs. */ |
| class loop *l; |
| if (scev_initialized_p () |
| && interesting |
| && (l = loop_containing_stmt (phi)) |
| && l->header == gimple_bb (phi)) |
| adjust_range_with_scev (&vr_result, l, phi, lhs); |
| } |
| update_value_range (lhs, &vr_result); |
| |
| /* Set the SSA with the value range. */ |
| if (m_update_global_ranges) |
| set_ssa_range_info (lhs, &vr_result); |
| } |
| } |
| |
| /* Record ranges from STMT into our VR_VALUES class. If TEMPORARY is |
| true, then this is a temporary equivalence and should be recorded |
| into the unwind table. Othewise record the equivalence into the |
| global table. */ |
| |
| void |
| evrp_range_analyzer::record_ranges_from_stmt (gimple *stmt, bool temporary) |
| { |
| tree output = NULL_TREE; |
| |
| if (!optimize) |
| return; |
| |
| if (dyn_cast <gcond *> (stmt)) |
| ; |
| else if (stmt_interesting_for_vrp (stmt)) |
| { |
| edge taken_edge; |
| value_range_equiv vr; |
| extract_range_from_stmt (stmt, &taken_edge, &output, &vr); |
| if (output) |
| { |
| /* Set the SSA with the value range. There are two cases to |
| consider. First (the the most common) is we are processing |
| STMT in a context where its resulting range globally holds |
| and thus it can be reflected into the global ranges and need |
| not be unwound as we leave scope. |
| |
| The second case occurs if we are processing a statement in |
| a context where the resulting range must not be reflected |
| into the global tables and must be unwound as we leave |
| the current context. This happens in jump threading for |
| example. */ |
| if (!temporary) |
| { |
| /* Case one. We can just update the underlying range |
| information as well as the global information. */ |
| update_value_range (output, &vr); |
| if (m_update_global_ranges) |
| set_ssa_range_info (output, &vr); |
| } |
| else |
| { |
| /* We're going to need to unwind this range. We cannot |
| use VR as that's a stack object. We have to allocate |
| a new range and push the old range onto the stack. We |
| also have to be very careful about sharing the underlying |
| bitmaps. Ugh. */ |
| value_range_equiv *new_vr = allocate_value_range_equiv (); |
| new_vr->set (vr.min (), vr.max (), NULL, vr.kind ()); |
| vr.equiv_clear (); |
| push_value_range (output, new_vr); |
| } |
| } |
| else |
| set_defs_to_varying (stmt); |
| } |
| else |
| set_defs_to_varying (stmt); |
| |
| /* See if we can derive a range for any of STMT's operands. */ |
| tree op; |
| ssa_op_iter i; |
| FOR_EACH_SSA_TREE_OPERAND (op, stmt, i, SSA_OP_USE) |
| { |
| tree value; |
| enum tree_code comp_code; |
| |
| /* If OP is used in such a way that we can infer a value |
| range for it, and we don't find a previous assertion for |
| it, create a new assertion location node for OP. */ |
| if (infer_value_range (stmt, op, &comp_code, &value)) |
| { |
| /* If we are able to infer a nonzero value range for OP, |
| then walk backwards through the use-def chain to see if OP |
| was set via a typecast. |
| If so, then we can also infer a nonzero value range |
| for the operand of the NOP_EXPR. */ |
| if (comp_code == NE_EXPR && integer_zerop (value)) |
| { |
| tree t = op; |
| gimple *def_stmt = SSA_NAME_DEF_STMT (t); |
| while (is_gimple_assign (def_stmt) |
| && CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt)) |
| && TREE_CODE |
| (gimple_assign_rhs1 (def_stmt)) == SSA_NAME |
| && POINTER_TYPE_P |
| (TREE_TYPE (gimple_assign_rhs1 (def_stmt)))) |
| { |
| t = gimple_assign_rhs1 (def_stmt); |
| def_stmt = SSA_NAME_DEF_STMT (t); |
| |
| /* Add VR when (T COMP_CODE value) condition is |
| true. */ |
| value_range_equiv *op_range |
| = try_find_new_range (t, t, comp_code, value); |
| if (op_range) |
| push_value_range (t, op_range); |
| } |
| } |
| /* Add VR when (OP COMP_CODE value) condition is true. */ |
| value_range_equiv *op_range = try_find_new_range (op, op, |
| comp_code, value); |
| if (op_range) |
| push_value_range (op, op_range); |
| } |
| } |
| } |
| |
| /* Unwind recorded ranges to their most recent state. */ |
| |
| void |
| evrp_range_analyzer::pop_to_marker (void) |
| { |
| gcc_checking_assert (!stack.is_empty ()); |
| while (stack.last ().first != NULL_TREE) |
| pop_value_range (); |
| stack.pop (); |
| } |
| |
| /* Restore/pop VRs valid only for BB when we leave BB. */ |
| |
| void |
| evrp_range_analyzer::leave (basic_block bb ATTRIBUTE_UNUSED) |
| { |
| if (!optimize) |
| return; |
| pop_to_marker (); |
| } |
| |
| |
| /* Push the Value Range of VAR to the stack and update it with new VR. */ |
| |
| void |
| evrp_range_analyzer::push_value_range (tree var, value_range_equiv *vr) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "pushing new range for "); |
| print_generic_expr (dump_file, var); |
| fprintf (dump_file, ": "); |
| dump_value_range (dump_file, vr); |
| fprintf (dump_file, "\n"); |
| } |
| value_range_equiv *old_vr = swap_vr_value (var, vr); |
| stack.safe_push (std::make_pair (var, old_vr)); |
| } |
| |
| /* Pop a Value Range from the vrp_stack. */ |
| |
| void |
| evrp_range_analyzer::pop_value_range () |
| { |
| std::pair<tree, value_range_equiv *> e = stack.pop (); |
| tree var = e.first; |
| value_range_equiv *vr = e.second; |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| { |
| fprintf (dump_file, "popping range for "); |
| print_generic_expr (dump_file, var); |
| fprintf (dump_file, ", restoring "); |
| dump_value_range (dump_file, vr); |
| fprintf (dump_file, "\n"); |
| } |
| /* We saved off a lattice entry, now give it back and release |
| the one we popped. */ |
| value_range_equiv *popped_vr = swap_vr_value (var, vr); |
| if (popped_vr) |
| free_value_range (popped_vr); |
| } |