From e70ab3b9849db45176f4ab6ec5b1c25b9d30b58a Mon Sep 17 00:00:00 2001 From: Aldy Hernandez Date: Tue, 15 Jun 2021 12:20:43 +0200 Subject: [PATCH 1/2] Implement basic block path solver. This is is the main basic block path solver for use in the ranger-based backwards threader. Given a path of BBs, the class can solve the final conditional or any SSA name used in calculating the final conditional. The main API is: // This class is a basic block path solver. Given a set of BBs // indicating a path through the CFG, range_in_path() will return the // range of an SSA as if the BBs in the path would have been executed // in order. // // Only SSA names passed in IMPORTS are precomputed, and can be // queried. // // Note that the blocks are in reverse order, thus the exit block is // path[0]. class path_solver { public: path_solver (gimple_ranger &ranger); virtual ~path_solver (); void precompute_ranges (const vec *path, const bitmap_head *imports); void range_in_path (irange &, tree name); void range_in_path (irange &, gimple *); }; gcc/ChangeLog: * Makefile.in (OBJS): Add tree-ssa-path-solver.o. * tree-ssa-path-solver.cc: New file. * tree-ssa-path-solver.h: New file. --- gcc/Makefile.in | 1 + gcc/tree-ssa-path-solver.cc | 306 ++++++++++++++++++++++++++++++++++++ gcc/tree-ssa-path-solver.h | 85 ++++++++++ 3 files changed, 392 insertions(+) create mode 100644 gcc/tree-ssa-path-solver.cc create mode 100644 gcc/tree-ssa-path-solver.h diff --git a/gcc/Makefile.in b/gcc/Makefile.in index ebf26442992..66cc5f9529e 100644 --- a/gcc/Makefile.in +++ b/gcc/Makefile.in @@ -1644,6 +1644,7 @@ OBJS = \ tree-ssa-loop.o \ tree-ssa-math-opts.o \ tree-ssa-operands.o \ + tree-ssa-path-solver.o \ tree-ssa-phiopt.o \ tree-ssa-phiprop.o \ tree-ssa-pre.o \ diff --git a/gcc/tree-ssa-path-solver.cc b/gcc/tree-ssa-path-solver.cc new file mode 100644 index 00000000000..9dca2937ecc --- /dev/null +++ b/gcc/tree-ssa-path-solver.cc @@ -0,0 +1,306 @@ +/* Basic block path solver. + Copyright (C) 2021 Free Software Foundation, Inc. + Contributed by Aldy Hernandez . + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify it under +the terms of the GNU General Public License as published by the Free +Software Foundation; either version 3, or (at your option) any later +version. + +GCC is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTY; without even the implied warranty of MERCHANTABILITY or +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + for more details. + +You should have received a copy of the GNU General Public License +along with GCC; see the file COPYING3. If not see +. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "backend.h" +#include "tree.h" +#include "gimple.h" +#include "cfganal.h" +#include "value-range.h" +#include "gimple-range.h" +#include "tree-pretty-print.h" +#include "tree-ssa-path-solver.h" +#include "ssa.h" + +// Internal construct to help facilitate debugging of solver. +#define DEBUG_SOLVER (0 && dump_file) + +path_solver::path_solver (gimple_ranger &ranger) + : m_ranger (ranger) +{ + m_cache = new ssa_global_cache; + m_has_cache_entry = BITMAP_ALLOC (NULL); + m_path = NULL; +} + +path_solver::~path_solver () +{ + BITMAP_FREE (m_has_cache_entry); + delete m_cache; +} + +// Mark cache entry for NAME as unused. + +void +path_solver::clear_cache (tree name) +{ + unsigned v = SSA_NAME_VERSION (name); + bitmap_clear_bit (m_has_cache_entry, v); +} + +// If NAME has a cache entry, return it in R, and return TRUE. + +inline bool +path_solver::get_cache (irange &r, tree name) +{ + if (!gimple_range_ssa_p (name)) + return get_global_range_query ()->range_of_expr (r, name); + + unsigned v = SSA_NAME_VERSION (name); + if (bitmap_bit_p (m_has_cache_entry, v)) + return m_cache->get_global_range (r, name); + + return false; +} + +// Set the cache entry for NAME to R. + +void +path_solver::set_cache (const irange &r, tree name) +{ + unsigned v = SSA_NAME_VERSION (name); + bitmap_set_bit (m_has_cache_entry, v); + m_cache->set_global_range (name, r); +} + +bool +path_solver::range_of_expr (irange &r, tree name, gimple *stmt) +{ + if (!irange::supports_type_p (TREE_TYPE (name))) + return false; + + if (get_cache (r, name)) + return true; + + if (stmt && range_defined_in_block (r, name, gimple_bb (stmt))) + { + set_cache (r, name); + return true; + } + + // Otherwise return varying. + r.set_varying (TREE_TYPE (name)); + return true; +} + +// Initialize the current path to PATH. The current block is set to +// the entry block to the path. +// +// Note that the blocks are in reverse order, so the exit block is +// path[0]. + +void +path_solver::set_path (const vec &path) +{ + gcc_checking_assert (path.length () > 1); + m_path = &path; + m_pos = m_path->length () - 1; + bitmap_clear (m_has_cache_entry); +} + +// Return the range of the result of PHI in R. + +void +path_solver::ssa_range_in_phi (irange &r, gphi *phi) +{ + tree name = gimple_phi_result (phi); + basic_block bb = gimple_bb (phi); + + // We experimented with querying ranger's range_on_entry here, but + // the performance penalty was too high, for hardly any improvements. + if (at_entry ()) + { + r.set_varying (TREE_TYPE (name)); + return; + } + + basic_block prev = prev_bb (); + edge e_in = find_edge (prev, bb); + for (size_t i = 0; i < gimple_phi_num_args (phi); ++i) + if (e_in == gimple_phi_arg_edge (phi, i)) + { + tree arg = gimple_phi_arg_def (phi, i); + + if (!get_cache (r, arg)) + r.set_varying (TREE_TYPE (name)); + + return; + } + gcc_unreachable (); +} + +// If NAME is defined in BB, set R to the range of NAME, and return +// TRUE. Otherwise, return FALSE. + +bool +path_solver::range_defined_in_block (irange &r, tree name, basic_block bb) +{ + gimple *def_stmt = SSA_NAME_DEF_STMT (name); + basic_block def_bb = gimple_bb (def_stmt); + + if (def_bb != bb) + return false; + + if (gimple_code (def_stmt) == GIMPLE_PHI) + ssa_range_in_phi (r, as_a (def_stmt)); + else if (!fold_range (r, def_stmt, this)) + r.set_varying (TREE_TYPE (name)); + + if (DEBUG_SOLVER) + { + fprintf (dump_file, "range_defined_in_block (BB%d) for ", bb->index); + print_generic_expr (dump_file, name, TDF_SLIM); + fprintf (dump_file, " is "); + r.dump (dump_file); + fprintf (dump_file, "\n"); + } + return true; +} + +// Precompute ranges defined in the current block, or ranges +// that are exported on an edge to the next block. The cache is +// updated accordingly. + +void +path_solver::precompute_ranges_in_block () +{ + basic_block bb = curr_bb (); + bitmap_iterator bi; + int_range_max r, cached_range; + unsigned i; + + // Force recalculation of any names in the cache that are defined in + // this block. This can happen on interdependent SSA/phis in loops. + EXECUTE_IF_SET_IN_BITMAP (m_imports, 0, i, bi) + { + tree name = ssa_name (i); + gimple *def_stmt = SSA_NAME_DEF_STMT (name); + basic_block def_bb = gimple_bb (def_stmt); + + if (def_bb == bb) + clear_cache (name); + } + + // Solve imports defined in this block. + EXECUTE_IF_SET_IN_BITMAP (m_imports, 0, i, bi) + { + tree name = ssa_name (i); + + if (range_defined_in_block (r, name, bb)) + set_cache (r, name); + } + + if (at_exit ()) + return; + + // Solve imports that are exported to the next block. + edge e = find_edge (bb, next_bb ()); + EXECUTE_IF_SET_IN_BITMAP (m_imports, 0, i, bi) + { + tree name = ssa_name (i); + gori_compute &g = m_ranger.gori (); + bitmap exports = g.exports (bb); + + if (bitmap_bit_p (exports, i)) + { + if (g.outgoing_edge_range_p (r, e, name, *this)) + { + if (get_cache (cached_range, name)) + r.intersect (cached_range); + + set_cache (r, name); + if (DEBUG_SOLVER) + { + fprintf (dump_file, "outgoing_edge_range_p for "); + print_generic_expr (dump_file, name, TDF_SLIM); + fprintf (dump_file, " on edge %d->%d ", + e->src->index, e->dest->index); + fprintf (dump_file, "is "); + r.dump (dump_file); + fprintf (dump_file, "\n"); + } + } + } + } +} + +// Precompute the ranges for IMPORTS along PATH. +// +// IMPORTS are the set of SSA names, any of which could potentially +// change the value of the final conditional in PATH. + +void +path_solver::precompute_ranges (const vec &path, + const bitmap_head *imports) +{ + set_path (path); + m_imports = imports; + + if (DEBUG_SOLVER) + { + extern void debug (vec &); + extern void debug (const bitmap_head *); + fprintf (dump_file, "\nPATH is:\n"); + debug (const_cast &> (path)); + fprintf (dump_file, "imports: "); + debug (imports); + } + + while (1) + { + precompute_ranges_in_block (); + if (at_exit ()) + break; + move_next (); + } +} + +// Return the range of NAME as it would be seen at the end of the path +// being analyzed. + +void +path_solver::range_in_path (irange &r, tree name) +{ + basic_block bb = exit_bb (); + + if (get_cache (r, name)) + return; + + if (range_defined_in_block (r, name, bb)) + return; + + // The path may not be deep enough to resolve NAME. + r.set_varying (TREE_TYPE (name)); +} + +// Return the range of STMT as it would be seen at the end of the path +// being analyzed. Anything but the final conditional in a BB will +// return VARYING. + +void +path_solver::range_in_path (irange &r, gimple *stmt) +{ + if (gimple_code (stmt) == GIMPLE_COND && fold_range (r, stmt, this)) + return; + + r.set_varying (gimple_expr_type (stmt)); +} diff --git a/gcc/tree-ssa-path-solver.h b/gcc/tree-ssa-path-solver.h new file mode 100644 index 00000000000..90bcf389f66 --- /dev/null +++ b/gcc/tree-ssa-path-solver.h @@ -0,0 +1,85 @@ +/* Header file for jump threading path solver. + Copyright (C) 2021 Free Software Foundation, Inc. + Contributed by Aldy Hernandez . + +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 +. */ + +#ifndef GCC_TREE_SSA_THREADSOLVER_H +#define GCC_TREE_SSA_THREADSOLVER_H + +// This class is a basic block path solver. Given a set of BBs +// indicating a path through the CFG, range_in_path() will return the +// range of an SSA as if the BBs in the path would have been executed +// in order. +// +// Only SSA names passed in IMPORTS are precomputed, and can be +// queried. +// +// Note that the blocks are in reverse order, thus the exit block is +// path[0]. + +class path_solver : private range_query +{ +public: + path_solver (gimple_ranger &ranger); + virtual ~path_solver (); + void precompute_ranges (const vec &path, + const bitmap_head *imports); + void range_in_path (irange &, tree name); + void range_in_path (irange &, gimple *); + +private: + bool range_of_expr (irange &r, tree name, gimple * = NULL) override; + + // Cache manipulation. + void set_cache (const irange &r, tree name); + bool get_cache (irange &r, tree name); + void clear_cache (tree name); + + // Methods to precompute ranges for the given path. + bool range_defined_in_block (irange &, tree name, basic_block bb); + void precompute_ranges_in_block (); + void ssa_range_in_phi (irange &r, gphi *phi); + + // Path navigation. + void set_path (const vec &); + basic_block entry_bb () { return (*m_path)[m_path->length () - 1]; } + basic_block exit_bb () { return (*m_path)[0]; } + basic_block curr_bb () { return (*m_path)[m_pos]; } + basic_block prev_bb () { return (*m_path)[m_pos + 1]; } + basic_block next_bb () { return (*m_path)[m_pos - 1]; } + bool at_entry () { return m_pos == m_path->length () - 1; } + bool at_exit () { return m_pos == 0; } + void move_next () { --m_pos; } + + // Range cache for SSA names. + ssa_global_cache *m_cache; + + // Set for each SSA that has an active entry in the cache. + bitmap m_has_cache_entry; + + // Path being analyzed. + const vec *m_path; + + // Current path position. + unsigned m_pos; + + const bitmap_head *m_imports; + gimple_ranger &m_ranger; +}; + +#endif // GCC_TREE_SSA_THREADSOLVER_H -- 2.31.1