Reviewed By: mbouaziz Differential Revision: D9460455 fbshipit-source-id: 7488c1a69master
Ezgi Çiçek
6 years ago
committed by
Facebook Github Bot
parent
66ef5f5c15
commit
49e582fa49
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(*
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* Copyright (c) 2018-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*)
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open! IStd
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open Graph
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module L = Logging
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module CFG = ProcCfg.Normal
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(* Use ocamlgraph's dominators functor to get the dominators *)
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module GDoms = Dominator.Make (ProcCfg.MakeOcamlGraph (CFG))
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let print_dominators cfg idom =
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L.(debug Analysis Medium) "@\n ----- **** Dominators TABLE **** -------@\n" ;
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Procdesc.get_nodes cfg
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|> List.iter ~f:(fun n ->
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L.(debug Analysis Medium) "@\n Node: %a Dominators:\n" Procdesc.Node.pp n ;
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List.iter
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~f:(L.(debug Analysis Medium) "%a;" Procdesc.Node.pp)
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(GDoms.idom_to_dominators idom n) )
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(* Computes the dominator tree, using ocamlgraph's Lengauer-Tarjan algorithm.
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[compute_idom cfg node] returns a function [idom : Procdesc.Node.t -> Procdesc.Node.t] s.t.
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[idom n] returns the immediate dominator of [n]. *)
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let get_idoms pdesc =
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let idom = GDoms.compute_idom pdesc (ProcCfg.Normal.start_node pdesc) in
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print_dominators pdesc idom ; idom
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(* make each node to be dominated by itself, i.e reflexive, unlike ocamlgraph *)
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let dominates idom x y = GDoms.idom_to_dom idom x y || Procdesc.Node.equal x y
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(*
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* Copyright (c) 2018-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*)
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open! IStd
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module F = Format
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module InstrCFG = ProcCfg.NormalOneInstrPerNode
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module Call = struct
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type t = {pname: Typ.Procname.t; loc: Location.t} [@@deriving compare]
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let pp fmt {pname; loc} =
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F.fprintf fmt "loop-invariant call to %a, at %a " Typ.Procname.pp pname Location.pp loc
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end
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module LoopNodes = AbstractDomain.FiniteSet (Procdesc.Node)
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module HoistCalls = AbstractDomain.FiniteSet (Call)
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(** Map loop_header -> instrs that can be hoisted out of the loop *)
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module LoopHeadToHoistInstrs =
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Procdesc.NodeMap
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(* A loop-invariant function call C(args) at node N can be hoisted out of the loop if
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*
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* 1. C is guaranteed to execute, i.e. N dominates all loop sources
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* 2. args are loop invariant *)
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let add_if_hoistable inv_vars instr node source_nodes idom hoistable_calls =
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match instr with
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| Sil.Call ((ret_id, _), Exp.Const (Const.Cfun pname), _, loc, _)
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when (* Check condition (1); N dominates all loop sources *)
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List.for_all ~f:(fun source -> Dominators.dominates idom node source) source_nodes
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&& (* Check condition (2); id should be invariant already *)
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LoopInvariant.InvariantVars.mem (Var.of_id ret_id) inv_vars ->
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HoistCalls.add {pname; loc} hoistable_calls
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| _ ->
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hoistable_calls
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let get_hoistable_calls inv_vars loop_nodes source_nodes idom =
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LoopNodes.fold
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(fun node hoist_calls ->
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let instr_in_node = Procdesc.Node.get_instrs node in
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Instrs.fold ~init:hoist_calls
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~f:(fun acc instr -> add_if_hoistable inv_vars instr node source_nodes idom acc)
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instr_in_node )
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loop_nodes HoistCalls.empty
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let get_hoist_inv_map tenv reaching_defs_invariant_map loop_head_to_source_nodes idom =
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Procdesc.NodeMap.fold
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(fun loop_head source_nodes inv_map ->
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(* get all the nodes in the loop *)
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let loop_nodes = Loop_control.get_all_nodes_upwards_until loop_head source_nodes in
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let inv_vars_in_loop =
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LoopInvariant.get_inv_vars_in_loop tenv reaching_defs_invariant_map loop_head loop_nodes
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~is_inv_by_default:true
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in
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let hoist_instrs = get_hoistable_calls inv_vars_in_loop loop_nodes source_nodes idom in
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LoopHeadToHoistInstrs.add loop_head hoist_instrs inv_map )
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loop_head_to_source_nodes LoopHeadToHoistInstrs.empty
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let do_report summary Call.({pname; loc}) loop_head_loc =
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let exp_desc =
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F.asprintf "Loop-invariant call to %a at %a" Typ.Procname.pp pname Location.pp loc
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in
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let ltr = [Errlog.make_trace_element 0 loc exp_desc []] in
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let exn =
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let message =
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F.asprintf "%s can be moved out of the loop at %a." exp_desc Location.pp loop_head_loc
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in
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Exceptions.Checkers (IssueType.invariant_call, Localise.verbatim_desc message)
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in
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Reporting.log_error summary ~loc ~ltr exn
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let checker {Callbacks.tenv; summary; proc_desc} : Summary.t =
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let cfg = InstrCFG.from_pdesc proc_desc in
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let proc_data = ProcData.make_default proc_desc tenv in
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(* computes reaching defs: node -> (var -> node set) *)
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let reaching_defs_invariant_map =
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ReachingDefs.Analyzer.exec_cfg cfg proc_data
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~initial:(ReachingDefs.init_reaching_defs_with_formals proc_desc)
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~debug:false
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in
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(* get dominators *)
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let idom = Dominators.get_idoms proc_desc in
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let loop_head_to_source_nodes = Loop_control.get_loop_head_to_source_nodes cfg in
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(* get a map, loop head -> instrs that can be hoisted out of the loop *)
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let loop_head_to_inv_instrs =
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get_hoist_inv_map tenv reaching_defs_invariant_map loop_head_to_source_nodes idom
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in
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(* report function calls to hoist (per loop) *)
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(* Note: we report the innermost loop for hoisting out. TODO: Future
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optimization, take out as further up as possible.*)
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LoopHeadToHoistInstrs.iter
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(fun loop_head inv_instrs ->
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let loop_head_loc = Procdesc.Node.get_loc loop_head in
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HoistCalls.iter (fun call -> do_report summary call loop_head_loc) inv_instrs )
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loop_head_to_inv_instrs ;
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summary
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@ -0,0 +1,143 @@
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/*
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* Copyright (c) 2018-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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class Hoist {
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int foo(int x, int y) {
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return x + y;
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}
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int bar(int x) {
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return 3 * x;
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}
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// will only report one even though both calls are invariant, due to
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// location clashing (no column information)
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void clash_function_calls_hoist(int size) {
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int x = 10;
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int y = 5;
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for (int i = 0; i < size; i++) {
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foo(x, foo(y, x + y));
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}
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}
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// will report both
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void two_function_call_hoist(int size) {
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int x = 10;
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int y = 5;
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for (int i = 0; i < size; i++) {
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foo(x, bar(y));
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}
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}
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// it is ok to move fun call to a temp. var
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void reassigned_temp_hoist(int size) {
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int x = 10;
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int y = 5;
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int d = 0;
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for (int i = 0; i < size; i++) {
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d = foo(x, y);
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d = 30;
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}
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}
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// it is ok to just hoist function call into a temp var.
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void used_in_loop_body_before_def_temp_hoist(int size, int[] M) {
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int x = 10;
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int y = 5;
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int d = 20;
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for (int i = 0; i < size; i++) {
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M[i] = d;
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d = foo(x, y);
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}
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}
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void loop_guard_hoist(int size, int[] M) {
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int x = 10;
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int d = 0;
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int y = 5;
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for (int i = 0; i < foo(d, size); i++) {}
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}
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void legit_hoist(int size, int[] M) {
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int x = 10;
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int y = 5;
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int d = 0;
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for (int i = 0; i < size; i++) {
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d = foo(x, x + y);
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M[i] = d;
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}
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}
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// x is not invariant, hence d won't be invariant as well
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void dep_not_invariant_dont_hoist(int size, int[] M) {
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int x = 10;
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int y = 5;
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int d = 20;
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for (int i = 0; i < size; i++) {
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if (i > 3) {
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x = 3;
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}
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d = foo(x, y); // shouldn't be hoisted
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}
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}
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// foo(x) is not guaranteed to execute
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void not_guaranteed_to_execute_dont_hoist(int size, int x, int y) {
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int i = 0;
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while (i < size) {
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if (i > 3) {
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foo(x, y);
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}
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i++;
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}
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}
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void x_not_invariant_dont_hoist(int size, int x, int y) {
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int i = 0;
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while (i < size) {
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x = foo(x, y) + y;
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i++;
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}
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}
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void array_store_hoist(int size, int[] M) {
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int x = 10;
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int y = 5;
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int d = 0;
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for (int i = 0; i < size; i++) {
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M[i] = foo(x, x + y);
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}
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}
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// y = ... can be taken out of the inner loop
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void nested_loop_hoist(int size, int x, int y) {
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int i = 0;
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while (i < size) {
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for (int j = 0; i < j; j++) {
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y = foo(i, x);
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}
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i++;
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}
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}
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// j is not invariant, y can't be taken out
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void nested_loop_dont_hoist(int size, int x, int y) {
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int i = 0;
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while (i < size) {
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for (int j = 0; j < i; j++) {
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y = foo(j, x);
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}
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i++;
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}
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}
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}
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@ -0,0 +1,13 @@
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# Copyright (c) 2018-present, Facebook, Inc.
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#
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# This source code is licensed under the MIT license found in the
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# LICENSE file in the root directory of this source tree.
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TESTS_DIR = ../../..
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ANALYZER = checkers
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INFER_OPTIONS = --loop-hoisting-only --debug-exceptions
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INFERPRINT_OPTIONS = --issues-tests
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SOURCES = $(wildcard *.java)
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include $(TESTS_DIR)/javac.make
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codetoanalyze/java/hoisting/Hoist.java, Hoist.array_store_hoist(int,int[]):void, 5, INVARIANT_CALL, no_bucket, ERROR, [Loop-invariant call to int Hoist.foo(int,int) at line 115]
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codetoanalyze/java/hoisting/Hoist.java, Hoist.clash_function_calls_hoist(int):void, 4, INVARIANT_CALL, no_bucket, ERROR, [Loop-invariant call to int Hoist.foo(int,int) at line 23]
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codetoanalyze/java/hoisting/Hoist.java, Hoist.legit_hoist(int,int[]):void, 5, INVARIANT_CALL, no_bucket, ERROR, [Loop-invariant call to int Hoist.foo(int,int) at line 71]
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codetoanalyze/java/hoisting/Hoist.java, Hoist.loop_guard_hoist(int,int[]):void, 4, INVARIANT_CALL, no_bucket, ERROR, [Loop-invariant call to int Hoist.foo(int,int) at line 63]
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codetoanalyze/java/hoisting/Hoist.java, Hoist.nested_loop_hoist(int,int,int):void, 5, INVARIANT_CALL, no_bucket, ERROR, [Loop-invariant call to int Hoist.foo(int,int) at line 126]
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codetoanalyze/java/hoisting/Hoist.java, Hoist.reassigned_temp_hoist(int):void, 5, INVARIANT_CALL, no_bucket, ERROR, [Loop-invariant call to int Hoist.foo(int,int) at line 43]
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codetoanalyze/java/hoisting/Hoist.java, Hoist.two_function_call_hoist(int):void, 4, INVARIANT_CALL, no_bucket, ERROR, [Loop-invariant call to int Hoist.foo(int,int) at line 32]
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codetoanalyze/java/hoisting/Hoist.java, Hoist.two_function_call_hoist(int):void, 4, INVARIANT_CALL, no_bucket, ERROR, [Loop-invariant call to int Hoist.bar(int) at line 32]
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codetoanalyze/java/hoisting/Hoist.java, Hoist.used_in_loop_body_before_def_temp_hoist(int,int[]):void, 6, INVARIANT_CALL, no_bucket, ERROR, [Loop-invariant call to int Hoist.foo(int,int) at line 55]
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