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Diffstat (limited to 'lib/compiler/src/beam_ssa_lint.erl')
| -rw-r--r-- | lib/compiler/src/beam_ssa_lint.erl | 349 |
1 files changed, 349 insertions, 0 deletions
diff --git a/lib/compiler/src/beam_ssa_lint.erl b/lib/compiler/src/beam_ssa_lint.erl new file mode 100644 index 0000000000..a003607dab --- /dev/null +++ b/lib/compiler/src/beam_ssa_lint.erl @@ -0,0 +1,349 @@ +%% +%% %CopyrightBegin% +%% +%% Copyright Ericsson AB 2018. All Rights Reserved. +%% +%% Licensed under the Apache License, Version 2.0 (the "License"); +%% you may not use this file except in compliance with the License. +%% You may obtain a copy of the License at +%% +%% http://www.apache.org/licenses/LICENSE-2.0 +%% +%% Unless required by applicable law or agreed to in writing, software +%% distributed under the License is distributed on an "AS IS" BASIS, +%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +%% See the License for the specific language governing permissions and +%% limitations under the License. +%% +%% %CopyrightEnd% +%% +%% Purpose: Internal consistency checks for the beam_ssa format. + +-module(beam_ssa_lint). + +-export([module/2, format_error/1]). + +-import(lists, [append/1, foldl/3, foreach/2]). + +-include("beam_ssa.hrl"). + +-spec module(#b_module{}, [compile:option()]) -> + {'ok',#b_module{}} | {'error',list()}. +module(#b_module{body=Fs,name=Name}=Mod0, _Options) -> + Es0 = append([validate_function(F) || F <- Fs]), + case [{?MODULE,E} || E <- Es0] of + [] -> + {ok, Mod0}; + [_|_]=Es -> + {error,[{atom_to_list(Name), Es}]} + end. + +-spec format_error(term()) -> iolist(). +format_error({{_M,F,A},{redefined_variable, Name, Old, I}}) -> + io_lib:format("~p/~p: Variable ~ts (~ts) redefined by ~ts", + [F, A, format_var(Name), format_instr(Old), format_instr(I)]); +format_error({{_M,F,A},{missing_phi_paths, Paths, I}}) -> + io_lib:format("~p/~p: Phi node ~ts doesn't define a value for these " + "branches: ~w", + [F, A, format_instr(I), Paths]); +format_error({{_M,F,A},{garbage_phi_paths, Paths, I}}) -> + io_lib:format("~p/~p: Phi node ~ts defines a value for these unreachable " + "or non-existent branches: ~w", + [F, A, format_instr(I), Paths]); +format_error({{_M,F,A},{unknown_phi_variable, Name, {From, _To}, I}}) -> + io_lib:format("~p/~p: Variable ~ts used in phi node ~ts is undefined on " + "branch ~w", + [F, A, format_var(Name), format_instr(I), From]); +format_error({{_M,F,A},{unknown_block, Label, I}}) -> + io_lib:format("~p/~p: Unknown block ~p referenced in ~ts", + [F, A, Label, I]); +format_error({{_M,F,A},{unknown_variable, Name, I}}) -> + io_lib:format("~p/~p: Unbound variable ~ts used in ~ts", + [F, A, format_var(Name), format_instr(I)]); +format_error({{_M,F,A},{phi_inside_block, Name, Id}}) -> + io_lib:format("~p/~p: Phi node defining ~ts is not at start of block ~p", + [F, A, format_var(Name), Id]); +format_error({{_M,F,A},{undefined_label_in_phi, Label, I}}) -> + io_lib:format("~p/~p: Unknown block label ~p in phi node ~ts", + [F, A, Label, format_instr(I)]). + +format_instr(I) -> + [$',beam_ssa_pp:format_instr(I),$']. + +format_var(V) -> + beam_ssa_pp:format_var(#b_var{name=V}). + +validate_function(F) -> + try + validate_variables(F), + [] + catch + throw:Reason -> + #{func_info:=MFA} = F#b_function.anno, + [{MFA,Reason}]; + Class:Error:Stack -> + io:fwrite("Function: ~p\n", [F#b_function.anno]), + erlang:raise(Class, Error, Stack) + end. + +-type defined_vars() :: gb_sets:set(beam_ssa:var_name()). + +-record(vvars, + {blocks :: #{ beam_ssa:label() => beam_ssa:b_blk() }, + branch_def_vars :: #{ + %% Describes the variable state at the time of this exact branch (phi + %% node validation). + {From :: beam_ssa:label(), To :: beam_ssa:label()} => defined_vars(), + %% Describes the variable state common to all branches leading to this + %% label (un/redefined variable validation). + beam_ssa:label() => defined_vars() }, + defined_vars :: defined_vars()}). + +-spec validate_variables(beam_ssa:b_function()) -> ok. +validate_variables(#b_function{ args = Args, bs = Blocks }) -> + %% Prefill the mapping with function arguments. + ArgNames = vvars_get_varnames(Args), + DefVars = gb_sets:from_list(ArgNames), + Entry = 0, + + State = #vvars{blocks = Blocks, + branch_def_vars = #{ Entry => DefVars }, + defined_vars = DefVars}, + ok = vvars_assert_unique(Blocks, ArgNames), + vvars_phi_nodes(vvars_block(Entry, State)). + +%% Checks the uniqueness of all variables across all blocks. +-spec vvars_assert_unique(Blocks, [beam_ssa:var_name()]) -> ok when + Blocks :: #{ beam_ssa:label() => beam_ssa:b_blk() }. +vvars_assert_unique(Blocks, Args) -> + BlockIs = [Is || #b_blk{is=Is} <- maps:values(Blocks)], + Defined0 = maps:from_list([{V,argument} || V <- Args]), + _ = foldl(fun(Is, Defined) -> + vvars_assert_unique_1(Is, Defined) + end, Defined0, BlockIs), + ok. + +-spec vvars_assert_unique_1(Is, Defined) -> ok when + Is :: list(beam_ssa:b_set()), + Defined :: #{ beam_ssa:var_name() => beam_ssa:b_set() }. +vvars_assert_unique_1([#b_set{dst=#b_var{name=DstName}}=I|Is], Defined) -> + case Defined of + #{DstName:=Old} -> throw({redefined_variable, DstName, Old, I}); + _ -> vvars_assert_unique_1(Is, Defined#{DstName=>I}) + end; +vvars_assert_unique_1([], Defined) -> + Defined. + +-spec vvars_phi_nodes(State :: #vvars{}) -> ok. +vvars_phi_nodes(#vvars{ blocks = Blocks }=State) -> + _ = [vvars_phi_nodes_1(Is, Id, State) || + {Id, #b_blk{ is = Is }} <- maps:to_list(Blocks)], + ok. + +-spec vvars_phi_nodes_1(Is, Id, State) -> ok when + Is :: list(beam_ssa:b_set()), + Id :: beam_ssa:label(), + State :: #vvars{}. +vvars_phi_nodes_1([#b_set{ op = phi, args = Phis }=I | Is], Id, State) -> + ok = vvars_assert_phi_paths(Phis, I, Id, State), + ok = vvars_assert_phi_vars(Phis, I, Id, State), + vvars_phi_nodes_1(Is, Id, State); +vvars_phi_nodes_1([_ | Is], Id, _State) -> + case [Dst || #b_set{op=phi,dst=#b_var{name=Dst}} <- Is] of + [Name|_] -> + throw({phi_inside_block, Name, Id}); + [] -> + ok + end; +vvars_phi_nodes_1([], _Id, _State) -> + ok. + +%% Checks whether all paths leading to this phi node are represented, and that +%% it doesn't reference any non-existent paths. +-spec vvars_assert_phi_paths(Phis, I, Id, State) -> ok when + Phis :: list({beam_ssa:argument(), beam_ssa:label()}), + Id :: beam_ssa:label(), + I :: beam_ssa:b_set(), + State :: #vvars{}. +vvars_assert_phi_paths(Phis, I, Id, State) -> + BranchKeys = maps:keys(State#vvars.branch_def_vars), + RequiredPaths = ordsets:from_list([From || {From, To} <- BranchKeys, To =:= Id]), + ProvidedPaths = ordsets:from_list([From || {_Value, From} <- Phis]), + case ordsets:subtract(RequiredPaths, ProvidedPaths) of + [_|_]=MissingPaths -> throw({missing_phi_paths, MissingPaths, I}); + [] -> ok + end. + %% %% The following test is sometimes useful to find missing optimizations. + %% %% It is commented out, though, because it can be triggered by + %% %% by weird but legal code. + %% case ordsets:subtract(ProvidedPaths, RequiredPaths) of + %% [_|_]=GarbagePaths -> throw({garbage_phi_paths, GarbagePaths, I}); + %% [] -> ok + %% end. + +%% Checks whether all variables used in this phi node are defined in the branch +%% they arrived on. +-spec vvars_assert_phi_vars(Phis, I, Id, State) -> ok when + Phis :: list({beam_ssa:argument(), beam_ssa:label()}), + Id :: beam_ssa:label(), + I :: beam_ssa:b_set(), + State :: #vvars{}. +vvars_assert_phi_vars(Phis, I, Id, #vvars{blocks=Blocks, + branch_def_vars=BranchDefVars}) -> + Vars = [{Var, From} || {#b_var{}=Var, From} <- Phis], + foreach(fun({#b_var{name=VarName}, From}) -> + BranchKey = {From, Id}, + case BranchDefVars of + #{BranchKey:=DefVars} -> + case gb_sets:is_member(VarName, DefVars) of + true -> ok; + false -> throw({unknown_variable, VarName, I}) + end; + #{} -> + throw({unknown_phi_variable, VarName, BranchKey, I}) + end + end, Vars), + Labels = [From || {#b_literal{},From} <- Phis], + foreach(fun(Label) -> + case Blocks of + #{Label:=_} -> + ok; + #{} -> + throw({undefined_label_in_phi, Label, I}) + end + end, Labels). + +-spec vvars_block(Id, State) -> #vvars{} when + Id :: beam_ssa:label(), + State :: #vvars{}. +vvars_block(Id, State0) -> + #{ Id := #b_blk{ is = Is, last = Terminator} } = State0#vvars.blocks, + #{ Id := DefVars } = State0#vvars.branch_def_vars, + State = State0#vvars{ defined_vars = DefVars }, + vvars_terminator(Terminator, Id, vvars_block_1(Is, State)). + +-spec vvars_block_1(Blocks, State) -> #vvars{} when + Blocks :: list(beam_ssa:b_blk()), + State :: #vvars{}. +vvars_block_1([], State) -> + State; +vvars_block_1([#b_set{ dst = #b_var{ name = DstName }, op = phi } | Is], State0) -> + %% We don't check phi node arguments at this point since we may not have + %% visited their definition yet. They'll be handled later on in + %% vvars_phi_nodes/1 after all blocks are processed. + vvars_block_1(Is, vvars_save_var(DstName, State0)); +vvars_block_1([#b_set{ dst = #b_var{ name = DstName }, args = Args }=I | Is], State0) -> + ok = vvars_assert_args(Args, I, State0), + vvars_block_1(Is, vvars_save_var(DstName, State0)). + +-spec vvars_terminator(Terminator, From, State) -> #vvars{} when + Terminator :: beam_ssa:terminator(), + From :: beam_ssa:label(), + State :: #vvars{}. +vvars_terminator(#b_ret{ arg = Arg }=I, _From, State) -> + ok = vvars_assert_args([Arg], I, State), + State; +vvars_terminator(#b_switch{arg=Arg,fail=Fail,list=Switch}=I, From, State) -> + ok = vvars_assert_args([Arg], I, State), + ok = vvars_assert_args([A || {A,_Lbl} <- Switch], I, State), + Labels = [Fail | [Lbl || {_Arg, Lbl} <- Switch]], + ok = vvars_assert_labels(Labels, I, State), + vvars_terminator_1(Labels, From, State); +vvars_terminator(#b_br{bool=#b_literal{val=true},succ=Succ}=I, From, State) -> + Labels = [Succ], + ok = vvars_assert_labels(Labels, I, State), + vvars_terminator_1(Labels, From, State); +vvars_terminator(#b_br{bool=#b_literal{val=false},fail=Fail}=I, From, State) -> + Labels = [Fail], + ok = vvars_assert_labels(Labels, I, State), + vvars_terminator_1(Labels, From, State); +vvars_terminator(#b_br{ bool = Arg, succ = Succ, fail = Fail }=I, From, State) -> + ok = vvars_assert_args([Arg], I, State), + Labels = [Fail, Succ], + ok = vvars_assert_labels(Labels, I, State), + vvars_terminator_1(Labels, From, State). + +-spec vvars_terminator_1(Labels, From, State) -> #vvars{} when + Labels :: list(beam_ssa:label()), + From :: beam_ssa:label(), + State :: #vvars{}. +vvars_terminator_1(Labels0, From, State0) -> + %% Filter out all branches that have already been taken. This should result + %% in either all of Labels0 or an empty list. + Labels = [To || To <- Labels0, + not maps:is_key({From, To}, State0#vvars.branch_def_vars)], + true = Labels =:= Labels0 orelse Labels =:= [], %Assertion + State1 = foldl(fun(To, State) -> + vvars_save_branch(From, To, State) + end, State0, Labels), + foldl(fun(To, State) -> + vvars_block(To, State) + end, State1, Labels). + +%% Gets all variable names in args, ignoring literals etc +-spec vvars_get_varnames(Args) -> list(beam_ssa:var_name()) when + Args :: list(beam_ssa:argument()). +vvars_get_varnames(Args) -> + [Name || #b_var{ name = Name } <- Args]. + +%% Checks that all variables in Args are defined in all paths leading to the +%% current State. +-spec vvars_assert_args(Args, I, State) -> ok when + Args :: list(beam_ssa:argument()), + I :: beam_ssa:terminator() | beam_ssa:b_set(), + State :: #vvars{}. +vvars_assert_args(Args, I, #vvars{defined_vars=DefVars}=State) -> + foreach(fun(#b_remote{mod=Mod,name=Name}) -> + vvars_assert_args([Mod,Name], I, State); + (#b_var{name=Name}) -> + case gb_sets:is_member(Name, DefVars) of + true -> ok; + false -> throw({unknown_variable,Name,I}) + end; + (_) -> ok + end, Args). + +%% Checks that all given labels are defined in State. +-spec vvars_assert_labels(Labels, I, State) -> ok when + Labels :: list(beam_ssa:label()), + I :: beam_ssa:terminator(), + State :: #vvars{}. +vvars_assert_labels(Labels, I, #vvars{blocks=Blocks}) -> + foreach(fun(Label) -> + case maps:is_key(Label, Blocks) of + false -> throw({unknown_block, Label, I}); + true -> ok + end + end, Labels). + +-spec vvars_save_branch(From, To, State) -> #vvars{} when + From :: beam_ssa:label(), + To :: beam_ssa:label(), + State :: #vvars{}. +vvars_save_branch(From, To, State) -> + DefVars = State#vvars.defined_vars, + Branches0 = State#vvars.branch_def_vars, + case Branches0 of + #{ To := LblDefVars } -> + MergedVars = vvars_merge_branches(DefVars, LblDefVars), + + Branches = Branches0#{ To => MergedVars, {From, To} => DefVars }, + State#vvars { branch_def_vars = Branches }; + _ -> + Branches = Branches0#{ To => DefVars, {From, To} => DefVars }, + State#vvars { branch_def_vars = Branches } + end. + +-spec vvars_merge_branches(New, Existing) -> defined_vars() when + New :: defined_vars(), + Existing :: defined_vars(). +vvars_merge_branches(New, Existing) -> + gb_sets:intersection(New, Existing). + +-spec vvars_save_var(VarName, State) -> #vvars{} when + VarName :: beam_ssa:var_name(), + State :: #vvars{}. +vvars_save_var(VarName, State0) -> + %% vvars_assert_unique guarantees that variables are never set twice. + DefVars = gb_sets:insert(VarName, State0#vvars.defined_vars), + State0#vvars{ defined_vars = DefVars }. |