From 4edd266876f2383ccc33b91a3bbe8550279368f5 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Fri, 31 Aug 2018 07:13:05 +0200 Subject: beam_ssa_opt: Add an optimization of tuple_size/1 This optimization working on the SSA format will replace the similar optimization in beam_dead. See the comment for an explanation of what the new optimization does. --- lib/compiler/src/beam_ssa_opt.erl | 121 +++++++++++++++++++++ lib/compiler/test/guard_SUITE.erl | 10 -- .../test/guard_SUITE_data/guard_SUITE_tuple_size.S | 30 ----- 3 files changed, 121 insertions(+), 40 deletions(-) delete mode 100644 lib/compiler/test/guard_SUITE_data/guard_SUITE_tuple_size.S (limited to 'lib/compiler') diff --git a/lib/compiler/src/beam_ssa_opt.erl b/lib/compiler/src/beam_ssa_opt.erl index 67c92d5ae2..0bb4a204a2 100644 --- a/lib/compiler/src/beam_ssa_opt.erl +++ b/lib/compiler/src/beam_ssa_opt.erl @@ -59,6 +59,7 @@ passes(Opts0) -> ?PASS(ssa_opt_bsm), ?PASS(ssa_opt_bsm_shortcut), ?PASS(ssa_opt_misc), + ?PASS(ssa_opt_tuple_size), ?PASS(ssa_opt_sw), ?PASS(ssa_opt_blockify), ?PASS(ssa_opt_sink), @@ -1088,6 +1089,126 @@ eval_or(Args) -> [_,_] -> error end. +%%% +%%% Optimize expressions such as "tuple_size(Var) =:= 2". +%%% +%%% Consider this code: +%%% +%%% 0: +%%% . +%%% . +%%% . +%%% Size = bif:tuple_size Var +%%% BoolVar1 = succeeded Size +%%% br BoolVar1, label 4, label 3 +%%% +%%% 4: +%%% BoolVar2 = bif:'=:=' Size, literal 2 +%%% br BoolVar2, label 6, label 3 +%%% +%%% 6: ... %% OK +%%% +%%% 3: ... %% Not a tuple of size 2 +%%% +%%% The BEAM code will look this: +%%% +%%% {bif,tuple_size,{f,3},[{x,0}],{x,0}}. +%%% {test,is_eq_exact,{f,3},[{x,0},{integer,2}]}. +%%% +%%% Better BEAM code will be produced if we transform the +%%% code like this: +%%% +%%% 0: +%%% . +%%% . +%%% . +%%% br label 10 +%%% +%%% 10: +%%% NewBoolVar = bif:is_tuple Var +%%% br NewBoolVar, label 11, label 3 +%%% +%%% 11: +%%% Size = bif:tuple_size Var +%%% br label 4 +%%% +%%% 4: +%%% BoolVar2 = bif:'=:=' Size, literal 2 +%%% br BoolVar2, label 6, label 3 +%%% +%%% (The key part of the transformation is the removal of +%%% the 'succeeded' instruction to signal to the code generator +%%% that the call to tuple_size/1 can't fail.) +%%% +%%% The BEAM code will look like: +%%% +%%% {test,is_tuple,{f,3},[{x,0}]}. +%%% {test_arity,{f,3},[{x,0},2]}. +%%% +%%% Those two instructions will be combined into a single +%%% is_tuple_of_arity instruction by the loader. +%%% + +ssa_opt_tuple_size(#st{ssa=Linear0,cnt=Count0}=St) -> + {Linear,Count} = opt_tup_size(Linear0, Count0, []), + St#st{ssa=Linear,cnt=Count}. + +opt_tup_size([{L,#b_blk{is=Is,last=Last}=Blk}|Bs], Count0, Acc0) -> + case {Is,Last} of + {[#b_set{op={bif,'=:='},dst=Bool,args=[#b_var{}=Tup,#b_literal{val=Arity}]}], + #b_br{bool=Bool}} when is_integer(Arity), Arity >= 0 -> + {Acc,Count} = opt_tup_size_1(Tup, L, Count0, Acc0), + opt_tup_size(Bs, Count, [{L,Blk}|Acc]); + {_,_} -> + opt_tup_size(Bs, Count0, [{L,Blk}|Acc0]) + end; +opt_tup_size([], Count, Acc) -> + {reverse(Acc),Count}. + +opt_tup_size_1(Size, EqL, Count0, [{L,Blk0}|Acc]) -> + case Blk0 of + #b_blk{is=Is0,last=#b_br{bool=Bool,succ=EqL,fail=Fail}} -> + case opt_tup_size_is(Is0, Bool, Size, []) of + none -> + {[{L,Blk0}|Acc],Count0}; + {PreIs,TupleSizeIs,Tuple} -> + opt_tup_size_2(PreIs, TupleSizeIs, L, EqL, + Tuple, Fail, Count0, Acc) + end; + #b_blk{} -> + {[{L,Blk0}|Acc],Count0} + end; +opt_tup_size_1(_, _, Count, Acc) -> + {Acc,Count}. + +opt_tup_size_2(PreIs, TupleSizeIs, PreL, EqL, Tuple, Fail, Count0, Acc) -> + IsTupleL = Count0, + TupleSizeL = Count0 + 1, + Bool = #b_var{name={'@ssa_bool',Count0+2}}, + Count = Count0 + 3, + + True = #b_literal{val=true}, + PreBr = #b_br{bool=True,succ=IsTupleL,fail=IsTupleL}, + PreBlk = #b_blk{is=PreIs,last=PreBr}, + + IsTupleIs = [#b_set{op={bif,is_tuple},dst=Bool,args=[Tuple]}], + IsTupleBr = #b_br{bool=Bool,succ=TupleSizeL,fail=Fail}, + IsTupleBlk = #b_blk{is=IsTupleIs,last=IsTupleBr}, + + TupleSizeBr = #b_br{bool=True,succ=EqL,fail=EqL}, + TupleSizeBlk = #b_blk{is=TupleSizeIs,last=TupleSizeBr}, + {[{TupleSizeL,TupleSizeBlk}, + {IsTupleL,IsTupleBlk}, + {PreL,PreBlk}|Acc],Count}. + +opt_tup_size_is([#b_set{op={bif,tuple_size},dst=Size,args=[Tuple]}=I, + #b_set{op=succeeded,dst=Bool,args=[Size]}], + Bool, Size, Acc) -> + {reverse(Acc),[I],Tuple}; +opt_tup_size_is([I|Is], Bool, Size, Acc) -> + opt_tup_size_is(Is, Bool, Size, [I|Acc]); +opt_tup_size_is([], _, _, _Acc) -> none. + %%% %%% Optimize #b_switch{} instructions. %%% diff --git a/lib/compiler/test/guard_SUITE.erl b/lib/compiler/test/guard_SUITE.erl index 73a8dc0fda..6ccc0c8fd4 100644 --- a/lib/compiler/test/guard_SUITE.erl +++ b/lib/compiler/test/guard_SUITE.erl @@ -1779,16 +1779,6 @@ t_tuple_size(Config) when is_list(Config) -> error = ludicrous_tuple_size({a,b,c}), error = ludicrous_tuple_size([a,b,c]), - %% Test the "unsafe case" - the register assigned the tuple size is - %% not killed. - DataDir = test_lib:get_data_dir(Config), - File = filename:join(DataDir, "guard_SUITE_tuple_size"), - {ok,Mod,Code} = compile:file(File, [from_asm,binary]), - code:load_binary(Mod, File, Code), - 14 = Mod:t({1,2,3,4}), - _ = code:delete(Mod), - _ = code:purge(Mod), - good_ip({1,2,3,4}), good_ip({1,2,3,4,5,6,7,8}), error = validate_ip({42,11}), diff --git a/lib/compiler/test/guard_SUITE_data/guard_SUITE_tuple_size.S b/lib/compiler/test/guard_SUITE_data/guard_SUITE_tuple_size.S deleted file mode 100644 index cffb792920..0000000000 --- a/lib/compiler/test/guard_SUITE_data/guard_SUITE_tuple_size.S +++ /dev/null @@ -1,30 +0,0 @@ -{module, guard_SUITE_tuple_size}. %% version = 0 - -{exports, [{t,1}]}. - -{attributes, []}. - -{labels, 5}. - - -{function, t, 1, 2}. - {label,1}. - {func_info,{atom,guard_SUITE_tuple_size},{atom,t},1}. - {label,2}. - {bif,tuple_size,{f,4},[{x,0}],{x,1}}. - {test,is_eq_exact,{f,4},[{x,1},{integer,4}]}. - {test,is_tuple,{f,3},[{x,0}]}. - {test,test_arity,{f,3},[{x,0},4]}. - {get_tuple_element,{x,0},0,{x,5}}. - {get_tuple_element,{x,0},1,{x,2}}. - {get_tuple_element,{x,0},2,{x,3}}. - {get_tuple_element,{x,0},3,{x,4}}. - {gc_bif,'+',{f,0},6,[{x,1},{x,2}],{x,0}}. - {gc_bif,'+',{f,0},6,[{x,0},{x,3}],{x,0}}. - {gc_bif,'+',{f,0},6,[{x,0},{x,4}],{x,0}}. - {gc_bif,'+',{f,0},6,[{x,0},{x,5}],{x,0}}. - return. - {label,3}. - {badmatch,{x,0}}. - {label,4}. - {jump,{f,1}}. -- cgit v1.2.3