From 183b9456855306d2be2c46bbb1f9cc0e89ddd16c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Sat, 9 Dec 2017 05:10:42 +0100 Subject: v3_codegen: Eliminate unused function arguments 758712d6294 changed the need_heap/2 function so that it stopped using its second argument. Remove the second argument from need_heap(), and update all callers to similarly remove unused arguments. --- lib/compiler/src/v3_codegen.erl | 53 +++++++++++++++++++---------------------- 1 file changed, 25 insertions(+), 28 deletions(-) diff --git a/lib/compiler/src/v3_codegen.erl b/lib/compiler/src/v3_codegen.erl index 74d64e1456..4c2a1c6dea 100644 --- a/lib/compiler/src/v3_codegen.erl +++ b/lib/compiler/src/v3_codegen.erl @@ -447,7 +447,7 @@ cg_fun(Les, Hvs, Vdb, AtomMod, NameArity, Anno, St0) -> put_reg(V, Reg) end, [], Hvs), stk=[]}, 0, Vdb), - {B,_Aft,St} = cg_list(Les, 0, Vdb, Bef, + {B,_Aft,St} = cg_list(Les, Vdb, Bef, St3#cg{bfail=0, ultimate_failure=UltimateMatchFail, is_top_block=true}), @@ -499,19 +499,19 @@ cg(#cg_need_heap{h=H}, _Vdb, Bef, St) -> %% cg_list([Kexpr], FirstI, Vdb, StackReg, St) -> {[Ainstr],StackReg,St}. -cg_list(Kes, I, Vdb, Bef, St0) -> +cg_list(Kes, Vdb, Bef, St0) -> {Keis,{Aft,St1}} = flatmapfoldl(fun (Ke, {Inta,Sta}) -> {Keis,Intb,Stb} = cg(Ke, Vdb, Inta, Sta), {Keis,{Intb,Stb}} - end, {Bef,St0}, need_heap(Kes, I)), + end, {Bef,St0}, need_heap(Kes)), {Keis,Aft,St1}. %% need_heap([Lkexpr], I, St) -> [Lkexpr]. %% Insert need_heap instructions in Kexpr list. Try to be smart and %% collect them together as much as possible. -need_heap(Kes0, _I) -> +need_heap(Kes0) -> {Kes,H} = need_heap_0(reverse(Kes0), 0, []), %% Prepend need_heap if necessary. @@ -742,26 +742,24 @@ block_cg(Es, Le, _Vdb, Bef, St) -> block_cg(Es, Le, Bef, St). block_cg(Es, Le, Bef, #cg{is_top_block=false}=St) -> - cg_block(Es, Le#l.i, Le#l.vdb, Bef, St); + cg_block(Es, Le#l.vdb, Bef, St); block_cg(Es, Le, Bef, St0) -> - {Is0,Aft,St} = cg_block(Es, Le#l.i, Le#l.vdb, Bef, + {Is0,Aft,St} = cg_block(Es, Le#l.vdb, Bef, St0#cg{is_top_block=false,need_frame=false}), Is = top_level_block(Is0, Aft, max_reg(Bef#sr.reg), St), {Is,Aft,St#cg{is_top_block=true}}. -cg_block([], _I, _Vdb, Bef, St0) -> +cg_block([], _Vdb, Bef, St0) -> {[],Bef,St0}; -cg_block(Kes0, I, Vdb, Bef, St0) -> +cg_block(Kes0, Vdb, Bef, St0) -> {Kes2,Int1,St1} = case basic_block(Kes0) of {Kes1,LastI,Args,Rest} -> - Ke = hd(Kes1), - #l{i=Fb} = get_kanno(Ke), - cg_basic_block(Kes1, Fb, LastI, Args, Vdb, Bef, St0); + cg_basic_block(Kes1, LastI, Args, Vdb, Bef, St0); {Kes1,Rest} -> - cg_list(Kes1, I, Vdb, Bef, St0) + cg_list(Kes1, Vdb, Bef, St0) end, - {Kes3,Int2,St2} = cg_block(Rest, I, Vdb, Int1, St1), + {Kes3,Int2,St2} = cg_block(Rest, Vdb, Int1, St1), {Kes2 ++ Kes3,Int2,St2}. basic_block(Kes) -> basic_block(Kes, []). @@ -839,12 +837,12 @@ func_vars(_) -> []. %% save_carefully/4 during code generation to only save the variables %% that can be saved without growing the stack frame. -cg_basic_block(Kes, Fb, Lf, As, Vdb, Bef, St0) -> +cg_basic_block(Kes, Lf, As, Vdb, Bef, St0) -> Int0 = reserve_arg_regs(As, Bef), Int = extend_stack(Int0, Lf, Lf+1, Vdb), {Keis,{Aft,St1}} = flatmapfoldl(fun(Ke, St) -> cg_basic_block(Ke, St, Lf, Vdb) end, - {Int,St0}, need_heap(Kes, Fb)), + {Int,St0}, need_heap(Kes)), {Keis,Aft,St1}. cg_basic_block(#cg_need_heap{}=Ke, {Bef,St0}, _Lf, Vdb) -> @@ -1479,8 +1477,8 @@ guard_clause_cg(#k_guard_clause{anno=#l{vdb=Vdb},guard=G,body=B}, Fail, Bef, St0 %% the correct exit point. Primops and tests all go to the next %% instruction on success or jump to a failure label. -guard_cg(#k_protected{arg=Ts,ret=Rs,anno=#l{i=I,vdb=Pdb}}, Fail, _Vdb, Bef, St) -> - protected_cg(Ts, Rs, Fail, I, Pdb, Bef, St); +guard_cg(#k_protected{arg=Ts,ret=Rs,anno=#l{vdb=Pdb}}, Fail, _Vdb, Bef, St) -> + protected_cg(Ts, Rs, Fail, Pdb, Bef, St); guard_cg(#k_test{anno=#l{i=I},op=Test0,args=As,inverted=Inverted}, Fail, Vdb, Bef, St0) -> #k_remote{mod=#k_atom{val=erlang},name=#k_atom{val=Test}} = Test0, @@ -1501,13 +1499,13 @@ guard_cg(G, _Fail, Vdb, Bef, St) -> %% guard_cg_list([Kexpr], Fail, I, Vdb, StackReg, St) -> %% {[Ainstr],StackReg,St}. -guard_cg_list(Kes, Fail, I, Vdb, Bef, St0) -> +guard_cg_list(Kes, Fail, Vdb, Bef, St0) -> {Keis,{Aft,St1}} = flatmapfoldl(fun (Ke, {Inta,Sta}) -> {Keis,Intb,Stb} = guard_cg(Ke, Fail, Vdb, Inta, Sta), {Keis,{Intb,Stb}} - end, {Bef,St0}, need_heap(Kes, I)), + end, {Bef,St0}, need_heap(Kes)), {Keis,Aft,St1}. %% protected_cg([Kexpr], [Ret], Fail, I, Vdb, Bef, St) -> {[Ainstr],Aft,St}. @@ -1517,15 +1515,14 @@ guard_cg_list(Kes, Fail, I, Vdb, Bef, St0) -> %% return values then these must be set to 'false' on failure, %% control always passes to the next instruction. -protected_cg(Ts, [], Fail, I, Vdb, Bef, St0) -> +protected_cg(Ts, [], Fail, Vdb, Bef, St0) -> %% Protect these calls, revert when done. - {Tis,Aft,St1} = guard_cg_list(Ts, Fail, I, Vdb, Bef, - St0#cg{bfail=Fail}), + {Tis,Aft,St1} = guard_cg_list(Ts, Fail, Vdb, Bef, St0#cg{bfail=Fail}), {Tis,Aft,St1#cg{bfail=St0#cg.bfail}}; -protected_cg(Ts, Rs, _Fail, I, Vdb, Bef, St0) -> +protected_cg(Ts, Rs, _Fail, Vdb, Bef, St0) -> {Pfail,St1} = new_label(St0), {Psucc,St2} = new_label(St1), - {Tis,Aft,St3} = guard_cg_list(Ts, Pfail, I, Vdb, Bef, + {Tis,Aft,St3} = guard_cg_list(Ts, Pfail, Vdb, Bef, St2#cg{bfail=Pfail}), %%ok = io:fwrite("cg ~w: ~p~n", [?LINE,{Rs,I,Vdb,Aft}]), %% Set return values to false. @@ -1897,17 +1894,17 @@ cg_recv_wait(#k_atom{val=infinity}, #cg_block{anno=Le,es=Tes}, I, Bef, St0) -> %% But to keep the stack and register information up to date, %% we will generate the code for the 'after' body, and then discard it. Int1 = clear_dead(Bef, I, Le#l.vdb), - {_,Int2,St1} = cg_block(Tes, Le#l.i, Le#l.vdb, + {_,Int2,St1} = cg_block(Tes, Le#l.vdb, Int1#sr{reg=clear_regs(Int1#sr.reg)}, St0), {[{wait,{f,St1#cg.recv}}],Int2,St1}; cg_recv_wait(#k_int{val=0}, #cg_block{anno=Le,es=Tes}, _I, Bef, St0) -> - {Tis,Int,St1} = cg_block(Tes, Le#l.i, Le#l.vdb, Bef, St0), + {Tis,Int,St1} = cg_block(Tes, Le#l.vdb, Bef, St0), {[timeout|Tis],Int,St1}; cg_recv_wait(Te, #cg_block{anno=Le,es=Tes}, I, Bef, St0) -> Reg = cg_reg_arg(Te, Bef), %% Must have empty registers here! Bug if anything in registers. Int0 = clear_dead(Bef, I, Le#l.vdb), - {Tis,Int,St1} = cg_block(Tes, Le#l.i, Le#l.vdb, + {Tis,Int,St1} = cg_block(Tes, Le#l.vdb, Int0#sr{reg=clear_regs(Int0#sr.reg)}, St0), {[{wait_timeout,{f,St1#cg.recv},Reg},timeout] ++ Tis,Int,St1}. @@ -1968,7 +1965,7 @@ catch_cg(#cg_block{es=C}, #k_var{name=R}, Le, Vdb, Bef, St0) -> CatchTag = Le#l.i, Int1 = Bef#sr{stk=put_catch(CatchTag, Bef#sr.stk)}, CatchReg = fetch_stack({catch_tag,CatchTag}, Int1#sr.stk), - {Cis,Int2,St2} = cg_block(C, Le#l.i, Le#l.vdb, Int1, + {Cis,Int2,St2} = cg_block(C, Le#l.vdb, Int1, St1#cg{break=B,in_catch=true}), [] = Int2#sr.reg, %Assertion. Aft = Int2#sr{reg=[{0,R}],stk=drop_catch(CatchTag, Int2#sr.stk)}, -- cgit v1.2.3 From 47f61b16efe9f4304a522f54a4b630a6ffc08b06 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Tue, 12 Dec 2017 14:48:50 +0100 Subject: beam_util: Fix bug in is_not_used/3 01835845579e9 fixed some problems, but introduced a bug where is_not_used/3 would report that a register was not used when it in fact was. --- lib/compiler/src/beam_utils.erl | 9 +++++++-- lib/compiler/test/beam_utils_SUITE.erl | 18 ++++++++++++++++-- 2 files changed, 23 insertions(+), 4 deletions(-) diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl index 1b2a2827cb..bd1423cb40 100644 --- a/lib/compiler/src/beam_utils.erl +++ b/lib/compiler/src/beam_utils.erl @@ -318,6 +318,10 @@ check_liveness(R, [{block,Blk}|Is], St0) -> case check_liveness_block(R, Blk, St0) of {transparent,St1} -> check_liveness(R, Is, St1); + {alloc_used,St1} -> + %% Used by an allocating instruction, but value not referenced. + %% Must check the rest of the instructions. + not_used(check_liveness(R, Is, St1)); {Other,_}=Res when is_atom(Other) -> Res end; @@ -588,7 +592,7 @@ check_liveness_ret(R, R, St) -> {used,St}; check_liveness_ret(_, _, St) -> {killed,St}. %% check_liveness_block(Reg, [Instruction], State) -> -%% {killed | not_used | used | transparent,State'} +%% {killed | not_used | used | alloc_used | transparent,State'} %% Finds out how Reg is used in the instruction sequence inside a block. %% Returns one of: %% killed - Reg is assigned a new value or killed by an @@ -596,6 +600,7 @@ check_liveness_ret(_, _, St) -> {killed,St}. %% not_used - The value is not used, but the register is referenced %% e.g. by an allocation instruction %% transparent - Reg is neither used nor killed +%% alloc_used - Used only in an allocate instruction %% used - Reg is explicitly used by an instruction %% %% '%live' annotations are not allowed. @@ -609,7 +614,7 @@ check_liveness_block({x,X}=R, [{set,Ds,Ss,{alloc,Live,Op}}|Is], St0) -> true -> case check_liveness_block_1(R, Ss, Ds, Op, Is, St0) of {killed,St} -> {not_used,St}; - {transparent,St} -> {not_used,St}; + {transparent,St} -> {alloc_used,St}; {_,_}=Res -> Res end end; diff --git a/lib/compiler/test/beam_utils_SUITE.erl b/lib/compiler/test/beam_utils_SUITE.erl index 3a07f3923f..d516b0c3c7 100644 --- a/lib/compiler/test/beam_utils_SUITE.erl +++ b/lib/compiler/test/beam_utils_SUITE.erl @@ -25,7 +25,7 @@ is_not_killed/1,is_not_used_at/1, select/1,y_catch/1,otp_8949_b/1,liveopt/1,coverage/1, y_registers/1,user_predef/1,scan_f/1,cafu/1, - receive_label/1]). + receive_label/1,read_size_file_version/1]). -export([id/1]). suite() -> [{ct_hooks,[ts_install_cth]}]. @@ -50,7 +50,8 @@ groups() -> y_registers, user_predef, scan_f, - cafu + cafu, + read_size_file_version ]}]. init_per_suite(Config) -> @@ -445,5 +446,18 @@ do_receive_label(Rec) -> do_receive_label(Rec) end. +read_size_file_version(_Config) -> + ok = do_read_size_file_version({ok,<<42>>}), + {ok,7777} = do_read_size_file_version({ok,<<7777:32>>}), + ok. + +do_read_size_file_version(E) -> + case E of + {ok,<>} when Version =:= 42 -> + ok; + {ok,<>} -> + {ok,MaxFiles} + end. + %% The identity function. id(I) -> I. -- cgit v1.2.3 From beb15397b746cb20d00f6585e115ac2a112b18ad Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Wed, 13 Dec 2017 10:39:22 +0100 Subject: beam_utils: Improve precision for is_not_used/3 --- lib/compiler/src/beam_utils.erl | 13 ++++++--- lib/compiler/test/beam_utils_SUITE.erl | 48 ++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+), 3 deletions(-) diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl index bd1423cb40..6f20fc94de 100644 --- a/lib/compiler/src/beam_utils.erl +++ b/lib/compiler/src/beam_utils.erl @@ -380,9 +380,16 @@ check_liveness(R, [{bs_init,_,_,none,Ss,Dst}|Is], St) -> check_liveness(R, [{bs_init,_,_,Live,Ss,Dst}|Is], St) -> case R of {x,X} -> - case X < Live orelse member(R, Ss) of - true -> {used,St}; - false -> {killed,St} + case member(R, Ss) of + true -> + {used,St}; + false -> + if + X < Live -> + not_used(check_liveness(R, Is, St)); + true -> + {killed,St} + end end; {y,_} -> case member(R, Ss) of diff --git a/lib/compiler/test/beam_utils_SUITE.erl b/lib/compiler/test/beam_utils_SUITE.erl index d516b0c3c7..7686e69b63 100644 --- a/lib/compiler/test/beam_utils_SUITE.erl +++ b/lib/compiler/test/beam_utils_SUITE.erl @@ -122,6 +122,15 @@ bs_init(_Config) -> {'EXIT',{badarg,_}} = (catch do_bs_init_2([0.5])), {'EXIT',{badarg,_}} = (catch do_bs_init_2([-1])), {'EXIT',{badarg,_}} = (catch do_bs_init_2([1 bsl 32])), + + <<>> = do_bs_init_3({tag,0}, 0, 0), + <<0>> = do_bs_init_3({tag,0}, 2, 1), + + <<"_build/shared">> = do_bs_init_4([], false), + <<"abc/shared">> = do_bs_init_4(<<"abc">>, false), + <<"foo/foo">> = do_bs_init_4(<<"foo">>, true), + error = do_bs_init_4([], not_boolean), + ok. do_bs_init_1([?MODULE], Sz) -> @@ -139,6 +148,45 @@ do_bs_init_2(SigNos) -> erlang:error(badarg) >>. +do_bs_init_3({tag,Pos}, Offset, Len) -> + N0 = Offset - Pos, + N = if N0 > Len -> Len; + true -> N0 + end, + <<0:N/unit:8>>. + +do_bs_init_4(Arg1, Arg2) -> + Build = + case id(Arg1) of + X when X =:= [] orelse X =:= false -> <<"_build">>; + X -> X + end, + case id(Arg2) of + true -> + id(< + Rewrite; + Rewrite -> + id(Rewrite) + end/binary, + "/", + case id(<<"foo">>) of + Rewrite when is_binary(Rewrite) -> + Rewrite; + Rewrite -> + id(Rewrite) + end/binary>>); + false -> + id(< + Rewrite; + Rewrite -> + id(Rewrite) + end/binary, + "/shared">>); + Other -> + error + end. bs_save(_Config) -> {a,30,<<>>} = do_bs_save(<<1:1,30:5>>), -- cgit v1.2.3 From 46400bc3f3bf9ab5066723bd463989557bf2aabf Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Mon, 11 Dec 2017 21:57:26 +0100 Subject: beam_utils: Add anno_defs/1 Add beam_utils:anno_defs/1 which will add an annotation to the beginning of each block indicating which X registers that are defined. Having that information can improve some optimizations. --- lib/compiler/src/beam_utils.erl | 227 +++++++++++++++++++++++++++++++++++++++- 1 file changed, 225 insertions(+), 2 deletions(-) diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl index 6f20fc94de..1195a6b560 100644 --- a/lib/compiler/src/beam_utils.erl +++ b/lib/compiler/src/beam_utils.erl @@ -26,7 +26,9 @@ empty_label_index/0,index_label/3,index_labels/1,replace_labels/4, code_at/2,bif_to_test/3,is_pure_test/1, live_opt/1,delete_live_annos/1,combine_heap_needs/2, - split_even/1]). + anno_defs/1, + split_even/1 + ]). -export_type([code_index/0,module_code/0,instruction/0]). @@ -293,6 +295,23 @@ combine_heap_needs(Words, {alloc,Alloc}) when is_integer(Words) -> combine_heap_needs(H1, H2) when is_integer(H1), is_integer(H2) -> H1+H2. +%% anno_defs(Instructions) -> Instructions' +%% Add {'%def',RegisterBitmap} annotations to the beginning of +%% each block. Iff bit X is set in the the bitmap, it means +%% that {x,X} is defined when the block is entered. + +-spec anno_defs([instruction()]) -> [instruction()]. + +anno_defs(Is0) -> + {Bef,[Fi|Is1]} = + splitwith(fun({func_info,_,_,_}) -> false; + (_) -> true + end, Is0), + {func_info,_,_,Arity} = Fi, + Regs = init_def_regs(Arity), + Is = defs(Is1, Regs, #{}), + Bef ++ [Fi|Is]. + %% split_even/1 %% [1,2,3,4,5,6] -> {[1,3,5],[2,4,6]} @@ -300,7 +319,6 @@ combine_heap_needs(H1, H2) when is_integer(H1), is_integer(H2) -> split_even(Rs) -> split_even(Rs, [], []). - %%% %%% Local functions. %%% @@ -965,3 +983,208 @@ split_even([], Ss, Ds) -> {reverse(Ss),reverse(Ds)}; split_even([S,D|Rs], Ss, Ds) -> split_even(Rs, [S|Ss], [D|Ds]). + +%%% +%%% Add annotations for defined registers. +%%% +%%% This analysis is done by scanning the instructions in +%%% execution order. +%%% + +defs([{apply,_}=I|Is], _Regs, D) -> + [I|defs(Is, 1, D)]; +defs([{bif,_,{f,Fail},_Src,Dst}=I|Is], Regs0, D) -> + Regs = def_regs([Dst], Regs0), + [I|defs(Is, Regs, update_regs(Fail, Regs0, D))]; +defs([{block,Block0}|Is], Regs0, D0) -> + {Block,Regs,D} = defs_list(Block0, Regs0, D0), + [{block,[{'%def',Regs0}|Block]}|defs(Is, Regs, D)]; +defs([{bs_init,{f,L},_,_,_,Dst}=I|Is], Regs0, D) -> + Regs = def_regs([Dst], Regs0), + [I|defs(Is, Regs, update_regs(L, Regs, D))]; +defs([{bs_put,{f,L},_,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, update_regs(L, Regs, D))]; +defs([build_stacktrace=I|Is], _Regs, D) -> + [I|defs(Is, 1, D)]; +defs([{call,_,_}=I|Is], _Regs, D) -> + [I|defs(Is, 1, D)]; +defs([{call_ext,_,{extfunc,M,F,A}}=I|Is], _Regs, D) -> + case erl_bifs:is_exit_bif(M, F, A) of + false -> + [I|defs(Is, 1, D)]; + true -> + [I|defs_unreachable(Is, D)] + end; +defs([{call_ext,_,_}=I|Is], _Regs, D) -> + [I|defs(Is, 1, D)]; +defs([{call_fun,_}=I|Is], _Regs, D) -> + [I|defs(Is, 1, D)]; +defs([{'catch',_,{f,L}}=I|Is], Regs, D) -> + RegsAtLabel = init_def_regs(1), + [I|defs(Is, Regs, update_regs(L, RegsAtLabel, D))]; +defs([{catch_end,_}=I|Is], _Regs, D) -> + Regs = init_def_regs(1), + [I|defs(Is, Regs, D)]; +defs([{gc_bif,_,{f,Fail},Live,_Src,Dst}=I|Is], Regs0, D) -> + true = all_defined(Live, Regs0), %Assertion. + Regs = def_regs([Dst], init_def_regs(Live)), + [I|defs(Is, Regs, update_regs(Fail, Regs0, D))]; +defs([{get_map_elements,{f,L},_Src,{list,DstList}}=I|Is], Regs0, D) -> + {_,Ds} = beam_utils:split_even(DstList), + Regs = def_regs(Ds, Regs0), + [I|defs(Is, Regs, update_regs(L, Regs0, D))]; +defs([{get_tuple_element,_,_,Dst}=I|Is], Regs0, D) -> + Regs = def_regs([Dst], Regs0), + [I|defs(Is, Regs, D)]; +defs([{jump,{f,L}}=I|Is], Regs, D) -> + [I|defs_unreachable(Is, update_regs(L, Regs, D))]; +defs([{label,L}=I|Is], Regs0, D) -> + case D of + #{L:=Regs1} -> + Regs = Regs0 band Regs1, + [I|defs(Is, Regs, D)]; + #{} -> + [I|defs(Is, Regs0, D)] + end; +defs([{loop_rec,{f,L},{x,0}}=I|Is], _Regs, D0) -> + RegsAtLabel = init_def_regs(0), + D = update_regs(L, RegsAtLabel, D0), + [I|defs(Is, init_def_regs(1), D)]; +defs([{loop_rec_end,_}=I|Is], _Regs, D) -> + [I|defs(Is, 0, D)]; +defs([{make_fun2,_,_,_,_}=I|Is], _Regs, D) -> + [I|defs(Is, 1, D)]; +defs([{move,_,Dst}=I|Is], Regs0, D) -> + Regs = def_regs([Dst], Regs0), + [I|defs(Is, Regs, D)]; +defs([{put_map,{f,Fail},_,_,Dst,_,_}=I|Is], Regs0, D) -> + Regs = def_regs([Dst], Regs0), + [I|defs(Is, Regs, update_regs(Fail, Regs0, D))]; +defs([return=I|Is], _Regs, D) -> + [I|defs_unreachable(Is, D)]; +defs([{select,_,_Src,Fail,List}=I|Is], Regs, D0) -> + D = update_list([Fail|List], Regs, D0), + [I|defs_unreachable(Is, D)]; +defs([{test,_,{f,L},_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, update_regs(L, Regs, D))]; +defs([{test,_,{f,L},Live,_,Dst}=I|Is], Regs0, D) -> + true = all_defined(Live, Regs0), %Assertion. + Regs = def_regs([Dst], init_def_regs(Live)), + [I|defs(Is, Regs, update_regs(L, Regs0, D))]; +defs([{'try',_,{f,L}}=I|Is], Regs, D) -> + RegsAtLabel = init_def_regs(3), + [I|defs(Is, Regs, update_regs(L, RegsAtLabel, D))]; +defs([{try_case,_}=I|Is], _Regs, D) -> + [I|defs(Is, init_def_regs(3), D)]; +defs([{wait,_}=I|Is], _Regs, D) -> + [I|defs_unreachable(Is, D)]; +defs([{wait_timeout,_,_}=I|Is], _Regs, D) -> + [I|defs(Is, 0, D)]; + +%% Exceptions. +defs([{badmatch,_}=I|Is], _Regs, D) -> + [I|defs_unreachable(Is, D)]; +defs([{case_end,_}=I|Is], _Regs, D) -> + [I|defs_unreachable(Is, D)]; +defs([if_end=I|Is], _Regs, D) -> + [I|defs_unreachable(Is, D)]; +defs([{try_case_end,_}=I|Is], _Regs, D) -> + [I|defs_unreachable(Is, D)]; + +%% Neutral instructions +defs([{bs_context_to_binary,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([{bs_restore2,_,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([{bs_save2,_,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([{deallocate,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([{kill,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([{line,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([{recv_mark,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([{recv_set,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([timeout=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([{trim,_,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([{try_end,_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([{'%',_}=I|Is], Regs, D) -> + [I|defs(Is, Regs, D)]; +defs([], _, _) -> []. + +defs_unreachable([{label,L}=I|Is], D) -> + case D of + #{L:=Regs} -> + [I|defs(Is, Regs, D)]; + #{} -> + defs_unreachable(Is, D) + end; +defs_unreachable([_|Is], D) -> + defs_unreachable(Is, D); +defs_unreachable([], _D) -> []. + +defs_list(Is, Regs, D) -> + defs_list(Is, Regs, D, []). + +defs_list([{set,Ds,_,{alloc,Live,Info}}=I|Is], Regs0, D0, Acc) -> + true = all_defined(Live, Regs0), %Assertion. + D = case Info of + {gc_bif,_,{f,Fail}} -> + update_regs(Fail, Regs0, D0); + {put_map,_,{f,Fail}} -> + update_regs(Fail, Regs0, D0); + _ -> + D0 + end, + Regs = def_regs(Ds, init_def_regs(Live)), + defs_list(Is, Regs, D, [I|Acc]); +defs_list([{set,Ds,_,Info}=I|Is], Regs0, D0, Acc) -> + D = case Info of + {bif,_,{f,Fail}} -> + update_regs(Fail, Regs0, D0); + {try_catch,'catch',{f,Fail}} -> + update_regs(Fail, init_def_regs(1), D0); + {try_catch,'try',{f,Fail}} -> + update_regs(Fail, init_def_regs(3), D0); + _ -> + D0 + end, + Regs = def_regs(Ds, Regs0), + defs_list(Is, Regs, D, [I|Acc]); +defs_list([], Regs, D, Acc) -> + {reverse(Acc),Regs,D}. + +init_def_regs(Arity) -> + (1 bsl Arity) - 1. + +def_regs([{x,X}|T], Regs) -> + def_regs(T, Regs bor (1 bsl X)); +def_regs([_|T], Regs) -> + def_regs(T, Regs); +def_regs([], Regs) -> Regs. + +update_list([{f,L}|T], Regs, D0) -> + D = update_regs(L, Regs, D0), + update_list(T, Regs, D); +update_list([_|T], Regs, D) -> + update_list(T, Regs, D); +update_list([], _Regs, D) -> D. + +update_regs(L, Regs0, D) -> + case D of + #{L:=Regs1} -> + Regs = Regs0 band Regs1, + D#{L:=Regs}; + #{} -> + D#{L=>Regs0} + end. + +all_defined(Live, Regs) -> + All = (1 bsl Live) - 1, + Regs band All =:= All. -- cgit v1.2.3 From 6a80fec6fdb754b82a9c92804802797195431729 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Wed, 13 Dec 2017 10:10:44 +0100 Subject: beam_utils: Add usage/3 To avoid having to call both is_killed/3 and is_not_used/3, add usage/3 to answer both questions in one call. --- lib/compiler/src/beam_utils.erl | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl index 1195a6b560..dcdbaa0bab 100644 --- a/lib/compiler/src/beam_utils.erl +++ b/lib/compiler/src/beam_utils.erl @@ -22,7 +22,7 @@ -module(beam_utils). -export([is_killed_block/2,is_killed/3,is_killed_at/3, - is_not_used/3, + is_not_used/3,usage/3, empty_label_index/0,index_label/3,index_labels/1,replace_labels/4, code_at/2,bif_to_test/3,is_pure_test/1, live_opt/1,delete_live_annos/1,combine_heap_needs/2, @@ -62,6 +62,23 @@ {lbl :: code_index(), %Label to code index. res :: result_cache()}). %Result cache for each label. +%% usage(Register, [Instruction], State) -> killed|not_used|used. +%% Determine the usage of Register in the instruction sequence. +%% The return value is one of: +%% +%% killed - The register is not used in any way. +%% not_used - The register is referenced only by an allocating instruction +%% (the actual value does not matter). +%% used - The register is used (its value do matter). + +-spec usage(beam_asm:reg(), [instruction()], code_index()) -> + 'killed' | 'not_used' | 'used'. + +usage(R, Is, D) -> + St = #live{lbl=D,res=gb_trees:empty()}, + {Usage,_} = check_liveness(R, Is, St), + Usage. + %% is_killed_block(Register, [Instruction]) -> true|false %% Determine whether a register is killed by the instruction sequence inside -- cgit v1.2.3 From 3d90ab4a134e5898e6f35c71c3076656f5860677 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Mon, 11 Dec 2017 21:58:03 +0100 Subject: beam_block: Improve moving of allocations Use annotations added by beam_utils:anno_defs/1 to move more allocations upwards in the instruction stream. That in turn allows us to optimize away more 'move' instructions. --- lib/compiler/src/beam_block.erl | 89 +++++++++++++++++++++++++++-------------- 1 file changed, 60 insertions(+), 29 deletions(-) diff --git a/lib/compiler/src/beam_block.erl b/lib/compiler/src/beam_block.erl index c640af224d..f799147da1 100644 --- a/lib/compiler/src/beam_block.erl +++ b/lib/compiler/src/beam_block.erl @@ -37,13 +37,14 @@ function({function,Name,Arity,CLabel,Is0}) -> %% Collect basic blocks and optimize them. Is1 = blockify(Is0), Is2 = embed_lines(Is1), - Is3 = move_allocates(Is2), - Is4 = beam_utils:live_opt(Is3), - Is5 = opt_blocks(Is4), - Is6 = beam_utils:delete_live_annos(Is5), - - %% Done. - {function,Name,Arity,CLabel,Is6} + Is3 = beam_utils:anno_defs(Is2), + Is4 = move_allocates(Is3), + Is5 = beam_utils:live_opt(Is4), + Is6 = opt_blocks(Is5), + Is = beam_utils:delete_live_annos(Is6), + + %% Done. + {function,Name,Arity,CLabel,Is} catch Class:Error -> Stack = erlang:get_stacktrace(), @@ -173,7 +174,7 @@ find_fixpoint(OptFun, Is0) -> %% safe to assume that if x(N) is initialized, then all lower-numbered %% x registers are also initialized. %% -%% For example, in general it is not safe to transform the following +%% For example, we must be careful when transforming the following %% instructions: %% %% get_tuple_element x(0) Element => x(1) @@ -185,13 +186,9 @@ find_fixpoint(OptFun, Is0) -> %% get_tuple_element x(0) Element => x(1) %% %% The transformation is safe if and only if x(1) has been -%% initialized previously. Unfortunately, beam_reorder may have moved -%% a get_tuple_element instruction so that x(1) is not always -%% initialized when this code is reached. To find whether or not x(1) -%% is initialized, we would need to analyze all code preceding these -%% two instructions (across branches). Since we currently don't have -%% any practical mechanism for doing that, we will have to -%% conservatively assume that the transformation is unsafe. +%% initialized previously. We will use the annotations added by +%% beam_utils:anno_defs/1 to determine whether x(a) has been +%% initialized. move_allocates([{block,Bl0}|Is]) -> Bl = move_allocates_1(reverse(Bl0), []), @@ -200,15 +197,20 @@ move_allocates([I|Is]) -> [I|move_allocates(Is)]; move_allocates([]) -> []. +move_allocates_1([{'%def',_}|Is], Acc) -> + move_allocates_1(Is, Acc); move_allocates_1([I|Is], [{set,[],[],{alloc,Live0,Info}}|Acc]=Acc0) -> - case {alloc_may_pass(I),alloc_live_regs(I, Live0)} of - {false,_} -> - move_allocates_1(Is, [I|Acc0]); - {true,not_possible} -> - move_allocates_1(Is, [I|Acc0]); - {true,Live} when is_integer(Live) -> - A = {set,[],[],{alloc,Live,Info}}, - move_allocates_1(Is, [A,I|Acc]) + case alloc_may_pass(I) of + false -> + move_allocates_1(Is, [I|Acc0]); + true -> + case alloc_live_regs(I, Is, Live0) of + not_possible -> + move_allocates_1(Is, [I|Acc0]); + Live when is_integer(Live) -> + A = {set,[],[],{alloc,Live,Info}}, + move_allocates_1(Is, [A,I|Acc]) + end end; move_allocates_1([I|Is], Acc) -> move_allocates_1(Is, [I|Acc]); @@ -472,16 +474,34 @@ count_ones(Bits, Acc) -> %% Calculate the new number of live registers when we move an allocate %% instruction upwards, passing a 'set' instruction. -alloc_live_regs({set,Ds,Ss,_}, Regs0) -> +alloc_live_regs({set,Ds,Ss,_}, Is, Regs0) -> Rset = x_live(Ss, x_dead(Ds, (1 bsl Regs0)-1)), - live_regs(0, Rset). + Live = live_regs(0, Rset), + case ensure_contiguous(Rset, Live) of + not_possible -> + %% Liveness information (looking forward in the + %% instruction stream) can't prove that moving this + %% allocation instruction is safe. Now use the annotation + %% of defined registers at the beginning of the current + %% block to see whether moving would be safe. + Def0 = defined_regs(Is, 0), + Def = Def0 band ((1 bsl Live) - 1), + ensure_contiguous(Rset bor Def, Live); + Live -> + %% Safe based on liveness information. + Live + end. live_regs(N, 0) -> N; -live_regs(N, Regs) when Regs band 1 =:= 1 -> - live_regs(N+1, Regs bsr 1); -live_regs(_, _) -> - not_possible. +live_regs(N, Regs) -> + live_regs(N+1, Regs bsr 1). + +ensure_contiguous(Regs, Live) -> + case (1 bsl Live) - 1 of + Regs -> Live; + _ -> not_possible + end. x_dead([{x,N}|Rs], Regs) -> x_dead(Rs, Regs band (bnot (1 bsl N))); x_dead([_|Rs], Regs) -> x_dead(Rs, Regs); @@ -490,3 +510,14 @@ x_dead([], Regs) -> Regs. x_live([{x,N}|Rs], Regs) -> x_live(Rs, Regs bor (1 bsl N)); x_live([_|Rs], Regs) -> x_live(Rs, Regs); x_live([], Regs) -> Regs. + +%% defined_regs(ReversedInstructions) -> RegBitmap. +%% Given a reversed instruction stream, determine the +%% the registers that are defined. + +defined_regs([{'%def',Def}|_], Regs) -> + Def bor Regs; +defined_regs([{set,Ds,_,{alloc,Live,_}}|_], Regs) -> + x_live(Ds, Regs bor ((1 bsl Live) - 1)); +defined_regs([{set,Ds,_,_}|Is], Regs) -> + defined_regs(Is, x_live(Ds, Regs)). -- cgit v1.2.3 From cd708cf3cd5ea4402ea8cec2d9570506b7bf8e92 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Mon, 11 Dec 2017 21:59:39 +0100 Subject: beam_record: Try harder to avoid fetching the tag element When rewriting tuple matching of the first element of a tuple to an is_tagged_tuple instruction, the get_tuple_element instruction that fetches the tag will be left unless the register that is fetched is subsequently killed. We can do better than that. If the register is referenced in an allocating instruction, but its value is never actually used, we can do one of two things: if the value is known to be defined earlier (using annotations added by beam_utils:anno_defs/1) the instruction can be removed altogether; if not, it can be replaced with a 'move nil TagRegister' instruction. --- lib/compiler/src/beam_record.erl | 126 +++++++++++++++++++++++---------------- 1 file changed, 76 insertions(+), 50 deletions(-) diff --git a/lib/compiler/src/beam_record.erl b/lib/compiler/src/beam_record.erl index 419089b1bc..cfad773fa4 100644 --- a/lib/compiler/src/beam_record.erl +++ b/lib/compiler/src/beam_record.erl @@ -15,19 +15,12 @@ %% %% %CopyrightEnd% %% -%% File: beam_record.erl -%% Author: Björn-Egil Dahlberg -%% Created: 2014-09-03 -%% - --module(beam_record). --export([module/2]). %% Rewrite the instruction stream on tagged tuple tests. -%% Tagged tuples means a tuple of any arity with an atom as its first element. -%% Typically records, ok-tuples and error-tuples. -%% -%% from: +%% Tagged tuples means a tuple of any arity with an atom as its +%% first element, such as records and error tuples. +%% +%% From: %% ... %% {test,is_tuple,Fail,[Src]}. %% {test,test_arity,Fail,[Src,Sz]}. @@ -36,13 +29,16 @@ %% ... %% {test,is_eq_exact,Fail,[Dst,Atom]}. %% ... -%% to: +%% To: %% ... %% {test,is_tagged_tuple,Fail,[Src,Sz,Atom]}. %% ... +%% +-module(beam_record). +-export([module/2]). --import(lists, [reverse/1]). +-import(lists, [reverse/1,reverse/2]). -spec module(beam_utils:module_code(), [compile:option()]) -> {'ok',beam_utils:module_code()}. @@ -51,10 +47,12 @@ module({Mod,Exp,Attr,Fs0,Lc}, _Opt) -> Fs = [function(F) || F <- Fs0], {ok,{Mod,Exp,Attr,Fs,Lc}}. -function({function,Name,Arity,CLabel,Is}) -> +function({function,Name,Arity,CLabel,Is0}) -> try - Idx = beam_utils:index_labels(Is), - {function,Name,Arity,CLabel,rewrite(Is,Idx)} + Is1 = beam_utils:anno_defs(Is0), + Idx = beam_utils:index_labels(Is1), + Is = rewrite(reverse(Is1), Idx), + {function,Name,Arity,CLabel,Is} catch Class:Error -> Stack = erlang:get_stacktrace(), @@ -62,45 +60,73 @@ function({function,Name,Arity,CLabel,Is}) -> erlang:raise(Class, Error, Stack) end. -rewrite(Is,Idx) -> - rewrite(Is,Idx,[]). +rewrite(Is, Idx) -> + rewrite(Is, Idx, 0, []). -rewrite([{test,is_tuple,Fail,[Src]}=I1, - {test,test_arity,Fail,[Src,N]}=I2|Is],Idx,Acc) -> - case is_tagged_tuple(Is,Fail,Src,Idx) of +rewrite([{test,test_arity,Fail,[Src,N]}=TA, + {test,is_tuple,Fail,[Src]}=TT|Is], Idx, Def, Acc0) -> + case is_tagged_tuple(Acc0, Def, Fail, Src, Idx) of no -> - rewrite(Is,Idx,[I2,I1|Acc]); - {Atom,[{block,[]}|Is1]} -> - rewrite(Is1,Idx,[{test,is_tagged_tuple,Fail,[Src,N,Atom]}|Acc]); - {Atom,Is1} -> - rewrite(Is1,Idx,[{test,is_tagged_tuple,Fail,[Src,N,Atom]}|Acc]) + rewrite(Is, Idx, 0, [TT,TA|Acc0]); + {yes,Atom,Acc} -> + I = {test,is_tagged_tuple,Fail,[Src,N,Atom]}, + rewrite(Is, Idx, Def, [I|Acc]) end; -rewrite([I|Is],Idx,Acc) -> - rewrite(Is,Idx,[I|Acc]); -rewrite([],_,Acc) -> reverse(Acc). - -is_tagged_tuple([{block,[{set,[Dst],[Src],{get_tuple_element,0}}=B|Bs]}, - {test,is_eq_exact,Fail,[Dst,{atom,_}=Atom]}|Is],Fail,Src,Idx) -> +rewrite([{block,[{'%def',Def}|Bl]}|Is], Idx, _Def, Acc) -> + rewrite(Is, Idx, Def, [{block,Bl}|Acc]); +rewrite([{label,L}=I|Is], Idx0, Def, Acc) -> + Idx = beam_utils:index_label(L, Acc, Idx0), + rewrite(Is, Idx, Def, [I|Acc]); +rewrite([I|Is], Idx, Def, Acc) -> + rewrite(Is, Idx, Def, [I|Acc]); +rewrite([], _, _, Acc) -> Acc. - %% if Dst is killed in the instruction stream and at fail label, - %% we can safely remove get_tuple_element. - %% - %% if Dst is not killed in the stream, we cannot remove get_tuple_element - %% since it is referenced. - - case is_killed(Dst,Is,Fail,Idx) of - true -> {Atom,[{block,Bs}|Is]}; - false -> {Atom,[{block,[B|Bs]}|Is]} +is_tagged_tuple([{block,Bl}, + {test,is_eq_exact,Fail,[Dst,{atom,_}=Atom]}|Is], + Def, Fail, Src, Idx) -> + case is_tagged_tuple_1(Bl, Is, Fail, Src, Dst, Idx, Def, []) of + no -> + no; + {yes,[]} -> + {yes,Atom,Is}; + {yes,[_|_]=Block} -> + {yes,Atom,[{block,Block}|Is]} end; -is_tagged_tuple([{block,[{set,_,_,_}=B|Bs]}, - {test,is_eq_exact,_,_}=I|Is],Fail,Src,Idx) -> - case is_tagged_tuple([{block,Bs},I|Is],Fail,Src,Idx) of - {Atom,[{block,Bsr}|Isr]} -> {Atom,[{block,[B|Bsr]}|Isr]}; - no -> no +is_tagged_tuple(_, _, _, _, _) -> + no. + +is_tagged_tuple_1([{set,[Dst],[Src],{get_tuple_element,0}}=I|Bl], + Is, Fail, Src, Dst, Idx, Def, Acc) -> + %% Check usage of Dst to find out whether the get_tuple_element + %% is needed. + case usage(Dst, Is, Fail, Idx) of + killed -> + %% Safe to remove the get_tuple_element instruction. + {yes,reverse(Acc, Bl)}; + used -> + %% Actively used. Must keep instruction. + {yes,reverse(Acc, [I|Bl])}; + not_used -> + %% Not actually used (but must be initialized). + case is_defined(Dst, Def) of + false -> + %% Dst must be initialized, but the + %% actual value does not matter. + Kill = {set,[Dst],[nil],move}, + {yes,reverse(Acc, [Kill|Bl])}; + true -> + %% The register is previously initialized. + %% We can remove the instruction. + {yes,reverse(Acc, Bl)} + end end; -is_tagged_tuple(_Is,_Fail,_Src,_Idx) -> +is_tagged_tuple_1([I|Bl], Is, Fail, Src, Dst, Idx, Def, Acc) -> + is_tagged_tuple_1(Bl, Is, Fail, Src, Dst, Idx, Def, [I|Acc]); +is_tagged_tuple_1(_, _, _, _, _, _, _, _) -> no. -is_killed(Dst,Is,{_,Lbl},Idx) -> - beam_utils:is_killed(Dst,Is,Idx) andalso - beam_utils:is_killed_at(Dst,Lbl,Idx). +usage(Dst, Is, Fail, Idx) -> + beam_utils:usage(Dst, [{test,is_number,Fail,[nil]}|Is], Idx). + +is_defined({x,X}, Def) -> + (Def bsr X) band 1 =:= 1. -- cgit v1.2.3 From b89044a800c4950072b14d5e372cb2db55f1966c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Mon, 11 Dec 2017 22:00:24 +0100 Subject: v3_codegen: Delay creation of stack frames v3_codegen currently wraps a stack frame around each clause in a function (unless the clause is simple without any 'case' or other complex constructions). Consider this function: f({a,X}) -> A = abs(X), case A of 0 -> {result,"0"}; _ -> {result,integer_to_list(A)} end; f(_) -> error. The first clause needs a stack frame because there is a function call to integer_to_list/1 not in the tail position. v3_codegen currently wraps the entire first clause in stack frame. We can delay the creation of the stack frame, and create a stack frame in each arm of the 'case' (if needed): f({a,X}) -> A = abs(X), case A of 0 -> %% Don't create a stack frame here. {result,"0"}; _ -> %% Create a stack frame here. {result,integer_to_list(A)} end; f(_) -> error. There are pros and cons of this approach. The cons are that the code size may increase if there are many 'case' clauses and each needs its own stack frame. The allocation instructions may also interfere with other optimizations, but the new optimizations introduced in previous commits will mitigate most of those issues. The pros are the following: * For some clauses in a 'case', there is no need to create any stack frame at all. * Often when moving an allocation instruction into a 'case' clause, the slightly cheaper 'allocate' instruction can be used instead of 'allocate_zero'. There is also the possibility that the allocate instruction can be be combined with a 'test_heap' instruction. * Each stack frame for each arm of the 'case' will have exactly as many slots as needed. --- lib/compiler/src/v3_codegen.erl | 41 ++++++++++++++++++++++++++++++++++++----- 1 file changed, 36 insertions(+), 5 deletions(-) diff --git a/lib/compiler/src/v3_codegen.erl b/lib/compiler/src/v3_codegen.erl index 4c2a1c6dea..2138321a39 100644 --- a/lib/compiler/src/v3_codegen.erl +++ b/lib/compiler/src/v3_codegen.erl @@ -743,11 +743,42 @@ block_cg(Es, Le, _Vdb, Bef, St) -> block_cg(Es, Le, Bef, #cg{is_top_block=false}=St) -> cg_block(Es, Le#l.vdb, Bef, St); -block_cg(Es, Le, Bef, St0) -> - {Is0,Aft,St} = cg_block(Es, Le#l.vdb, Bef, - St0#cg{is_top_block=false,need_frame=false}), - Is = top_level_block(Is0, Aft, max_reg(Bef#sr.reg), St), - {Is,Aft,St#cg{is_top_block=true}}. +block_cg(Es, Le, Bef, #cg{is_top_block=true}=St0) -> + %% No stack frame has been established yet. Do we need one? + case need_stackframe(Es) of + true -> + %% We need a stack frame. Generate the code and add the + %% code for creating and deallocating the stack frame. + {Is0,Aft,St} = cg_block(Es, Le#l.vdb, Bef, + St0#cg{is_top_block=false,need_frame=false}), + Is = top_level_block(Is0, Aft, max_reg(Bef#sr.reg), St), + {Is,Aft,St#cg{is_top_block=true}}; + false -> + %% This sequence of instructions ending in a #k_match{} (a + %% 'case' or 'if') in the Erlang code does not need a + %% stack frame yet. Delay the creation (if a stack frame + %% is needed at all, it will be created inside the + %% #k_match{}). + cg_list(Es, Le#l.vdb, Bef, St0) + end. + +%% need_stackframe([Kexpr]) -> true|false. +%% Does this list of instructions need a stack frame? +%% +%% A sequence of instructions that don't clobber the X registers +%% followed by a single #k_match{} doesn't need a stack frame. + +need_stackframe([H|T]) -> + case H of + #k_bif{op=#k_internal{}} -> true; + #k_put{arg=#k_binary{}} -> true; + #k_bif{} -> need_stackframe(T); + #k_put{} -> need_stackframe(T); + #k_guard_match{} -> need_stackframe(T); + #k_match{} when T =:= [] -> false; + _ -> true + end; +need_stackframe([]) -> false. cg_block([], _Vdb, Bef, St0) -> {[],Bef,St0}; -- cgit v1.2.3