From a10fb1edf471602be01bd5b4c1f019cc5534b9f5 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?John=20H=C3=B6gberg?= Date: Fri, 28 Jun 2019 09:14:43 +0200 Subject: compiler: Explain and rename ?BADARG_BLOCK --- lib/compiler/src/beam_kernel_to_ssa.erl | 3 ++- lib/compiler/src/beam_ssa.hrl | 12 ++++++++++-- lib/compiler/src/beam_ssa_bsm.erl | 6 +++--- lib/compiler/src/beam_ssa_codegen.erl | 18 +++++++++--------- lib/compiler/src/beam_ssa_opt.erl | 2 +- lib/compiler/src/beam_ssa_pre_codegen.erl | 16 ++++++++-------- lib/compiler/src/beam_ssa_share.erl | 4 ++-- lib/compiler/src/beam_ssa_type.erl | 6 +++--- 8 files changed, 38 insertions(+), 29 deletions(-) (limited to 'lib/compiler/src') diff --git a/lib/compiler/src/beam_kernel_to_ssa.erl b/lib/compiler/src/beam_kernel_to_ssa.erl index b2d824b648..474cb1a851 100644 --- a/lib/compiler/src/beam_kernel_to_ssa.erl +++ b/lib/compiler/src/beam_kernel_to_ssa.erl @@ -34,7 +34,7 @@ -type label() :: beam_ssa:label(). %% Main codegen structure. --record(cg, {lcount=1 :: label(), %Label counter +-record(cg, {lcount=1 :: label(), %Label counter bfail=1 :: label(), catch_label=none :: 'none' | label(), vars=#{} :: map(), %Defined variables. @@ -83,6 +83,7 @@ function(#k_fdef{anno=Anno0,func=Name,arity=Arity, cg_fun(Ke, St0) -> {UltimateFail,FailIs,St1} = make_failure(badarg, St0), + ?EXCEPTION_BLOCK = UltimateFail, %Assertion. St2 = St1#cg{bfail=UltimateFail,ultimate_failure=UltimateFail}, {B,St} = cg(Ke, St2), Asm = [{label,0}|B++FailIs], diff --git a/lib/compiler/src/beam_ssa.hrl b/lib/compiler/src/beam_ssa.hrl index fa76b08453..509a94135e 100644 --- a/lib/compiler/src/beam_ssa.hrl +++ b/lib/compiler/src/beam_ssa.hrl @@ -62,5 +62,13 @@ -record(b_local, {name :: beam_ssa:b_literal(), arity :: non_neg_integer()}). -%% If this block exists, it calls erlang:error(badarg). --define(BADARG_BLOCK, 1). +%% This is a psuedo-block used to express that certain instructions and BIFs +%% throw exceptions on failure. The code generator rewrites all branches to +%% this block to {f,0} which causes the instruction to throw an exception +%% instead of branching. +%% +%% Since this is not an ordinary block, it's illegal to merge it with other +%% blocks, and jumps are only valid when we know that an exception will be +%% thrown by the operation that branches here; the *block itself* does not +%% throw an exception. +-define(EXCEPTION_BLOCK, 1). diff --git a/lib/compiler/src/beam_ssa_bsm.erl b/lib/compiler/src/beam_ssa_bsm.erl index 927a06edbf..7a8dc127d7 100644 --- a/lib/compiler/src/beam_ssa_bsm.erl +++ b/lib/compiler/src/beam_ssa_bsm.erl @@ -684,9 +684,9 @@ aca_copy_successors(Lbl0, Blocks0, Counter0) -> Lbl = maps:get(Lbl0, BRs), {Lbl, Blocks, Counter}. -aca_cs_build_brs([?BADARG_BLOCK=Lbl | Path], Counter, Acc) -> - %% ?BADARG_BLOCK is a marker and not an actual block, so renaming it will - %% break exception handling. +aca_cs_build_brs([?EXCEPTION_BLOCK=Lbl | Path], Counter, Acc) -> + %% ?EXCEPTION_BLOCK is a marker and not an actual block, so renaming it + %% will break exception handling. aca_cs_build_brs(Path, Counter, Acc#{ Lbl => Lbl }); aca_cs_build_brs([Lbl | Path], Counter0, Acc) -> aca_cs_build_brs(Path, Counter0 + 1, Acc#{ Lbl => Counter0 }); diff --git a/lib/compiler/src/beam_ssa_codegen.erl b/lib/compiler/src/beam_ssa_codegen.erl index 7102f524d0..10c3419314 100644 --- a/lib/compiler/src/beam_ssa_codegen.erl +++ b/lib/compiler/src/beam_ssa_codegen.erl @@ -115,14 +115,14 @@ functions(Forms, AtomMod) -> function(#b_function{anno=Anno,bs=Blocks}, AtomMod, St0) -> #{func_info:={_,Name,Arity}} = Anno, try - assert_badarg_block(Blocks), %Assertion. + assert_exception_block(Blocks), %Assertion. Regs = maps:get(registers, Anno), St1 = St0#cg{labels=#{},used_labels=gb_sets:empty(), regs=Regs}, {Fi,St2} = new_label(St1), %FuncInfo label {Entry,St3} = local_func_label(Name, Arity, St2), {Ult,St4} = new_label(St3), %Ultimate failure - Labels = (St4#cg.labels)#{0=>Entry,?BADARG_BLOCK=>0}, + Labels = (St4#cg.labels)#{0=>Entry,?EXCEPTION_BLOCK=>0}, St5 = St4#cg{labels=Labels,used_labels=gb_sets:singleton(Entry), ultimate_fail=Ult}, {Body,St} = cg_fun(Blocks, St5#cg{fc_label=Fi}), @@ -138,10 +138,10 @@ function(#b_function{anno=Anno,bs=Blocks}, AtomMod, St0) -> erlang:raise(Class, Error, Stack) end. -assert_badarg_block(Blocks) -> - %% Assertion: ?BADARG_BLOCK must be the call erlang:error(badarg). +assert_exception_block(Blocks) -> + %% Assertion: ?EXCEPTION_BLOCK must be a call erlang:error(badarg). case Blocks of - #{?BADARG_BLOCK:=Blk} -> + #{?EXCEPTION_BLOCK:=Blk} -> #b_blk{is=[#b_set{op=call,dst=Ret, args=[#b_remote{mod=#b_literal{val=erlang}, name=#b_literal{val=error}}, @@ -149,7 +149,7 @@ assert_badarg_block(Blocks) -> last=#b_ret{arg=Ret}} = Blk, ok; #{} -> - %% ?BADARG_BLOCK has been removed because it was never used. + %% ?EXCEPTION_BLOCK has been removed because it was never used. ok end. @@ -631,7 +631,7 @@ liveness_get(S, LiveMap) -> end. liveness_successors(Terminator) -> - successors(Terminator) -- [?BADARG_BLOCK]. + successors(Terminator) -- [?EXCEPTION_BLOCK]. liveness_is([#cg_alloc{}=I0|Is], Regs, Live, Acc) -> I = I0#cg_alloc{live=num_live(Live, Regs)}, @@ -965,7 +965,7 @@ cg_block(Is0, Last, Next, St0) -> case Last of #cg_br{succ=Next,fail=Next} -> cg_block(Is0, none, St0); - #cg_br{succ=Same,fail=Same} when Same =:= ?BADARG_BLOCK -> + #cg_br{succ=Same,fail=Same} when Same =:= ?EXCEPTION_BLOCK -> %% An expression in this block *always* throws an exception, so we %% terminate it with an 'if_end' to make sure the validator knows %% that the following instructions won't actually be reached. @@ -1839,7 +1839,7 @@ linearize(Blocks) -> Linear = beam_ssa:linearize(Blocks), linearize_1(Linear, Blocks). -linearize_1([{?BADARG_BLOCK,_}|Ls], Blocks) -> +linearize_1([{?EXCEPTION_BLOCK,_}|Ls], Blocks) -> linearize_1(Ls, Blocks); linearize_1([{L,Block0}|Ls], Blocks) -> Block = translate_block(L, Block0, Blocks), diff --git a/lib/compiler/src/beam_ssa_opt.erl b/lib/compiler/src/beam_ssa_opt.erl index f77eeecc94..a9f8daaada 100644 --- a/lib/compiler/src/beam_ssa_opt.erl +++ b/lib/compiler/src/beam_ssa_opt.erl @@ -2274,7 +2274,7 @@ non_guards_1([{L,#b_blk{is=Is}}|Bs]) -> non_guards_1(Bs) end; non_guards_1([]) -> - [?BADARG_BLOCK]. + [?EXCEPTION_BLOCK]. rel2fam(S0) -> S1 = sofs:relation(S0), diff --git a/lib/compiler/src/beam_ssa_pre_codegen.erl b/lib/compiler/src/beam_ssa_pre_codegen.erl index ee55d55861..d3cedc3617 100644 --- a/lib/compiler/src/beam_ssa_pre_codegen.erl +++ b/lib/compiler/src/beam_ssa_pre_codegen.erl @@ -709,12 +709,12 @@ et_1([L | Ls], Trampolines, Blocks) -> case {Is, Last0} of {[#b_set{op=exception_trampoline}], #b_br{succ=Succ}} -> et_1(Ls, Trampolines#{ L => Succ }, maps:remove(L, Blocks)); - {_, #b_br{succ=Same,fail=Same}} when Same =:= ?BADARG_BLOCK -> - %% The "badarg block" is just a marker saying that we should raise + {_, #b_br{succ=Same,fail=Same}} when Same =:= ?EXCEPTION_BLOCK -> + %% The exception block is just a marker saying that we should raise %% an exception (= {f,0}) instead of jumping to a particular fail %% block. Since it's not a reachable block we can't allow %% unconditional jumps to it except through a trampoline. - error({illegal_jump_to_badarg_block, L}); + error({illegal_jump_to_exception_block, L}); {_, #b_br{succ=Succ0,fail=Fail0}} -> Succ = maps:get(Succ0, Trampolines, Succ0), Fail = maps:get(Fail0, Trampolines, Fail0), @@ -1338,10 +1338,10 @@ place_frame_here(L, Blocks, Doms, Frames) -> Descendants = beam_ssa:rpo([L], Blocks), PhiPredecessors = phi_predecessors(L, Blocks), MustDominate = ordsets:from_list(PhiPredecessors ++ Descendants), - Dominates = all(fun(?BADARG_BLOCK) -> + Dominates = all(fun(?EXCEPTION_BLOCK) -> %% This block defines no variables and calls %% erlang:error(badarg). It does not matter - %% whether L dominates ?BADARG_BLOCK or not; + %% whether L dominates ?EXCEPTION_BLOCK or not; %% it is still safe to put the frame in L. true; (Bl) -> @@ -1823,7 +1823,7 @@ collect_yregs([], Yregs) -> Yregs. copy_retval_2([L|Ls], Yregs, Copy0, Blocks0, Count0) -> #b_blk{is=Is0,last=Last} = Blk = map_get(L, Blocks0), RC = case {Last,Ls} of - {#b_br{succ=Succ,fail=?BADARG_BLOCK},[Succ|_]} -> + {#b_br{succ=Succ,fail=?EXCEPTION_BLOCK},[Succ|_]} -> true; {_,_} -> false @@ -2562,9 +2562,9 @@ reserve_xregs_is([], Res, Xs, _Used) -> {Res,Xs}. %% Pick up register hints from the successors of this blocks. -reserve_terminator(_L, _Is, #b_br{bool=#b_var{},succ=Succ,fail=?BADARG_BLOCK}, +reserve_terminator(_L, _Is, #b_br{bool=#b_var{},succ=Succ,fail=?EXCEPTION_BLOCK}, _Blocks, XsMap, _Res) -> - %% We know that no variables are used at ?BADARG_BLOCK, so + %% We know that no variables are used at ?EXCEPTION_BLOCK, so %% any register hints from the success blocks are safe to use. map_get(Succ, XsMap); reserve_terminator(L, Is, #b_br{bool=#b_var{},succ=Succ,fail=Fail}, diff --git a/lib/compiler/src/beam_ssa_share.erl b/lib/compiler/src/beam_ssa_share.erl index 426efa2cc9..85ab088d14 100644 --- a/lib/compiler/src/beam_ssa_share.erl +++ b/lib/compiler/src/beam_ssa_share.erl @@ -117,8 +117,8 @@ share_terminator(_Last, _Blocks) -> none. %% possible if the blocks are not equivalent, as that is the common %% case. -are_equivalent(_Succ, _, ?BADARG_BLOCK, _, _Blocks) -> - %% ?BADARG_BLOCK is special. Sharing could be incorrect. +are_equivalent(_Succ, _, ?EXCEPTION_BLOCK, _, _Blocks) -> + %% ?EXCEPTION_BLOCK is special. Sharing could be incorrect. false; are_equivalent(_Succ, #b_blk{is=Is1,last=#b_ret{arg=RetVal1}=Ret1}, _Fail, #b_blk{is=Is2,last=#b_ret{arg=RetVal2}=Ret2}, _Blocks) -> diff --git a/lib/compiler/src/beam_ssa_type.erl b/lib/compiler/src/beam_ssa_type.erl index f87acdb500..5e7b54a064 100644 --- a/lib/compiler/src/beam_ssa_type.erl +++ b/lib/compiler/src/beam_ssa_type.erl @@ -108,7 +108,7 @@ opt_continue_1(Linear0, Args, Id, Ts, FuncDb0) -> D = #d{ func_db=FuncDb0, func_id=Id, ds=Defs, - ls=#{0=>Ts,?BADARG_BLOCK=>#{}}, + ls=#{0=>Ts,?EXCEPTION_BLOCK=>#{}}, once=UsedOnce }, {Linear, FuncDb, NewRet} = opt(Linear0, D, []), @@ -892,8 +892,8 @@ sub_sw_list_1(Type, [{Val,_}|T], Ts) -> sub_sw_list_1(Type, [], _Ts) -> Type. -update_successor(?BADARG_BLOCK, _Ts, #d{}=D) -> - %% We KNOW that no variables are used in the ?BADARG_BLOCK, +update_successor(?EXCEPTION_BLOCK, _Ts, #d{}=D) -> + %% We KNOW that no variables are used in the ?EXCEPTION_BLOCK, %% so there is no need to update the type information. That %% can be a huge timesaver for huge functions. D; -- cgit v1.2.3