diff options
| -rw-r--r-- | lib/compiler/src/beam_trim.erl | 57 |
1 files changed, 44 insertions, 13 deletions
diff --git a/lib/compiler/src/beam_trim.erl b/lib/compiler/src/beam_trim.erl index c11ecab927..f8efc38d53 100644 --- a/lib/compiler/src/beam_trim.erl +++ b/lib/compiler/src/beam_trim.erl @@ -21,7 +21,7 @@ -module(beam_trim). -export([module/2]). --import(lists, [member/2,reverse/1,reverse/2,splitwith/2,sort/1]). +-import(lists, [any/2,member/2,reverse/1,reverse/2,splitwith/2,sort/1]). -record(st, {safe :: cerl_sets:set(beam_asm:label()) %Safe labels. @@ -221,22 +221,53 @@ remap_block([{set,Ds0,Ss0,Info}|Is], Map, Acc) -> Ss = [Map(S) || S <- Ss0], remap_block(Is, Map, [{set,Ds,Ss,Info}|Acc]); remap_block([], _, Acc) -> reverse(Acc). - -safe_labels([{label,L},{line,_},{badmatch,{Tag,_}}|Is], Acc) when Tag =/= y -> - safe_labels(Is, [L|Acc]); -safe_labels([{label,L},{line,_},{case_end,{Tag,_}}|Is], Acc) when Tag =/= y -> - safe_labels(Is, [L|Acc]); -safe_labels([{label,L},{line,_},if_end|Is], Acc) -> - safe_labels(Is, [L|Acc]); -safe_labels([{label,L}, - {block,[{set,[{x,0}],[{Tag,_}],move}]}, - {line,_}, - {call_ext,1,{extfunc,erlang,error,1}}|Is], Acc) when Tag =/= y -> - safe_labels(Is, [L|Acc]); + +%% safe_labels([Instruction], Accumulator) -> gb_set() +%% Build a gb_set of safe labels. The code at a safe +%% label does not depend on the values in a specific +%% Y register, only that all Y registers are initialized +%% so that it safe to scan the stack when an exception +%% is generated. +%% +%% In other words, code at a safe label will continue +%% to work if Y registers have been renumbered and +%% the size of the stack frame has changed. + +safe_labels([{label,L}|Is], Acc) -> + case is_safe_label(Is) of + true -> safe_labels(Is, [L|Acc]); + false -> safe_labels(Is, Acc) + end; safe_labels([_|Is], Acc) -> safe_labels(Is, Acc); safe_labels([], Acc) -> cerl_sets:from_list(Acc). +is_safe_label([{line,_}|Is]) -> + is_safe_label(Is); +is_safe_label([{badmatch,{Tag,_}}|_]) -> + Tag =/= y; +is_safe_label([{case_end,{Tag,_}}|_]) -> + Tag =/= y; +is_safe_label([{try_case_end,{Tag,_}}|_]) -> + Tag =/= y; +is_safe_label([if_end|_]) -> + true; +is_safe_label([{block,Bl}|Is]) -> + is_safe_label_block(Bl) andalso is_safe_label(Is); +is_safe_label([{call_ext,_,{extfunc,M,F,A}}|_]) -> + erl_bifs:is_exit_bif(M, F, A); +is_safe_label(_) -> false. + +is_safe_label_block([{set,Ds,Ss,_}|Is]) -> + IsYreg = fun({y,_}) -> true; + (_) -> false + end, + %% This instruction is safe if the instruction + %% neither reads or writes Y registers. + not (any(IsYreg, Ss) orelse any(IsYreg, Ds)) andalso + is_safe_label_block(Is); +is_safe_label_block([]) -> true. + %% frame_layout([Instruction], [{kill,_}], St) -> %% [{kill,Reg} | {live,Reg} | {dead,Reg}] %% Figure out the layout of the stack frame. |