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-rw-r--r--lib/compiler/src/beam_z.erl30
1 files changed, 25 insertions, 5 deletions
diff --git a/lib/compiler/src/beam_z.erl b/lib/compiler/src/beam_z.erl
index 1c56b95a9e..6c3a6995d7 100644
--- a/lib/compiler/src/beam_z.erl
+++ b/lib/compiler/src/beam_z.erl
@@ -24,18 +24,20 @@
-export([module/2]).
--import(lists, [dropwhile/2]).
+-import(lists, [dropwhile/2,map/2]).
-spec module(beam_utils:module_code(), [compile:option()]) ->
{'ok',beam_asm:module_code()}.
-module({Mod,Exp,Attr,Fs0,Lc}, _Opt) ->
- Fs = [function(F) || F <- Fs0],
+module({Mod,Exp,Attr,Fs0,Lc}, Opts) ->
+ NoGetHdTl = proplists:get_bool(no_get_hd_tl, Opts),
+ Fs = [function(F, NoGetHdTl) || F <- Fs0],
{ok,{Mod,Exp,Attr,Fs,Lc}}.
-function({function,Name,Arity,CLabel,Is0}) ->
+function({function,Name,Arity,CLabel,Is0}, NoGetHdTl) ->
try
- Is = undo_renames(Is0),
+ Is1 = undo_renames(Is0),
+ Is = maybe_eliminate_get_hd_tl(Is1, NoGetHdTl),
{function,Name,Arity,CLabel,Is}
catch
Class:Error:Stack ->
@@ -65,6 +67,10 @@ undo_renames([{bif,raise,_,_,_}=I|Is0]) ->
(_) -> true
end, Is0),
[I|undo_renames(Is)];
+undo_renames([{get_hd,Src,Dst1},{get_tl,Src,Dst2}|Is]) ->
+ [{get_list,Src,Dst1,Dst2}|undo_renames(Is)];
+undo_renames([{get_tl,Src,Dst2},{get_hd,Src,Dst1}|Is]) ->
+ [{get_list,Src,Dst1,Dst2}|undo_renames(Is)];
undo_renames([I|Is]) ->
[undo_rename(I)|undo_renames(Is)];
undo_renames([]) -> [].
@@ -107,3 +113,17 @@ undo_rename({get_map_elements,Fail,Src,{list,List}}) ->
undo_rename({select,I,Reg,Fail,List}) ->
{I,Reg,Fail,{list,List}};
undo_rename(I) -> I.
+
+%%%
+%%% Eliminate get_hd/get_tl instructions if requested by
+%%% the no_get_hd_tl option.
+%%%
+
+maybe_eliminate_get_hd_tl(Is, true) ->
+ map(fun({get_hd,Cons,Hd}) ->
+ {get_list,Cons,Hd,{x,1022}};
+ ({get_tl,Cons,Tl}) ->
+ {get_list,Cons,{x,1022},Tl};
+ (I) -> I
+ end, Is);
+maybe_eliminate_get_hd_tl(Is, false) -> Is.