%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1999-2010. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%
%% Purpose : Converts intermediate assembly code to final format.
-module(beam_flatten).
-export([module/2]).
-import(lists, [reverse/1,reverse/2]).
module({Mod,Exp,Attr,Fs,Lc}, _Opt) ->
{ok,{Mod,Exp,Attr,[function(F) || F <- Fs],Lc}}.
function({function,Name,Arity,CLabel,Is0}) ->
Is1 = block(Is0),
Is = opt(Is1),
{function,Name,Arity,CLabel,Is}.
block(Is) ->
block(Is, []).
block([{block,Is0}|Is1], Acc) -> block(Is1, norm_block(Is0, Acc));
block([I|Is], Acc) -> block(Is, [I|Acc]);
block([], Acc) -> reverse(Acc).
norm_block([{set,[],[],{alloc,R,Alloc}}|Is], Acc0) ->
case insert_alloc_in_bs_init(Acc0, Alloc) of
impossible ->
norm_block(Is, reverse(norm_allocate(Alloc, R), Acc0));
Acc ->
norm_block(Is, Acc)
end;
norm_block([I|Is], Acc) -> norm_block(Is, [norm(I)|Acc]);
norm_block([], Acc) -> Acc.
norm({set,[D],As,{bif,N,F}}) -> {bif,N,F,As,D};
norm({set,[D],As,{alloc,R,{gc_bif,N,F}}}) -> {gc_bif,N,F,R,As,D};
norm({set,[D],[S],move}) -> {move,S,D};
norm({set,[D],[S],fmove}) -> {fmove,S,D};
norm({set,[D],[S],fconv}) -> {fconv,S,D};
norm({set,[D],[S1,S2],put_list}) -> {put_list,S1,S2,D};
norm({set,[D],[],{put_tuple,A}}) -> {put_tuple,A,D};
norm({set,[],[S],put}) -> {put,S};
norm({set,[D],[S],{get_tuple_element,I}}) -> {get_tuple_element,S,I,D};
norm({set,[],[S,D],{set_tuple_element,I}}) -> {set_tuple_element,S,D,I};
norm({set,[D1,D2],[S],get_list}) -> {get_list,S,D1,D2};
norm({set,[],[],remove_message}) -> remove_message;
norm({set,[],[],fclearerror}) -> fclearerror;
norm({set,[],[],fcheckerror}) -> {fcheckerror,{f,0}}.
norm_allocate({_Zero,nostack,Nh,[]}, Regs) ->
[{test_heap,Nh,Regs}];
norm_allocate({zero,0,Nh,[]}, Regs) ->
norm_allocate({nozero,0,Nh,[]}, Regs);
norm_allocate({zero,Ns,0,[]}, Regs) ->
[{allocate_zero,Ns,Regs}];
norm_allocate({zero,Ns,Nh,[]}, Regs) ->
[{allocate_heap_zero,Ns,Nh,Regs}];
norm_allocate({nozero,Ns,0,Inits}, Regs) ->
[{allocate,Ns,Regs}|Inits];
norm_allocate({nozero,Ns,Nh,Inits}, Regs) ->
[{allocate_heap,Ns,Nh,Regs}|Inits].
%% insert_alloc_in_bs_init(ReverseInstructionStream, AllocationInfo) ->
%% impossible | ReverseInstructionStream'
%% A bs_init/6 instruction should not be followed by a test heap instruction.
%% Given the AllocationInfo from a test heap instruction, merge the
%% allocation amounts into the previous bs_init/6 instruction (if any).
%%
insert_alloc_in_bs_init([{bs_put,_,_,_}=I|Is], Alloc) ->
%% The instruction sequence ends with an bs_put/4 instruction.
%% We'll need to search backwards for the bs_init/6 instruction.
insert_alloc_1(Is, Alloc, [I]);
insert_alloc_in_bs_init(_, _) -> impossible.
insert_alloc_1([{bs_init=Op,Fail,Info0,Live,Ss,Dst}|Is],
{_,nostack,Ws2,[]}, Acc) when is_integer(Live) ->
%% The number of extra heap words is always in the second position
%% in the Info tuple.
Ws1 = element(2, Info0),
Al = beam_utils:combine_heap_needs(Ws1, Ws2),
Info = setelement(2, Info0, Al),
I = {Op,Fail,Info,Live,Ss,Dst},
reverse(Acc, [I|Is]);
insert_alloc_1([{bs_put,_,_,_}=I|Is], Alloc, Acc) ->
insert_alloc_1(Is, Alloc, [I|Acc]).
%% opt(Is0) -> Is
%% Simple peep-hole optimization to move a {move,Any,{x,0}} past
%% any kill up to the next call instruction. (To give the loader
%% an opportunity to combine the 'move' and the 'call' instructions.)
%%
opt(Is) ->
opt_1(Is, []).
opt_1([{move,_,{x,0}}=I|Is0], Acc0) ->
case move_past_kill(Is0, I, Acc0) of
impossible -> opt_1(Is0, [I|Acc0]);
{Is,Acc} -> opt_1(Is, Acc)
end;
opt_1([I|Is], Acc) ->
opt_1(Is, [I|Acc]);
opt_1([], Acc) -> reverse(Acc).
move_past_kill([{kill,Src}|_], {move,Src,_}, _) ->
impossible;
move_past_kill([{kill,_}=I|Is], Move, Acc) ->
move_past_kill(Is, Move, [I|Acc]);
move_past_kill([{trim,N,_}=I|Is], {move,Src,Dst}=Move, Acc) ->
case Src of
{y,Y} when Y < N-> impossible;
{y,Y} -> {Is,[{move,{y,Y-N},Dst},I|Acc]};
_ -> {Is,[Move,I|Acc]}
end;
move_past_kill(Is, Move, Acc) ->
{Is,[Move|Acc]}.
