diff options
Diffstat (limited to 'lib/compiler/src/beam_block.erl')
| -rw-r--r-- | lib/compiler/src/beam_block.erl | 48 |
1 files changed, 26 insertions, 22 deletions
diff --git a/lib/compiler/src/beam_block.erl b/lib/compiler/src/beam_block.erl index d4a4ddca8a..c45874597a 100644 --- a/lib/compiler/src/beam_block.erl +++ b/lib/compiler/src/beam_block.erl @@ -1,19 +1,19 @@ %% %% %CopyrightBegin% -%% -%% Copyright Ericsson AB 1999-2009. All Rights Reserved. -%% +%% +%% 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 : Partitions assembly instructions into basic blocks and @@ -36,12 +36,13 @@ function({function,Name,Arity,CLabel,Is0}, Lc0) -> %% Collect basic blocks and optimize them. Is2 = blockify(Is1), - Is3 = beam_utils:live_opt(Is2), - Is4 = opt_blocks(Is3), - Is5 = beam_utils:delete_live_annos(Is4), + Is3 = move_allocates(Is2), + Is4 = beam_utils:live_opt(Is3), + Is5 = opt_blocks(Is4), + Is6 = beam_utils:delete_live_annos(Is5), %% Optimize bit syntax. - {Is,Lc} = bsm_opt(Is5, Lc0), + {Is,Lc} = bsm_opt(Is6, Lc0), %% Done. {{function,Name,Arity,CLabel,Is},Lc} @@ -140,7 +141,6 @@ collect({move,S,D}) -> {set,[D],[S],move}; collect({put_list,S1,S2,D}) -> {set,[D],[S1,S2],put_list}; collect({put_tuple,A,D}) -> {set,[D],[],{put_tuple,A}}; collect({put,S}) -> {set,[],[S],put}; -collect({put_string,L,S,D}) -> {set,[D],[],{put_string,L,S}}; collect({get_tuple_element,S,I,D}) -> {set,[D],[S],{get_tuple_element,I}}; collect({set_tuple_element,S,D,I}) -> {set,[],[S,D],{set_tuple_element,I}}; collect({get_list,S,D1,D2}) -> {set,[D1,D2],[S],get_list}; @@ -157,11 +157,7 @@ opt_blocks([I|Is]) -> opt_blocks([]) -> []. opt_block(Is0) -> - %% We explicitly move any allocate instruction upwards before optimising - %% moves, to avoid any potential problems with the calculation of live - %% registers. - Is1 = move_allocates(Is0), - Is = find_fixpoint(fun opt/1, Is1), + Is = find_fixpoint(fun opt/1, Is0), opt_alloc(Is). find_fixpoint(OptFun, Is0) -> @@ -171,11 +167,21 @@ find_fixpoint(OptFun, Is0) -> end. %% move_allocates(Is0) -> Is -%% Move allocates upwards in the instruction stream, in the hope of -%% getting more possibilities for optimizing away moves later. - -move_allocates(Is) -> - move_allocates_1(reverse(Is), []). +%% Move allocate instructions upwards in the instruction stream, in the +%% hope of getting more possibilities for optimizing away moves later. +%% +%% NOTE: Moving allocation instructions is only safe because it is done +%% immediately after code generation so that we KNOW that if {x,X} is +%% initialized, all x registers with lower numbers are also initialized. +%% That assumption may not be true after other optimizations, such as +%% the beam_utils:live_opt/1 optimization. + +move_allocates([{block,Bl0}|Is]) -> + Bl = move_allocates_1(reverse(Bl0), []), + [{block,Bl}|move_allocates(Is)]; +move_allocates([I|Is]) -> + [I|move_allocates(Is)]; +move_allocates([]) -> []. move_allocates_1([{set,[],[],{alloc,_,_}=Alloc}|Is0], Acc0) -> {Is,Acc} = move_allocates_2(Alloc, Is0, Acc0), @@ -202,9 +208,7 @@ move_allocates_2(Alloc, [], Acc) -> alloc_may_pass({set,_,_,{alloc,_,_}}) -> false; alloc_may_pass({set,_,_,{set_tuple_element,_}}) -> false; alloc_may_pass({set,_,_,put_list}) -> false; -alloc_may_pass({set,_,_,{put_tuple,_}}) -> false; alloc_may_pass({set,_,_,put}) -> false; -alloc_may_pass({set,_,_,{put_string,_,_}}) -> false; alloc_may_pass({set,_,_,_}) -> true. combine_alloc({_,Ns,Nh1,Init}, {_,nostack,Nh2,[]}) -> |