From 8fa837e84dbeeb01d9dd4525719558b4909bd2b1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= Date: Wed, 11 May 2016 13:22:11 +0200 Subject: beam_utils: Simplify the return value for check_liveness/3 check_liveness/3 returns {unknown,State} if an instruction is not handled. All callers will handle 'unknown' the same way as 'used'. Therefore, we can simplify the code and improve the coverage if we return {used,State} instead of {unknown,State}. --- lib/compiler/src/beam_utils.erl | 45 +++++++++++++++++------------------------ 1 file changed, 18 insertions(+), 27 deletions(-) (limited to 'lib/compiler/src/beam_utils.erl') diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl index 9169a494f6..5c54680403 100644 --- a/lib/compiler/src/beam_utils.erl +++ b/lib/compiler/src/beam_utils.erl @@ -67,8 +67,7 @@ is_killed(R, Is, D) -> St = #live{bl=check_killed_block_fun(),lbl=D,res=gb_trees:empty()}, case check_liveness(R, Is, St) of {killed,_} -> true; - {used,_} -> false; - {unknown,_} -> false + {used,_} -> false end. %% is_killed_at(Reg, Lbl, State) -> true|false @@ -78,8 +77,7 @@ is_killed_at(R, Lbl, D) when is_integer(Lbl) -> St0 = #live{bl=check_killed_block_fun(),lbl=D,res=gb_trees:empty()}, case check_liveness_at(R, Lbl, St0) of {killed,_} -> true; - {used,_} -> false; - {unknown,_} -> false + {used,_} -> false end. %% is_not_used(Register, [Instruction], State) -> true|false @@ -93,8 +91,7 @@ is_not_used(R, Is, D) -> St = #live{bl=fun check_used_block/3,lbl=D,res=gb_trees:empty()}, case check_liveness(R, Is, St) of {killed,_} -> true; - {used,_} -> false; - {unknown,_} -> false + {used,_} -> false end. %% is_not_used(Register, [Instruction], State) -> true|false @@ -108,8 +105,7 @@ is_not_used_at(R, Lbl, D) -> St = #live{bl=fun check_used_block/3,lbl=D,res=gb_trees:empty()}, case check_liveness_at(R, Lbl, St) of {killed,_} -> true; - {used,_} -> false; - {unknown,_} -> false + {used,_} -> false end. %% index_labels(FunctionIs) -> State @@ -237,13 +233,11 @@ combine_heap_needs(H1, H2) when is_integer(H1), is_integer(H2) -> %%% -%% check_liveness(Reg, [Instruction], {State,BlockCheckFun}) -> -%% {killed | used | unknown,UpdateState} -%% Finds out how Reg is used in the instruction sequence. Returns one of: -%% killed - Reg is assigned a new value or killed by an allocation instruction -%% used - Reg is used (or possibly referenced by an allocation instruction) -%% unknown - not possible to determine (perhaps because of an instruction -%% that we don't recognize) +%% check_liveness(Reg, [Instruction], #live{}) -> +%% {killed | used, #live{}} +%% Find out whether Reg is used or killed in instruction sequence. +%% 'killed' means that Reg is assigned a new value or killed by an +%% allocation instruction. 'used' means that Reg is used in some way. check_liveness(R, [{set,_,_,_}=I|_], St) -> erlang:error(only_allowed_in_blocks, [R,I,St]); @@ -458,8 +452,9 @@ check_liveness(R, [{loop_rec,{f,_},{x,0}}|_], St) -> {x,_} -> {killed,St}; _ -> - %% y register. Rarely happens. Be very conversative. - {unknown,St} + %% y register. Rarely happens. Be very conversative and + %% assume it's used. + {used,St} end; check_liveness(R, [{loop_rec_end,{f,Fail}}|_], St) -> check_liveness_at(R, Fail, St); @@ -490,7 +485,8 @@ check_liveness(R, [{put_map,{f,_},_,Src,_D,Live,{list,_}}|_], St0) -> {x,_} -> {killed,St0}; {y,_} -> - {unknown,St0} + %% Conservatively mark it as used. + {used,St0} end; check_liveness(R, [{test_heap,N,Live}|Is], St) -> I = {block,[{set,[],[],{alloc,Live,{nozero,nostack,N,[]}}}]}, @@ -502,12 +498,8 @@ check_liveness(R, [{get_list,S,D1,D2}|Is], St) -> I = {block,[{set,[D1,D2],[S],get_list}]}, check_liveness(R, [I|Is], St); check_liveness(_R, Is, St) when is_list(Is) -> -%% case Is of -%% [I|_] -> -%% io:format("~p ~p\n", [_R,I]); -%% _ -> ok -%% end, - {unknown,St}. + %% Not implemented. Conservatively assume that the register is used. + {used,St}. check_liveness_everywhere(R, [{f,Lbl}|T], St0) -> case check_liveness_at(R, Lbl, St0) of @@ -526,7 +518,7 @@ check_liveness_at(R, Lbl, #live{lbl=Ll,res=ResMemorized}=St0) -> none -> {Res,St} = case gb_trees:lookup(Lbl, Ll) of {value,Is} -> check_liveness(R, Is, St0); - none -> {unknown,St0} + none -> {used,St0} end, {Res,St#live{res=gb_trees:insert(Lbl, Res, St#live.res)}} end. @@ -633,8 +625,7 @@ is_reg_used_at_1(_, 0, St) -> is_reg_used_at_1(R, Lbl, St0) -> case check_liveness_at(R, Lbl, St0) of {killed,St} -> {false,St}; - {used,St} -> {true,St}; - {unknown,St} -> {true,St} + {used,St} -> {true,St} end. index_labels_1([{label,Lbl}|Is0], Acc) -> -- cgit v1.2.3