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authorBjörn Gustavsson <[email protected]>2016-05-11 13:22:11 +0200
committerBjörn Gustavsson <[email protected]>2016-05-13 10:52:25 +0200
commit8fa837e84dbeeb01d9dd4525719558b4909bd2b1 (patch)
treefc86d0f28dee600e4c82c96e11aa8ba41a982f9b /lib/compiler
parent3701f7078627d6a4daab3049f09036c4e410d5fb (diff)
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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}.
Diffstat (limited to 'lib/compiler')
-rw-r--r--lib/compiler/src/beam_utils.erl45
1 files changed, 18 insertions, 27 deletions
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) ->