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-rw-r--r--lib/compiler/src/beam_utils.erl105
1 files changed, 60 insertions, 45 deletions
diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl
index 4dcce30583..814cfb8265 100644
--- a/lib/compiler/src/beam_utils.erl
+++ b/lib/compiler/src/beam_utils.erl
@@ -118,7 +118,7 @@ is_killed(R, Is, D) ->
St = #live{lbl=D,res=gb_trees:empty()},
case check_liveness(R, Is, St) of
{killed,_} -> true;
- {exit_not_used,_} -> true;
+ {exit_not_used,_} -> false;
{_,_} -> false
end.
@@ -131,7 +131,7 @@ is_killed_at(R, Lbl, D) when is_integer(Lbl) ->
St0 = #live{lbl=D,res=gb_trees:empty()},
case check_liveness_at(R, Lbl, St0) of
{killed,_} -> true;
- {exit_not_used,_} -> true;
+ {exit_not_used,_} -> false;
{_,_} -> false
end.
@@ -148,7 +148,7 @@ is_not_used(R, Is, D) ->
St = #live{lbl=D,res=gb_trees:empty()},
case check_liveness(R, Is, St) of
{used,_} -> false;
- {exit_not_used,_} -> false;
+ {exit_not_used,_} -> true;
{_,_} -> true
end.
@@ -440,8 +440,11 @@ check_liveness(R, [{bs_init,_,_,Live,Ss,Dst}|Is], St) ->
case member(R, Ss) of
true -> {used,St};
false ->
+ %% If the exception is taken, the stack may
+ %% be scanned. Therefore the register is not
+ %% guaranteed to be killed.
if
- R =:= Dst -> {killed,St};
+ R =:= Dst -> {not_used,St};
true -> not_used(check_liveness(R, Is, St))
end
end
@@ -735,8 +738,8 @@ check_liveness_block_1(R, Ss, Ds, Op, Is, St0) ->
end
end.
-check_liveness_block_2(R, {gc_bif,_Op,{f,Lbl}}, _Ss, St) ->
- check_liveness_block_3(R, Lbl, St);
+check_liveness_block_2(R, {gc_bif,Op,{f,Lbl}}, Ss, St) ->
+ check_liveness_block_3(R, Lbl, {Op,length(Ss)}, St);
check_liveness_block_2(R, {bif,Op,{f,Lbl}}, Ss, St) ->
Arity = length(Ss),
case erl_internal:comp_op(Op, Arity) orelse
@@ -744,16 +747,23 @@ check_liveness_block_2(R, {bif,Op,{f,Lbl}}, Ss, St) ->
true ->
{killed,St};
false ->
- check_liveness_block_3(R, Lbl, St)
+ check_liveness_block_3(R, Lbl, {Op,length(Ss)}, St)
end;
check_liveness_block_2(R, {put_map,_Op,{f,Lbl}}, _Ss, St) ->
- check_liveness_block_3(R, Lbl, St);
+ check_liveness_block_3(R, Lbl, {unsafe,0}, St);
check_liveness_block_2(_, _, _, St) ->
{killed,St}.
-check_liveness_block_3(_, 0, St) ->
+check_liveness_block_3({x,_}, 0, _FA, St) ->
{killed,St};
-check_liveness_block_3(R, Lbl, St0) ->
+check_liveness_block_3({y,_}, 0, {F,A}, St) ->
+ %% If the exception is thrown, the stack may be scanned,
+ %% thus implicitly using the y register.
+ case erl_bifs:is_safe(erlang, F, A) of
+ true -> {killed,St};
+ false -> {used,St}
+ end;
+check_liveness_block_3(R, Lbl, _FA, St0) ->
check_liveness_at(R, Lbl, St0).
index_labels_1([{label,Lbl}|Is0], Acc) ->
@@ -994,47 +1004,52 @@ live_opt([{recv_mark,_}=I|Is], Regs, D, Acc) ->
live_opt([], _, _, Acc) -> Acc.
-live_opt_block([{set,Ds,Ss,Op0}|Is], Regs0, D, Acc) ->
- Regs1 = x_live(Ss, x_dead(Ds, Regs0)),
- {Op, Regs} = live_opt_block_op(Op0, Regs1, D),
- I = {set, Ds, Ss, Op},
-
- case Ds of
- [{x,X}] ->
- case (not is_live(X, Regs0)) andalso Op =:= move of
- true ->
- live_opt_block(Is, Regs0, D, Acc);
- false ->
- live_opt_block(Is, Regs, D, [I|Acc])
- end;
- _ ->
- live_opt_block(Is, Regs, D, [I|Acc])
+live_opt_block([{set,[{x,X}]=Ds,Ss,move}=I|Is], Regs0, D, Acc) ->
+ Regs = x_live(Ss, x_dead(Ds, Regs0)),
+ case is_live(X, Regs0) of
+ true ->
+ live_opt_block(Is, Regs, D, [I|Acc]);
+ false ->
+ %% Useless move, will never be used.
+ live_opt_block(Is, Regs, D, Acc)
end;
-live_opt_block([{'%anno',_}|Is], Regs, D, Acc) ->
- live_opt_block(Is, Regs, D, Acc);
-live_opt_block([], Regs, _, Acc) -> {Acc,Regs}.
-
-live_opt_block_op({alloc,Live0,AllocOp}, Regs0, D) ->
- Regs =
- case AllocOp of
- {Kind, _N, Fail} when Kind =:= gc_bif; Kind =:= put_map ->
- live_join_label(Fail, D, Regs0);
- _ ->
- Regs0
- end,
+live_opt_block([{set,Ds,Ss,{alloc,Live0,AllocOp}}|Is], Regs0, D, Acc) ->
+ %% Calculate liveness from the point of view of the GC.
+ %% There will never be a GC if the instruction fails, so we should
+ %% ignore the failure branch.
+ GcRegs1 = x_dead(Ds, Regs0),
+ GcRegs = x_live(Ss, GcRegs1),
+ Live = live_regs(GcRegs),
%% The life-time analysis used by the code generator is sometimes too
%% conservative, so it may be possible to lower the number of live
%% registers based on the exact liveness information. The main benefit is
%% that more optimizations that depend on liveness information (such as the
- %% beam_bool and beam_dead passes) may be applied.
- Live = live_regs(Regs),
- true = Live =< Live0,
- {{alloc,Live,AllocOp}, live_call(Live)};
-live_opt_block_op({bif,_N,Fail} = Op, Regs, D) ->
- {Op, live_join_label(Fail, D, Regs)};
-live_opt_block_op(Op, Regs, _D) ->
- {Op, Regs}.
+ %% beam_dead pass) may be applied.
+ true = Live =< Live0, %Assertion.
+ I = {set,Ds,Ss,{alloc,Live,AllocOp}},
+
+ %% Calculate liveness from the point of view of the preceding instruction.
+ %% The liveness is the union of live registers in the GC and the live
+ %% registers at the failure label.
+ Regs1 = live_call(Live),
+ Regs = live_join_alloc(AllocOp, D, Regs1),
+ live_opt_block(Is, Regs, D, [I|Acc]);
+live_opt_block([{set,Ds,Ss,{bif,_,Fail}}=I|Is], Regs0, D, Acc) ->
+ Regs1 = x_dead(Ds, Regs0),
+ Regs2 = x_live(Ss, Regs1),
+ Regs = live_join_label(Fail, D, Regs2),
+ live_opt_block(Is, Regs, D, [I|Acc]);
+live_opt_block([{set,Ds,Ss,_}=I|Is], Regs0, D, Acc) ->
+ Regs = x_live(Ss, x_dead(Ds, Regs0)),
+ live_opt_block(Is, Regs, D, [I|Acc]);
+live_opt_block([{'%anno',_}|Is], Regs, D, Acc) ->
+ live_opt_block(Is, Regs, D, Acc);
+live_opt_block([], Regs, _, Acc) -> {Acc,Regs}.
+
+live_join_alloc({Kind,_Name,Fail}, D, Regs) when Kind =:= gc_bif; Kind =:= put_map ->
+ live_join_label(Fail, D, Regs);
+live_join_alloc(_, _, Regs) -> Regs.
live_join_labels([{f,L}|T], D, Regs0) when L =/= 0 ->
Regs = gb_trees:get(L, D) bor Regs0,
generated by cgit v1.2.3 (git 2.25.1) at 2024-08-28 16:23:39 +0000