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authorBjörn Gustavsson <[email protected]>2016-10-07 14:19:29 +0200
committerBjörn Gustavsson <[email protected]>2016-10-07 14:19:29 +0200
commit16f2daa48333cced93f4f31d9a57e5d2e3a8f9e8 (patch)
tree4ddef6b09c76b957fdd83a44e6844379f0cb64dd
parent1f0ce3e83982c80a84e31ab16a89dd65b45157f8 (diff)
parentc8fb8c177b9f74ddea36d9c002df4f9c1bf4fb27 (diff)
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Merge branch 'maint'
* maint: beam_bsm: Eliminate unsafe optimization
-rw-r--r--lib/compiler/src/beam_bsm.erl31
-rw-r--r--lib/compiler/test/bs_match_SUITE.erl23
2 files changed, 44 insertions, 10 deletions
diff --git a/lib/compiler/src/beam_bsm.erl b/lib/compiler/src/beam_bsm.erl
index 286307a4be..ae1b34ba49 100644
--- a/lib/compiler/src/beam_bsm.erl
+++ b/lib/compiler/src/beam_bsm.erl
@@ -205,8 +205,15 @@ btb_reaches_match_1(Is, Regs, D) ->
btb_reaches_match_2([{block,Bl}|Is], Regs0, D) ->
Regs = btb_reaches_match_block(Bl, Regs0),
btb_reaches_match_1(Is, Regs, D);
-btb_reaches_match_2([{call,Arity,{f,Lbl}}|Is], Regs, D) ->
- btb_call(Arity, Lbl, Regs, Is, D);
+btb_reaches_match_2([{call,Arity,{f,Lbl}}|Is], Regs0, D) ->
+ case is_tail_call(Is) of
+ true ->
+ Regs1 = btb_kill_not_live(Arity, Regs0),
+ Regs = btb_kill_yregs(Regs1),
+ btb_tail_call(Lbl, Regs, D);
+ false ->
+ btb_call(Arity, Lbl, Regs0, Is, D)
+ end;
btb_reaches_match_2([{apply,Arity}|Is], Regs, D) ->
btb_call(Arity+2, apply, Regs, Is, D);
btb_reaches_match_2([{call_fun,Live}=I|Is], Regs, D) ->
@@ -360,6 +367,10 @@ btb_reaches_match_2([{line,_}|Is], Regs, D) ->
btb_reaches_match_2([I|_], Regs, _) ->
btb_error({btb_context_regs(Regs),I,not_handled}).
+is_tail_call([{deallocate,_}|_]) -> true;
+is_tail_call([return|_]) -> true;
+is_tail_call(_) -> false.
+
btb_call(Arity, Lbl, Regs0, Is, D0) ->
Regs = btb_kill_not_live(Arity, Regs0),
case btb_are_x_registers_empty(Regs) of
@@ -369,15 +380,15 @@ btb_call(Arity, Lbl, Regs0, Is, D0) ->
D = btb_tail_call(Lbl, Regs, D0),
%% No problem so far (the called function can handle a
- %% match context). Now we must make sure that the rest
- %% of this function following the call does not attempt
- %% to use the match context in case there is a copy
- %% tucked away in a y register.
+ %% match context). Now we must make sure that we don't
+ %% have any copies of the match context tucked away in an
+ %% y register.
RegList = btb_context_regs(Regs),
- YRegs = [R || {y,_}=R <- RegList],
- case btb_are_all_unused(YRegs, Is, D) of
- true -> D;
- false -> btb_error({multiple_uses,RegList})
+ case [R || {y,_}=R <- RegList] of
+ [] ->
+ D;
+ [_|_] ->
+ btb_error({multiple_uses,RegList})
end;
true ->
%% No match context in any x register. It could have been
diff --git a/lib/compiler/test/bs_match_SUITE.erl b/lib/compiler/test/bs_match_SUITE.erl
index f8af070c44..6742571b86 100644
--- a/lib/compiler/test/bs_match_SUITE.erl
+++ b/lib/compiler/test/bs_match_SUITE.erl
@@ -769,6 +769,11 @@ multiple_uses(Config) when is_list(Config) ->
{344,62879,345,<<245,159,1,89>>} = multiple_uses_1(<<1,88,245,159,1,89>>),
true = multiple_uses_2(<<0,0,197,18>>),
<<42,43>> = multiple_uses_3(<<0,0,42,43>>, fun id/1),
+
+ ok = first_after(<<>>, 42),
+ <<1>> = first_after(<<1,2,3>>, 0),
+ <<2>> = first_after(<<1,2,3>>, 1),
+
ok.
multiple_uses_1(<<X:16,Tail/binary>>) ->
@@ -790,6 +795,24 @@ multiple_uses_match(<<Y:16,Z:16>>) ->
multiple_uses_cmp(<<Y:16>>, <<Y:16>>) -> true;
multiple_uses_cmp(<<_:16>>, <<_:16>>) -> false.
+first_after(Data, Offset) ->
+ case byte_size(Data) > Offset of
+ false ->
+ {First, Rest} = {ok, ok},
+ ok;
+ true ->
+ <<_:Offset/binary, Rest/binary>> = Data,
+ %% 'Rest' saved in y(0) before the call.
+ {First, _} = match_first(Data, Rest),
+ %% When beam_bsm sees the code, the following line
+ %% which uses y(0) has been optimized away.
+ {First, Rest} = {First, Rest},
+ First
+ end.
+
+match_first(_, <<First:1/binary, Rest/binary>>) ->
+ {First, Rest}.
+
zero_label(Config) when is_list(Config) ->
<<"nosemouth">> = read_pols(<<"FACE","nose","mouth">>),
<<"CE">> = read_pols(<<"noFACE">>),