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authorBjörn Gustavsson <[email protected]>2014-12-28 09:56:54 +0100
committerBjörn Gustavsson <[email protected]>2015-01-09 13:18:45 +0100
commit5e495894c82575e426a3a45b08c24e1538d75129 (patch)
tree5ceda2179fbd1eedc6f5ea145fc756fe165e5b9d /lib/compiler/src/beam_dead.erl
parentc4e9c42a0a4b662d4e85fe583191267e135d5176 (diff)
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Extend count_bits_matched/3 to handle the UTF instructions
While we are, clean up the comments and rearrange the code for clarity. Also add a test to cover the last uncovered line in beam_dead.erl.
Diffstat (limited to 'lib/compiler/src/beam_dead.erl')
-rw-r--r--lib/compiler/src/beam_dead.erl42
1 files changed, 24 insertions, 18 deletions
diff --git a/lib/compiler/src/beam_dead.erl b/lib/compiler/src/beam_dead.erl
index 9c1c60a92e..aaad7f4095 100644
--- a/lib/compiler/src/beam_dead.erl
+++ b/lib/compiler/src/beam_dead.erl
@@ -453,31 +453,26 @@ remove_from_list(Lit, [Val,{f,_}=Fail|T]) ->
[Val,Fail|remove_from_list(Lit, T)];
remove_from_list(_, []) -> [].
-%% shortcut_bs_test(TargetLabel, [Instruction], D) -> TargetLabel'
-%% Try to shortcut the failure label for a bit syntax matching.
-%% We know that the binary contains at least Bits bits after
-%% the latest save point.
+%% shortcut_bs_test(TargetLabel, ReversedInstructions, D) -> TargetLabel'
+%% Try to shortcut the failure label for bit syntax matching.
shortcut_bs_test(To, Is, D) ->
shortcut_bs_test_1(beam_utils:code_at(To, D), Is, To, D).
-shortcut_bs_test_1([{bs_restore2,Reg,SavePoint}|Is], PrevIs, To, D) ->
- shortcut_bs_test_2(Is, {Reg,SavePoint}, PrevIs, To, D);
-shortcut_bs_test_1([_|_], _, To, _) -> To.
-
-shortcut_bs_test_2([{label,_}|Is], Save, PrevIs, To, D) ->
- shortcut_bs_test_2(Is, Save, PrevIs, To, D);
-shortcut_bs_test_2([{test,bs_test_tail2,{f,To},[_,TailBits]}|_],
- {Reg,_Point} = RP, PrevIs, To0, D) ->
- case count_bits_matched(PrevIs, RP, 0) of
+shortcut_bs_test_1([{bs_restore2,Reg,SavePoint},
+ {label,_},
+ {test,bs_test_tail2,{f,To},[_,TailBits]}|_],
+ PrevIs, To0, D) ->
+ case count_bits_matched(PrevIs, {Reg,SavePoint}, 0) of
Bits when Bits > TailBits ->
%% This instruction will fail. We know because a restore has been
- %% done from the previous point SavePoint in the binary, and we also know
- %% that the binary contains at least Bits bits from SavePoint.
+ %% done from the previous point SavePoint in the binary, and we
+ %% also know that the binary contains at least Bits bits from
+ %% SavePoint.
%%
%% Since we will skip a bs_restore2 if we shortcut to label To,
- %% we must now make sure that code at To does not depend on the position
- %% in the context in any way.
+ %% we must now make sure that code at To does not depend on
+ %% the position in the context in any way.
case shortcut_bs_pos_used(To, Reg, D) of
false -> To;
true -> To0
@@ -485,8 +480,19 @@ shortcut_bs_test_2([{test,bs_test_tail2,{f,To},[_,TailBits]}|_],
_Bits ->
To0
end;
-shortcut_bs_test_2([_|_], _, _, To, _) -> To.
+shortcut_bs_test_1([_|_], _, To, _) -> To.
+%% counts_bits_matched(ReversedInstructions, SavePoint, Bits) -> Bits'
+%% Given a reversed instruction stream, determine the minimum number
+%% of bits that will be matched by bit syntax instructions up to the
+%% given save point.
+
+count_bits_matched([{test,bs_get_utf8,{f,_},_,_,_}|Is], SavePoint, Bits) ->
+ count_bits_matched(Is, SavePoint, Bits+8);
+count_bits_matched([{test,bs_get_utf16,{f,_},_,_,_}|Is], SavePoint, Bits) ->
+ count_bits_matched(Is, SavePoint, Bits+16);
+count_bits_matched([{test,bs_get_utf32,{f,_},_,_,_}|Is], SavePoint, Bits) ->
+ count_bits_matched(Is, SavePoint, Bits+32);
count_bits_matched([{test,_,_,_,[_,Sz,U,{field_flags,_}],_}|Is], SavePoint, Bits) ->
case Sz of
{integer,N} -> count_bits_matched(Is, SavePoint, Bits+N*U);