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-rw-r--r--lib/compiler/src/beam_bsm.erl48
-rw-r--r--lib/compiler/test/bs_match_SUITE.erl30
2 files changed, 64 insertions, 14 deletions
diff --git a/lib/compiler/src/beam_bsm.erl b/lib/compiler/src/beam_bsm.erl
index c9c5b59bf2..02794a8e18 100644
--- a/lib/compiler/src/beam_bsm.erl
+++ b/lib/compiler/src/beam_bsm.erl
@@ -241,21 +241,45 @@ btb_reaches_match_2([{bif,_,{f,F},Ss,Dst}=I|Is], Regs0, D0) ->
Regs = btb_kill([Dst], Regs0),
D = btb_follow_branch(F, Regs, D0),
btb_reaches_match_1(Is, Regs, D);
-btb_reaches_match_2([{test,bs_start_match2,_,_,[Ctx,_],Ctx}|Is], Regs, D) ->
- case btb_context_regs(Regs) of
- [Ctx] ->
- D;
- CtxRegs ->
- case member(Ctx, CtxRegs) of
- false -> btb_reaches_match_2(Is, Regs, D);
- true -> btb_error(unsuitable_bs_start_match)
+btb_reaches_match_2([{test,bs_start_match2,{f,F},Live,[Ctx,_],Ctx}=I|Is],
+ Regs0, D0) ->
+ CtxRegs = btb_context_regs(Regs0),
+ case member(Ctx, CtxRegs) of
+ false ->
+ %% This bs_start_match2 instruction does not use "our"
+ %% match state. Therefore we can continue the search
+ %% for another bs_start_match2 instruction.
+ D = btb_follow_branch(F, Regs0, D0),
+ Regs = btb_kill_not_live(Live, Regs0),
+ btb_reaches_match_2(Is, Regs, D);
+ true ->
+ %% OK. This instruction will use "our" match state,
+ %% but we must make sure that all other copies of the
+ %% match state are killed in the code that follows
+ %% the instruction. (We know that the fail branch cannot
+ %% be taken in this case.)
+ OtherCtxRegs = CtxRegs -- [Ctx],
+ case btb_are_all_unused(OtherCtxRegs, Is, D0) of
+ false -> btb_error({OtherCtxRegs,not_all_unused_after,I});
+ true -> D0
end
end;
-btb_reaches_match_2([{test,bs_start_match2,_,_,[Bin,_],Ctx}|Is], Regs, D) ->
- CtxRegs = btb_context_regs(Regs),
+btb_reaches_match_2([{test,bs_start_match2,{f,F},Live,[Bin,_],Ctx}|Is],
+ Regs0, D0) ->
+ CtxRegs = btb_context_regs(Regs0),
case member(Bin, CtxRegs) orelse member(Ctx, CtxRegs) of
- false -> btb_reaches_match_2(Is, Regs, D);
- true -> btb_error(unsuitable_bs_start_match)
+ false ->
+ %% This bs_start_match2 does not reference any copy of the
+ %% match state. Therefore it can safely be passed on the
+ %% way to another (perhaps more suitable) bs_start_match2
+ %% instruction.
+ D = btb_follow_branch(F, Regs0, D0),
+ Regs = btb_kill_not_live(Live, Regs0),
+ btb_reaches_match_2(Is, Regs, D);
+ true ->
+ %% This variant of the bs_start_match2 instruction does
+ %% not accept a match state as source.
+ btb_error(unsuitable_bs_start_match)
end;
btb_reaches_match_2([{test,_,{f,F},Ss}=I|Is], Regs, D0) ->
btb_ensure_not_used(Ss, I, Regs),
diff --git a/lib/compiler/test/bs_match_SUITE.erl b/lib/compiler/test/bs_match_SUITE.erl
index e8f5c55c1a..d63d2235d7 100644
--- a/lib/compiler/test/bs_match_SUITE.erl
+++ b/lib/compiler/test/bs_match_SUITE.erl
@@ -33,7 +33,7 @@
matching_meets_construction/1,simon/1,matching_and_andalso/1,
otp_7188/1,otp_7233/1,otp_7240/1,otp_7498/1,
match_string/1,zero_width/1,bad_size/1,haystack/1,
- cover_beam_bool/1,matched_out_size/1]).
+ cover_beam_bool/1,matched_out_size/1,follow_fail_branch/1]).
-export([coverage_id/1,coverage_external_ignore/2]).
@@ -57,7 +57,7 @@ groups() ->
matching_meets_construction,simon,
matching_and_andalso,otp_7188,otp_7233,otp_7240,
otp_7498,match_string,zero_width,bad_size,haystack,
- cover_beam_bool,matched_out_size]}].
+ cover_beam_bool,matched_out_size,follow_fail_branch]}].
init_per_suite(Config) ->
@@ -1108,6 +1108,32 @@ mos_bin(<<L,Bin:L/binary,"abcdefghij">>) ->
L = byte_size(Bin),
Bin.
+follow_fail_branch(_) ->
+ 42 = ffb_1(<<0,1>>, <<0>>),
+ 8 = ffb_1(<<0,1>>, [a]),
+ 42 = ffb_2(<<0,1>>, <<0>>, 17),
+ 8 = ffb_2(<<0,1>>, [a], 0),
+ ok.
+
+ffb_1(<<_,T/bitstring>>, List) ->
+ case List of
+ <<_>> ->
+ 42;
+ [_|_] ->
+ %% The fail branch of the bs_start_match2 instruction
+ %% pointing to here would be ignored, making the compiler
+ %% incorrectly assume that the delayed sub-binary
+ %% optimization was safe.
+ bit_size(T)
+ end.
+
+ffb_2(<<_,T/bitstring>>, List, A) ->
+ case List of
+ <<_>> when A =:= 17 -> 42;
+ [_|_] -> bit_size(T)
+ end.
+
+
check(F, R) ->
R = F().