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authorBjörn Gustavsson <[email protected]>2010-11-26 11:47:50 +0100
committerBjörn Gustavsson <[email protected]>2010-12-02 17:12:24 +0100
commit2b03fbacf1ac0c06a84439baac90d418916a1778 (patch)
treea42ca97705f775998d0bc779db20b47b4e752816
parent8836ebccae92886decf5645944ae4ce8a2f99947 (diff)
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beam_utils: Fix check_liveness/3 for receive loops
Sometimes the beam_bool pass wants to know whether an y register will be killed by the code that follows and will do (effectively): beam_utils:is_killed({y,Y}, Code, L) When asked to calculate the liveness for an y register, beam_utils:is_killed/3 will loop forever if the code includes a receive loop. Since this rarely occurs, fix the problem in the simplest and most conservative way. Reported-by: Christopher Williams
-rw-r--r--lib/compiler/src/beam_utils.erl9
-rw-r--r--lib/compiler/test/compilation_SUITE.erl20
2 files changed, 25 insertions, 4 deletions
diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl
index dc8079d0b7..45cdf8a659 100644
--- a/lib/compiler/src/beam_utils.erl
+++ b/lib/compiler/src/beam_utils.erl
@@ -489,10 +489,13 @@ check_liveness(R, [{bs_context_to_binary,S}|Is], St) ->
S -> {used,St};
_ -> check_liveness(R, Is, St)
end;
-check_liveness(R, [{loop_rec,{f,_},{x,0}}|Is], St) ->
+check_liveness(R, [{loop_rec,{f,_},{x,0}}|_], St) ->
case R of
- {x,_} -> {killed,St};
- _ -> check_liveness(R, Is, St)
+ {x,_} ->
+ {killed,St};
+ _ ->
+ %% y register. Rarely happens. Be very conversative.
+ {unknown,St}
end;
check_liveness(R, [{loop_rec_end,{f,Fail}}|_], St) ->
check_liveness_at(R, Fail, St);
diff --git a/lib/compiler/test/compilation_SUITE.erl b/lib/compiler/test/compilation_SUITE.erl
index 7b6975f912..935e384d2d 100644
--- a/lib/compiler/test/compilation_SUITE.erl
+++ b/lib/compiler/test/compilation_SUITE.erl
@@ -46,7 +46,7 @@ all(suite) ->
trycatch_4, opt_crash,
otp_5404,otp_5436,otp_5481,otp_5553,otp_5632,
otp_5714,otp_5872,otp_6121,otp_6121a,otp_6121b,
- otp_7202,otp_7345,on_load,string_table,otp_8949_a
+ otp_7202,otp_7345,on_load,string_table,otp_8949_a,otp_8949_a
].
-define(comp(N),
@@ -628,5 +628,23 @@ otp_8949_a() ->
end
end.
+otp_8949_b(Config) when is_list(Config) ->
+ self() ! something,
+ ?line value = otp_8949_b([], false),
+ ?line {'EXIT',_} = (catch otp_8949_b([], true)),
+ ok.
+
+%% Would cause an endless loop in beam_utils.
+otp_8949_b(A, B) ->
+ Var = id(value),
+ if
+ A == [], B == false ->
+ ok
+ end,
+ receive
+ something ->
+ id(Var)
+ end.
+
id(I) -> I.