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authorBjörn Gustavsson <bjorn@erlang.org>2012-01-18 09:04:05 +0100
committerBjörn Gustavsson <bjorn@erlang.org>2012-01-18 15:50:57 +0100
commit4c6e2c2d775bc785db7de174e12227e87d2bc542 (patch)
treed4dc2557c3bbfca28169dbe5ff99f8d8d1620ca5
parent11d255627033bb96e7c737d35badbacae32a8631 (diff)
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compiler: Correct live calculation when get/1 is used in try...catch
In the following code excerpt, the instruction marked below was incorrectly removed: . . . {'try',{y,2},{f,TryCaseLabel}}. {bif,get,{f,0},[{x,0}],{x,0}}. {move,{x,1},{y,0}}. {move,{x,3},{y,1}}. <======= Incorrectly removed {jump,{f,TryEndLabel}}. {label,TryEndLabel}. {try_end,{y,2}}. {deallocate,3}. return. {label,TryCaseLabel}. {try_case,{y,2}}. . . . beam_utils indicated that {y,1} was not used at TryEndLabel, which by itself is correct. But it is still not safe to remove the instruction, because {y,1} might be used at TryCaseLabel if an exception occurs. Noticed-by: Eric Merritt
-rw-r--r--lib/compiler/src/beam_utils.erl11
-rw-r--r--lib/compiler/test/trycatch_SUITE.erl18
2 files changed, 25 insertions, 4 deletions
diff --git a/lib/compiler/src/beam_utils.erl b/lib/compiler/src/beam_utils.erl
index a631b8cd69..116ede0bc9 100644
--- a/lib/compiler/src/beam_utils.erl
+++ b/lib/compiler/src/beam_utils.erl
@@ -474,8 +474,15 @@ check_liveness(R, [{make_fun2,_,_,_,NumFree}|Is], St) ->
end;
check_liveness(R, [{try_end,Y}|Is], St) ->
case R of
- Y -> {killed,St};
- _ -> check_liveness(R, Is, St)
+ Y ->
+ {killed,St};
+ {y,_} ->
+ %% y registers will be used if an exception occurs and
+ %% control transfers to the label given in the previous
+ %% try/2 instruction.
+ {used,St};
+ _ ->
+ check_liveness(R, Is, St)
end;
check_liveness(R, [{catch_end,Y}|Is], St) ->
case R of
diff --git a/lib/compiler/test/trycatch_SUITE.erl b/lib/compiler/test/trycatch_SUITE.erl
index 760cf17225..09a23724fe 100644
--- a/lib/compiler/test/trycatch_SUITE.erl
+++ b/lib/compiler/test/trycatch_SUITE.erl
@@ -24,7 +24,7 @@
catch_oops/1,after_oops/1,eclectic/1,rethrow/1,
nested_of/1,nested_catch/1,nested_after/1,
nested_horrid/1,last_call_optimization/1,bool/1,
- plain_catch_coverage/1,andalso_orelse/1]).
+ plain_catch_coverage/1,andalso_orelse/1,get_in_try/1]).
-include_lib("test_server/include/test_server.hrl").
@@ -35,7 +35,7 @@ all() ->
[basic, lean_throw, try_of, try_after, catch_oops,
after_oops, eclectic, rethrow, nested_of, nested_catch,
nested_after, nested_horrid, last_call_optimization,
- bool, plain_catch_coverage, andalso_orelse].
+ bool, plain_catch_coverage, andalso_orelse, get_in_try].
groups() ->
[].
@@ -928,3 +928,17 @@ andalso_orelse_2({Type,Keyval}) ->
zero() ->
0.0.
+
+get_in_try(_) ->
+ undefined = get_valid_line([a], []),
+ ok.
+
+get_valid_line([_|T]=Path, Annotations) ->
+ try
+ get(Path)
+ %% beam_dead used to optimize away an assignment to {y,1}
+ %% because it didn't appear to be used.
+ catch
+ _:not_found ->
+ get_valid_line(T, Annotations)
+ end.