aboutsummaryrefslogtreecommitdiffstats
path: root/lib/compiler/src/beam_bool.erl
diff options
context:
space:
mode:
authorBjörn Gustavsson <[email protected]>2016-05-13 15:59:31 +0200
committerBjörn Gustavsson <[email protected]>2016-05-16 07:51:26 +0200
commit7f4f4ef02349b4bf973cbc3bacc4d53a6a6abad2 (patch)
treef1b894393bd7471edf8d486443cbaa98ced0d21e /lib/compiler/src/beam_bool.erl
parentf679efe1c19cb7d6bab8a68226a9d748474ef902 (diff)
downloadotp-7f4f4ef02349b4bf973cbc3bacc4d53a6a6abad2.tar.gz
otp-7f4f4ef02349b4bf973cbc3bacc4d53a6a6abad2.tar.bz2
otp-7f4f4ef02349b4bf973cbc3bacc4d53a6a6abad2.zip
Eliminate crash in beam_bool
beam_bool would crash when attempting to optimize BEAM code similar to this code: bif '=:=' Reg1 SomeValue => y(0) bif '=:=' Reg2 {atom,true} => x(2) bif '=:=' Reg3 {atom,true} => x(3) bif 'or' x(2) x(3) => x(2) is_eq_exact Fail x(2) {atom,true} The problem is that the first instruction that assigns a value to a Y register. beam_bool:ssa_assign/2 will not accept a Y register argument. We could change ssa_assign/2 to accept a Y register, but that would only cause the entire optimization to be rejected later because the Y register is alive in the code that follows. Therefore, a better solution is to modify extend_block/3 so that the instruction that assign to Y registers are not added to the block. That is, the optimizer will only operate on the following code: bif '=:=' Reg2 {atom,true} => x(2) bif '=:=' Reg3 {atom,true} => x(3) bif 'or' x(2) x(3) => x(2) is_eq_exact Fail x(2) {atom,true} Usually the optimization will succeed, rewriting the four instructions to a select_val instruction. Assembly code such as the above can be produced by code similar to: Y = Something == SomethingElse, case Y of Condition; OtherCondition -> . . . end, . . ., Y. Reported-by: http://bugs.erlang.org/browse/ERL-143 Reported-by: José Valim
Diffstat (limited to 'lib/compiler/src/beam_bool.erl')
-rw-r--r--lib/compiler/src/beam_bool.erl4
1 files changed, 2 insertions, 2 deletions
diff --git a/lib/compiler/src/beam_bool.erl b/lib/compiler/src/beam_bool.erl
index f9a08f8718..359fdb6d3c 100644
--- a/lib/compiler/src/beam_bool.erl
+++ b/lib/compiler/src/beam_bool.erl
@@ -238,9 +238,9 @@ extend_block(BlAcc0, Fail, [{block,Is0}|OldAcc]) ->
end;
extend_block(BlAcc, _, OldAcc) -> {BlAcc,OldAcc}.
-extend_block_1([{set,[_],_,{bif,_,{f,Fail}}}=I|Is], Fail, Acc) ->
+extend_block_1([{set,[{x,_}],_,{bif,_,{f,Fail}}}=I|Is], Fail, Acc) ->
extend_block_1(Is, Fail, [I|Acc]);
-extend_block_1([{set,[_],As,{bif,Bif,_}}=I|Is]=Is0, Fail, Acc) ->
+extend_block_1([{set,[{x,_}],As,{bif,Bif,_}}=I|Is]=Is0, Fail, Acc) ->
case safe_bool_op(Bif, length(As)) of
false -> {Acc,reverse(Is0)};
true -> extend_block_1(Is, Fail, [I|Acc])