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author | Björn Gustavsson <[email protected]> | 2018-09-28 05:57:47 +0200 |
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committer | Björn Gustavsson <[email protected]> | 2018-09-28 10:47:56 +0200 |
commit | 0bb261b730eff06cca524ea9999ff035585ef5b4 (patch) | |
tree | e057e70bc7fe53a7ec74577dfdb836707e7ae60b /lib/compiler/src/beam_bsm.erl | |
parent | 377f19f25aeec6939a6728bd0c4910086c22ccdc (diff) | |
download | otp-0bb261b730eff06cca524ea9999ff035585ef5b4.tar.gz otp-0bb261b730eff06cca524ea9999ff035585ef5b4.tar.bz2 otp-0bb261b730eff06cca524ea9999ff035585ef5b4.zip |
Fix rare bug in binary matching (again)
2e40d8d1c51a attempted fix a bug in binary matching, but it only
fixed the bug for the minimized test case.
This commit removes the previous fix and fixes the bug in a more
effective way. See the comments in the new code in `sys_core_bsm`
for an explanation.
This commit restores the optimizations in string.erl and dets_v9.erl
that the previous fix disabled.
I have not found any code where this commit will disable optimizations
when they are actually safe. There are some changes to the code
in ssl_cipher.erl in that some bs_start_match2 instruction did not
reuse the binary register for the match context, but the delayed
sub binary optimizations was never applied to the code in the first
place.
https://bugs.erlang.org/browse/ERL-689
Diffstat (limited to 'lib/compiler/src/beam_bsm.erl')
-rw-r--r-- | lib/compiler/src/beam_bsm.erl | 13 |
1 files changed, 1 insertions, 12 deletions
diff --git a/lib/compiler/src/beam_bsm.erl b/lib/compiler/src/beam_bsm.erl index abc6e96c85..1c8e0e9854 100644 --- a/lib/compiler/src/beam_bsm.erl +++ b/lib/compiler/src/beam_bsm.erl @@ -310,18 +310,7 @@ btb_reaches_match_2([{test,bs_start_match2,{f,F},Live,[Bin,_],Ctx}|Is], end; btb_reaches_match_2([{test,_,{f,F},Ss}=I|Is], Regs, D0) -> btb_ensure_not_used(Ss, I, Regs), - D1 = btb_follow_branch(F, Regs, D0), - D = case Is of - [{bs_context_to_binary,_}|_] -> - %% bs_context_to_binary following a test instruction - %% probably needs the current position to be saved as - %% the new start position, but we can't be sure. - %% Therefore, conservatively disable the optimization - %% (instead of forcing a saving of the position). - D1#btb{must_save=true,must_not_save=true}; - _ -> - D1 - end, + D = btb_follow_branch(F, Regs, D0), btb_reaches_match_1(Is, Regs, D); btb_reaches_match_2([{test,_,{f,F},_,Ss,_}=I|Is], Regs, D0) -> btb_ensure_not_used(Ss, I, Regs), |