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author | Björn Gustavsson <[email protected]> | 2017-08-09 14:19:18 +0200 |
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committer | Björn Gustavsson <[email protected]> | 2017-08-10 12:14:56 +0200 |
commit | 3e1d141e4d22708788af1a14401f257f4153fbae (patch) | |
tree | 669e57ef3cd513a78091c18cbfc9a2c2ac48c1f4 /lib/mnesia/info | |
parent | e25f673d520342bfe7cd479ef6b850a57f8ab1ea (diff) | |
download | otp-3e1d141e4d22708788af1a14401f257f4153fbae.tar.gz otp-3e1d141e4d22708788af1a14401f257f4153fbae.tar.bz2 otp-3e1d141e4d22708788af1a14401f257f4153fbae.zip |
Generalize optimization of "one-armed" cases
A 'case' expression will force a stack frame (essentially in the same
way as a function call), unless it is at the end of a function.
In sys_core_fold there is an optimization that can optimize one-armed
cases such as:
case Expr of
Pat1 ->
DoSomething;
Pat2 ->
erlang:error(bad)
end,
MoreCode.
Because only one arm of the 'case' can succeed, the code after the
case can be move into the successful arm:
case Expr of
Pat1 ->
DoSomething,
MoreCode;
Pat2 ->
erlang:error(bad)
end.
Thus, the 'case' is at the end of the function and it will no longer
need a stack frame.
However, the optimization in sys_core_fold would not be applied if
there were more than one failing clause such as in this code:
case Expr of
Pat1 ->
DoSomething,
MoreCode;
Pat2 ->
erlang:error(bad);
_ ->
erlang:error(case_clause)
end.
Generalize the optimization to handle any number of failing
clauses at the end of the case.
Reported-by: bugs.erlang.org/browse/ERL-452
Diffstat (limited to 'lib/mnesia/info')
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