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author | Björn Gustavsson <[email protected]> | 2018-06-04 06:14:19 +0200 |
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committer | Björn Gustavsson <[email protected]> | 2018-06-04 10:41:21 +0200 |
commit | 7eb06ed5ac1687d38245db2e0aef2756cb43b1ae (patch) | |
tree | 8f796f9c5bb2ec8f059a9ba7ef37aea9fd9a6cda /lib/compiler/test/core_SUITE_data | |
parent | 7f3a501cada228c2fedbe34d0d30080e98560665 (diff) | |
download | otp-7eb06ed5ac1687d38245db2e0aef2756cb43b1ae.tar.gz otp-7eb06ed5ac1687d38245db2e0aef2756cb43b1ae.tar.bz2 otp-7eb06ed5ac1687d38245db2e0aef2756cb43b1ae.zip |
sys_core_fold: Fix name capture problem
sys_core_fold could do unsafe transformations on the
code from the old inliner (invoked using the compiler
option `{inline,[{F/A}]}` to request inlining of specific
functions).
To explain the bug, let's first look at an example that
sys_core_fold handles correctly. Consider this code:
'foo'/2 =
fun (Arg1,Arg2) ->
let <B> = Arg2
in let <A,B> = <B,Arg1>
in {A,B}
In this example, the lets can be completely eliminated,
since the arguments for the lets are variables (as opposed
to expressions). Since the variable B is rebound in the
inner let, `sys_core_fold` must take special care when
doing the substitutions.
Here is the correct result:
'foo'/2 =
fun (Arg1, Arg2) ->
{Arg2,Arg1}
Consider a slight modifictation of the example:
'bar'/2 =
fun (Arg1,Arg2) ->
let <B> = [Arg2]
in let <A,B> = <B,[Arg1]>
in {A,B}
Here some of the arguments for the lets are expressions, so
the lets must be kept. sys_core_fold does not handle this
example correctly:
'bar'/2 =
fun (Arg1,Arg2) ->
let <B> = [Arg2]
in let <B> = [Arg1]
in {B,B}
In the inner let, the variable A has been eliminated and
replaced with the variable B in the body (the first B in
the tuple). Since the B in the outer let is never used,
the outer let will be eliminated, giving:
'bar'/2 =
fun (Arg1,Arg2) ->
let <B> = [Arg1]
in {B,B}
To handle this example correctly, sys_core_fold must
rename the variable B in the inner let like this to
avoid capturing B:
'bar'/2 =
fun (Arg1,Arg2) ->
let <B> = [Arg2]
in let <NewName> = [Arg1]
in {B,NewName}
(Note: The `v3_kernel` pass alreday handles those examples correctly
in case `sys_core_fold` has been disabled.)
Diffstat (limited to 'lib/compiler/test/core_SUITE_data')
-rw-r--r-- | lib/compiler/test/core_SUITE_data/name_capture.core | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/lib/compiler/test/core_SUITE_data/name_capture.core b/lib/compiler/test/core_SUITE_data/name_capture.core new file mode 100644 index 0000000000..0969f95b72 --- /dev/null +++ b/lib/compiler/test/core_SUITE_data/name_capture.core @@ -0,0 +1,110 @@ +module 'name_capture' ['module_info'/0, + 'module_info'/1, + 'name_capture'/0] + attributes ['compile' = + [{'inline',[{'badarg_exit',2}]}]] +'name_capture'/0 = + fun () -> + case <> of + <> when 'true' -> + let <_0> = + catch + apply 'first'/1 + ('badarg') + in case _0 of + <{'EXIT',{'badarg',_7}}> when 'true' -> + let <Seq> = + call 'lists':'seq' + (7, 17) + in case apply 'first'/1 + ({'ok',Seq}) of + <_8> + when call 'erlang':'=:=' + (_8, + Seq) -> + let <SomeOtherTerm> = + {'some','other','term'} + in let <_5> = + catch + apply 'first'/1 + (SomeOtherTerm) + in case _5 of + <{'EXIT',_9}> + when call 'erlang':'=:=' + (_9, + SomeOtherTerm) -> + 'ok' + <_6> when 'true' -> + primop 'match_fail' + ({'badmatch',_6}) + end + <_3> when 'true' -> + primop 'match_fail' + ({'badmatch',_3}) + end + <_1> when 'true' -> + primop 'match_fail' + ({'badmatch',_1}) + end + <> when 'true' -> + primop 'match_fail' + ({'function_clause'}) + end +'first'/1 = + fun (_0) -> + case _0 of + <Tab> when 'true' -> + let <_1> = + apply 'treq'/2 + (Tab, 'first') + %% The _1 variable in the `let` must be renamed + %% to avoid a name capture problem. + in let <_0,_1> = + <_1,[Tab|[]]> + in case <_0,_1> of + <'badarg',A> when 'true' -> + call 'erlang':'error' + ('badarg', A) + <{'ok',Reply},_X_A> when 'true' -> + Reply + <Reply,_X_A> when 'true' -> + call 'erlang':'exit' + (Reply) + <_3,_2> when 'true' -> + primop 'match_fail' + ({'function_clause',_3,_2}) + end + <_2> when 'true' -> + primop 'match_fail' + ({'function_clause',_2}) + end +'treq'/2 = + fun (_0,_1) -> + case <_0,_1> of + <Action,_4> when 'true' -> + Action + <_3,_2> when 'true' -> + primop 'match_fail' + ({'function_clause',_3,_2}) + end +'module_info'/0 = + fun () -> + case <> of + <> when 'true' -> + call 'erlang':'get_module_info' + ('name_capture') + <> when 'true' -> + primop 'match_fail' + ({'function_clause'}) + end +'module_info'/1 = + fun (_0) -> + case _0 of + <X> when 'true' -> + call 'erlang':'get_module_info' + ('name_capture', X) + <_1> when 'true' -> + primop 'match_fail' + ({'function_clause',_1}) + end +end |