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authorBjörn Gustavsson <[email protected]>2018-06-04 06:14:19 +0200
committerBjörn Gustavsson <[email protected]>2018-06-04 10:41:21 +0200
commit7eb06ed5ac1687d38245db2e0aef2756cb43b1ae (patch)
tree8f796f9c5bb2ec8f059a9ba7ef37aea9fd9a6cda /lib/compiler/test
parent7f3a501cada228c2fedbe34d0d30080e98560665 (diff)
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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')
-rw-r--r--lib/compiler/test/core_SUITE.erl5
-rw-r--r--lib/compiler/test/core_SUITE_data/name_capture.core110
2 files changed, 113 insertions, 2 deletions
diff --git a/lib/compiler/test/core_SUITE.erl b/lib/compiler/test/core_SUITE.erl
index 0e07e8dd2e..d07cd3b8b7 100644
--- a/lib/compiler/test/core_SUITE.erl
+++ b/lib/compiler/test/core_SUITE.erl
@@ -29,7 +29,7 @@
bs_shadowed_size_var/1,
cover_v3_kernel_1/1,cover_v3_kernel_2/1,cover_v3_kernel_3/1,
cover_v3_kernel_4/1,cover_v3_kernel_5/1,
- non_variable_apply/1]).
+ non_variable_apply/1,name_capture/1]).
-include_lib("common_test/include/ct.hrl").
@@ -58,7 +58,7 @@ groups() ->
bs_shadowed_size_var,
cover_v3_kernel_1,cover_v3_kernel_2,cover_v3_kernel_3,
cover_v3_kernel_4,cover_v3_kernel_5,
- non_variable_apply
+ non_variable_apply,name_capture
]}].
@@ -93,6 +93,7 @@ end_per_group(_GroupName, Config) ->
?comp(cover_v3_kernel_4).
?comp(cover_v3_kernel_5).
?comp(non_variable_apply).
+?comp(name_capture).
try_it(Mod, Conf) ->
Src = filename:join(proplists:get_value(data_dir, Conf),
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