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* maint:
beam_bsm: Eliminate unsafe optimization
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The following code causes a compiler failure:
first_after(Data, Offset) ->
case byte_size(Data) > Offset of
false ->
{First, Rest} = {ok, ok},
ok;
true ->
<<_:Offset/binary, Rest/binary>> = Data,
%% 'Rest' saved in y(0) before the call.
{First, _} = match_first(Data, Rest),
%% When beam_bsm sees the code, the following line
%% which uses y(0) has been optimized away.
{First, Rest} = {First, Rest},
First
end.
match_first(_, <<First:1/binary, Rest/binary>>) ->
{First, Rest}.
Here is the error message from beam_validator:
t: function first_after/2+15:
Internal consistency check failed - please report this bug.
Instruction: {call,2,{f,7}}
Error: {multiple_match_contexts,[{x,1},0]}:
Basically, what happens is that at time of code generation,
the variable 'Rest' is needed after the call to match_first/2
and is therefore saved in y(0). When beam_bsm (a late optimization
pass) sees the code, the use of y(0) following the call
to match_first/2 has been optimized away. beam_bsm therefore
assumes that the delayed sub-binary creation is safe. (Actually,
it is safe, but beam_validator does not realize it.)
The bug was caused by two separate commits:
e199e2471a reduced the number of special cases to handle in BEAM
optimization passed by breaking apart the tail-recursive call
instructions (call_only and call_last) into separate instructions.
Unfortunately, the special handling for tail calls was lost, which
resulted in worse code (i.e. the delayed sub-binary creation
optimization could not be applied).
e1aa422290 tried to compensate, but did so in a way that was not
always safe.
Teaching beam_validator that this kind of code is safe would be
expensive.
Instead, we will undo the damage caused by the two
commits. Re-introduce the special handling of tail-recursive calls in
beam_bsm that was lost in the first commit. (Effectively) revert the
change in the second commit.
ERL-268
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* maint:
Update primary bootstrap
beam_block: Avoid unsafe inclusion of get_map_elements in blocks
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c2035ebb8b restricted the get_map_elements instruction so that it
could only occur at the beginning of a block. It turns out that
including it anywhere in a block is unsafe.
Therefore, never put get_map_elements instruction in blocks.
(Also remove the beam_utils:join_even/2 function since it is no
longer used.)
ERL-266
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* rickard/time-unit/OTP-13831:
Replace usage of deprecated time units
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* josevalim/compiler/at-var/PR-1081/OTP-13924:
Use @ in variable names generated by core and kernel
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Run the optimizations until a fixpoint is reached, or until
the maximum iteration count is reached.
The hope is that in the future we can many small optimizations
instead of optimizations that try to do everything in one pass.
This change allows us to remove the ad-hoc calls to expr/2
to run more optimizations on a piece of code.
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The optimization that avoids building a tuple in a case
expression would not work if any clause matched a tuple
as in the following example:
f(A, B) ->
case {A,B} of
{<<X>>,Y} ->
{X,Y}
end.
The generated Core Erlang code would look like this (note
the tuples in the case expression and the pattern):
'f'/2 =
fun (_cor1,_cor0) ->
case {_cor1,_cor0} of
<{#{#<X>(8,1,'integer',['unsigned'|['big']])}#,Y}>
when 'true' ->
{X,Y}
.
.
.
end
It is expected that the code should look like this (note
that tuples have been replaced with "values"):
'f'/2 =
fun (_cor1,_cor0) ->
%% Line 5
case <_cor1,_cor0> of
<#{#<X>(8,1,'integer',['unsigned'|['big']])}#,Y> ->
{X,Y}
.
.
.
end
While at it, also fix bugs in the handling of pattern with
aliases. The bindings were produced in the wrong order (creating
'let's with referring to free variables), but in most cases
the incorrect bindings were discarded later without causing any
harm.
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703e8f4490bf broke the scope verification code (by calling
ordsets:is_subset/2 with an unsorted second argument).
While we are it, also optimize the verification function
by avoiding converting the map to a sorted list.
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The previous variable names can be generated by
projects like LFE and Elixir, leading to possible
conflicts. Our first to choice to solve such conflicts
was to use $ but that's not a valid variable name in core.
Therefore we picked @ which is currently supported and
still reduces the chance of conflicts.
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Do a simpler translation of internal BIFs.
While we are it, also remove the dummy values of Index and Uniq
from the make_fun internal operation.
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Remove the special handling #k_try{} in guards in v3_life. If we
introduce a new #k_protected{} record in v3_kernel, v3_life no longer
needs to know whether it is processing guards or bodies.
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When beam_utils was first written, it did not have the functions
for testing whether a register was not used. Those were added
later, in sort of a hacky way.
Also, is_killed*() and is_not_used*() for Y registers would
return the same answer. Fix that to make the API more consistent
(an Y register can only be killed by a deallocate/1 instruction).
We will need to change beam_trim to call beam_utils:is_not_used/3
instead of beam_utils:is_killed/3.
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During development, a bug in beam_utils caused a compiler failure
in xmerl. If the bug reappears, make sure that we catch it when
compiling the compiler test suite.
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There is no need to list every obscure safe BIF in erl_bifs:is_safe/3.
The purpose of erl_bifs:is_safe/3 is merely to warn when the
return value of one of the safe BIFs is ignored.
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The error would be:
{multiple_match_contexts,[{x,0},2]}
instead of:
{multiple_match_contexts,[{x,0},{y,2}]}
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Since the beam_a pass has always been run and have removed any
unused label, there can never be a label as the very last
instruction in a function.
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eliminate_fallthroughs/2 has special code to handle two labels next to
each other, but that does not seem to ever happen and there was one
line uncovered in is_label/1. Since inserting an extra jump between
two labels would not cause any real problems, remove the extra
handling of two consecutive labels.
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The compiler stopped using sys_pre_expand in ae3e177c514c354831.
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=== OTP-19.1 ===
Changed Applications:
- asn1-4.0.4
- common_test-1.12.3
- compiler-7.0.2
- crypto-3.7.1
- debugger-4.2.1
- dialyzer-3.0.2
- diameter-1.12.1
- edoc-0.8
- erl_docgen-0.6
- erl_interface-3.9.1
- erts-8.1
- eunit-2.3.1
- gs-1.6.2
- hipe-3.15.2
- ic-4.4.2
- inets-6.3.3
- jinterface-1.7.1
- kernel-5.1
- mnesia-4.14.1
- observer-2.2.2
- odbc-2.11.3
- parsetools-2.1.3
- reltool-0.7.2
- runtime_tools-1.10.1
- sasl-3.0.1
- snmp-5.2.4
- ssh-4.3.2
- ssl-8.0.2
- stdlib-3.1
- syntax_tools-2.1
- tools-2.8.6
- wx-1.7.1
- xmerl-1.3.12
Unchanged Applications:
- cosEvent-2.2.1
- cosEventDomain-1.2.1
- cosFileTransfer-1.2.1
- cosNotification-1.2.2
- cosProperty-1.2.1
- cosTime-1.2.2
- cosTransactions-1.3.2
- eldap-1.2.2
- et-1.6
- megaco-3.18.1
- orber-3.8.2
- os_mon-2.4.1
- otp_mibs-1.1.1
- percept-0.9
- public_key-1.2
- typer-0.9.11
Conflicts:
OTP_VERSION
lib/gs/doc/src/notes.xml
lib/gs/vsn.mk
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* maint:
beam_validator: Handle unreachable instructions
Turn off parallel make for start scripts Makefile
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ab03678e introduced an optimization in the beam_z pass that could
introduce unreachable code in BEAM files (a 'jump' instruction is
removed after a 'raise' instruction, but the code following the
target of the 'jump' is not removed).
Since this situation happens very rarely, there is no point in adding
another pass that can remove unreachable code after beam_z. Instead we
will make sure that beam_validator can skip the unreachable code.
Skipping unreachable code is already done in valfun_1/2 (for
historical reasons), but we will also need to do it in val_dsetel/2.
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* maint:
[snmp] Correct bug when path to mib contains UTF-8 characters
[ic] Fix but when UTF-8 character in path to idl spec
sys_core_fold: Don't move a fun into a guard
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Moving a fun into a guard may cause code that is not accepted
by beam_validator.
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* bjorn/floor-ceiling/OTP-13692:
Add math:floor/1 and math:ceil/1
Implement the new ceil/1 and floor/1 guard BIFs
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Add math:floor/1 and math:ceil/1 to avoid unnecessary conversions
in floating point expressions. That is, instead of having to write
float(floor(X)) as part of a floating point expressions, we can
write simply math:floor(X).
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Implement as ceil/1 and floor/1 as new guard BIFs (essentially part of
Erlang language). They are guard BIFs because trunc/1 is a guard
BIF. It would be strange to have trunc/1 as a part of the language, but
not ceil/1 and floor/1.
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The filters in a list comprehension can be guard expressions or
an ordinary expressions.
If a guard expression is used as a filter, an exception will basically
mean the same as 'false':
t() ->
L = [{some_tag,42},an_atom],
[X || X <- L, element(1, X) =:= some_tag]
%% Returns [{some_tag,42}]
On the other hand, if an ordinary expression is used as a filter, there
will be an exception:
my_element(N, T) -> element(N, T).
t() ->
L = [{some_tag,42},an_atom],
[X || X <- L, my_element(1, X) =:= some_tag]
%% Causes a 'badarg' exception when element(1, an_atom) is evaluated
It has been allowed for several releases to override a BIF with
a local function. Thus, if we define a function called element/2,
it will be called instead of the BIF element/2 within the module.
We must use the "erlang:" prefix to call the BIF.
Therefore, the following code is expected to work the same way as in
our second example above:
-compile({no_auto_import,[element/2]}).
element(N, T) ->
erlang:element(N, T).
t() ->
L = [{some_tag,42},an_atom],
[X || X <- L, element(1, X) =:= some_tag].
%% Causes a 'badarg' exception when element(1, an_atom) is evaluated
But the compiler refuses to compile the code with the following
diagnostic:
call to local/imported function element/2 is illegal in guard
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* bjorn/eliminate-sys_pre_expand/OTP-13856:
Remove sys_pre_expand
xref: Eliminate use of sys_pre_expand
debugger: Eliminate use of sys_pre_expand
compiler: Eliminate use of sys_pre_expand
shell_SUITE: Eliminate references to sys_pre_expand in comments
qlc_pt: Simplify code because of updated erl_expand_records
Teach erl_expand_records to translate module-less calls
erl_internal: Add add_predefined_functions/1
cover: Remove always stale comment
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* maint:
doc: Correct errors introduced by Editorial changes
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The previous commits have made sys_pre_expand superfluous. Since
sys_pre_expand is undocumented and unsupported it can be removed in
a major release without prior deprecation.
Also remove code in erl_parse that handles abstract code that has
passed through sys_pre_expand.
We considered deprecating sys_pre_expand just in case, but decided
against it for the following reasons:
- Anyone brave and knowledgeable enough to use sys_pre_expand should
be able to cope with sys_pre_expand being removed.
- If we kept it, but didn't test it anywhere in OTP, it could
potentially stop working. So we would probably have to add some test
cases.
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sys_pre_expand previously did a lot more work, for example,
translating records and funs, but now is merely a grab bag
of small transformations. Move those transformations to
v3_core.
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Fix some older errors as well.
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105c5b0071 was reverted in dd1162846e because clauses that were
supposed to match would not match. (See 8b83bc0b.)
Reintroduce the optimization, but make sure that we only shortcut
bs_context_to_binary instructions and not bs_start_match2 instructions.
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Don't only test the case that failed; test it exhaustively.
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* maint:
asn1_test_lib: Compile ASN.1 modules in parallel
Support 'make -j' when compiling ASN.1 modules
[ERL-209] Fix ambiguous_catch_try_state inconsistency error
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It is not safe to share code between 'catch' blocks.
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* josevalim/large-binary-strings/PR-1131/OTP-13794:
Move expansion of strings in binaries to v3_core
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* maint:
Update primary bootstrap
beam_block: Fix potentially unsafe optimization in move_allocates/1
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beam_block has an optimization that only is safe when it is applied
immediately after code generation. That is pointed out in a comment:
NOTE: Moving allocation instructions is only safe because it is done
immediately after code generation so that we KNOW that if {x,X} is
initialized, all x registers with lower numbers are also initialized.
That assumption may not be true after other optimizations, such as
the beam_utils:live_opt/1 optimization.
The new beam_reorder pass added in OTP 19 runs before beam_block.
Therefore, the optimization is potentially unsafe. The optimization
is also unsafe if compilation is started from assembly code in a
.S file.
Rewrite the optimization to make it safe. See the newly added comment
for details.
ERL-202
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This speeds up the compilation of binary literals
with string values in them. For example, compiling
a file with a ~340kB binary would yield the following
times by the compiler:
Compiling "foo"
parse_module : 0.130 s 5327.6 kB
transform_module : 0.000 s 5327.6 kB
lint_module : 0.011 s 5327.8 kB
expand_module : 0.508 s 71881.2 kB
v3_core : 0.463 s 11.5 kB
Notice the increase in memory and processing time
in expand_module and v3_core. This happened because
expand_module would expand the string in binaries
into chars. For example, the binary <<"foo">>, which
is represented as
{bin, 1, [
{bin_element, 1, {string, 1, "foo"}, default, default}
]}
would be converted to
{bin, 1, [
{bin_element, 1, {char, 1, $f}, default, default},
{bin_element, 1, {char, 1, $o}, default, default},
{bin_element, 1, {char, 1, $o}, default, default}
]}
However, v3_core would then traverse all of those
characters and convert it into an actual binary, as it
is a literal value.
This patch addresses this issue by moving the expansion
of string into chars to v3_core and only if a literal
value cannot not be built. This reduces the compilation
time of the file mentioned above to the values below:
Compiling "bar"
parse_module : 0.134 s 5327.6 kB
transform_module : 0.000 s 5327.6 kB
lint_module : 0.005 s 5327.8 kB
expand_module : 0.000 s 5328.7 kB
v3_core : 0.013 s 11.2 kB
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Conflicts:
OTP_VERSION
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This reverts commit 105c5b0071056dc062797e58772e098d2a3a4627.
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The following regression was introduced in 19.0:
foo(bar, <<"x">>) -> 1;
foo(_, <<"x">>) -> 2;
foo(_, <<"y">>) -> 3;
foo(_, _) -> fail.
The call foo(bar,<<"y">>) would errorneous return 'fail' instead of 3.
A testcase in match_SUITE has been added to verify this.
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