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The expansion of record field updates, when more than one field is
updated, but not a majority of the fields, will create a sequence of
calls to `erlang:setelement(Index, Value, Tuple)` where Tuple in the
first call is the original record tuple, and in the subsequent calls
Tuple is the result of the previous call. Furthermore, all Index
values are constant positive integers, and the first call to
`setelement` will have the greatest index. Thus all the following
calls do not actually need to test at run-time whether Tuple has type
tuple, nor that the index is within the tuple bounds.
Since OTP R7, the `sys_core_dsetel` pass, run as the very last Core
Erlang pass, has optimized this sequence of `setelement` calls to use
a special destructive version of `setelement` (called
`set_tuple_element`) for all but the very first `setelement` in the
sequence.
It turns out that the presence of the `set_tuple_element` in SSA code
is awkward and can prevent or complicate type analysis and aggressive
optimizations.
Therefore, this commit removes the `sys_core_dsetel` pass and
reimplements it for SSA code. The optimization will be done in the
`beam_ssa_pre_codegen` pass (that is, just before code generation and
after running all other SSA code optimization passes).
In most cases, the resulting BEAM code is identical to previous
code. For a few modules, the BEAM code is actually slightly better,
with smaller stack frames.
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This fixes compiling against older OTP versions with the +r?VSN
options, which often expand to disabling certain SSA passes to
avoid new instructions.
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This commit lets the type optimization pass work across functions,
tracking return and argument types to eliminate redundant tests.
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Do the optimizations of bs_put* instructions in beam_ssa_opt
and remove the beam_bs pass. This can lead to a slight improvement
of compilation times.
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Share code for semantically equivalent blocks referred to to by `br`
and `switch` instructions.
A similar optimization is done in `beam_jump`, but doing it here as
well is beneficial as it may enable other optimizations. Also, if
there are many semantically equivalent clauses, this optimization can
substanstially decrease compilation times.
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Add the `diffable` option to produce a more diff-friendly output in
a .S file. In a diffable .S file, label numbers starts from 1 in each
function and local function calls use function names instead of labels.
scripts/diffable produces diff-friendly files but only for a hard-coded
sub set of files in OTP. Having the option directly in the compiler
makes is easier to diff the BEAM code for arbitrary source modules.
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* maint:
compiler: Forward +source flag to epp and fix bug in +deterministic
epp: Allow user to set source name independently of input file name
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The source file path as given to `erlc` was included in an implicit
file attribute inserted by epp, even when the +source flag was
set to something else which was a bit surprising. It was also
included when +deterministic was specified, breaking the flag's
promise.
This commit forwards the +source flag to epp so it inserts the
right information, and if +deterministic is given it will be shaved
to just the base name of the file, guaranteeing the same result
regardless of how the input is reached.
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jhogberg/john/compiler/improve-named-funs/OTP-15273/ERL-639
Optimize named funs and fun-wrapped macros
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If a fun is defined locally and only used for calls, it can be replaced
with direct calls to the relevant function. This greatly speeds up "named
functions" (which rely on make_fun to recreate themselves) and macros that
wrap their body in a fun.
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By default, all code is compiled in a separate process
which is terminated at the end of compilation. However,
some tools, like Dialyzer or compilers for other BEAM languages,
may already manage their own worker processes and spawning
an extra process may slow the compilation down.
In such scenarios, you can pass this option to stop the
compiler from spawning an additional process.
This generalizes commit 657760e18087b0cdbaecc5e96e46f6f66bc9497a.
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This commit improves the bit-syntax match optimization pass,
leveraging the new SSA intermediate format to perform much more
aggressive optimizations. Some highlights:
* Watch contexts can be reused even after being passed to a
function or being used in a try block.
* Sub-binaries are no longer eagerly extracted, making it far
easier to keep "happy paths" free from binary creation.
* Trivial wrapper functions no longer disable context reuse.
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Replace beam_dead with beam_ssa_dead
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Most of the optimizations in beam_dead have been superseded
by the optimizations in beam_ssa_dead.
The forward/1 pass of beam_dead has been moved to beam_jump.
The beam_split pass splits blocks that contain instructions with
non-zero labels. Because there are no optimizations left that optimize
instructions within blocks, beam_block never needs to put such
instructions into blocks in the first place. beam_split also moved
'move' instructions out block to help beam_dead. That is no longer
necessary since beam_dead no longer exists.
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Add beam_ssa_dead to perform the main optimizations done
by beam_dead:
* Shortcut branches that jump to another block with a branch.
If it can be seen that the second branch will always branch
to a specific block, replace the target of the first branch.
* Combined nested sequences of '=:=' tests and switch
instructions operating on the same variable to a single switch.
Diffing the compiler output, it seems that beam_ssa_dead finds
many more opportunities for optimizations than beam_dead,
although it does not find all opportunities that beam_dead does.
In total, beam_ssa_dead is such improvement over beam_dead that
there is no reason to keep beam_dead as well as beam_ssa_dead.
Note that beam_ssa_dead does not attempt to optimize away
redundant bs_context_binary instructions, because that instruction
will be superseded by new instructions in the near future.
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* maint:
Updated OTP version
Update release notes
Update version numbers
erts: Fix "Prevent inconsistent node lists" fix
Fix include-path regression caused by dd0a39c
Restore default SIGTERM behaviour for port programs
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Include paths don't actually affect code generation in any way, but
it's reasonable for a build tool like rebar3 to recompile when the
include paths change. This commit restores the old behavior without
the +deterministic flag.
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Sometimes when building a tuple, there is no way to avoid an
extra `move` instruction. Consider this code:
make_tuple(A) -> {ok,A}.
The corresponding BEAM code looks like this:
{test_heap,3,1}.
{put_tuple,2,{x,1}}.
{put,{atom,ok}}.
{put,{x,0}}.
{move,{x,1},{x,0}}.
return.
To avoid overwriting the source register `{x,0}`, a `move`
instruction is necessary.
The problem doesn't exist when building a list:
%% build_list(A) -> [A].
{test_heap,2,1}.
{put_list,{x,0},nil,{x,0}}.
return.
Introduce a new `put_tuple2` instruction that builds a tuple in a
single instruction, so that the `move` instruction can be eliminated:
%% make_tuple(A) -> {ok,A}.
{test_heap,3,1}.
{put_tuple2,{x,0},{list,[{atom,ok},{x,0}]}}.
return.
Note that the BEAM loader already combines `put_tuple` and `put`
instructions into an internal instruction similar to `put_tuple2`.
Therefore the introduction of the new instruction will not speed up
execution of tuple building itself, but it will be less work for
the loader to load the new instruction.
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v3_codegen is replaced by three new passes:
* beam_kernel_to_ssa which translates the Kernel Erlang format
to a new SSA-based intermediate format.
* beam_ssa_pre_codegen which prepares the SSA-based format
for code generation, including register allocation. Registers
are allocated using the linear scan algorithm.
* beam_ssa_codegen which generates BEAM assembly code from the
SSA-based format.
It easier and more effective to optimize the SSA-based format before X
and Y registers have been assigned. The current optimization passes
constantly have to make sure no "holes" in the X register assignments
are created (that is, that no X register becomes undefined that an
allocation instruction depends on).
This commit also introduces the following optimizations:
* Replacing of tuple matching of records with the is_tagged_tuple
instruction. (Replacing beam_record.)
* Sinking of get_tuple_element instructions to just before the first
use of the extracted values. As well as potentially avoiding
extracting tuple elements when they are not actually used on all
executions paths, this optimization could also reduce the number
values that will need to be stored in Y registers. (Similar to
beam_reorder, but more effective.)
* Live optimizations, removing the definition of a variable that is
not subsequently used (provided that the operation has no side
effects), as well strength reduction of binary matching by replacing
the extraction of value from a binary with a skip instruction. (Used
to be done by beam_block, beam_utils, and v3_codegen.)
* Removal of redundant bs_restore2 instructions. (Formerly done
by beam_bs.)
* Type-based optimizations across branches. More effective than
the old beam_type pass that only did type-based optimizations in
basic blocks.
* Optimization of floating point instructions. (Formerly done
by beam_type.)
* Optimization of receive statements to introduce recv_mark and
recv_set instructions. More effective with far fewer restrictions
on what instructions are allowed between creating the reference
and entering the receive statement.
* Common subexpression elimination. (Formerly done by beam_block.)
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As a preparation for replacing v3_codegen with a new code generator,
remove unsafe optimization passes. Especially the older compiler
passes have implicit assumptions about how the code is generated.
Remove the optimizations in beam_block (keep the code that creates
blocks) because they are unsafe. beam_block also calls
beam_utils:live_opt/1, which is unsafe.
Remove beam_type because it calls beam_utils:live_opt/1, and also
because it recalculates the number of heaps words and number of live
registers in allocation instructions, thus potentially hiding bugs in
other passes.
Remove beam_receive because it is unsafe.
Remove beam_record because it is the only remaining user
of beam_utils:anno_defs/1.
Remove beam_reorder because it makes much more sense to run it
as an early SSA-based optimization pass.
Remove the now unused functions in beam_utils:
anno_def/1
delete_annos/1
is_killed_block/2
live_opt/1
usage/3
Note that the following test cases will fail because of the
removed optimizations:
compile_SUITE:optimized_guards/1
compile_SUITE:bc_options/1
receive_SUITE:ref_opt/1
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'john/compiler/fix-deterministic-include-paths/OTP-15204/ERL-679' into maint-21
* john/compiler/fix-deterministic-include-paths/OTP-15204/ERL-679:
Omit include path debug info for +deterministic builds
# Conflicts:
# lib/compiler/test/compile_SUITE.erl
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'john/compiler/fix-deterministic-include-paths/OTP-15204/ERL-679' into maint
* john/compiler/fix-deterministic-include-paths/OTP-15204/ERL-679:
Omit include path debug info for +deterministic builds
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Compiling the same file with different include paths resulted in
different files with the `+deterministic` flag even if everything
but the paths were identical. This was caused by the absolute path
of each include directory being unconditionally included in a
debug information chunk.
This commit fixes this by only including this information in
non-deterministic builds.
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Instructions that produce more than one result complicate
optimizations. get_list/3 is one of two instructions that
produce multiple results (get_map_elements/3 is the other).
Introduce the get_hd/2 and get_tl/2 instructions
that return the head and tail of a cons cell, respectively,
and use it internally in all optimization passes.
For efficiency, we still want to use get_list/3 if both
head and tail are used, so we will translate matching pairs
of get_hd and get_tl back to get_list instructions.
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Running beam_block again after the other optimizations have run will
give it more opportunities for optimizations. In particular, more
allocate_zero/2 instructions can be turned into allocate/2
instructions, and more get_tuple_element/3 instructions can store the
retrieved value into the correct register at once.
Out of a sample of about 700 modules in OTP, 64 modules were improved
by this commit.
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Add -MMD option to erlc
OTP-14830
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The compile option makedep_side_effect, erlc -MMD, instructs
the compiler to emit dependencies and continue to compile
as normal.
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d8d07a7593d811 that added the to_dis option to the compiler no longer
works when merged to master. That is because of 79f28cfd8df1b7
that removed some unused code in erts_debug.
Fix this by adding a new function erts_debug:dis_to_file/2 and
use it from compile module where we have access to the filename
(in beam_listing we only have an opened file).
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Conflicts:
lib/compiler/src/beam_listing.erl
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* maint:
Recognize 'deterministic' when given in a -compile() attribute
Conflicts:
lib/compiler/src/beam_asm.erl
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The v3_life pass does not do enough to be worth being its own
pass. Essentially it does two things:
* Calculates life-time information starting from the annotations
that v3_kernel provides. That part can be moved into v3_codegen.
* Rewrites the Kernel Erlang records to similar plain tuples
(for example, #k_cons{hd=Hd,tl=Tl} is rewritten to {cons,Hd,Tl}).
That rewriting is not needed and can be eliminated.
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This allows compilers built on top of the compile module
to attach external compilation metadata to the compile_info
chunk.
For example, Erlang uses this chunk to store the compiler
version. Elixir and LFE may augment this by also adding
their own compiler versions, which can be useful when
debugging.
The deterministic option does not affect the user supplied
compile_info. It is therefore the responsibility of external
compilers to guarantee any added information does not violate
the determinsitic option, if such option is supported.
Finally, this code moves the building of the compile_info
options to the compile module instead of beam_asm, moving
all of the option mangling code to a single place.
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The goal of this pass is to find values that are built from
patterns and generate aliases for those values to remove
pressure from the GC. For example, this code:
example({ok, Val}) ->
{ok, Val}.
shall become:
example({ok, Val} = Tuple) ->
Tuple.
Currently this pass aliases tuple and cons nodes made of literals,
variables and other cons. The tuple/cons may appear anywhere in the
pattern and it will be aliased if used later on.
Notice a tuple/cons made only of literals is not aliased as it may
be part of the literal pool.
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* hasse/unicode_atoms/OTP-14285:
compiler: Handle (bad) Unicode parse transform module names
kernel: Improve handling of Unicode filenames
stdlib: Handle Unicode atoms in ms_transform
stdlib: Improve Unicode handling of the Erlang parser
stdlib: Handle unknown compiler options with Unicode
stdlib: Handle Unicode macro names
stdlib: Correct Unicode handling in escript
dialyzer: Improve handling of Unicode
parsetools: Improve handling of Unicode atoms
stdlib: Handle Unicode atoms when formatting stacktraces
stdlib: Add more checks of module names to the linter
stdlib: Handle Unicode atoms better in io_lib_format
stdlib: Handle Unicode atoms in c.erl
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As part of sys_core_fold, variables involved in bit syntax
matching would be annotated when it would be safe for a later
pass to do the delayed sub-binary creation optimization.
An implicit assumption regarding the annotation was that the
code must not be further optimized. That assumption was broken
in 05130e48555891, which introduced a fixpoint iteration
(applying the optimizations until there were no more changes).
That means that a variable could be annotated as safe for
reusing the match context in one iteration, but a later iteration
could rewrite the code in a way that would make the optimization
unsafe.
One way to fix this would be to clear all reuse_for_context
annotations before each iteration. But that would be wasteful.
Instead I chose to fix the problem by moving out the annotation
code to a separate pass (sys_core_bsm) that is run later after
all major optimizations of Core Erlang has been done.
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compile:forms/1,2 is documented to return:
{ok,ModuleName,BinaryOrCode}
However, if one of the options 'from_core', 'from_asm', or
'from_beam' is given, ModuleName will be returned as [].
A worse problem is that is that if one those options are
combined with the 'native' option, compilation will crash.
Correct compile:forms/1,2 to pick up the module name from
the forms provided (either Core Erlang, Beam assembly code,
or a Beam file).
Reported here: https://bugs.erlang.org/browse/ERL-417
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By moving to effects_code_generation/1, there is no need
to explicitly remove those options when storing compile
information in the DebugInfo chunk.
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The new Dbgi chunk returns data in the following format:
{debug_info_v1, Backend, Data}
This allows compilers to store the debug info in different
formats. In order to retrieve a particular format, for
instance, Erlang Abstract Format, one may invoke:
Backend:debug_info(erlang_v1, Module, Data, Opts)
Besides introducing the chunk above, this commit also:
* Changes beam_lib:chunk(Beam, [:abstract_code]) to
read from the new Dbgi chunk while keeping backwards
compatibility with old .beams
* Adds the {debug_info, {Backend, Data}} option to
compile:file/2 and friends that are stored in the
Dbgi chunk. This allows the debug info encryption
mechanism to work across compilers
* Improves dialyzer to work directly on Core Erlang,
allowing languages that do not have the Erlang
Abstract Format to be dialyzer as long as they emit
the new chunk and their backend implementation is
available
Backwards compatibility is kept across the board except
for those calling beam_lib:chunk(Beam, ["Abst"]), as the
old chunk is no longer available. Note however the "Abst"
chunk has always been optional.
Future OTP versions may remove parsing the "Abst" chunk
altogether from beam_lib once Erlang 19 and earlier is no
longer supported.
The current Dialyzer implementation still supports earlier
.beam files and such may also be removed in future versions.
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The main purpose of these options is compatibility with
old Erlang systems. Since it is no longer possible to
communicate with R15B or earlier, we no longer need the
r12 through r15 options.
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Rewrite the instruction stream on tagged tuple tests.
Tagged tuples means a tuple of any arity with an atom as its first element.
Typically records, ok-tuples and error-tuples.
from:
...
{test,is_tuple,Fail,[Src]}.
{test,test_arity,Fail,[Src,Sz]}.
...
{get_tuple_element,Src,0,Dst}.
...
{test,is_eq_exact,Fail,[Dst,Atom]}.
...
to:
...
{test,is_tagged_tuple,Fail,[Src,Sz,Atom]}.
...
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This allow languages such as Elixir and LFE to attach
extra chunks to the .beam file without having to parse
the beam file after compilation.
This commit also cleans up the interface to beam_asm,
allowing chunks to be passed from the compiler without
a need to change beam_asm API on every new chunk.
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The new chunk stores atoms encoded in UTF-8.
beam_lib has also been modified to handle the new
'utf8_atoms' attribute while the 'atoms' attribute
may be a missing chunk from now on.
The binary_to_atom/2 BIF can now encode any utf8
binary with up to 255 characters.
The list_to_atom/1 BIF can now accept codepoints
higher than 255 with up to 255 characters (thanks
to Björn Gustavsson).
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