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beam_utils:is_not_used_at/3 could be very slow for complex guards,
because the cached result for previously encountered labels were
neither used nor updated within blocks.
Reported-by: Magnus Müller
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Commits 53bd4974a101 and 726f6e4c7afe simplified the handling of
match_fail (used to generated exceptions such as 'function_clause')
by first rewriting them to a call to erlang/error{1,2} and later
rewriting them to specialized BEAM instructions (to reduce the
code size).
There was one flaw, though, which only was exposed when more
aggressive optimizations were added in c3b60f86c622. Here is an
example to explain it:
t(V) ->
fun(get) -> V end.
The following BEAM code will be initially generated for the fun:
{function, '-t/1-fun-0-', 2, 5}.
{label,1}.
{line,[{location,"t.erl",5}]}.
{func_info,{atom,t},{atom,'-t/1-fun-0-'},2}.
{label,2}.
{test,is_eq_exact,{f,2},[{x,0},{atom,get}]}.
{move,{x,1},{x,0}}.
return.
{label,2}.
{test_heap,2,1}.
{put_list,{x,0},nil,{x,1}}.
{move,{atom,function_clause},{x,0}}.
{line,[{location,"t.erl",5}]}.
{call_ext_only,2,{extfunc,erlang,error,2}}.
Translating back to Erlang code, that would be roughly:
'-t/1-fun-0-'(get, V) -> V;
'-t/1-fun-0-'(Arg1, _) -> erlang:error(function_clause, [Arg1]).
Note that the second argument (the free variable V) is not included
in the call to erlang:error/2.
The beam_except pass will simplify the code to:
{function, '-t/1-fun-0-', 2, 8}.
{label,1}.
{line,[{location,"t.erl",5}]}.
{func_info,{atom,t},{atom,'-t/1-fun-0-'},2}.
{label,2}.
{test,is_eq_exact,{f,1},[{x,0},{atom,get}]}.
{move,{x,1},{x,0}}.
return.
The code has been shortened by jumping to the func_info/3 instruction.
Translating back to Erlang:
'-t/1-fun-0-'(get, V) -> V;
'-t/1-fun-0-'(Arg1, Arg2) -> erlang:error(function_clause, [Arg1,Arg2]).
it is clear that both arguments are now included in the
'function_clause' exception, even though the initially generated
code only included the first argument.
That is no problem in this particular case, but for some more complex
funs, optimizing the first version based on variable usage could make
the second version unsafe.
I rejected the following potential solutions:
- Including the free arguments in the call to erlang:error/2:
'-t/1-fun-0-'(get, V) -> V;
'-t/1-fun-0-'(Arg1, Arg2) -> erlang:error(function_clause, [Arg1,Arg2]).
Unfortunately, that is tricky. The free variables are only known
after the second pass in v3_kernel when variable usage has been
calculated. We would need to add a third pass (only for funs) that
would the free arguments to the second argument for erlang:error/2
*and* update the variable usage information.
- Calling beam_except earlier, from within beam_block before any
optimizations based on variable usages are done. But means that the
problem could reappear in some other form in the future when other
updates are done to the code generator and/or optimization passes.
The solution I have chosen is to modify beam_except to only replace
a call to erlang:error(function_class, Args) if the length of Args
is the same as the arity in the func_info/3 instruction. The code
will be slightly larger. Also, the free variables for funs and list
comprehensions will no longer be included in the function_clause
exception (that could be less confusing, but it also means less
information during debugging).
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* nox/fix-seq-opt/OTP-10818:
Add two tests for unused multiple values in effect context
Forbid multiple values in Core Erlang sequence arguments
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The following code:
check(<<"string">>, a1) ->
one;
check(_, a2) ->
two;
check(undefined, a3) ->
three.
produces an internal consistency failure:
check: function check/2+17:
Internal consistency check failed - please report this bug.
Instruction: {test,is_eq_exact,{f,7},[{x,0},{atom,undefined}]}
Error: {match_context,{x,0}}:
Actually, in the current implementation of the run-time system,
comparing a match context to an atom is safe, so I briefly considered
updating the beam_validator to let this code pass through. I
abandoned that approach because not all terms would be safe to
compare to a match context, and the implementation might change
in the future.
Therefore, fix this problem by not allowing any matching of non-variables
(in the argument position for binary being matched) following binary
matching. That solution is simple and safe, and since this kind of
code seems to be rare in practice, there is no need to pursue any
more compilicated solution.
Reported-by: Viktor Sovietov
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* bjorn/remove-parameterized-modules/OTP-10616:
Remove support for parameterized modules
xref_SUITE: Don't test parameterized modules
shell_SUITE: Don't test parameterized modules
erl_expand_records_SUITE: Don't test parameterized modules
erl_eval: Don't test parameterized modules
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* nox/promote-inline_list_funcs/OTP-10690:
Raise a function_clause error with the right arguments when inlining
Properly guard against badly-typed arguments when inlining
Make inlined list functions fail with function_clause
Document compiler option 'inline_list_funcs'
Silence some wrong warnings triggered by inline_list_funcs
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The inlined lists functions raised an error with only the list instead
of all their given arguments.
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The inlining code for inline_list_funcs silenced the function_clause
error that should occur when calling lists:map(3.5, []).
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The function_clause errors produced by inline_list_funcs should properly
be annotated with their function names to avoid kernel_v3 making them
into case_clauses errors. See v3_kernel:translate_match_fail_1/4.
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The handling of bs_start_match2 was both too conservative and too
careless. It was too conservative in that would not do the
optimization if the were copies of the match state in other
registers. It was careless in that it did not consider the
failure branch.
Reorganize the code and fix both these issues. Add a test case
to test that the failure branch is considered.
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* maint:
Fix compiler crash for binary matching and a complicated guard
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Commit c4375a62cfaabfd8de757f59714623ba1a8cb915 added a parallel
group, but incorrectly, so no test cases at all were run in
receive_SUITE.
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The compiler would crash when attempting to compile a function
head that did binary matching and had a complex expression using
'andalso' and 'not'.
Noticed-by: José Valim
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It should be beam_except_SUITE, since it tests the beam_except
module (introduced in 726f6e4c7afe8ce37b30eedbebe583e7b9bfc51b).
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Run testcases in parallel will make the test suite run slightly
faster. Another reason for this change is that we want more testing
of parallel testcase support in common_test.
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Introduce the mandary beam_a pass that will be run directly after code
generation, and the mandatory beam_z pass that will be run just before
beam_asm. Since these passes surround the optimizations, beam_a can
(for example) do instruction renaming to simplify the optimization
passes and beam_z can undo those renamings.
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Don't throw the parse tree in the face of the user.
OTP-8707
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beam_jump moves short code sequences ending in an instruction that causes
an exception to the end of the function, in the hope that a jump around
the moved blocked can be replaced with a fallthrough. Therefore, moving
a block that is entered via a fallthrough defeats the purpose of the
optimization.
Also add two more test cases for the beam_receive module to ensure that
all lines are still covered.
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When matched variable is used as a size field in multiple clauses,
as in:
foo(<<L:8,A:L>>) -> A;
foo(<<L:8,A:L,B:8>>) -> {A,B}.
the match tree would branch out before the segment that used the
matched-out variable (in this example, the tree would branch out before
the matching of A:L). That happens because the pattern matching
compilator did not take variable substitutions into account when
grouping clauses that match the same value.
That is, the generated code would work similarly to this code:
foo(<<L:8,T/binary>>) ->
case T of
<<A:L>> ->
A;
_ ->
case T of
<<A:L,B:8>> -> %% A matched out again!
{A,B}
end
end.
We would like the matching to work more like:
foo(<<L,A:L,T/binary>>) ->
case T of
<<>> -> A;
<<B:8>> -> {A,B}
end.
Fix the problem by taking the substitutions into account when grouping
clauses that match out the same value.
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The bs_match_string instruction is used to speed up matching of
binary literals. For example, given this source code:
foo1(<<1,2,3>>) -> ok.
The matching part of the code will look like:
{test,bs_start_match2,{f,1},1,[{x,0},0],{x,0}}.
{test,bs_match_string,{f,3},[{x,0},24,{string,[1,2,3]}]}.
{test,bs_test_tail2,{f,3},[{x,0},0]}.
Nice. However, if we do a simple change to the source code:
foo2(<<1,2,3>>) -> ok;
foo2(<<>>) -> error.
the resulting matching code will look like (sligthly simplified):
{test,bs_start_match2,{f,4},1,[{x,0},0],{x,0}}.
{test,bs_get_integer2,{f,7},1,[{x,0},{integer,8},1,Flags],{x,1}}.
{test,is_eq_exact,{f,8},[{x,1},{integer,1}]}.
{test,bs_match_string,{f,6},[{x,0},16,{string,[2,3]}]}.
{test,bs_test_tail2,{f,6},[{x,0},0]}.
{move,{atom,ok},{x,0}}.
return.
{label,6}.
{bs_restore2,{x,0},{atom,start}}.
{label,7}.
{test,bs_test_tail2,{f,8},[{x,0},0]}.
That is, matching of the first byte is not combined into the
bs_match_string instruction that follows.
Fix this problem by allowing a bs_match_string instruction to be
used if all clauses will match either the same integer literal or
the empty binary.
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The code generator uses conservative liveness information. Therefore
the number of live registers in allocation instructions (such as
test_heap/2) may be too high. Use the actual liveness information
to lower the number of live register if it's too high.
The main reason we want to do this is to enable more optimizations
that depend on liveness analysis, such as the beam_bool and beam_dead
passes.
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* bjorn/compiler/illegal-size/OTP-10197:
compiler: Warn if the size of a binary segment is invalid
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Column numbers was merged without understanding all the whole
story. See mail on erlang-patches for details.
This reverts commit df8e67e203b83f95d1e098fec88ad5d0ad840069, reversing
changes made to 0c9d90f314f364e5b1301ec89d762baabc57c7aa.
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The compiler would silently accept and Dialyzer would crash on
code like:
<<X:(2.5)>>
It is never acceptable for Dialyzer to crash. The compiler should
at least generate a warning for such code. It is tempting to let
the compiler generate an error, but that would mean that code like:
Sz = 42.0,
<<X:Sz>>.
would be possible to compile with optimizations disabled, but not
with optimizations enabled.
Dialyzer crashes because it calls cerl:bitstr_bitsize/1, which
crashes if the type of size for the segment is invalid. The easiest
way to avoid that crash is to extend the sanity checks in v3_core
to also include the size field of binary segments. That will cause
the compiler to issue a warning and to replace the bad binary
construction with a call to erlang:error/1. (It also means that
Dialyzer will not issue a warning for bad size fields.)
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* bjorn/compiler/minor-fixes/OTP-10185:
erl_lint: Add a deprecated warning for literal tuple funs
beam_utils:live_opt/1: Correct handling of try_case_end/1
Correct guard_SUITE_tuple_size.S
beam_type: Print the offending function if this pass crashes
beam_validator: Validate the size operand in bs_init_bits and bs_init2
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The number of live registers in the gc_bif instructions was wrong.
It was not noticed because the beam_type pass silently corrected it.
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* nox/compile-column-numbers:
Fix messages ordering with column numbers
Fix type compile:err_info/0
Test column number reporting in error_SUITE
Fix printing of errors with column numbers
Create a new "column" option in compile
Allow setting of initial position in epp
Export type erl_scan:location/0
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If a process trap exits, calling the compiler would leave an EXIT
message in the message queue of the calling process because the
compiler spawns a temporary work process. Eliminate the EXIT process
by monitoring the temporary process instead of linking to it.
Reported-by: Jeremy Heater
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Correct the forms_2 test case introduced in 2d785c07fbf9f533bf so
that it will work on Windows. As originally written, the test case
assumed that filename:absname("/foo/bar") would return "/foo/bar",
which is not true on Windows (typically, the result will be
"c:/foo/bar").
While at it, clean up indentation, the overlong line, and comments.
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* jv/forms-source:
Allow the source to be set when compiling forms
OTP-10150
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Because of a copy-and-paste error in erlc.c, the -MP flag had the same
effect as -MG. As a workaround, you had to pass +makedep_phony to enable
the MP option. This patch makes -MP work as intended.
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OTP-10106
OTP-10107
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This commit adds a source option to compile:forms() that
sets the source value returned by module_info(compile).
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* bjorn/compiler/coverage-and-minor-fixes/OTP-9982:
v3_life: Use common code for guards and bodies
v3_core: Don't put negative line numbers in annotations
v3_kernel: Dig out the line number only when generating a warning
v3_kernel: Clean up handling of guards
v3_kernel: Introduce is_in_guard/1
v3_kernel: Removed unreached clause for #k_bin_int{} in sub_size_var/1
v3_kernel: Remove unreached handling of #k_bin_int{} in arg_con/1
v3_codegen: Eliminate the special case of 'put' without destination
v3_kernel: Don't attempt to share identical literals
v3_kernel: Handle sequences in guards
v3_kernel: Remove clauses that are never executed in arg_val/1
v3_kernel.hrl: Remove unused record #k_string{}
v3_kernel.erl: Remove unused define of EXPENSIVE_BINARY_LIMIT
sys_core_fold: Refactor previous_ctx_to_binary/2 to cover it completely
sys_core_fold: Fix opt_guard_try/1
sys_core_fold: Simplify opt_bool_not() to cover it completely
sys_core_fold: Remove duplicate optimization
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* ks/compile_info-fix:
compiler: Fix discrepancy in compile_info
OTP-9917
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