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The following code would crash v3_codegen:
order(From) ->
catch
if
From#{[] => sufficient} ->
saint
end.
Before explaining the crash, first some background on the stack
frame and the Y registers.
Certain instructions, most notably the 'call' instructions, clobber
all X registers. Before any such instruction, all X registers that
have values that will be used after the call must be saved to Y
registers (i.e. to the stack frame). adjust_stack/4 will be called
when X registers must be saved.
There is also another situation when X registers must be saved, namely
within a 'catch' if we are about to execute any instruction that may
cause an exception. Examples of such instructions are some guard BIFs
(such as length/1) and construction of binaries or maps. Within a
'catch', X registers must be be saved because if an exception is
thrown and catched all X registers will be destroyed. The same
adjust_stack/4 function will be called for those instructions, but
only if they occur within a 'catch'.
There is actually one more complication. If there is code in
a guard within a catch, the X registers should not be saved, because
the code in a guard never clobbers any X registers that were alive
before the guard code was entered. v3_codegen is written with the
implicit assumption that code in guards never cause anything
to be saved to Y registers.
The code for building maps and binaries would incorrectly save X
registers within a guard inside a 'catch'.
For construction of binaries, that would mean that a useless but
harmelss 'move' instruction was generated.
But for construction of maps, the saving of the Y register would not
be harmless. There would be a crash when attempting to merge #sr{}
records. #sr{} records keeps track of the contents of X and Y
registers. When two separate code paths are joined (e.g. at the end of
'case' statement), the register descriptors must be reconciled.
Basically, the register descriptors for both paths must be identical.
The #sr{} record for one path must not claim that {y,0} contains
a certain value, while another path claims that {y,0} is dead.
Thus, the crash occurs in sr_merge/2 when failing to reconcile the
Y registers.
To fix this bug this bug we will introduce a new function called
maybe_adjust_stack/5. It will save X registers on the stack only
if the code is inside a catch but not inside a guard. We will
change all existing code to use this new function when appropriate.
Reported-by: Thomas Arts
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beam_bool would make the following code unsafe (which would be
reported by beam_validator):
scotland(Echo) ->
found(case Echo of
Echo when true; Echo, Echo, Echo ->
Echo;
echo ->
[]
end,
Echo = placed).
found(_, _) -> million.
Basically, beam_bool would see that the 'case' would always return
the value of Echo. Thus:
scotland(Echo) ->
found(Echo, Echo = placed).
The only problem is that beam_bool would also remove a 'move'
instruction that would save Echo to the stack. Here is the
assembly code for part of the function:
{allocate_zero,1,1}.
{move,{x,0},{y,0}}. %% Save Echo on stack.
{bif,'=:=',{f,7},[{x,0},{atom,true}],{x,1}}.
{bif,'=:=',{f,7},[{x,0},{atom,true}],{x,2}}.
{bif,'=:=',{f,7},[{x,0},{atom,true}],{x,3}}.
{bif,'and',{f,7},[{x,2},{x,3}],{x,2}}.
{bif,'and',{f,7},[{x,1},{x,2}],{x,1}}.
{jump,{f,8}}.
{label,7}.
{move,{atom,false},{x,1}}.
{label,8}.
{bif,'or',{f,6},[{atom,true},{x,1}],{x,1}}.
{test,is_eq_exact,{f,6},[{x,1},{atom,true}]}. %% Jump never taken.
{jump,{f,5}}.
{label,6}.
{test,is_eq_exact,{f,9},[{x,0},{atom,echo}]}.
{move,nil,{x,0}}.
{jump,{f,5}}.
{label,9}.
{test_heap,3,0}.
{put_tuple,2,{x,0}}.
{put,{atom,case_clause}}.
{put,{y,0}}.
{line,[{location,"t.erl",5}]}.
{call_ext,1,{extfunc,erlang,error,1}}.
{jump,{f,5}}.
{label,5}.
{test,is_eq_exact,{f,12},[{atom,placed},{y,0}]}.
beam_bool would see that the is_eq_exact test at label 8 would
always succeed. It could therefore remove most of the code before
the jump to label 5. Unfortunately it also removed the essential
move of Echo to the stack:
{allocate_zero,1,1}.
%% Instruction incorrectly removed: {move,{x,0},{y,0}}.
{jump,{f,5}}.
{label,5}.
{test,is_eq_exact,{f,12},[{atom,placed},{y,0}]}.
The root cause of the problem is that the 'move' instruction is
included in the block of 'bif' instructions before label 8.
Normally the 'move' instruction would not have been discarded,
but because the left operand to the 'or' BIF is 'true', the
entire block with 'bif' instructions are dropped.
As far as I can see, there is no gain by including 'move'
instructions in the first place. There is no way that better
code will be produced. In fact, the entire optimization can
be given up if 'move' instructions are found in the block.
Thus we can fix this bug by never including any 'move' instructions
in the block of 'bif' instructions. We can also remove all the
code that deals with 'move' instructions within blocks.
Reported-by: Thomas Arts
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The .core or .S files that are compiled in the test cases
may lack module_info/0,1 functions, which will cause problems if
we (for example) try to run eprof later. To avoid that problem,
unload each module directly after testing it.
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When calculating the number of live registers for allocation
instruction, it is not always safe to start with the number of live
registers at the start of the block. We will need to use the register
map to know whether there are any holes (dead registers) that are not
subsequently filled.
If the allocation instruction already has a number of live registers
calculated, there is nothing to be gained by raising it.
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I have spent too much time lately waiting for 'cover' to finish,
so now its time to optimize the running time of the tests suite
in coverage mode.
Basically, when 'cover' is running, the test suites would not
run any tests in parallel. The reason is that using too many
parallel processes when running 'cover' would be slower than
running them sequentially. But those measurements were made
several years ago, and many improvements have been made to
improve the parallelism of the run-time system.
Experimenting with the test_lib:p_run/2 function, I found that
increasing the number of parallel processes would speed up the
self_compile tests cases in compilation_SUITE. The difference
between using 3 processes or 4 processes was slight, though,
so it seems that we should not use more than 4 processes when
running 'cover'.
We don't want to change test_lib:parallel/0, because there is
no way to limit the number of test cases that will be run in
parallel by common_test. However, there as test suites (such as
andor_SUITE) that don't invoke the compiler at run-time. We can
run the cases in such test suites in parallel even if 'cover'
is running.
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* egil/fix-maps-compiler-coverage/OTP-12425:
compiler: Rename util function to adhere to name policy
compiler: Remove get_map_elements label check in blocks
compiler: Remove unnecassary guard for get_map_elements
compiler: Remove dead code in beam_flatten
compiler: Increase Maps code coverage
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* maint:
Update primary bootstrap
beam_bool: Correct live calculation for GC BIFs
beam_bool: Correct indentation for try...catch
sys_core_fold: Correct optimization of 'case'
Conflicts:
bootstrap/bin/start.boot
bootstrap/bin/start_clean.boot
bootstrap/lib/compiler/ebin/beam_asm.beam
bootstrap/lib/stdlib/ebin/io_lib_pretty.beam
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When optimizing boolean expressions, it is not always possible
to find a number of live registers for a GC BIF that both preserves
all source registers that will be tested and at the same time
does not include registers that are not initialized.
As currently implemented, we have incomplete information about
the register calculated from the free variables. Some registers
are marked as "reserved". Reserved registers means that we don't
know anything about them; they may or may not be initialized.
As a conservative correction (suitable for a maintenance release), we
will abort the optimization if we find any reserved registers when
calculating the number of live registers. We will not attempt to
improve the information about the registers in this commit.
By examining the coverage when running the existing compiler test
suite we find that the optimization is aborted 15 times (before
adding any new test cases). To put that in perspective, the
optimization is successfully applied 4927 times, and aborted for
other reasons 547 times.
Reported-by: Ulf Norell
Reported-by: Anthony Ramine
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This commit covers 'split_block_label_used' in the beam_bool pass for Maps.
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The BEAM compiler translates code such as:
is_hex_digit(D) when $0 =< D, D =< $9 -> true;
is_hex_digit(D) when $a =< D, D =< $z -> true;
is_hex_digit(D) when $A =< D, D =< $Z -> true;
is_hex_digit(_) -> false.
to something like this:
L0: test is_ge L1 {x,0} 48
test is_ge L1 57 {x,0}
move true {x,0}
return.
L1: test is_ge L2 {x,0} 97
test is_ge L2 122 {x,0}
move true {x,0}
return
L2: test is_ge L3 {x,0} 65
test is_ge L3 90 {x,0}
move true {x,0}
return
L3: move false {x,0}
return
We can see that tests will be repeated even if they cannot possibly
succeed. For instance, if we pass in {x,0} equal to 32, the first
test that {x,0} is greater than or equal to 48 at L0 will fail.
The control will transfer to L1, where it will be tested whether
{x,0} is greater than 97. That test will fail and control
will pass to L2, where again the test will fail.
The compiler can do better by short-circuiting repeating tests:
L0: test is_ge L3 {x,0} 48
test is_ge L1 57 {x,0}
move true {x,0}
return.
L1: test is_ge L2 {x,0} 97
test is_ge L3 122 {x,0}
move true {x,0}
return
L2: test is_ge L3 {x,0} 65
test is_ge L3 90 {x,0}
move true {x,0}
return
L3: move false {x,0}
return
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* nox/compiler/beam_bool-bad-protected:
Properly detect nonboolean protected expressions in beam_bool
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Silly code such as the following could make the compiler crash:
f() when erlang:float(self()); true -> ok.
Reported-by: Ulf Norell
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Calls to erlang:is_function/2 where the second is not a literal nonnegative
integer can crash at runtime and thus can't be marked as safe.
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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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In 3d0f4a3085f11389e5b22d10f96f0cbf08c9337f (an update to conform
with common_test), in all test_lib:recompile(?MODULE) calls, ?MODULE
was changed to the actual name of the module. That would cause
test_lib:recompile/1 to compile the module with the incorrect
compiler options in cloned modules such as record_no_opt_SUITE,
causing worse coverage.
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Added only a few testcases in compiler:error_SUITE and guard_SUITE
The new behaviour of warnings and errors when overriding autoimported BIF's:
Bifs that were autoimported before R14 are dangerous because old code
using them and overriding them in exports can start behaving
differently. For newly added autoimports this can't happen to the new
code that wants to (or dont want to) use them, why only warnings are
added for the BIFs autoimported after the compilator change. Errors
are issued only for code that could have worked in one way in R13 and
now will behave in a different way.
If overriding autoimport with local function:
- if explicit -compile directive supresses autoimport
-> no message
else
- if called from inside module
- if pre R14 autoimported bif
-> error
else
-> warning
else
-> no message
If overriding autoimport with import directive
- if explicit -compile directive supresses autoimport
-> no message
else (regardless of actual usage)
- if pre R14 autoimported bif
-> error
else
-> warning
Calls of local functions or imports overriding autoimported functions
(either post R14 or by using explicit -compile supressions of
autoimport) always goes to the local function or the imported.
The compileation errors are added to not let code like this silently
and disastrously change its semantic (probably to an infinite loop)
between R13 and R14:
----------
-module(m).
-export([length/1]).
length(X) ->
...
Y = length(Z),
....
----------
The user has to select if he/she wants to call length in 'erlang' explicitly
or if the overriding semantics is desired, in which case the -compile
directive has to be used.
-compile({no_auto_import,[F/A]}). Is added to allow to override the
autoimports so that code gets unanbiguous. The directive will remove
an autoimport even if there is no local function or import overriding,
because any other behaviour would be inconsistent and confusing.
record_info and module_info can never be overridden.
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Add the gc_bif's to the VM.
Add infrastructure for gc_bif's (guard bifs that can gc) with two and.
three arguments in VM (loader and VM).
Add compiler support for gc_bif with three arguments.
Add compiler (and interpreter) support for new guard BIFs.
Add testcases for new guard BIFs in compiler and emulator.
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* bg/compiler-inliner:
pmod_SUITE: Again test inlining parameterized modules
compiler tests: Cope with missing args in function_clause for native code
compiler tests: Compile a few more modules with 'inline'
Consistently rewrite an inlined function_clause exception to case_clause
compiler tests: Test the 'inline' option better
compiler: Suppress bs_context_to_binary/1 for a literal operand
compiler: Fix binary matching bug in the inliner
sys_core_inline: Don't generated multiple compiler_generated annos
OTP-8552 bg/compiler-inliner
Several problems in the inliner have been fixed.
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Since a function_clause exception in an inlined function will
be changed to a case_clause exception, we must test for both.
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