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kqueue is broken on earlier versions of OS X.
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It is not longer relevant when using the poll thread
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This is needed with the new poll-thread implementation
as now closed fd's in the pollset will be triggered much
faster than before.
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OTP-14652
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for non scheduler threads by using ERTS_THR_PREF_QUICK_ALLOC_IMPL.
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usable from any (managed?) thread.
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temp_alloc is used in such a way that if it ever results
in a malloc/free sequence it will slow down the system
alot. So it will no longer be possible to disable it and
it will not be disabled when using +Mea min.
OTP-14651
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Move out from the head the variables that are only used in the excute
phase.
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All other instructions that increment the stack pointer takes a 'Q'
operand.
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Add the CHECK_ALIGNED() macro that can be used for testing that
the storage destination is word-aligned.
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In the 'P' operator, don't assume that a packed target label ('f'
or 'j') is always the leftmost argument. Instead, transfer the
patch position from the accumulator to the stack.
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process_main() is already too big.
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Introduce the IsOpCode() macro that can be used to compare
instructions.
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Consider the types in the code below:
BeamInstr* I;
.
.
.
BeamInstr* next;
next = (BeamInstr *) *I;
Goto(next);
This is illogical. If 'I' points to a BeamInstr, then 'next' should
be a BeamInstr, not a pointer to a BeamInstr. The Goto() macros does
not require a pointer, because it will cast its argument to a void*
anyway.
Therefore, this code example can be simplified to:
BeamInstr* I;
.
.
.
BeamInstr next;
next = *I;
Goto(next);
Similarly, we can remove the casts in the macros when NO_JUMP_TABLE
is defined.
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The BeamOp() macro in erl_vm.h is clumsy to use. All users
cast the return value to BeamInstr.
Define new macros that are easier to use. In the future,
we might want to pack an operand into the same word as
the pointer to the instruction, so we will define two macros.
BeamIsOpCode() is used to rewrite code like this:
if (Instr == (BeamInstr) BeamOp(op_i_func_info_IaaI) {
...
}
to:
if (BeamIsOpCode(Instr, op_i_func_info_IaaI)) {
...
}
BeamOpCodeAddr(op_apply_bif) is used when we need the address
for an instruction.
Also elimiminate the global variables em_* in beam_emu.c.
They are not really needed. Use the BeamOpCodeAddr() macro
instead.
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The inconsistent order has annoyed me for a long time.
While at it, also remove the unecessary definition of LabelAddr() if
NO_JUMP_TABLE is defined.
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Test more instructions and use register numbers >= 512.
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Sometimes the line number in a stack trace could be wrong,
for example for this code:
t() ->
Res = id(x), %<== Wrong line number.
Res + 1.
id(I) -> I.
The line number pointed out in the stack trace would be the
line before the line where the exception occurred.
The reason is the way the increment instruction instruction
is implemented:
OpCase(i_increment_rWtd):
{
increment_reg_val = r(0);
}
I -= 1;
goto increment__execute;
OpCase(i_increment_xWtd):
{
increment_reg_val = xb(I[1]);
}
goto increment__execute;
increment__execute:
/* Common code for increment */
.
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(The implementation in OTP 20 is similar, but hand-coded directly
in beam_emu.c instead of generated.)
The instruction i_increment_rWtd decrements the instruction pointer (I)
before jumping to the common code. That means that I points *before*
the 'increment' instruction. If there is a 'line' instruction directly
before the 'increment' instruction (as there is in this example), the
instruction pointer will point before that line. Thus the previous line
will be picked up instead.
To eliminate this bug, we must never decrement the instruction pointer.
Instead, we can increment the other (longer) instructions in the
same group of combined instructions:
OpCase(i_increment_rWtd):
{
increment_reg_val = r(0);
}
goto increment__execute;
OpCase(i_increment_xWtd):
{
increment_reg_val = xb(I[1]);
}
I += 1;
goto increment__execute;
increment__execute:
/* Common code for increment */
.
.
.
Also fix a bug that was only a potential bug when ddaed7774eb0a
introduced relative jumps, but is now a real bug. See the added
comment for SET_I_REL() in macros.tab.
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Quoting RFC 1952:
"A gzip file consists of a series of "members" (compressed data
sets). [...] The members simply appear one after another in the
file, with no additional information before, between, or after
them."
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When presented with multiple valid but concatenated streams, the
old driver returned an empty result once the end of the first
stream was reached, and kept doing so even if fed new data. The
new driver/NIF returned a data_error instead.
zlib:inflateInit/3 has been added to control this behavior, but is
not yet ready for public use.
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Use 'no_dot_erlang' start script for tools. Options and
paths should be stated on the command line, via a
Makefile, rebar.config etc.
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Previously you could not opt out on loading .erlang, change the
default to not load the resource file. The escript author
can invoke c:erlangrc(PathList) to find and load .erlang if needed.
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Use 'no_dot_erlang' start script for tools.
Options and paths should be stated on the command line.
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For a long time, there has been the two macros IS_SSMALL() and
MY_IS_SSMALL() that do exactly the same thing.
There should only be one, and it should be called IS_SSMALL().
However, we must decide which implementation to use. When
MY_IS_SSMALL() was introduced a long time ago, it was the most
efficient. In a modern C compiler, there might not be any
difference.
To find out, I used the following small C program to examine
the code generation:
#include <stdio.h>
typedef unsigned int Uint32;
typedef unsigned long Uint64;
typedef long Sint;
#define SWORD_CONSTANT(Const) Const##L
#define SMALL_BITS (64-4)
#define MAX_SMALL ((SWORD_CONSTANT(1) << (SMALL_BITS-1))-1)
#define MIN_SMALL (-(SWORD_CONSTANT(1) << (SMALL_BITS-1)))
#define MY_IS_SSMALL32(x) (((Uint32) ((((x)) >> (SMALL_BITS-1)) + 1)) < 2)
#define MY_IS_SSMALL64(x) (((Uint64) ((((x)) >> (SMALL_BITS-1)) + 1)) < 2)
#define MY_IS_SSMALL(x) (sizeof(x) == sizeof(Uint32) ? MY_IS_SSMALL32(x) : MY_IS_SSMALL64(x))
#define IS_SSMALL(x) (((x) >= MIN_SMALL) && ((x) <= MAX_SMALL))
void original(Sint n)
{
if (IS_SSMALL(n)) {
printf("yes\n");
}
}
void enhanced(Sint n)
{
if (MY_IS_SSMALL(n)) {
printf("yes\n");
}
}
gcc 7.2 produced the following code for the original() function:
.LC0:
.string "yes"
original(long):
movabs rax, 576460752303423488
add rdi, rax
movabs rax, 1152921504606846975
cmp rdi, rax
jbe .L4
rep ret
.L4:
mov edi, OFFSET FLAT:.LC0
jmp puts
clang 5.0.0 produced the following code which is slightly better:
original(long):
movabs rax, 576460752303423488
add rax, rdi
shr rax, 60
jne .LBB0_1
mov edi, .Lstr
jmp puts # TAILCALL
.LBB0_1:
ret
.Lstr:
.asciz "yes"
However, in the context of beam_emu.c, clang could produce
similar to what gcc produced.
gcc 7.2 produced the following code when MY_IS_SSMALL() was used:
.LC0:
.string "yes"
enhanced(long):
sar rdi, 59
add rdi, 1
cmp rdi, 1
jbe .L4
rep ret
.L4:
mov edi, OFFSET FLAT:.LC0
jmp puts
clang produced similar code.
This code seems to be the cheapest. There are four instructions, and
there is no loading of huge integer constants.
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It may be confusing that "hidden" .erlang is loaded from the current
working directory. Use c:erlangrc([Dir1,..]) to search and
load .erlang from other places than "$HOME/.erlang".
Implies that c:erlangrc() needs to be documented.
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* lukas/erts/fix_threads_error_printout:
erts: Print the error reason when threads fail to start
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* kvakvs/zero-size-read_file/ERL-327/PR-1524/OTP-14637:
erts: On zero-size files attempt to read until EOF
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fix off by one error in docs
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* bjorn/speed-up-disassembler:
Add testing of erts_debug:df() to the emulator smoke tests
Speed up erts_debug:df()
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The byte_offset of sub-binaries wasn't taken into account for
ProcBins, subtly ruining the results. The test suite didn't catch
it since it didn't check for sub-binaries in particular, and only
checked for equality between variations -- not whether the output
was equal to the input.
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It is too easy to break the disassembler. Make sure that we notice.
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