[Observer] Save opline before calling begin/end handlers

Cleanup observer API and add JIT support

Remove specialization of SPEC(OBSERVER) handlers

Add zend_observer API

Closes GH-5857.

Co-authored-by: Nikita Popov <nikita.ppv@gmail.com>
Co-authored-by: Sammy Powers <sammyk@datadoghq.com>

SAVE_OPLINE in NULL_HANDLER

Let's avoid crashing before the nice error message gets printed...

Implement named parameters

From an engine perspective, named parameters mainly add three
concepts:

* The SEND_* opcodes now accept a CONST op2, which is the
argument nam

Implement named parameters

From an engine perspective, named parameters mainly add three
concepts:

* The SEND_* opcodes now accept a CONST op2, which is the
argument name. For now, it is looked up by linear scan and
runtime cached.
* This may leave UNDEF arguments on the stack. To avoid having
to deal with them in other places, a CHECK_UNDEF_ARGS opcode
is used to either replace them with defaults, or error.
* For variadic functions, EX(extra_named_params) are collected
and need to be freed based on ZEND_CALL_HAS_EXTRA_NAMED_PARAMS.

RFC: https://wiki.php.net/rfc/named_params

Closes GH-5357.

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Remove FREE_UNFETCHED concept

In master normal FREE_OPs work like FREE_UNFETCHED_OP used to, so
there is no point in keeping this distinction anymore, it's just
confusing.

Assert exception set in HANDLE_EXCEPTION()

Some code paths were checking this manually, but we can turn this
into a general assertion to avoid surprises (functions returning
failure

Assert exception set in HANDLE_EXCEPTION()

Some code paths were checking this manually, but we can turn this
into a general assertion to avoid surprises (functions returning
failure without throwing).

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Remove #undefs from vm_gen

Possibly these were needed for VM_EXPORT, but they don't serve a
purpose now.

Remove ZEND_VM_EXPORT functionality

This hasn't been used since forever and makes things more confusing
than they already are.

[ci skip] Various typo fixes in stub comments and CHANGES file

Prevent CGG reordering if hanlers order is defined by zend_vm_order.txt

Remove spurious const qualifier from function return type

Merge branch 'PHP-7.4'

* PHP-7.4:
Apply tidy formatting

Apply tidy formatting

Mostly reindent PHP scripts to spaces.

Support the same handler for multiple opcodes

Optimize int === int/double === double

Do this by reusing the implementation used for `==`
when both arguments are ints (IS_LONG) or both are floats (IS_DOUBLE)

```php
// Be

Optimize int === int/double === double

Do this by reusing the implementation used for `==`
when both arguments are ints (IS_LONG) or both are floats (IS_DOUBLE)

```php
// Before: nestedloop_ni took 0.442 seconds
// After: nestedloop_ni takes 0.401 seconds (same as nestedloop_ne)
function nestedloop_ni(int $k) {
$x = 0;
for ($i=0; $i < 50000000; $i++) {
if ($i === $k) {
$x++;
}
}
print "$x\n";
}
function nestedloop_ne(int $k) {
$x = 0;
for ($i=0; $i < 50000000; $i++) {
if ($i == $k) {
$x++;
}
}
print "$x\n";
}
```

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SAMRT BRANCH improvement.

Avoid need of insertion NOP opcoes between unrelated SMART BRANCH instruction and following JMPZ/JMPNZ.
Now instead of checking the opcode of following instruct

SAMRT BRANCH improvement.

Avoid need of insertion NOP opcoes between unrelated SMART BRANCH instruction and following JMPZ/JMPNZ.
Now instead of checking the opcode of following instruction, the same information is encoded into SMART BRANH result_type.

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Encapsulate all SMART BRANCH related logic inside macros. Result of SMART BRANCH may be uninitialized (on exception).

Throw Error when writing property of non-object

This removes object auto-vivification support.

This also means that we can remove the corresponding special
handling for typed pr

Throw Error when writing property of non-object

This removes object auto-vivification support.

This also means that we can remove the corresponding special
handling for typed properites: We no longer need to check that a
property is convertible to stdClass if such a conversion might
take place indirectly due to a nested property write.

Additionally OBJ_W style operations now no longer modify the
object operand, and as such we no longer need to treat op1 as a
def in SSA form.

The next step would be to actually compile the whole LHS of OBJ_W
operations in R rather than W mode, but that causes issues with
SimpleXML, whose object handlers depend on the current compilation
structure.

Part of https://wiki.php.net/rfc/engine_warnings.

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Avoid code dupliction

ceanup

Merge branch 'PHP-7.4'

* PHP-7.4:
Remove HOT attribute from some VM handlers. Comparisons almost always followed by JMPZ/JMPNZ; JMPZNZ is rare used.
Remove --with-zlib-dir option

Merge branch 'PHP-7.4'

* PHP-7.4:
Remove HOT attribute from some VM handlers. Comparisons almost always followed by JMPZ/JMPNZ; JMPZNZ is rare used.
Remove --with-zlib-dir option from mysqlnd config

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Remove HOT attribute from some VM handlers. Comparisons almost always followed by JMPZ/JMPNZ; JMPZNZ is rare used.

Simplify TMP/VAR operand releasing