Introduce BIND_LEXICAL

This opcodes inserts a local CV into the closure static variable
table. This replaces the previous mechanism of having static
variables marked as LEXICAL, whic

Introduce BIND_LEXICAL

This opcodes inserts a local CV into the closure static variable
table. This replaces the previous mechanism of having static
variables marked as LEXICAL, which perform a symtable lookup
during copying.

This means a) functions which contain closures no longer have to
rebuild their symtable (better performance) and b) we can now track
used variables in SSA.

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Don't reuse SSA var in UNSET_VAR

Instead use the SSA var that UNSET_VAR actually defines. Otherwise
we get issues trying to DCE unsets.

Fixed SSA construction for CFG with unreachable BB

Always create ARRAY_ELEM ssa var for ELEM_REF

Skip "useless" SSA variables for INIT_ARRAY, ADD_ARRAY_ELEMENT, FE_RESET_R

Add ability to prevent "useless" SSA variable creation for "refcounting inference".

Protect against overflows in pi constraints

long -> zend_long in range inference

Fix Pi constraint for -LONG_MIN adjustments

-LONG_MIN == LONG_MIN so bad things will happen.
Example of JIT miscompile:

function test($n) {
if ($n + PHP_INT_MIN

Fix Pi constraint for -LONG_MIN adjustments

-LONG_MIN == LONG_MIN so bad things will happen.
Example of JIT miscompile:

function test($n) {
if ($n + PHP_INT_MIN == 0) {
$n2 = (int) ($n + PHP_INT_MAX);
var_dump($n2);
}
}
test(PHP_INT_MAX + 1);

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Extrace find_adjusted_tmp_var() function

This code was duplicated for op1 and op2

Simplify bf/bt computation in pi placement

The meaning of the successors is well-defined, no need to check it.

Fix typo in pi placement

Added simple DFA optimisation pattern (just to prove the concept)

Use do_alloca() instead of alloca()

Added e-SSA based DFA optimisation framework (incomplete)

ws fixes

Added e-SSA based DFA optimisation framework (incomplete)