The coroutine transformation would leave locals in the local
variable table across the code that reloads local variables from
the continuation on reentry. However, when reentering the function
the local has no value until after the reloads from the
continuation.
This change splits the locals in the local variable table to
avoid such uninitialized locals. A local alive across a
suspension point has its range split in two. One that goes
from the original start to the state label for the restart
after the suspension. The other goes from after the local
has been reloaded from the continuation until the previous
end of the local.
1. consider reads of fields from the same file "stable" just like
functions, i.e. assume their nullability information is correct
2. apply if-null fusion repeatedly until the subject is no longer a
nested if-null expression
The difference is how we deal with intermediate fake overrides
E.g., in case
interface A { /* $1 */ fun foo() }
interface B : A {
/* $2 */ fake_override fun foo()
}
interface C : B {
/* $3 */ override fun foo()
}
We've got FIR declarations only for $1 and $3, but we've got
a fake override for $2 in IR.
Previously, override $3 had $1 as its overridden IR symbol, just because
FIR declaration of $3 doesn't know anything about $2.
Now, when generating IR for $2, we save the necessary information
and using it for $3, so it has $2 as overridden.
So, it's consistent with the overridden structure of FE 1.0 and this
structure is necessary prerequisite for proper building of bridges
for special built-ins.
FIR translates:
```
when (x) {
1, 2, 3 -> action
else -> other_action
}
```
to an IR structure with nested ors:
```
if ((x == 1 || x == 2) || (x == 3)) action
else other_action
```
This change allows that to turn into switch instructions in the
JVM backend.
i.e. remove the condition that there must be an LVT entry. Such
temporary `Ref`s can be created, for example, by the JVM_IR backend
if a lambda inlined at an IR level (e.g. argument to `assert`/`Array`)
is the target of a non-local return from a function inlined at bytecode
level (e.g. `run`):
IntArray(n) { i ->
intOrNull?.let { return@IntArray it }
someInt
}
->
val `tmp$0` = IntArray(n)
for (i in 0 until `tmp$0`.size) {
var `tmp$1`: Int
do {
intOrNull?.let {
`tmp$1` = it // causes `tmp$1` to become an IntRef
break
}
`tmp$1` = someInt
} while (false)
`tmp$0`[i] = `tmp$1`
}
Andrey Zinovyev