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.
- Merge `duplicatingItemsSameHashCode.kt` and
`duplicatingItemsSameHashCode2.kt` into one test enabled on both
backends, and rename it to
`duplicatingItemsSameHashCodeFewBranches.kt`.
- Rename `duplicatingItemsSameHashCode3.kt` to
`duplicatingItemsSameHashCodeMoreBranches.kt`, and also enable it for
both backends.
- Use JVM_TEMPLATES/JVM_IR_TEMPLATES to check backend-specific behavior:
1) JVM IR does not optimize less than 2 branches by design
2) JVM IR does not generate duplicate branches, also by design
Related to KT-36846.
Effectively, the following when structure:
when (s) {
s1, s2 -> e1,
s3 -> e2,
s4 -> e3,
...
else -> e
}
is implemented as:
when (s.hashCode()) {
h1 -> {
if (s == s1)
e1
else if (s == s2)
e1
else if (s == s3)
e2
else
e
}
h2 -> if (s == s3) e2 else e,
...
else -> e
}
where s1.hashCode() == s2.hashCode() == s3.hashCode() == h1,
s4.hashCode() == h2.
A tableswitch or lookupswitch is used for the hash code lookup.
Change-Id: I087bf623dbb4a41d3cc64399a1b42342a50757a6
Most of these tests used this directive as a way to opt in to a new
language feature, and most of those features are already stable for a
long time, so no opt-in is needed. Some other tests used the directive
to opt out from a language feature, replace those by the `LANGUAGE`
directive. One test used the directive to test behavior that actually
depended on the API version; use `API_VERSION` directive there instead.
Mikhail Glukhikh