A lookupswitch or tableswitch can be used if all conditions are equality
checks to constants. To be more specific, it can be done if:
1. All conditions are CALL 'EQEQ(Any?, Any?)': Boolean
2. All types of variables involved in comparison are in the same group
of Char/Byte/Short/Int, String or enum.
3. All arg0 refer to the same value.
4. All arg1 are IrConst<*>.
Change-Id: Ifd7cb618395f6c5cc64601018b446f0bb7f5891c
Simplify ifs when branches have condition true/false.
Simplify blocks containing only a variable declaration
and a variable get of the same variable. Simplify to
just the condition.
Do not introduce temporary variables for constants for
null checks. Constants have no side-effects and can be
reloaded freely instead of going through a local.
This simplifies code such as "42.toLong()!!" so that the
resulting code has no branches and uses no locals. The
simplifications happen as follows:
```
block
temp = 42.toLong()
when
(temp == null) throw NPE
(true) load temp
---> null test simplification
block
temp = 42.toLong()
when
(false) throw NPE
(true) load temp
---> when simplification
block
temp = 42.toLong()
load temp
---> block simplification
42.toLong()
```
Introduce lowering to remove null checks for primitive type
expressions and replace them with true/false. Side-effects
are preserved.
Generate ifnull/ifnonnull instructions for null checks instead
of materializing a null literal for an equality check.
All bytecode text tests are run with stdlib in the classpath and only
for JVM backend, therefore directives WITH_RUNTIME, TARGET_BACKEND,
IGNORE_BACKEND are not needed
Ting-Yuan Huang