Refine Initial Switch Construction

[jnhols]

Proposal

Detect switch nodes in nested if-conditions.
More precisely, when restructuring test6 of binary test_condition.zip we do not reconstruct a switch, although it would improve readability.
The CFG before the restructuring has the following form:

The restructuring starts with the region containing nodes 12, 14, and 15 and restructures it as an if-else. Step by step the restructuring adds first nodes 10 & 13, then 8 & 11, and so on to the region. Thus, we never have a sequence node where we start the initial switch node. Therefore, the resulting AST has the following form:

Approach

Improve the InitialSwitchConstructer as follows:

In the function construct we first iterate over all sequence nodes. Add a second iteration over all conditions nodes with a body trying to construct an initial switch node from a condition node, i.e., something like initial_switch_constructor._try_to_construct_initial_switch_from_condition(cond_node).

The condition node must have a concrete structure.

• Check whether the condition of the condition node is expr == const1 or expr != const2.
• In the second case switch the branches (condition_node.switch_branches())
• Check whether the false_branch is also a condition node whose condition is expr == const2 or expr != const2. The compared expression of both conditions must be the same.
• Again, in the second case, switch the branches.
• Now, the two true branches are two cases of a switch node and we can construct an initial
  Here, is a possible reconstruction of a sequence node where two children are possible case nodes of a switch node.
  

[jnhols]

/cib

[github-actions]

Branch issue-113-Refine_Initial_Switch_Construction created!