This is a first try at redundant jump removal (jumps that target the very next instruction). It's too basic in several ways.
- The statement is replaced by a ';' instead of removed.
- If the jump was the only statement in an if, when the if becomes empty, it's not folded.
- Jumps that are last in the 'then' branch of if+else are not visible. This would need either to track multiple last statements, or to have some means to anticipate what the next statement is at every statement. A Control Flow Graph would help a lot.
- When a label is immediately followed by a jump, all jumps to that label should target the destination of that jump if it's in scope. Added to TODO.
- It misses some optimizations when not expanding WHILE and FOR into IF/JUMP.
Moving everything to an earlier stage would help with some of these, especially with ';' and 'if' folding. Unconditionally expanding WHILE and FOR would also help.
Since we need to add variables, we need to know which scope to add them to. Add this information to the {} node, which is what creates a new scope.
An alternative would be to scan for any variable or label declaration within the braces and use that or create a new one if none, which is more expensive and may waste symbol tables.
That was long overdue. Obviously, this is a large commit.
The new nr (node record) class has built-in dump capabilities, rather than using print_node().
SEF always exists now, and is a boolean, rather than using the existence of SEF as the flag. This was changed for sanity. However, other flags like 'X' are still possibly absent, and in some cases the absence itself has meaning (in the case of 'X', its absence means that the node has not yet been analyzed).
Similarly, an event is distinguished from a UDF by checking for the existence of the 'scope' attribute. This trick works because events are not in the symbol table therefore they have no scope. But this should probably be changed in future to something more rational and faster.
A few minor bugfixes were applied while going through the code.
- Some tabs used as Unicode were written as byte strings. Add the u'\t' prefix.
- After simplifying a%1 -> a&0, fold again the node and return. It's not clear why it didn't return, and whether it depended on subsequent passes (e.g. after DCR) for possibly optimizing out the result. Now we're sure.
- A few places lacked a SEF declaration.
- Formatting changes to split lines that spilled the margin.
- Some comment changes.
- Expanded lazy_list_set definition while adapting it to object format. The plan was to re-compress it after done, but decided to leave it in expanded form.
- Added a few TODOs & FIXMEs, resisting the temptation to fix them in the same commit:
- TODO: ~-~-~-expr -> expr + -3.
- FIXME: Now that we have CompareTrees, we can easily check if expr + -expr cancels out and remove a TODO. Low-hanging fruit.
- TODO: Check what we can do when comparing non-SEF and non-CONST values in '>' (current code relies on converting '>' to '<' for applying more optimizations, but that may miss some opportunities).
- FIXME: Could remove one comparison in nt == '&&' or nt == '||'. Low-hanging fruit.
Implements another TODO.
There was a TODO about a new counter per scope, but that makes no sense. The renamer only acts on global variables, global function and parameter names, state names, and event parameters. We're already restarting the counters at every function, which is the closest to what that TODO was about.
This has been a TODO item for long. Now that we have lsllastpass, it's actually easy to implement.
Adds an LSLTypeDefaults dictionary to lslcommon, just in case the state-changing function returns a value and we need to insert a return statement.
We've also added subtree-local info to lsllastpass (lost when we return to the parent after visiting a subtree).
This fixes a bug where naked switch statements could appear as a result of optimization, and cause the compilation to fail.
lslcleanup: Variables renamed, order changed, comments added.
Other changes: remove semicolon at end of sentence, use self.Cast instead of creating a CAST node on the fly.
