[SR-340] Refactor SILParser::parseSILInstruction

[gottesmm]

Previous ID	SR-340
Radar	None
Original Reporter	@gottesmm
Type	Bug
Status	In Progress
Resolution

Additional Detail from JIRA

Votes	1
Component/s	Compiler
Labels	Bug, StarterBug
Assignee	d066z (JIRA)
Priority	Medium

md5: ee6df5ef735c9655c56ca6ce06200e7e

Issue Description:

parseSILInstruction is horrible and makes me cry every time I see it. It is a method that is ~1900 lines with a huge switch in it. We should refactor it into a visitor structure. In fact it is large enough that we should consider moving it into its own file if it is possible.

[belkadan]

Resetting assignee for all Starter Bugs not modified since 2018.

[Kyle-Ye]

After this commit, parseSILInstruction was optimized into 76 lines of code. Maybe we should close this issue.

[AnthonyLatsis]

This is still relevant because no visitor-oriented refactoring took place. The referenced commit simply decouples the problematic code into a dedicated function.

[oozoofrog]

@AnthonyLatsis I found that these functions are called within parseTopLevelSIL in ParseDecl.cpp. :)
I've been tracing the call hierarchy of parseSpecificSILInstruction through parseSILInstruction and up to parseDeclSIL and parseSILGlobal, but I'm unable to find where parseDeclSIL and parseSILGlobal is actually being used in the codebase. Could help me understand where and how parseDeclSIL and parseSILGlobal is invoked in the Swift compiler? Are there any entry points or higher-level parsing functions that call parseDeclSIL? I'd appreciate any insights into how this SIL parsing chain is initiated and utilized in the broader context of the compiler.

[AnthonyLatsis]

@oozoofrog Are you working on this? Let me know if you want to be assigned.

[oozoofrog]

@oozoofrog Are you working on this? Let me know if you want to be assigned.

Yes I'm working on this, can I get assigned?

[oozoofrog]

@AnthonyLatsis Thanks for the assign on this issue.
I've begun working on separating the numerous switch cases in the 'parseSpecificSILInstruction' function into a separate visitor. I've focused on this function as I believe it's the most problematic. I'd appreciate your thoughts on whether this approach is sufficient or if there are any shortcomings.