[SR-7274] More UnsafePointer operations should be @transparent

[rjmccall]

Previous ID	SR-7274
Radar	None
Original Reporter	@rjmccall
Type	Improvement
Status	Closed
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	Standard Library
Labels	Improvement
Assignee	@belkadan
Priority	Medium

md5: 836bb66959851c430085bd51b2dd3190

relates to:

• SR-7277 -Onone should inline @inline(__always)

Issue Description:

Unoptimized code involving UnsafePointers still very frequently results in calls into the library, which in turns forces the compiler to produce type metadata for the generic call.

For example, CommandLine.arguments contains a call to UnsafePointer.advanced(by: ) and therefore a call to get metadata for UnsafePointer<Int8>?. Since this is CommandLine.arguments, this means that we create multiple type metadata at the start of basically every Swift process.

[belkadan]

"Transparent" isn't supposed to just be used for optimization, but in this case the semantic effects are probably desirable as well.

cc @moiseev, @atrick

[atrick]

I would think it's looking up Int8 metadata, not UnsafePointer. At any rate, it's something that we should optimize away at -Onone.

-Onone should have an inlining pass to handle things like @inline(__always) and noescape closures (-Onone is quite a misnomer anyway). I could have sworn I had a bug on that but can't find it now.

Then it's just a matter of the right stdlib annotations. I'm fine abusing @transparent a bit until @inline(__always) works.

[atrick]

I created SR-7277 -Onone should inline @inline(__always) and linked to that.

[belkadan]

In this case I think it isn't really abuse. We don't want to treat a call to advanced(by:) as actually a call you can step into anyway.

[atrick]

Yes, I think this bug title is still accurate. The @inline(__always) issue is tangential.

[belkadan]

I ran into this being necessary for parseable interfaces to get proper optimization behavior, so I think #21126 covers it.

[atrick]

@belkadan's PR above should fix this.

[belkadan]

This probably shouldn't be closed until I merge the PR…

[belkadan]

Okay, now it's merged (master only).