swiftlang/swift

[SR-6889] [IRGen Opportunity] Use argmemonly for runtime functions

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#49,438 opened on Feb 1, 2018

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Description
Previous ID SR-6889
Radar None
Original Reporter @aschwaighofer
Type Improvement
Votes 0
Component/s Compiler
Labels Improvement, StarterBug
Assignee None
Priority Medium

md5: 050d922fc6f6b8f37d1f70d51229bf7b

Issue Description:

It should be possible to mark some of our runtime functions with argmemonly readonly as they receive their type arguments indirectly via an array of type arguments.

I tried this in https://github.com/apple/swift/pull/14310 but tests failed. I did not have time to investigate why.

I mentioned that if that following situation in some form or another this annotation is not legal:

Type *args[5];
pointer->field = // inlined initialization
arg[1] = pointer
argmemonly(args)

However, we believe that this situation should? not arise. It might be worth investigating the failures.

Contributor guide

Research direction
Investigate why tests fail when marking runtime functions with argmemonly. Look at the linked PR to see the specific test failures and trace the code paths that might violate the argmemonly assumption.
Tech stack
swiftcpp
Domain
None
Issue type
Refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
Swift compiler internalsLLVM IR knowledge
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40