Change _stringsByHashCode to store the string.

[Erarndt]

Fixes #

Context

The WeakStringCache used to store all the strings in the same dictionary, but was recently switched to use separate collections to store the longer strings that are held by weak references vs shorter strings that always used a string reference. In both cases, a StringWeakHandled was allocated to track the value in the dictionary. This is only needed when we use a handle to track larger strings, so we can avoid the allocation in most cases and simplify StringWeakHandle since it no longer has to potentially store a strong reference to a string. This saves ~20MB of allocations when building Roslyn.

Before:

After:

Changes Made

Testing

Notes

[Copilot]

Pull Request Overview

This PR simplifies the weak‐string caching logic by storing short strings directly in the concurrent cache and removing the extra strong‐reference path from the single‐threaded cache.

• Removed the referencedString field and length check in StringWeakHandle, using only a weak GCHandle
• Switched _stringsByHashCode in the concurrent cache to hold raw strings and introduced _weakHandlesByHashCode for long strings
• Inlined and refactored GetOrCreateEntry into two local functions for the strong‐ and weak‐handle paths

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/StringTools/WeakStringCache.cs	Dropped referencedString and always uses weakHandle; removed the length constant
src/StringTools/WeakStringCache.Concurrent.cs	Changed strong‐string cache to ConcurrentDictionary<int, string>, refactored retrieval logic into local functions

Comments suppressed due to low confidence (1)

src/StringTools/WeakStringCache.cs:74

• [nitpick] All strings now use a weak GCHandle, which may introduce extra allocation and collection overhead for short strings. If preserving short‐string references was intentional, consider reintroducing a strong‐reference path for those below a length threshold.

                if (weakHandle.IsAllocated)

[SimaTian]

Reasonable change in an are we recently modified - so it should be safe enough to update.