[IR Container] Phase2 Basic shared ptr

[mdavis36]

Change Fusion::ir_container_ from unique_ptr to shared_ptr to enable future container sharing between Fusions. Add Fusion tracking API to IrContainer (addFusion/removeFusion/transferFusion/sharingCount). Disable parallel compilation during the shared_ptr transition.

[mdavis36]

!test

[github-actions]

Review updated until commit 53e5045

Description

• Transition Fusion::ir_container_ from unique_ptr to shared_ptr for container sharing

• Replace parent_ pointer with sharing_fusions_ set for multi-Fusion container support

• Add Fusion tracking API (addFusion/removeFusion/transferFusion/sharingCount)

• Disable parallel compilation during shared_ptr transition with kPhase2DisableParallelCompile

Changes walkthrough

	Relevant files
Enhancement	fusion.cpp Update Fusion class for shared_ptr IrContainer                      csrc/fusion.cpp Change ir_container_ from unique_ptr to shared_ptr Remove parent_ pointer updates in swap function Update copy constructor to pass dest_fusion parameter Use addFusion in constructor, removeFusion in destructor Minor formatting improvements +8/-10    container.cpp Implement shared container with Fusion tracking                    csrc/ir/container.cpp Remove parent_ member from swap function Update copy function to use dest_fusion instead of parent() Replace parent_ checks with sharing_fusions_ in inContainer Add Fusion tracking API implementation Replace parent_ with sharing_fusions_ unordered_set +31/-5    fusion.h Update Fusion header for shared_ptr                                            csrc/fusion.h Change ir_container_ from unique_ptr to shared_ptr Add ir_container_ptr() method for shared_ptr access Update comments for new ownership model +5/-2      container.h Update IrContainer header for shared ownership                      csrc/ir/container.h Remove parent_ member variable Update copy function signature with dest_fusion parameter Add Fusion tracking API declarations Add sharing_fusions_ unordered_set member +11/-9
Configuration changes	fusion_kernel_runtime.cpp Disable parallel compilation during transition                      csrc/runtime/fusion_kernel_runtime.cpp Add kPhase2DisableParallelCompile constant set to true Update parallel compilation checks to use the new constant +7/-2

PR Reviewer Guide

Here are some key observations to aid the review process:

🧪 No relevant tests

⚡ Recommended focus areas for review

Missing Error Handling In the destructor, the code calls ir_container_->removeFusion(this) without checking if ir_container_ is null. While there's a null check, the error message suggests this should never happen, but defensive programming would be safer. if (ir_container_) { ir_container_->removeFusion(this); } Potential Race Condition The new fusion tracking methods (addFusion, removeFusion, transferFusion) modify the sharing_fusions_ set, but there's no synchronization mechanism visible. If multiple threads could access these methods concurrently, this could lead to race conditions. void IrContainer::addFusion(Fusion* fusion) { sharing_fusions_.insert(fusion); } void IrContainer::removeFusion(Fusion* fusion) { sharing_fusions_.erase(fusion); } void IrContainer::transferFusion(Fusion* from, Fusion* to) { sharing_fusions_.erase(from); sharing_fusions_.insert(to); } size_t IrContainer::sharingCount() const { return sharing_fusions_.size(); } bool IrContainer::hasMultipleFusions() const { return sharing_fusions_.size() > 1; } const std::unordered_set<Fusion*>& IrContainer::sharingFusions() const { return sharing_fusions_; } Hardcoded Flag The kPhase2DisableParallelCompile flag is hardcoded to true with a TODO comment to remove when std::shared_mutex is added. This should be made configurable or have a clear timeline for removal to avoid accidentally leaving parallel compilation disabled in production. constexpr bool kPhase2DisableParallelCompile = true;