[Enhancement] Refactored buffer detection logic in warp_specialized_rewriter.cc

[chengyupku]

• Renamed TMAFinder to ProducerBufferDetector and improved handling of CallNode and BufferLoadNode.
• This change aims to enhance code maintainability and performance by more accurately tracking producer buffer usage.

[github-actions]

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[gemini-code-assist]

Summary of Changes

Hello @chengyupku, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on enhancing the buffer detection logic within warp_specialized_rewriter.cc. The primary goal is to improve the accuracy and maintainability of identifying producer buffers, which is crucial for the WarpSpecializedRewriter's performance and correctness. This involves renaming and refactoring key classes and their methods, along with a minor optimization related to register management.

Highlights

• Refactoring Buffer Detection: I've refactored the TMAFinder class, renaming it to ProducerBufferDetector. This new class now has enhanced logic to more accurately identify producer buffers, including handling BufferLoadNode and being initialized with a set of existing producer buffers.
• Improved Producer Buffer Tracking: The ProducerUsedBufferFinder has been improved to iteratively discover all relevant producer buffers. It now also considers buffers involved in BufferStoreNode operations, ensuring a more comprehensive detection.
• Code Clarity and Consistency: Internal variable names like has_tma_load_ and used_in_producer_cond_ have been updated to has_producer_buffer_ and producer_buffers_ respectively, improving code readability and consistency across the buffer detection logic.
• Minor Optimization: A small optimization was added in WarpSpecializedRewriter to prevent unnecessary set_max_nreg calls when SimtCopy is present, which can help with register allocation efficiency.

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[gemini-code-assist]

Code Review

This pull request refactors the buffer detection logic in warp_specialized_rewriter.cc. The changes, particularly the fixed-point iteration for finding producer buffers, improve the correctness and robustness of the analysis. The feedback focuses on opportunities to optimize performance by avoiding potentially expensive operations on std::unordered_set.

[gemini-code-assist]

To improve performance, consider passing cur_producer_buffers by const reference to avoid copying the set. This is safe because ProducerBufferDetector is short-lived and the referenced set will outlive it.

Suggested change

	ProducerBufferDetector(
	std::unordered_set<const BufferNode *> cur_producer_buffers)
	: cur_producer_buffers_(cur_producer_buffers) {}
	ProducerBufferDetector(
	const std::unordered_set<const BufferNode *>& cur_producer_buffers)
	: cur_producer_buffers_(cur_producer_buffers) {}

[gemini-code-assist]

To correspond with the change in the constructor to pass by reference, this member variable should also be a const reference to avoid making a copy of the set.

Suggested change

	std::unordered_set<const BufferNode *> cur_producer_buffers_;
	const std::unordered_set<const BufferNode *>& cur_producer_buffers_;

[gemini-code-assist]

The current fixed-point loop copies the producer_buffers_ set and performs an element-wise comparison in each iteration. This can be inefficient, especially for large sets. A more performant approach is to check if the size of the set has changed after visiting the statement. This avoids both the expensive set copy and the element-wise comparison.

Suggested change

	for (;;) {
	VisitStmt(stmt);
	if (producer_buffers_ == last_producer_buffers_) {
	break;
	}
	last_producer_buffers_ = producer_buffers_;
	for (;;) {
	size_t num_buffers_before = producer_buffers_.size();
	VisitStmt(stmt);
	if (producer_buffers_.size() == num_buffers_before) {
	break;
	}
	}