manual schedule of a transpose in output cached smem

[liqiangxl]

This PR adds a manual scheduling test case demonstrating how to perform a transpose on cached output shared memory using a TMA store.
The transpose scheduler may choose to apply the transpose on either cached input or cached output, depending on the number of inputs and outputs. The guiding principle is to minimize the total number of required transposes, e.g. will do output transpose when there are more inputs than outputs.

[github-actions]

Review updated until commit 7bd7044

Auto-merge Status

✅ Internal CI is finished
✅ No failed checks
✅ PR is mergeable
ℹ️ PR mergeable_state: clean

Description

• Adds new test case TransposeOutputSmem demonstrating manual transpose scheduling on output cached shared memory

• Implements TMA store with output swizzle for transpose operations (loads rows, writes columns)

• Includes detailed tiling, swizzling, and parallelization scheduling for optimal memory access

• Provides performance comparison between TMA load vs non-TMA load approaches (852ms vs 814ms on GB200)

Changes walkthrough

Relevant files

Enhancement

test_transpose.cpp Add output cached transpose scheduling test                            tests/cpp/test_transpose.cpp Add new test TransposeInputSmem replacing TransposeTMALoadOptionalStore Add comprehensive TransposeOutputSmem test demonstrating output-cached transpose scheduling Implement TMA store with output swizzle, tiling, and parallelization strategies Include performance metrics and detailed scheduling comments +156/-1

PR Reviewer Guide

Here are some key observations to aid the review process:

🧪 PR contains tests

⚡ No major issues detected

[greptile-apps]

Greptile Summary

Adds TransposeOutputSmem test demonstrating manual scheduling of transpose operation on output cached shared memory with TMA store. The test complements the existing TransposeInputSmem test by showing the alternative approach where transpose happens at output rather than input.

Key changes:

• New test case manually schedules a 2D transpose [I0, I1] → [I1, I0] with TMA store on output
• Thread scheduling: each thread loads multiple rows from input, writes as multiple columns to output
• Uses 128-byte TMA swizzle with configurable tile sizes (tile_i0=32, tile_i1=64)
• Test validates correctness on 16384×32768 float tensors

Issues found:

• Comment/code mismatch on line 1717 (says tile_i1 but checks tile_i0)

Confidence Score: 4/5

• Safe to merge - test-only change with minor documentation inconsistency
• Test-only change that adds new manual scheduling demonstration. Found one comment/code mismatch that should be corrected but doesn't affect functionality. Issues from previous review threads remain unaddressed but were already flagged.
• No files require special attention beyond addressing the comment on line 1717

Important Files Changed

Filename	Overview
tests/cpp/test_transpose.cpp	Adds TransposeOutputSmem test demonstrating transpose on output cached smem with TMA store; minor comment inconsistency found

_{Last reviewed commit: 7bd7044}

[greptile-apps]

_{1 file reviewed, 3 comments}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

comment appears to have incorrect merge operation description - merge result should be tile_i0/chunk/cpt * tile_i1 not tile_i1/chunk/cpt * tile_i0

Suggested change

	// [BIDx, tile_i1/chunk/cpt * tile_i0, cpt, chunk]
	// [BIDx, tile_i0/chunk/cpt * tile_i1, cpt, chunk]

[greptile-apps]

hardcoded to false makes the TMA load path untested - consider parameterizing or adding second test variant

_{Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!}

[greptile-apps]

comment says tile_i1 but code checks tile_i0

Suggested change

	// tile_i1 must equal tma_swizzle_bytes / dtype_bytes.
	// tile_i0 must equal tma_swizzle_bytes / dtype_bytes.

[liqiangxl]

!build