Fix type errors in reduce.h

[LJC00118]

Summary by CodeRabbit

• Refactor
  • Internal optimization of warp-reduction operations to improve code organization and maintainability. No changes to user-facing functionality.

[coderabbitai]

Walkthrough

Replaces two direct calls to __shfl_down_sync with tl::shfl_down_sync in the SharedReduceWarp and CumSum1D functions within the CUDA reduce header. This refactoring changes symbol resolution to use the tl namespace wrapper while maintaining existing behavior.

Changes

Cohort / File(s)	Change Summary
Warp-level shuffle intrinsic refactoring src/tl_templates/cuda/reduce.h	Replaced direct __shfl_down_sync CUDA intrinsic calls with tl::shfl_down_sync namespace-qualified wrappers in two locations within SharedReduceWarp and CumSum1D reduction functions

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

• Straightforward symbol resolution change in two locations
• No logic or control-flow modifications
• Namespace wrapper substitution with preserved behavior

Possibly related PRs

• [Bugfix] Support 16bits shfl_sync #1169: Modifies the same file with related CUDA shuffle intrinsic wrapping refactors, replacing __shfl_* calls with tl::shfl_* equivalents in reduction and cumsum code paths.

Poem

🐰 A shuffle through the tl namespace we go,
Two calls wrapped up in a refactoring glow,
SharedReduceWarp and CumSum align,
With namespace'd intrinsics, now truly divine! ✨

Pre-merge checks and finishing touches

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Title check	⚠️ Warning	The title claims to fix 'type errors' but the actual changes involve replacing direct __shfl_down_sync calls with tl::shfl_down_sync (namespace resolution), not type corrections.	Revise the title to accurately reflect the actual changes, such as 'Use tl namespace for shuffle-down intrinsic in reduce.h' or 'Replace direct __shfl_down_sync with tl::shfl_down_sync'.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (1 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 0592834 and c088f4c.

📒 Files selected for processing (1)

• src/tl_templates/cuda/reduce.h (2 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

src/tl_templates/cuda/reduce.h (1)

src/tl_templates/cuda/common.h (7)

• tl (195-289)
• tl (518-520)
• tl (521-523)
• tl (538-618)
• shfl_down_sync (547-549)
• shfl_down_sync (569-573)
• shfl_down_sync (598-602)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)

• GitHub Check: Quick Lint

🔇 Additional comments (3)

src/tl_templates/cuda/reduce.h (3)

76-76: LGTM! Type compatibility fix for custom types.

This change correctly uses the tl::shfl_down_sync wrapper instead of the direct CUDA intrinsic, ensuring proper support for custom types like half_t and bfloat16_t through the specializations defined in common.h.

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162-162: LGTM! Consistent type compatibility fix.

This change correctly applies the same fix as line 76, ensuring type compatibility for custom types in the cumulative sum operation.

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172-198: I need to examine the actual code changes at lines 76 and 162 to verify the pattern, and find the wrapper functions in the codebase.

Verify wrapper functions and inspect lines 76 and 162 to confirm consistency pattern.

I've confirmed the presence of 5 direct CUDA warp shuffle calls at lines 172, 175, 185, 195, and 198 as stated in your review. However, I cannot independently verify whether:

1. Lines 76 and 162 actually use wrapped tl::shfl_sync / tl::shfl_up_sync versions (as claimed in the review)
2. These wrapper functions exist in common.h or elsewhere in the codebase
3. These wrappers properly handle type compatibility for custom types like half_t and bfloat16_t

To complete the review verification, please confirm:

• Check lines 76 and 162 in src/tl_templates/cuda/reduce.h to verify they use wrapped functions
• Confirm the existence and implementation of tl::shfl_sync and tl::shfl_up_sync in the codebase
• Verify these wrappers include necessary template specializations for custom types

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