[Fix][CuteDSL] add support for tanh/tanhf (fixes #1595)

[lucifer1004]

Summary by CodeRabbit

• New Features
  • Added support for the tanh (hyperbolic tangent) function in the math interface.
  • Introduced a fastmath-optimized tanh variant for faster approximate evaluation when fast-math optimizations are enabled, offering improved performance with minimal precision trade-offs.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Adds tanh/tanhf fastmath canonicalization to CuTeDSL codegen and a fastmath-backed tanh user-op in the CuTeDSL math DSL, enabling selection of an inline-assembly fastmath tanh path.

Changes

Cohort / File(s)	Summary
CuTeDSL fastmath mapping src/target/codegen_cutedsl.cc	Added tanh and tanhf entries to kFastMathMap inside CanonicalizeFastmathFunctionName_, enabling canonicalization of tanh with fastmath.
CuTeDSL math DSL tilelang/contrib/cutedsl/math.py	Added __tanhf DSL user-op (inline-assembly fastmath tanh) and public tanh(x, fastmath=False) that dispatches to the fastmath path when requested; updated imports and typing to support the new op.

Sequence Diagram(s)

(omitted — changes are localized and do not introduce multi-component sequential flows)

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related issues

• [BUG] CuTe-DSL backend wrongly converts tanh to tanhf(op) as opposed to tanh(op, fastmath=True) #1595: Fixes emission of an undefined tanhf symbol by adding tanh/tanhf mappings and a fastmath tanh path in the CuTeDSL layers.

Poem

🐰 I hopped through bytes and tiny tags,
I stitched a fastmath path in fabled flags.
Tanh now darts with nimble cheer,
A rabbit’s tweak—precision near! ✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
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 (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: adding tanh/tanhf support to CuteDSL, and references the related issue.

✨ Finishing touches

• 📝 Generate docstrings

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[coderabbitai]

Actionable comments posted: 1

📜 Review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between e5d8451 and 3142f8a.

📒 Files selected for processing (1)

• tilelang/contrib/cutedsl/math.py

🧰 Additional context used

🪛 Ruff (0.14.10)

tilelang/contrib/cutedsl/math.py

5-5: Unused noqa directive (non-enabled: F401)

Remove unused noqa directive

(RUF100)

---

15-15: Unused function argument: fastmath

(ARG001)

🔇 Additional comments (2)

tilelang/contrib/cutedsl/math.py (2)

4-4: LGTM! Imports are appropriate.

All added imports are utilized in the new tanh implementation.

Also applies to: 7-9

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30-32: LGTM! The fastmath delegation logic is correct.

The function correctly delegates to __tanhf for fast approximation when fastmath=True, or to math.tanh for standard precision when fastmath=False. Passing False as the second parameter to _math_op is appropriate since the operation choice already encodes the fast/slow decision.