[sepcnt]

Split the C/CPU clz support out of #3265 for independent review.

Add scalar clz lowering for signed and unsigned 32-bit and 64-bit integers in the CPU C and C host code generators.

• Share helpers using GCC/Clang builtins, MSVC intrinsics, or portable fallbacks.
• Return the input bit width for zero and emit helpers only when needed.
• Include CPU regression tests and C host tests covering CUDA graph capture and replay.

Summary

• Add shared tl_clz32 and tl_clz64 helpers for C and C++ code generation. They return the input bit width for zero and use compiler builtins, MSVC intrinsics, or fallback logic.
• Update the CPU C and C host code generators to support scalar signed and unsigned 32-bit and 64-bit tirx.clz inputs. Each generator emits the helper definitions once per initialization.
• Add CPU tests for all four integer types. Add host tests for CUDA graph capture and replay.

C++ style / lint notes

• The PR adds C++ code. The C++ style guide describes the C++ API style audit, but the available evidence does not show whether the changes touch a specific documented style rule.
• CI runs the C++ API Style Audit (warning only) step. No findings or audit results were provided.

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• Repository: tile-ai/tilelang
• Branch: main
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• Commit: 741bf8b
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Reviewing files that changed from the base of the PR and between 7f6b2f9 and 0af8b45.

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• src/transform/loop_vectorize.cc

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📝 Walkthrough

This change adds shared 32-bit and 64-bit leading-zero-count helpers for CPU and host C code generation. It also changes VectorizeLoop to pass a cloned analyzer to VectorizeRewriter. New tests cover CPU execution and CUDA host code generation across four integer dtypes.

Changes: C/C++ CLZ code generation

Layer / File(s)	Summary
Shared leading-zero-count helpers src/backend/common/codegen/c_bit_intrinsics.h	Adds 32-bit and 64-bit helpers with zero handling and compiler-specific or fallback implementations.
CPU and host codegen integration src/backend/common/codegen/codegen_c_host.h, src/backend/common/codegen/codegen_c_host.cc, src/cpu/codegen/codegen_c.h, src/cpu/codegen/codegen_c.cc	Both code generators validate supported tirx.clz inputs, emit the shared definitions once per initialization, and call the matching width-specific helper with an unsigned argument.
CPU and CUDA-host coverage testing/python/cpu/test_tilelang_cpu_clz.py, testing/python/jit/test_tilelang_jit_host_clz.py	Adds tests for four integer dtypes, generated helper names, leading-zero results, and CUDA graph replay outputs.

Vectorization analyzer handling

Layer / File(s)	Summary
Clone analyzer for vectorization src/transform/loop_vectorize.cc	VectorizeLoop passes a cloned analyzer to VectorizeRewriter.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Suggested labels: enhancement, cpu

Suggested reviewers: siriusneo, ljc00118, penguin-wwy

Merge Risk: ⚪ Minimal · up to 0af8b

No actionable merge-blocking risk is established from the reviewed changes.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 5.56% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 18 functions across 8 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Title check		The title clearly summarizes the main change: adding scalar clz support to CPU C and C host code generation.

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