---
id: pr-flash-attention-1868
repo: Dao-AILab/flash-attention
pr: 1868
title: flash-attn-cute bwd sm90
author: tzadouri
date: '2025-09-13'
url: https://github.com/Dao-AILab/flash-attention/pull/1868
source_category: upstream-code
architectures:
- sm90
tags:
- hopper
- tma
techniques:
- async-copy
hardware_features:
- hopper
- tma
kernel_types:
- attention
languages:
- cute-dsl
captured_at: '2026-05-16'
status: merged
merge_sha: 2cc6fd6abbc5f1100e51eab63d92b678fda06c7d
inclusion_reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.
changed_paths:
- flash_attn/cute/block_info.py
- flash_attn/cute/flash_bwd_postprocess.py
- flash_attn/cute/flash_bwd_sm90.py
- flash_attn/cute/hopper_helpers.py
- flash_attn/cute/named_barrier.py
artifact_dir: evidence/pull-bundles/flash-attention/gh-1868
head_ref_oid: 87f68ac32ca0049baa0c86156b2e9df4de55e378
---
# flash-attn-cute bwd sm90

- Repository: `Dao-AILab/flash-attention`
- PR: [1868](https://github.com/Dao-AILab/flash-attention/pull/1868)
- Decision: `Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.`
- Reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.

## Changed Paths

- `flash_attn/cute/block_info.py`
- `flash_attn/cute/flash_bwd_postprocess.py`
- `flash_attn/cute/flash_bwd_sm90.py`
- `flash_attn/cute/hopper_helpers.py`
- `flash_attn/cute/named_barrier.py`

## Evidence Bundle

`evidence/pull-bundles/flash-attention/gh-1868`
