1. Dual-tile: add both bn0=64 (preferred) and bn0=32 (fallback) for
hdim=64 on gfx9 and gfx12. The dispatch checks page_block_size %
bn0 == 0 at runtime to select the optimal tile. bn0=64 halves KV
iterations when page_block_size >= 64.
2. Tile dict now supports lists per hdim. The codegen loop iterates
over all tile variants, generating separate kernel instances for
each. Combine kernels are unaffected (tile-independent).
3. Enable kMergeNumHeadGroupsSeqLenQ for hdim=64 decode (previously
hdim=128 only). For GQA-8 with max_seqlen_q=1, this packs 8 head
groups into the M dimension. Only activates for no-mask instances
(kernel static_assert requires !kHasMask).
4. Add qr (non-async) pipeline for fwd non-bias group mode as
fallback after qr_async. The async pipeline on this branch has a
kernel-level bug where fmha_fwd launches but writes no output.
Made-with: Cursor
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