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SMEM-backed kv_coord counter — JIT can't constant-fold SMEM reads

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biondizzle
2026-05-22 20:34:52 +00:00
parent e90e25c6da
commit 8d6fe8075d
1 changed files with 8 additions and 3 deletions
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11
tests/unit/test_fmha_v3_stage_c.py
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@@ -148,6 +148,7 @@ class FmhaV3StageCMulti:
s_bar: cute.struct.MemRange[cutlass.Int64, 2]
acc_bar: cute.struct.MemRange[cutlass.Int64, self.num_acc_stage*2]
tmem_dealloc: cutlass.Int64; holding: cutlass.Int32
kv_coord_smem: cute.struct.MemRange[Int32, 1]
smem = utils.SmemAllocator(); st = smem.allocate(SS)
qp,qc = pipeline.PipelineTmaUmma.create(barrier_storage=st.q_bar.data_ptr(),num_stages=self.q_stage,producer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread),consumer_group=pipeline.CooperativeGroup(pipeline.Agent.Thread,1),tx_count=self.q_tx_bytes,cta_layout_vmnk=cl_vmnk,defer_sync=True).make_participants()
@@ -224,11 +225,15 @@ class FmhaV3StageCMulti:
cute.copy(tma_q, tAgQ[(None, Int32(0))], tAsQ[(None, qh.index)], tma_bar_ptr=qh.barrier)
qp.tail()
kvp.reset()
# DEBUG: Use constant Int32(1) to test if TMA can read from tile 1 at all
# Use SMEM-backed counter — the JIT can't constant-fold SMEM reads.
# Initialize to 0, read before each copy, increment after.
st.kv_coord_smem[0] = Int32(0)
for kt in range(n_kv_tiles):
kv_coord = st.kv_coord_smem[0] # Dynamic read from SMEM
kvh = kvp.acquire_and_advance()
cute.copy(tma_k, tBgK[(None, Int32(1))], tBsK[(None, kvh.index)], tma_bar_ptr=kvh.barrier)
cute.copy(tma_v, tVgV[(None, Int32(1))], tVsV[(None, kvh.index)], tma_bar_ptr=kvh.barrier)
cute.copy(tma_k, tBgK[(None, kv_coord)], tBsK[(None, kvh.index)], tma_bar_ptr=kvh.barrier)
cute.copy(tma_v, tVgV[(None, kv_coord)], tVsV[(None, kvh.index)], tma_bar_ptr=kvh.barrier)
st.kv_coord_smem[0] = kv_coord + 1 # Write back to SMEM
kvp.tail()
# ===== MMA warp =====