dylanyunlon
84c18150e6
fix(tuning_select_if): restore 3 collapsed dispatch dimensions
Previous version collapsed 77 CCCL specializations into 4 if/else
branches by elem_size only, losing:
1. may_alias dimension: now dispatches LOAD_CA (alias-safe) vs
LOAD_DIRECT+LOAD_LDG (no-alias, ~5-10% faster for common case).
CCCL SM100 no-alias small-type uses BLOCK_LOAD_DIRECT.
2. has_flags dimension: flagged path now gets 2-4 fewer items_per_thread
because flag array takes additional SMEM. SMEM check includes flag_tile.
3. delay dimension: type-size-dependent delays instead of fixed(350,450).
Scaled from CCCL SM100 benchmarks: ns*0.5, l2w*0.6 for BI-V100 L2.
SMEM check: input_tile + output_scatter + flag_tile ≤ 48KB.