Fix SM120 FP8xFP4 MoE undefined symbol when both FP8 and FP4 QMoE enabled

[tianleiwu]

Description

Fixes an undefined-symbol link failure that occurs when both --enable_fp8_qmoe and --enable_fp4_qmoe are enabled together (the FP8+FP4 CUDA build config). The build only breaks in that combined config because it is the only one that instantiates MoeGemmRunner<__nv_fp8_e4m3, __nv_fp4_e2m1, ...>.

Root cause

The SM120 compile-time tile-shape gate are_tile_shapes_supported_sm120() in moe_gemm_template_dispatch_tma_ws.h allowed several extra tile shapes (128×128×64/256, 128×256×64/128, 256×128×64/128) for an FP8 activation type. However, the launcher generator generate_moe_gemm_tma_ws_sm120_fp4.py emits only the 128×128×128 tile for FP8×FP4 — that is the only shape that fits in shared memory with ≥2 pipeline stages. The dispatch cascade therefore referenced launcher template instantiations that were never generated, producing undefined symbols at link time.

Fix

Restrict the SM120 compile-time dispatch to 128×128×128 when the activation type is __nv_fp8_e4m3, matching both the generator and the runtime heuristic:

• On SM120, isValidSM120MOESpecialisation only supports FP4×FP4 and FP8×FP4, so DataType == __nv_fp8_e4m3 always means FP8×FP4.
• The runtime config heuristic get_candidate_configs_sm120() only ever selects CtaShape128x128x128B.

So the prune causes no functional loss — the removed tiles were never generated nor selected. FP4×FP4 tiles are unchanged.

Validation

Object-level verification on build/cu130_fp8_fp4 (nm -Cu on moe_gemm_kernels_fp8_fp4.cu.o):

• Before: 12 undefined SM120 FP8×FP4 launcher references (the extra tiles) → link failure.
• After: only 2 remaining references, both <128,128,128> (fp16 + bf16). Both are defined (weak) by the generated launcher objects moe_gemm_tma_ws_sm120_fp4_fp8_{fp16,bf16}_m128_n128_k128.generated.cu.o, so the link resolves.

Motivation and Context

Unblocks building ONNX Runtime with FP8 and FP4 QMoE enabled simultaneously. Delivered as a standalone change independent of the FP8/FP4 QMoE feature PRs.