onnxruntime

e91a5c33 - Extend DQ→MatMulNBits fusion to support 2/8-bit weights and Cast(fp16→fp32) patterns (#27614)

Extend DQ→MatMulNBits fusion to support 2/8-bit weights and Cast(fp16→fp32) patterns (#27614) ### Description Extends the QDQ selector-action `DQ → MatMul → MatMulNBits` fusion in two ways: **1. Support 2-bit and 8-bit quantized weights** The existing fusion only handled 4-bit (`Int4x2`/`UInt4x2`) DQ weights. This PR broadens it to also support 2-bit (`Int2x4`/`UInt2x4`) and 8-bit (`int8`/`uint8`) quantized weights. - qdq_selectors.cc: Added `Is2BitIntType`, `Is8BitIntType`, and `IsNBitsIntType` helpers. Updated `DQMatMulNodeGroupSelector::Check` to accept 2/4/8-bit weight types. - qdq_actions.cc: Added `DQWeightBits` and `IsDQWeightSigned` helpers to dispatch the correct bit-width and signedness for MLAS transpose and MatMulNBits attributes. - `q4_dq.cpp` (MLAS): Added 8-bit `GetElem`/`SetElem` specializations and an 8-bit `TransposeColumnWiseQuantized` path. Added 6 new template instantiations for 2-bit (signed/unsigned, float/float16) and 8-bit (signed/unsigned, float/float16). **2. Handle `Cast(fp16→fp32)` between DQ and MatMul (FP16 model fusion)** FP16 models often have `DQ(int4→fp16) → Cast(fp16→fp32) → MatMul(fp32)` patterns that the existing selector couldn't match. This PR adds a new `DQCastMatMulToMatMulNBitsSelector` / `DQCastMatMulToMatMulNBitsAction` pair that: - Matches the `DQ → Cast(fp16→fp32) → MatMul` pattern on input B. - Creates a `MatMulNBits` node operating in the DQ scale dtype (fp16). - Always inserts `Cast` on input A (to DQ dtype) and `Cast` on output (DQ dtype to MatMul output dtype), relying on ORT's existing `CastElimination` optimizer to remove redundant back-to-back casts in subsequent passes. - Removes the original DQ, Cast (on B), and MatMul nodes. ### Motivation and Context - Many quantized models (e.g., from Olive, AutoAWQ) use 2-bit or 8-bit quantization, but the `DQ → MatMulNBits` fusion only supported 4-bit weights, leaving these models unoptimized. - FP16 models produce `DQ(→fp16) → Cast(fp16→fp32) → MatMul` patterns because the DQ output type matches the scale type (fp16), but the MatMul operates in fp32. Without handling the intermediate Cast, the fusion was blocked entirely for these models.