Fix QNN include path and provide QNN Offline usage guide

[Juude]

This change updates the source/backend/qnn/CMakeLists.txt to include ${_QNN_ROOT}/include/ in the search path. This ensures compatibility with the directory structure created by prepare_qnn_deps.sh (where headers are directly under include/) as well as the standard Qualcomm QNN SDK structure (where headers are under include/QNN/).

Usage Guide for MNN QNN (Offline Mode)

This guide explains how to compile and use mnn_qnn for offline model conversion and Android execution.

1. Prerequisites

• Qualcomm QNN SDK: Required for running the conversion tool (host) and providing runtime libraries (device).
• MNN Source Code: Clone the repository.
• Dependencies: Run ./prepare_qnn_deps.sh to download necessary headers and libs to source/backend/qnn/3rdParty/, OR have the full QNN SDK installed.

2. Compile Model Converter (Host - Linux x86_64)

The MNN2QNNModel tool converts an MNN model into a QNN-compatible model (.mnn + .bin). It requires MNN_QNN and MNN_QNN_CONVERT_MODE enabled.

mkdir build_host
cd build_host
cmake .. \
    -DMNN_QNN=ON \
    -DMNN_QNN_CONVERT_MODE=ON \
    -DQNN_SDK_ROOT=/path/to/qnn/sdk_or_deps
make -j4 MNN2QNNModel

(Note: If using prepare_qnn_deps.sh, set QNN_SDK_ROOT to path/to/source/backend/qnn/3rdParty).

3. Convert Model (Host)

Running MNN2QNNModel requires the full QNN SDK (specifically bin/x86_64-linux-clang tools like qnn-context-binary-generator).

# Usage: ./MNN2QNNModel <qnnSDKPath> <socId> <hexagonArch> <srcMNNPath> <outputDir>
./MNN2QNNModel /opt/qcom/qnn/sdk 43 73 model.mnn ./output

• socId: e.g., 43 for Snapdragon 8 Gen 2.
• hexagonArch: e.g., 73 for Hexagon V73.
• Output: model_43_73.mnn and model_43_73.bin.

4. Compile Runtime (Android - ARM64)

Build libMNN.so with QNN support. Crucially, MNN_WITH_PLUGIN=ON is required for loading offline models, and MNN_QNN_CONVERT_MODE must be OFF.

mkdir build_android
cd build_android
cmake .. \
    -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
    -DANDROID_ABI="arm64-v8a" \
    -DANDROID_STL=c++_static \
    -DANDROID_NATIVE_API_LEVEL=android-21 \
    -DMNN_QNN=ON \
    -DMNN_WITH_PLUGIN=ON \
    -DQNN_SDK_ROOT=/path/to/qnn/sdk_or_deps
make -j4 libMNN

5. Run on Android

1. Push Libraries:

   • libMNN.so (built above).
   • libQnnHtp.so, libQnnHtpVxxSkel.so, libQnnHtpVxxStub.so, libQnnSystem.so (from QNN SDK lib/aarch64-android/).
   • Push these to /data/local/tmp (or app lib dir).

2. Push Model:

   • model_43_73.mnn and model_43_73.bin.

3. Execute:

   • Set LD_LIBRARY_PATH to include the directory with QNN libs.
   • Run your MNN application loading model_43_73.mnn.

export LD_LIBRARY_PATH=/data/local/tmp:$LD_LIBRARY_PATH
./your_mnn_app /data/local/tmp/model_43_73.mnn

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PR created automatically by Jules for task 4451591356993808856 started by @Juude

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Note

Low Risk
Build-system-only change that broadens header search paths; low functional risk, with the main concern being potential include-order/header ambiguity if both layouts are present.

Overview
Fixes QNN builds against alternate SDK layouts by adding ${_QNN_ROOT}/include/ to MNN_QNN's include directories (in addition to the existing ${_QNN_ROOT}/include/QNN/).

^{Written by Cursor Bugbot for commit 3bef715. This will update automatically on new commits. Configure here.}

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