Qualcomm AI Engine Direct - Add QNN Windows MSVC Build to CI (#20802)

### Summary
- This PR adds a CI workflow that validates the QNN Windows MSVC build.
- Fix Linux-specific file path to Windows-compatible.
- Add helper function in `backends/qualcomm/scripts/build.ps1` to
validate the CMake version after dev-shell activation.

### Test plan
Passing `.github/workflows/qnn-windows-msvc.yml`.

Author: zhaoxul-qti

.ci/scripts/build-qnn-windows-msvc.ps1

@@ -0,0 +1,70 @@
+# Copyright (c) Qualcomm Innovation Center, Inc.
+# All rights reserved
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+$ErrorActionPreference = "Stop"
+
+conda create --yes --quiet -n et python=3.12
+conda activate et
+
+# Install CI requirements
+pip install -r .ci/docker/requirements-ci.txt
+
+# Provision the QNN SDK
+if ($env:QNN_SDK_ROOT -and (Test-Path -Path $env:QNN_SDK_ROOT)) {
+    Write-Host "Using existing QNN SDK at $env:QNN_SDK_ROOT"
+} else {
+    # Resolve the QNN_VERSION and QNN_ZIP_URL
+    $qnnInfo = python -c "import sys; sys.path.insert(0, r'backends\qualcomm\scripts'); import download_qnn_sdk as d; print(d.QNN_VERSION); print(d.QNN_ZIP_URL)"
+    if ($LASTEXITCODE -ne 0 -or $qnnInfo.Count -lt 2) {
+        Write-Error "Failed to read QNN_VERSION and QNN_ZIP_URL from download_qnn_sdk.py."
+        exit 1
+    }
+    $qnnVersion = $qnnInfo[0].Trim()
+    $qnnZipUrl  = $qnnInfo[1].Trim()
+
+    $qnnInstallDir = Join-Path $env:TEMP "qnn"
+    New-Item -Path $qnnInstallDir -ItemType Directory -Force | Out-Null
+    $qnnZip = Join-Path $env:TEMP "qnn_sdk.zip"
+    Write-Host "Downloading QNN SDK v$qnnVersion ..."
+    $ProgressPreference = "SilentlyContinue"
+    Invoke-WebRequest -Uri $qnnZipUrl -OutFile $qnnZip
+    Write-Host "Extracting QNN SDK ..."
+    Expand-Archive -Path $qnnZip -DestinationPath $qnnInstallDir -Force
+    Remove-Item -Path $qnnZip -Force
+
+    $env:QNN_SDK_ROOT = Join-Path $qnnInstallDir "qairt\$qnnVersion"
+    Write-Host "Set QNN_SDK_ROOT=$env:QNN_SDK_ROOT"
+}
+
+if (-not (Test-Path -Path (Join-Path $env:QNN_SDK_ROOT "include\QNN"))) {
+    Write-Error "QNN SDK layout unexpected: missing include\QNN under $env:QNN_SDK_ROOT"
+    exit 1
+}
+
+# Test x86_64 Windows host build
+.\backends\qualcomm\scripts\build.ps1 -SkipArm64Windows -Release
+
+$x86Artifacts = @(
+    "build-x86_64-windows\backends\qualcomm\Release\PyQnnManagerAdaptor*.pyd",
+    "build-x86_64-windows\backends\qualcomm\Release\qnn_executorch_backend.dll",
+    "build-x86_64-windows\examples\qualcomm\executor_runner\Release\qnn_executor_runner.exe"
+)
+foreach ($artifact in $x86Artifacts) {
+    if (-not (Get-ChildItem -Path $artifact -ErrorAction SilentlyContinue)) {
+        Write-Error "ERROR: x86_64 artifact not found: $artifact"
+        exit 1
+    }
+}
+
+# The ARM64 MSVC toolchain is currently not installed in the Windows CI
+# environment. Enabling this build configuration results in build failures
+# due to the missing ARM64 platform definition.
+# `.\backends\qualcomm\scripts\build.ps1 -SkipX86Windows -Release`
+#
+# Temporarily disable this build option until ARM64 MSVC support is available
+# in CI. The configuration can be re-enabled in a future update.
+
+Write-Host "PASSED: QNN backend Windows MSVC build completed"

.github/workflows/qnn-windows-msvc.yml

@@ -0,0 +1,74 @@
+name: Test QNN Windows MSVC build
+
+# Changes to backends/qualcomm/, top-level CMake files, extension/,
+# examples/, runtime/, and other shared infrastructure can affect
+# the QNN Windows MSVC build. Rather than maintaining a fragile list
+# of relevant path filters, this workflow runs on every PR to ensure
+# build coverage.
+#
+# Reasons for keeping qnn-windows-msvc.yml separate from test-backend-qnn.yml:
+#
+# - Two workflows are triggered by different tags.
+#   - test-backend-qnn.yml runs under ciflow/nightly/*.
+#   - qnn-windows-msvc.yml runs under ciflow/trunk/*.
+#   Merging them would introduce the behavior change to the existing flow.
+#
+# - Workflow reruns are more efficient when they remain separate.
+#   A Windows-only failure would still require rerunning jobs in test-backend-qnn.yml
+#   if they are combined into a single workflow, resulting in unnecessary CI
+#   resource consumption (and vice versa).
+#
+# - Failure signals are clearer when the workflows are isolated.
+#   With a combined workflow, additional inspection of the job list would be required to
+#   identify the root cause of a failing status. Keeping the workflows separate provides
+#   distinct top-level CI statuses, making the failure domain immediately obvious.
+#
+# For now, qnn-windows-msvc.yml should remain separate from trunk.yml and pull.yml:
+#
+# - trunk.yml is only triggered for PRs that modify files matching:
+#     - .ci/docker/ci_commit_pins/pytorch.txt
+#     - .ci/scripts/**
+#     - zephyr/**
+#   As a result, trunk.yml would not run for PRs that touch backends/qualcomm/**.
+#
+# - pull.yml runs on every PR without path filters, but currently contains only
+#   Linux jobs. Keeping qnn-windows-msvc.yml as a standalone workflow provides
+#   independent status visibility and more efficient reruns for QNN Windows build.
+#
+# Once the QNN Windows CI path has demonstrated sufficient stability, we can revisit
+# whether it makes sense to consolidate qnn-windows-msvc.yml into pull.yml.
+
+on:
+  push:
+    branches:
+      - main
+      - release/*
+    tags:
+      - ciflow/trunk/*
+  pull_request:
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}-${{ github.event_name == 'workflow_dispatch' }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  build-qnn-windows-msvc:
+    name: build-qnn-windows-msvc
+    uses: pytorch/test-infra/.github/workflows/windows_job.yml@main
+    with:
+      ref: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}
+      timeout: 90
+      script: |
+        git config --global http.sslBackend openssl
+        git submodule update --init --recursive
+        conda init powershell
+        powershell -Command "& {
+          Set-PSDebug -Trace 1
+          \$ErrorActionPreference = 'Stop'
+          \$PSNativeCommandUseErrorActionPreference = \$true
+          .ci/scripts/build-qnn-windows-msvc.ps1
+        }"

backends/qualcomm/runtime/backends/QnnBackendUnifiedRegistry.cpp

@@ -16,6 +16,8 @@
 #include <executorch/backends/qualcomm/runtime/backends/lpai/LpaiBackend.h>
 #include <executorch/backends/qualcomm/runtime/backends/lpai/LpaiDevice.h>
 
+#include <pal/Path.h>
+
 #include <string>
 
 namespace executorch {
@@ -154,7 +156,8 @@ Error QnnBackendUnifiedRegistry::GetOrCreateBackendBundle(
   }
   // 5. Create QnnSystemImplementation and load qnn library
   std::unique_ptr<QnnSystemImplementation> system_implementation =
-      std::make_unique<QnnSystemImplementation>("libQnnSystem.so");
+      std::make_unique<QnnSystemImplementation>(
+          pal::path::GetLibraryName("QnnSystem"));
   ret = system_implementation->Load();
   ET_CHECK_OR_RETURN_ERROR(
       ret == Error::Ok, Internal, "Fail to load Qnn system library");