add CI configs for msvc build

Author: JacobSzwejbka

.ci/scripts/setup-windows-msvc.ps1

@@ -0,0 +1,49 @@
+conda create --yes --quiet -n et python=3.12
+conda activate et
+
+# Activate the VS environment - this is required for MSVC to work
+# There are a bunch of environment variables that it requires.
+# See https://learn.microsoft.com/en-us/cpp/build/building-on-the-command-line.
+& "C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\Common7\Tools\Launch-VsDevShell.ps1" -Arch amd64
+
+# Install CI requirements
+pip install -r .ci/docker/requirements-ci.txt
+
+# Create build directory
+$buildDir = "cmake-out-msvc"
+if (Test-Path -Path $buildDir) {
+    Remove-Item -Path $buildDir -Recurse -Force
+}
+New-Item -Path $buildDir -ItemType Directory
+
+# Configure CMake with MSVC (not ClangCL) and disable custom/quantized ops
+cmake -S . -B $buildDir `
+    -DCMAKE_BUILD_TYPE=Release `
+    -DEXECUTORCH_BUILD_EXECUTOR_RUNNER=ON `
+    -DEXECUTORCH_BUILD_EXTENSION_DATA_LOADER=ON `
+    -DEXECUTORCH_BUILD_EXTENSION_MODULE=ON `
+    -DEXECUTORCH_BUILD_EXTENSION_TENSOR=ON `
+    -DEXECUTORCH_BUILD_EXTENSION_FLAT_TENSOR=ON `
+    -DEXECUTORCH_BUILD_EXTENSION_NAMED_DATA_MAP=ON `
+    -DEXECUTORCH_BUILD_KERNELS_OPTIMIZED=ON `
+    -DEXECUTORCH_BUILD_KERNELS_CUSTOM=OFF `
+    -DEXECUTORCH_BUILD_KERNELS_CUSTOM_AOT=OFF `
+    -DEXECUTORCH_BUILD_KERNELS_QUANTIZED=OFF `
+    -DEXECUTORCH_BUILD_XNNPACK=ON `
+    -DEXECUTORCH_BUILD_EXTENSION_LLM=ON `
+    -DEXECUTORCH_BUILD_EXTENSION_LLM_RUNNER=ON
+
+if ($LASTEXITCODE -ne 0) {
+    Write-Host "CMake configuration failed. Exit code: $LASTEXITCODE."
+    exit $LASTEXITCODE
+}
+
+# Build with MSVC
+cmake --build $buildDir --config Release -j16
+
+if ($LASTEXITCODE -ne 0) {
+    Write-Host "Build failed. Exit code: $LASTEXITCODE."
+    exit $LASTEXITCODE
+}
+
+Write-Host "MSVC build completed successfully!"

.github/workflows/windows-msvc.yml

@@ -0,0 +1,37 @@
+name: Windows MSVC Build
+
+on:
+  push:
+    branches:
+      - main
+      - release/*
+    tags:
+      - ciflow/trunk/*
+  pull_request:
+    paths:
+      - .ci/docker/ci_commit_pins/pytorch.txt
+      - .ci/scripts/**
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}-${{ github.event_name == 'workflow_dispatch' }}-${{ github.event_name == 'schedule' }}
+  cancel-in-progress: true
+
+jobs:
+  build-windows-msvc:
+    name: build-windows-msvc
+    uses: pytorch/test-infra/.github/workflows/windows_job.yml@main
+    with:
+      submodules: 'recursive'
+      ref: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}
+      timeout: 60
+      script: |
+        conda init powershell
+
+        powershell -Command "& {
+          Set-PSDebug -Trace 1
+          \$ErrorActionPreference = 'Stop'
+          \$PSNativeCommandUseErrorActionPreference = \$true
+
+          .ci/scripts/setup-windows-msvc.ps1
+        }"

setup.py

@@ -751,9 +751,14 @@ def run(self):  # noqa C901
             f"-DCMAKE_BUILD_TYPE={cmake_build_type}",
         ]
 
-        # Use ClangCL on Windows.
+        # Use ClangCL on Windows by default, unless EXECUTORCH_USE_MSVC is set.
         if _is_windows():
-            cmake_configuration_args += ["-T ClangCL"]
+            if os.environ.get("EXECUTORCH_USE_MSVC"):
+                # Use default MSVC toolchain
+                pass
+            else:
+                # Use ClangCL toolchain
+                cmake_configuration_args += ["-T ClangCL"]
 
         # Allow adding extra cmake args through the environment. Used by some
         # tests and demos to expand the set of targets included in the pip