[litertlm] add Windows DXC to WORKSPACE and for Python GPU API

LiteRT-LM-PiperOrigin-RevId: 908294380

Author: whhone

BUILD.directx_shader_compiler

@@ -0,0 +1,19 @@
+package(default_visibility = ["//visibility:public"])
+
+filegroup(
+    name = "dxcompiler",
+    srcs = ["bin/x64/dxcompiler.dll"],
+)
+
+filegroup(
+    name = "dxil",
+    srcs = ["bin/x64/dxil.dll"],
+)
+
+filegroup(
+    name = "dxc_dlls",
+    srcs = [
+        "bin/x64/dxcompiler.dll",
+        "bin/x64/dxil.dll",
+    ],
+)

WORKSPACE

@@ -496,3 +496,11 @@ pip_parse(
 load("@custom_pip_deps//:requirements.bzl", install_custom_deps = "install_deps")
 
 install_custom_deps()
+
+# DirectX Shader Compiler DLLs for Windows
+http_archive(
+    name = "directx_shader_compiler",
+    build_file = "@//:BUILD.directx_shader_compiler",
+    sha256 = "a1e89031421cf3c1fca6627766ab3020ca4f962ac7e2caa7fab2b33a8436151e",
+    url = "https://github.com/microsoft/DirectXShaderCompiler/releases/download/v1.9.2602/dxc_2026_02_20.zip",
+)

python/litert_lm/BUILD

@@ -143,13 +143,19 @@ pytype_strict_library(
     ],
 )
 
+config_setting(
+    name = "use_prebuilt_c_api",
+    define_values = {
+        "use_prebuilt_c_api": "true",
+    },
+)
+
 pytype_strict_library(
     name = "litert_lm",
     srcs = ["__init__.py"],
-    data = ["//python/litert_lm:litert-lm"] + select({
-        "@platforms//os:macos": [":copy_prebuilt_libs_dylib"],
-        "@platforms//os:windows": [], # the cc_binary rule already properly provisions this DLL into the package directory on Windows.
-        "//conditions:default": [":copy_prebuilt_libs_so"],
+    data = select({
+        ":use_prebuilt_c_api": [":prebuilt_litert_lm_lib"],
+        "//conditions:default": [":default_libs"],
     }),
     deps = [
         ":_ffi",
@@ -249,6 +255,129 @@ genrule(
     tags = ["manual"],
 )
 
+genrule(
+    name = "copy_prebuilt_libs_dll",
+    srcs = select({
+        ":wheel_platform_windows_x86_64": ["//prebuilt/windows_x86_64:" + lib + ".dll" for lib in _PREBUILT_LIBS],
+        "//conditions:default": [],
+    }),
+    outs = [lib + ".dll" for lib in _PREBUILT_LIBS],
+    cmd = """
+        SRCS_ARRAY=($(SRCS))
+        OUTS_ARRAY=($(OUTS))
+        if [ $${#SRCS_ARRAY[@]} -gt 0 ]; then
+            for i in $${!SRCS_ARRAY[@]}; do
+                cp $${SRCS_ARRAY[$$i]} $${OUTS_ARRAY[$$i]}
+            done
+        else
+            for out in $${OUTS_ARRAY[@]}; do
+                touch $$out
+            done
+        fi
+    """,
+    tags = ["manual"],
+)
+
+genrule(
+    name = "copy_prebuilt_litert_lm_so",
+    srcs = select({
+        "//build_config:linux_x86_64": ["//prebuilt/linux_x86_64:liblitert-lm.so"],
+        "//build_config:linux_arm64": ["//prebuilt/linux_arm64:liblitert-lm.so"],
+        "//conditions:default": [],
+    }),
+    outs = ["liblitert-lm.so"],
+    cmd = """
+        SRCS_ARRAY=($(SRCS))
+        OUTS_ARRAY=($(OUTS))
+        if [ $${#SRCS_ARRAY[@]} -gt 0 ]; then
+            cp $${SRCS_ARRAY[0]} $${OUTS_ARRAY[0]}
+            chmod +w $${OUTS_ARRAY[0]}
+            patchelf --set-rpath '$$ORIGIN' $${OUTS_ARRAY[0]}
+        else
+            touch $${OUTS_ARRAY[0]}
+        fi
+    """,
+    tags = ["manual"],
+)
+
+copy_file(
+    name = "copy_prebuilt_litert_lm_dylib",
+    src = "//prebuilt/macos_arm64:liblitert-lm.dylib",
+    out = "liblitert-lm.dylib",
+    tags = ["manual"],
+)
+
+copy_file(
+    name = "copy_prebuilt_litert_lm_dll",
+    src = "//prebuilt/windows_x86_64:litert-lm.dll",
+    out = "litert-lm.dll",
+    tags = ["manual"],
+)
+
+copy_file(
+    name = "copy_dxcompiler_dll",
+    src = "@directx_shader_compiler//:dxcompiler",
+    out = "dxcompiler.dll",
+)
+
+copy_file(
+    name = "copy_dxil_dll",
+    src = "@directx_shader_compiler//:dxil",
+    out = "dxil.dll",
+)
+
+filegroup(
+    name = "prebuilt_litert_lm_lib",
+    srcs = select({
+        ":wheel_platform_macos_arm64": [":copy_prebuilt_litert_lm_dylib"],
+        ":wheel_platform_windows_x86_64": [
+            ":copy_prebuilt_litert_lm_dll",
+            ":copy_dxcompiler_dll",
+            ":copy_dxil_dll",
+        ],
+        ":wheel_platform_linux_x86_64": [":copy_prebuilt_litert_lm_so"],
+        ":wheel_platform_linux_arm64": [":copy_prebuilt_litert_lm_so"],
+        "//conditions:default": [],
+    }),
+)
+
+filegroup(
+    name = "default_libs",
+    srcs = ["//python/litert_lm:litert-lm"] + select({
+        "@platforms//os:macos": [":copy_prebuilt_libs_dylib"],
+        "@platforms//os:windows": [
+            ":copy_prebuilt_libs_dll",
+            ":copy_dxcompiler_dll",
+            ":copy_dxil_dll",
+        ],
+        ":wheel_platform_linux_x86_64": [":copy_prebuilt_libs_so"],
+        ":wheel_platform_linux_arm64": [":copy_prebuilt_libs_so"],
+        "//conditions:default": [],
+    }),
+)
+
+
+# Use "wheel_platform" to allow cross-compliling the wheel package.
+config_setting(
+    name = "wheel_platform_linux_x86_64",
+    define_values = {"wheel_platform": "linux_x86_64"},
+)
+
+config_setting(
+    name = "wheel_platform_linux_arm64",
+    define_values = {"wheel_platform": "linux_arm64"},
+)
+
+config_setting(
+    name = "wheel_platform_windows_x86_64",
+    define_values = {"wheel_platform": "windows_x86_64"},
+)
+
+config_setting(
+    name = "wheel_platform_macos_arm64",
+    define_values = {"wheel_platform": "macos_arm64"},
+)
+
 py_package(
     name = "package",
     # Explicitly specify packages to avoid including transitively linked shared
@@ -274,10 +403,10 @@ py_wheel(
         "//conditions:default": "litert-lm-api",
     }),
     platform = select({
-        "//build_config:linux_x86_64": "manylinux_2_35_x86_64",
-        "//build_config:linux_arm64": "manylinux_2_35_aarch64",
-        "@platforms//os:macos": "macosx_12_0_arm64",
-        "@platforms//os:windows": "win_amd64",
+        ":wheel_platform_linux_x86_64": "manylinux_2_35_x86_64",
+        ":wheel_platform_linux_arm64": "manylinux_2_35_aarch64",
+        ":wheel_platform_macos_arm64": "macosx_12_0_arm64",
+        ":wheel_platform_windows_x86_64": "win_amd64",
         "//conditions:default": "any",
     }),
     python_tag = "py3",