Fixes a few issues found when debugging powderluv's setup.

* It is optional to link against Python3_LIBRARIES. Check that and don't do it if they don't exist for this config.
* Clean and auditwheel need to operate on sanitized package names. So "torch_mlir" vs "torch-mlir".
* Adds a pyproject.toml file that pins the build dependencies needed to detect both Torch and Python (the MLIR Python build was failing to detect because Numpy wasn't in the pip venv).
* Commented out auditwheel: These wheels are not PyPi compliant since they weak link to libtorch at runtime. However, they should be fine to deploy to users.
* Adds the --extra-index-url to the pip wheel command, allowing PyTorch to be found.
* Hack setup.py to remove the _mlir_libs dir before building. This keeps back-to-back versions from accumulating in the wheels for subsequent versions. IREE has a more principled way of doing this, but what I have here should work.

build_tools/python_deploy/build_linux_packages.sh

@@ -81,9 +81,9 @@ function run_in_docker() {
       echo ":::: Python version $(python --version)"
       case "$package" in
         torch-mlir)
-          clean_wheels torch-mlir $python_version
+          clean_wheels torch_mlir $python_version
           build_torch_mlir
-          run_audit_wheel torch-mlir $python_version
+          #run_audit_wheel torch_mlir $python_version
           ;;
         *)
           echo "Unrecognized package '$package'"
@@ -95,10 +95,9 @@ function run_in_docker() {
 }
 
 function build_torch_mlir() {
-  python -m pip install --pre torch torchvision --extra-index-url https://download.pytorch.org/whl/nightly/cpu
-  python -m pip install -r /main_checkout/torch-mlir/requirements.txt
   CMAKE_GENERATOR=Ninja \
-  python -m pip wheel -v -w /wheelhouse /main_checkout/torch-mlir/
+  python -m pip wheel -v -w /wheelhouse /main_checkout/torch-mlir/ \
+    --extra-index-url https://download.pytorch.org/whl/nightly/cpu
 }
 
 function run_audit_wheel() {

pyproject.toml

@@ -0,0 +1,21 @@
+[build-system]
+requires = [
+    "setuptools>=42",
+    "wheel",
+    # There is no fundamental reason to pin this CMake version, beyond
+    # build stability.
+    "cmake==3.22.2",
+    "ninja==1.10.2",
+    "packaging",
+    # Version 2.7.0 excluded: https://github.com/pybind/pybind11/issues/3136
+    "pybind11>=2.6.0,!=2.7.0",
+    "PyYAML",
+
+    # The torch-mlir CMake build requires numpy and torch to be installed.
+    # Further, the setup.py will pin the version selected here into built
+    # artifacts.
+    # TODO: Come up with a better way to pin the version.
+    "numpy",
+    "torch==1.12.0.dev20220419+cpu",
+]
+build-backend = "setuptools.build_meta"

python/torch_mlir/dialects/torch/importer/jit_ir/csrc/CMakeLists.txt

@@ -24,10 +24,19 @@ add_library(TorchMLIRJITIRImporter MODULE
 target_link_libraries(TorchMLIRJITIRImporter
   TorchMLIRAggregateCAPI
   ${TORCH_LIBRARIES}
-  ${Python3_LIBRARIES}
   torch_python
 )
 
+# On static Python builds, there may not be Python libraries to link against
+# (they will late bind at runtime from the executable). We have to condition
+# this because in that case it is set to NOTFOUND and CMake will consider
+# this an error.
+if(Python3_LIBRARIES)
+  target_link_libraries(TorchMLIRJITIRImporter
+    ${Python3_LIBRARIES}
+  )
+endif()
+
 message(STATUS "TORCH_CXXFLAGS=${TORCH_CXXFLAGS}")
 set_target_properties(TorchMLIRJITIRImporter PROPERTIES
   LIBRARY_OUTPUT_DIRECTORY "${TORCH_MLIR_PYTHON_PACKAGES_DIR}/torch_mlir/torch_mlir/_mlir_libs"

setup.py

@@ -61,6 +61,10 @@ def run(self):
         if not cmake_build_dir:
             cmake_build_dir = os.path.abspath(
                 os.path.join(target_dir, "..", "cmake_build"))
+        python_package_dir = os.path.join(cmake_build_dir,
+                                          "tools", "torch-mlir", "python_packages",
+                                          "torch_mlir")
+
         if not os.getenv("TORCH_MLIR_CMAKE_BUILD_DIR_ALREADY_BUILT"):
             src_dir = os.path.abspath(os.path.dirname(__file__))
             llvm_dir = os.path.join(
@@ -83,15 +87,26 @@ def run(self):
             cmake_cache_file = os.path.join(cmake_build_dir, "CMakeCache.txt")
             if os.path.exists(cmake_cache_file):
                 os.remove(cmake_cache_file)
+            # NOTE: With repeated builds for different Python versions, the
+            # prior version binaries will continue to accumulate. IREE uses
+            # a separate install step and cleans the install directory to
+            # keep this from happening. That is the most robust. Here we just
+            # delete the directory where we build native extensions to keep
+            # this from happening but still take advantage of most of the
+            # build cache.
+            mlir_libs_dir = os.path.join(python_package_dir, "torch_mlir", "_mlir_libs")
+            if os.path.exists(mlir_libs_dir):
+                print(f"Removing _mlir_mlibs dir to force rebuild: {mlir_libs_dir}")
+                shutil.rmtree(mlir_libs_dir)
+            else:
+                print(f"Not removing _mlir_libs dir (does not exist): {mlir_libs_dir}")
+
             subprocess.check_call(["cmake", llvm_dir] +
                                   cmake_args, cwd=cmake_build_dir)
             subprocess.check_call(["cmake",
                                    "--build",  ".",
                                    "--target", "TorchMLIRPythonModules"],
                                   cwd=cmake_build_dir)
-        python_package_dir = os.path.join(cmake_build_dir,
-                                          "tools", "torch-mlir", "python_packages",
-                                          "torch_mlir")
 
         if os.path.exists(target_dir):
             shutil.rmtree(target_dir, ignore_errors=False, onerror=None)
@@ -131,8 +146,11 @@ def build_extension(self, ext):
         CMakeExtension("torch_mlir._mlir_libs._jit_ir_importer"),
     ],
     install_requires=[
+        "numpy",
         # To avoid issues with drift for each nightly build, we pin to the
         # exact version we built against.
+        # TODO: This includes the +cpu specifier which is overly
+        # restrictive and a bit unfortunate.
         f"torch=={torch.__version__}",
     ],
     zip_safe=False,