Reuse LLVM build tree for MLIR python bindings

docker/build/devdeps.manylinux.Dockerfile

@@ -83,14 +83,17 @@ RUN curl -L https://github.com/Kitware/CMake/releases/download/v3.28.4/cmake-3.2
 
 # Build the the LLVM libraries and compiler toolchain needed to build CUDA-Q.
 ADD ./scripts/build_llvm.sh /scripts/build_llvm.sh
+ADD ./scripts/build_mlir_python_bindings.sh /scripts/build_mlir_python_bindings.sh
 ADD ./cmake/caches/LLVM.cmake /cmake/caches/LLVM.cmake
 ADD ./tpls/customizations/llvm/ /tpls/customizations/llvm/
 RUN LLVM_PROJECTS='clang;lld;mlir' LLVM_SOURCE=/llvm-project \
     LLVM_CMAKE_CACHE=/cmake/caches/LLVM.cmake \
     LLVM_CMAKE_PATCHES=/tpls/customizations/llvm \
     bash /scripts/build_llvm.sh -c Release -v
-    # No clean up of the build or source directory,
-    # since we need to re-build llvm for each python version to get the bindings.
+    # The build directory at /llvm-project/build is intentionally retained:
+    # build_mlir_python_bindings.sh reuses it in the wheel container to add
+    # the python-binding targets per Python version without recompiling
+    # the rest of the LLVM/MLIR/clang/lld tree.
 
 # Install CUDA
 

docker/release/cudaq.wheel.Dockerfile

@@ -51,11 +51,11 @@ RUN --mount=from=ccache-data,target=/tmp/ccache-import,rw \
     fi
 RUN echo "Building MLIR bindings for python${python_version}" && \
     CCACHE_DISABLE=1 python${python_version} -m pip install --no-cache-dir numpy "nanobind>=2.9.0" && \
-    rm -rf "$LLVM_INSTALL_PREFIX/src" "$LLVM_INSTALL_PREFIX/python_packages" && \
+    rm -rf "$LLVM_INSTALL_PREFIX/python_packages" && \
     Python3_EXECUTABLE="$(which python${python_version})" \
-    LLVM_PROJECTS='clang;lld;mlir;python-bindings' \
-    LLVM_CMAKE_CACHE=/cmake/caches/LLVM.cmake LLVM_SOURCE=/llvm-project \
-    bash /scripts/build_llvm.sh -c Release -v
+    LLVM_SOURCE=/llvm-project \
+    LLVM_INSTALL_PREFIX="$LLVM_INSTALL_PREFIX" \
+    bash /scripts/build_mlir_python_bindings.sh
 
 # Build wheel using unified wheel build script
 RUN cd /cuda-quantum && \

scripts/build_mlir_python_bindings.sh

@@ -0,0 +1,80 @@
+#!/bin/bash
+
+# ============================================================================ #
+# Copyright (c) 2022 - 2026 NVIDIA Corporation & Affiliates.                   #
+# All rights reserved.                                                         #
+#                                                                              #
+# This source code and the accompanying materials are made available under     #
+# the terms of the Apache License 2.0 which accompanies this distribution.     #
+# ============================================================================ #
+
+# Builds the MLIR Python bindings against an existing LLVM build tree and
+# installs them into LLVM_INSTALL_PREFIX. Requires the manylinux devdeps
+# base image, where build_llvm.sh has already configured and built the
+# LLVM/MLIR libraries (without python-bindings) at LLVM_SOURCE/build.
+#
+# This avoids reconfiguring/rebuilding the full LLVM tree once per Python
+# version: only the binding objects (linked against the active interpreter
+# ABI) and a small amount of tablegen output get produced.
+#
+# Required environment:
+#   LLVM_SOURCE              path to the llvm-project source (default: /llvm-project)
+#   LLVM_INSTALL_PREFIX      install destination (default: /usr/local/llvm)
+#   Python3_EXECUTABLE       interpreter to bind against
+#   NANOBIND_INSTALL_PREFIX  nanobind install dir (default: /usr/local/nanobind)
+#
+# Usage:
+#   Python3_EXECUTABLE=$(which python3.11) bash scripts/build_mlir_python_bindings.sh
+
+set -e
+
+LLVM_SOURCE=${LLVM_SOURCE:-/llvm-project}
+LLVM_INSTALL_PREFIX=${LLVM_INSTALL_PREFIX:-/usr/local/llvm}
+NANOBIND_INSTALL_PREFIX=${NANOBIND_INSTALL_PREFIX:-/usr/local/nanobind}
+LLVM_BUILD_FOLDER=${LLVM_BUILD_FOLDER:-build}
+
+if [ -z "$Python3_EXECUTABLE" ]; then
+  echo "Python3_EXECUTABLE must be set."
+  exit 1
+fi
+
+llvm_build_dir="$LLVM_SOURCE/$LLVM_BUILD_FOLDER"
+if [ ! -f "$llvm_build_dir/CMakeCache.txt" ]; then
+  echo "Expected pre-configured LLVM build at $llvm_build_dir."
+  echo "This script must run on top of the manylinux devdeps base image."
+  exit 1
+fi
+
+this_file_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# nanobind links against the active interpreter ABI; build it if missing.
+if [ ! -d "$NANOBIND_INSTALL_PREFIX" ] || [ -z "$(ls -A "$NANOBIND_INSTALL_PREFIX"/* 2>/dev/null)" ]; then
+  echo "Building nanobind..."
+  cd "$this_file_dir/.." && repo_root=$(git rev-parse --show-toplevel) && cd "$repo_root"
+  git submodule update --init --recursive --recommend-shallow --single-branch tpls/nanobind
+  mkdir -p tpls/nanobind/build && cd tpls/nanobind/build
+  cmake -G Ninja ../ \
+    -DCMAKE_INSTALL_PREFIX="$NANOBIND_INSTALL_PREFIX" \
+    -DPython3_EXECUTABLE="$Python3_EXECUTABLE" \
+    -DNB_TEST=False
+  cmake --build . --target install --config Release
+fi
+
+cd "$llvm_build_dir"
+
+# Reconfigure the existing build tree: enable MLIR python bindings and
+# point at the active interpreter. Other cache entries (compiler flags,
+# enabled projects, ccache launcher, build type) are preserved.
+echo "Reconfiguring LLVM build for python bindings (Python: $Python3_EXECUTABLE)..."
+cmake . \
+  -DMLIR_ENABLE_BINDINGS_PYTHON=ON \
+  -DPython3_EXECUTABLE="$Python3_EXECUTABLE" \
+  -Dnanobind_DIR="$NANOBIND_INSTALL_PREFIX/nanobind/cmake"
+
+# Build and install only the python-binding components. Other targets in
+# the existing tree are left untouched and remain installed at
+# LLVM_INSTALL_PREFIX from the base image.
+echo "Building and installing MLIR python bindings..."
+ninja install-MLIRPythonModules install-mlir-python-sources
+
+echo "Installed MLIR python bindings into $LLVM_INSTALL_PREFIX."