emscripten-build-llvm.sh

#!/usr/bin/env bash

set -euo pipefail

INSTALL_DIR="${PWD}/llvm18.0-emscripten"
mkdir -p "${INSTALL_DIR}"

# Check if EMSDK_ROOT is defined
if [ -z "${EMSDK_ROOT:-}" ]; then
    echo "Error: EMSDK_ROOT is not defined."
    echo "Please set the EMSDK_ROOT environment variable to the root directory of your Emscripten SDK."
    exit 1
fi

source "${EMSDK_ROOT}/emsdk_env.sh"

LLVM_SRC="${PWD}/llvm-project"
LLVM_NATIVE="${PWD}/build/llvm-tools"
LLVM_WASM="${PWD}/build/llvm-wasm"

./clone-llvm.sh "${LLVM_SRC}"

# Cross-compiling LLVM requires a native build of "llvm-tblgen", "clang-tblgen" and "llvm-config"
if [ ! -d "${LLVM_NATIVE}" ]; then
    cmake -G Ninja \
        -S "${LLVM_SRC}/llvm" \
        -B "${LLVM_NATIVE}" \
        -DCMAKE_BUILD_TYPE=Release \
        -DLLVM_TARGETS_TO_BUILD=WebAssembly \
        -DLLVM_ENABLE_PROJECTS="clang"
fi

cmake --build "${LLVM_NATIVE}" -- llvm-tblgen clang-tblgen llvm-config

if [ ! -d "${LLVM_WASM}" ]; then
    EMCC_DEBUG=2 \
    CXXFLAGS="-Dwait4=__syscall_wait4" \
    LDFLAGS="-lnodefs.js -s NO_INVOKE_RUN -s EXIT_RUNTIME -s INITIAL_MEMORY=64MB -s ALLOW_MEMORY_GROWTH -s \
        EXPORTED_RUNTIME_METHODS=FS,callMain,NODEFS -s MODULARIZE -s EXPORT_ES6 -s WASM_BIGINT" \
    emcmake cmake -G Ninja \
        -S "${LLVM_SRC}/llvm" \
        -B "${LLVM_WASM}" \
        -DCMAKE_BUILD_TYPE=Release \
        -DLLVM_TARGETS_TO_BUILD='RISCV' \
        -DLLVM_ENABLE_PROJECTS="clang;lld" \
        -DLLVM_ENABLE_DUMP=OFF \
        -DLLVM_ENABLE_ASSERTIONS=OFF \
        -DLLVM_ENABLE_EXPENSIVE_CHECKS=OFF \
        -DLLVM_ENABLE_BACKTRACES=OFF \
        -DLLVM_BUILD_TOOLS=OFF \
        -DLLVM_ENABLE_THREADS=OFF \
        -DLLVM_BUILD_LLVM_DYLIB=OFF \
        -DLLVM_INCLUDE_TESTS=OFF \
        -DLLVM_ENABLE_TERMINFO=Off \
        -DLLVM_ENABLE_LIBXML2=Off \
        -DLLVM_ENABLE_ZLIB=Off \
        -DLLVM_ENABLE_ZSTD=Off \
        -DLLVM_TABLEGEN="${LLVM_NATIVE}/bin/llvm-tblgen" \
        -DCLANG_TABLEGEN="${LLVM_NATIVE}/bin/clang-tblgen" \
        -DCMAKE_INSTALL_PREFIX="${INSTALL_DIR}"
fi

cmake --build "${LLVM_WASM}"
cmake --install "${LLVM_WASM}"

cp "${LLVM_NATIVE}/bin/llvm-config" "${INSTALL_DIR}/bin"

echo ""
echo "LLVM cross-compilation for WebAssembly completed successfully."