build-llvm-clang.sh

#!/usr/bin/env bash
# SPDX-License-Identifier: Apache-2.0
# Copyright 2020 Google LLC.
# Author: Marco Elver
#
# Helper script to checkout and build a recent Git version of Clang/LLVM.

set -ue

readonly LLVM_REPO="https://github.com/llvm/llvm-project.git"
readonly LLVM_SRC="llvm-project"

# May be overridden from environment.
: ${LLVM_COMMIT:="origin/release/11.x"}

pr_info() { printf '\e[1;32mINFO: \e[0m'"$@"  1>&2;         }
die()     { printf '\e[1;31mERROR: \e[0m'"$@" 1>&2; exit 1; }

check_have() { type -p "$1" &>/dev/null || die "'%s' not found!\n" "$1"; }
check_deps() {
	check_have make
	check_have cmake
}

prepare_and_cwd_build() {
	pr_info "Preparing ...\n"
	local dst_dir="${1%/}" # Strip trailing '/'
	mkdir -p "$dst_dir" && cd "$dst_dir"

	# Get the source and point it to the commit we want
	if [[ ! -d "$LLVM_SRC" ]]; then
		git clone "$LLVM_REPO" "$LLVM_SRC"
	fi
	if [[ -n "$LLVM_COMMIT" ]]; then
		(cd "$LLVM_SRC" && git fetch && git checkout -B for-build "$LLVM_COMMIT")
	fi

	mkdir -p build && cd build
}

build() {
	local prefix="$1"
	# Let's build *with* assertions on, since we're pulling in a Git version.
	local cmake_args=(
		-DLLVM_ENABLE_PROJECTS="clang;compiler-rt"
		-DCMAKE_BUILD_TYPE=Release
		-DLLVM_ENABLE_ASSERTIONS=On
	)
	[[ -n "$prefix" ]] && cmake_args+=("-DCMAKE_INSTALL_PREFIX:PATH=$prefix") || :
	if [[ -n "${LLVM_USE_COMPILER:-}" ]]; then
		cmake_args+=(
			-DCMAKE_C_COMPILER="${LLVM_USE_COMPILER% *}"
			-DCMAKE_CXX_COMPILER="${LLVM_USE_COMPILER#* }"
		)
	fi

	pr_info "Building ...\n"
	echo cmake "${cmake_args[@]}" "../${LLVM_SRC}/llvm"
	cmake "${cmake_args[@]}" "../${LLVM_SRC}/llvm"
	make -j$(nproc)
}

check_install() {
	local prefix="$1"

	pr_info "Checking ...\n"
	# At least run check-clang. All tests would probably be a little too much.
	make -j$(nproc) check-clang

	if [[ -z "$prefix" ]]; then
		local expect_clang="$(pwd)/bin/clang"
	else
		make -j$(nproc) install
		local expect_clang="${prefix}/bin/clang"
	fi
	[[ ! -x "$expect_clang" ]] && die "could not find: %s\n" "$expect_clang" || :
	pr_info "Clang binary available at: %s\n" "$expect_clang"
}

main() {
	if (( $# < 1 )); then
		echo "Usage: $0 <build-dir> [<install-prefix>]"
		echo "Optional: If <install-prefix> is provided, installs Clang/LLVM into <install-prefix>."
		exit 42
	fi
	local build_dir="$1"
	local prefix="${2:-}"
	if [[ -n "$prefix" ]]; then
		[[ ! -d "$prefix" ]] && die "Directory does not exist: %s\n" "$prefix" || :
		# Get prefix before we cwd.
		prefix="$(cd "$prefix" && pwd)"
	fi

	check_deps
	prepare_and_cwd_build "$build_dir"
	build "$prefix"
	check_install "$prefix"
}
main "$@"