Cross-compiling LLVM for iOS

LLVM_for_iOS.sh

#! /bin/bash

# Bail out on error
set -e

LLVM_SRC=http://releases.llvm.org/6.0.0/llvm-6.0.0.src.tar.xz
CLANG_SRC=http://releases.llvm.org/6.0.0/cfe-6.0.0.src.tar.xz
LIBCXX_SRC=http://releases.llvm.org/6.0.0/libcxx-6.0.0.src.tar.xz
LIBCXXABI_SRC=http://releases.llvm.org/6.0.0/libcxxabi-6.0.0.src.tar.xz

LLVM_SRCDIR=$(pwd)/llvm_src
OSX_BUILDDIR=$(pwd)/build_osx
IOS_BUILDDIR=$(pwd)/build_ios

IOS_SDKROOT=$(xcrun --sdk iphoneos --show-sdk-path)

# Check for ninja requirement
if [ ! hash ninja 2>/dev/null ]; then
  echo "Ninja was not found. Please install before executing this script."
  exit 1
fi

# Parse arguments
for i in "$@"
do
case $i in
  -c|--clean)
    CLEAN=YES
  shift
  ;;
  *)
    # unknown option
  ;;
esac
done

# Download LLVM into llvm_src
if [ ! -d $LLVM_SRCDIR ]; then
  mkdir $LLVM_SRCDIR
  curl $LLVM_SRC | tar xz -C $LLVM_SRCDIR --strip-components 1
fi
pushd $LLVM_SRCDIR

# get clang
pushd tools

if [ ! -d clang ]; then
  mkdir clang
  curl $CLANG_SRC | tar xz -C clang --strip-components 1
fi
popd

# Get libcxx and libcxxabi
pushd projects

if [ ! -d libcxx ]; then
  mkdir libcxx
  curl $LIBCXX_SRC | tar xz -C libcxx --strip-components 1
fi
if [ ! -d libcxxabi ]; then
  mkdir libcxxabi
  curl $LIBCXXABI_SRC | tar xz -C libcxxabi --strip-components 1
fi
popd

# End downloading source
popd

# compile for OSX (about 6h, 18GB of disk space)
if [ $CLEAN ]; then
  rm -rf $OSX_BUILDDIR
fi
if [ ! -d $OSX_BUILDDIR ]; then
  mkdir $OSX_BUILDDIR
fi
pushd $OSX_BUILDDIR
cmake -GNinja $LLVM_SRCDIR
time ninja
popd

# get libcxx and libcxxabi out of the way:
rm -rf dontBuild
mkdir dontBuild
mv llvm_src/projects/libcxx dontBuild
mv llvm_src/projects/libcxxabi dontBuild
# TODO: some combination of build variables might allow us to build these too. 
# Right now, they fail. Maybe CFLAGS with: -D__need_size_t -D_LIBCPP_STRING_H_HAS_CONST_OVERLOADS 

# Now, compile for iOS using the previous build:
# About 24h, 13 GB of disk space
# Flags you could use: LLVM_LINK_LLVM_DYLIB and BUILD_SHARED_LIBS, to make everything use dynamic libraries
# (I did not test these)

if [ $CLEAN ]; then
  rm -rf $IOS_BUILDDIR
fi
if [ ! -d $IOS_BUILDDIR ]; then
  mkdir $IOS_BUILDDIR
fi
pushd $IOS_BUILDDIR
cmake -GNinja -DLLVM_TARGET_ARCH=ARM \
-DLLVM_TARGETS_TO_BUILD=ARM \
-DLLVM_DEFAULT_TARGET_TRIPLE=arm64-apple-darwin10 \
-DLLVM_ENABLE_THREADS=OFF \
-DLLVM_TABLEGEN=${OSX_BUILDDIR}/bin/llvm-tblgen \
-DCLANG_TABLEGEN=${OSX_BUILDDIR}/bin/clang-tblgen \
-DCMAKE_OSX_SYSROOT=${IOS_SDKROOT} \
-DCMAKE_C_COMPILER=${OSX_BUILDDIR}/bin/clang \
-DCMAKE_LIBRARY_PATH=${OSX_BUILDDIR}/lib/ \
-DCMAKE_INCLUDE_PATH=${OSX_BUILDDIR}/include/ \
-DCMAKE_C_FLAGS="-arch arm64 -target arm64-apple-darwin10 -I${OSX_BUILDDIR}/include/ -miphoneos-version-min=11" \
-DCMAKE_CXX_FLAGS="-arch arm64 -target arm64-apple-darwin10 -I${OSX_BUILDDIR}/include/c++/v1/ -miphoneos-version-min=11" \
$LLVM_SRCDIR
time ninja
popd